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(Circulation. 1997;95:1686-1744.)
© 1997 American Heart Association, Inc.
Articles |
ACC/AHA Guidelines for the Clinical Application of Echocardiography
A Report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee on Clinical Application of Echocardiography) Developed in Collaboration With the American Society of Echocardiography
Key Words: diagnosis • AHA Medical/Scientific Statements • echocardiography
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Contents |
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Top
Contents
II. Murmurs and Valvular...- Preamble
I. Introduction, General Considerations, and Scope
II. Murmurs and Valvular Heart Disease
- Murmurs
Native Valvular Stenosis
Native Valvular Regurgitation
Repeated Studies in Valvular Heart Disease
Mitral Valve Prolapse
Infective Endocarditis: Native Valves
Prosthetic Valves
Prosthetic Valve Dysfunction and Endocarditis
IV. Ischemic Heart Disease
- Acute Ischemic Syndromes
Chronic Ischemic Heart Disease
- Assessment of Ejection Fraction
Edema and Dyspnea
Regional Left Ventricular Function
Ventricular Dysfunction
Dilated Cardiomyopathy
Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Heart Failure With Normal Systolic Function
Evaluation of the Right Ventricle
- Pericardial Effusion
Cardiac Tamponade
Increased Pericardial Thickness
Pericardial Tumors and Cysts
Constrictive Pericarditis
Congenital Absence of the Pericardium and Pericardial Disease After Open-Heart Surgery
VIII. Diseases of the Great Vessels
- Aortic Dissection
Aortic Aneurysm
Aortic Rupture and Thoracic Aortic Degenerative Disease
The Great Veins
- Pulmonary Thromboembolism
XI. Neurological Disease and Other Cardioembolic Disease
XII. Arrhythmias and Palpitation
- Cardioversion of Patients With Atrial Fibrillation
Syncope
Screening
- Echocardiography in the Trauma Patient
XV. Echocardiography in the Pediatric Patient
- Resource Utilization and Age
Congenital Cardiovascular Disease in the Neonate
Cardiopulmonary Disease
Arrhythmias
Myocardial Disease in the Neonate
Congenital Cardiovascular Disease in the Infant, Child, and Adolescent
Arrhythmias/Conduction Disturbances
Acquired Cardiovascular Disease
Pulmonary Diseases in Pediatric Acquired Cardiovascular Disease
Thrombus/Tumor
Transesophageal Echocardiography
Fetal Echocardiography
Preamble
It is clearly important that the medical profession plays a
significant role in critically evaluation of the use of diagnostic
procedures and therapies in the management or prevention of disease.
Rigorous and expert analysis of the available data documenting relative
benefits and risks of those procedures and therapies can produce
helpful guidelines that improve the effectiveness of care, optimize
patient outcomes, and impact the overall cost of care favorably by
focusing resources on the most effective strategies.
The American College of Cardiology (ACC) and the American Heart Association (AHA) have jointly engaged in the production of such guidelines in the area of cardiovascular disease since 1980. This effort is directed by the ACC/AHA Task Force on Practice Guidelines. Its charge is to develop and revise practice guidelines for important cardiovascular diseases and procedures. Experts in the subject under consideration are selected from both organizations to examine subject-specific data and write guidelines. The process includes additional representatives from other medical practitioner and specialty groups as appropriate. Writing groups are specifically charged to perform a formal literature review, weigh the strength of evidence for or against a particular treatment or procedure, and include estimates of expected health outcomes where data exist. Patient-specific modifiers, comorbidities, and issues of patient preference that might influence the choice of particular tests or therapies are considered as well as frequency of follow-up and cost-effectiveness.
These practice guidelines are intended to assist physicians in clinical decision making by describing a range of generally acceptable approaches for the diagnosis, management, or prevention of specific diseases or conditions. These guidelines attempt to define practices that meet the needs of most patients in most circumstances. The ultimate judgment regarding care of a particular patient must be made by the physician and patient in light of all of the circumstances presented by that patient.
The Committee on Clinical Application of Echocardiography was chaired by Melvin D. Cheitlin, MD, FACC, and included the following members: Joseph S. Alpert, MD, FACC, William F. Armstrong, MD, FACC, Gerard P. Aurigemma, MD, FACC, George A. Beller, MD, FACC, Fredrick Z. Bierman, MD, FACC, Thomas W. Davidson, MD, FAAFP, Jack L. Davis, MD, FACC, Pamela S. Douglas, MD, FACC, Linda D. Gillam, MD, FACC, Richard P. Lewis, MD, FACC, Alan S. Pearlman, MD, FACC, John T. Philbrick, MD, FACP, Pravin M. Shah, MD, FACC, and Roberta G. Williams, MD, FACC.
The committee is composed of both university-affiliated and practicing physicians and those with specific echocardiographic expertise and senior clinicians who use the technique. Two general physicians (one general internal medicine and one family practitioner) also served on the committee.
The document was reviewed by three outside reviewers nominated by the ACC and three outside reviewers nominated by the AHA as well as other individuals from the American Society of Echocardiography, Society of Pediatric Echocardiography, American College of Physicians, and American Academy of Family Physicians.
The executive summary and recommendations are published in the March 15, 1997, issue of Journal of the American College of Cardiology. The full text is published in Circulation. Reprints of both the full text and the executive summary and recommendations are available from both organizations. The document will be reviewed 2 years after publication and yearly thereafter and considered current unless the task force revises or withdraws it from distribution. The document was endorsed by the American Society of Echocardiography.
James L. Ritchie, MD, FACC Chair, ACC/AHA Task Force on Practice Guidelines
I. Introduction, General Considerations, and
Scope
The previous guidelines for the use of echocardiography were
published in December 1990. Since that time there have been significant
advances in the technology of Doppler echocardiography and growth in
its clinical use and in the scientific evidence leading to
recommendations for its proper use.
The recommendations are based on a Medline search of the English literature from 1990 to May 1995. Echocardiography was cross-referenced with the following terms: antineoplastic agents, aortic or dissecting aneurysm, arrhythmias, athletes, atrial fibrillation, cardioversion, Marfan syndrome, bacterial endocarditis, myocardial infarction, myocardial ischemia, coronary disease, chest pain, cardiomyopathies, cerebrovascular disorders or cerebral ischemia, embolism, heart neoplasms, heart valve disease, heart murmurs, hypertension, mitral valve prolapse, pericarditis, pericardial effusion, cardiac tamponade, pericardium, pulmonary embolism or pulmonary heart disease or cor pulmonale, screening, shock or aortic rupture or heart rupture, syncope, transplantation, unstable angina, congenital heart disease in the adult, specific congenital lesions, arrhythmias in children, pediatric echocardiography, and fetal echocardiography.
The search yielded over 3000 references, which the committee reviewed. This document includes recommendations for the use of Doppler echocardiography in both adult and pediatric patients. The pediatric guidelines also include recommendations for fetal Doppler echocardiography, an increasingly important field. The guidelines include recommendations for the use of Doppler echocardiography in both specific cardiovascular disorders and in the evaluation of patients with frequently observed cardiovascular symptoms and signs, common presenting complaints, or findings of dyspnea, chest discomfort, and cardiac murmur. In this way the guidelines will provide assistance to physicians regarding the use of Doppler echocardiographic techniques in the evaluation of such common clinical problems.
The recommendations concerning the use of Doppler echocardiography follow the indication classification system (eg, Class I, II, and III) used in other ACC/AHA guidelines:
Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.
Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.
IIa: Weight of evidence/opinion is in favor of usefulness/efficacy.
IIb: Usefulness/efficacy is less well established by evidence/opinion.
Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective and in some cases may be harmful.
Evaluation of the clinical utility of a diagnostic test such as echocardiography is far more difficult than assessment of the efficacy of a therapeutic intervention, because the diagnostic test can never have the same direct impact on patient survival or recovery. Nevertheless, a series of hierarchical criteria are generally accepted as a scale by which to judge worth.1 2 3
Hierarchical Levels of Echocardiography
Assessment
- Technical capacity
- Diagnostic performance
- Impact on diagnostic and prognostic thinking
- Therapeutic impact
- Health-related outcomes
The most fundamental criterion is technical capacity, including adequacy of equipment and study performance. The next is diagnostic performance, which encompasses much of traditional diagnostic test assessment, including delineation of the range of clinical circumstances in which a test is applicable, as well as test sensitivity, specificity, and accuracy for individual applications. The third criterion is the capability of a test to alter diagnostic and prognostic thinking, ie, to offer added value. This level depends on the context in which the test is performed and is therefore affected by such factors as what is already known, the judged value of confirmatory data, and the importance of reassurance in a particular clinical situation. Impact on diagnostic and prognostic thinking is an important link between test results and patient treatment. Subsequent criteria include therapeutic impact and health-related outcomes. Because there are essentially no randomized trials assessing health outcomes for diagnostic tests, the committee has not ranked the available scientific evidence in an A, B, C fashion (as in other ACC/AHA documents) but rather has compiled the evidence in tables. All recommendations are thus based on either this evidence from observational studies or on the expert consensus of the committee.
Two-dimensional echocardiography can provide excellent images of the heart, paracardiac structures, and the great vessels. Because it depends on satisfactory examining windows from the body surface to the cardiovascular structures, there may be limitations on its use for adult patients. For patients with chronic obstructive pulmonary disease, the interposition of air-filled lung between the body surface and the heart severely limits access, and complete examination may not be possible. Other circumstances limit the use of transthoracic echocardiography (TTE), especially for patients in the intensive care unit. For example, patients on ventilators, those who cannot be rotated into a lateral position, and those with incisions may not have satisfactory precordial or apical windows. TEE may avoid most of these limitations because there is no interposed lung tissue between the transducer and the heart.
The definition of echocardiography used in this document incorporates Doppler analysis, M-mode echocardiography, two-dimensional TTE, and, when indicated, TEE. Intravascular ultrasound is not considered here but will be reviewed in the revised guidelines for coronary angiography (in preparation). Echocardiography for evaluating the patient with cardiovascular disease for noncardiac surgery is considered in the ACC/AHA Guidelines for Perioperative Cardiovascular Evaluation for Noncardiac Surgery.4 The techniques of three-dimensional echocardiography are in the developmental stages and also are not considered here. Intraoperative TEE is not considered in this document because it is the subject of practice guidelines for perioperative TEE.5
New techniques that are still rapidly evolving are also not addressed in this document. Echocardiography-contrast substances that can pass through the pulmonary circulation and opacify the left heart are in development. Echocardiography-contrast injections into the coronary artery to quantitate myocardium at risk and perfusion territories and the second harmonic echocardiogram to enhance echocardiographic contrast also are not addressed.
With the development of Doppler echocardiography and proof that the
modified Bernoulli equation permitted the conversion of instantaneous
velocities of blood flow into instantaneous pressure gradients across
obstructions, it became possible to precisely localize and quantitate
obstruction in the cardiovascular system. This information, when
considered with flow volume information provided by Doppler flow
velocity integrals, allows a plethora of physiological and functional
information to be obtained noninvasively. The differing capabilities of
the several types of available Doppler echocardiographic techniques are
outlined in Table 1
. Recognizing the strengths of each
technique will enable the physician to order the appropriate study.
Generally a complete transthoracic echocardiogram and Doppler study is
called for unless otherwise specified.
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When faced with a patient needing cardiovascular evaluation and testing, the clinician must choose among available tests. Echocardiography, nuclear testing, magnetic resonance imaging (MRI), and positron emission tomography can yield overlapping if not identical information, often with similar or comparable accuracy. Decisions concerning which technique to use must then be based on such factors as local expertise in performance and interpretation, test availability, cost, and patient preference. Therefore, it is impossible in this document to judge competing tests or recommend the use of one over another.
TTE is associated with little if any patient discomfort, and no risks with this procedure have been identified. Moreover, the use of TTE with exercise or vasoactive drugs such as dipyridamole or dobutamine involves the minimal risks of arrhythmia, ischemia, and hypotension seen with exercise and the aforementioned drugs. In TEE, the echocardiographic transducer is mounted on a flexible endoscope and passed into the esophagus and stomach. This involves some discomfort and minimal but definite risk of pharyngeal and esophageal trauma and even rarely esophageal perforation. Rare instances of infective endocarditis have been associated with the use of TEE. An occasional patient has a reaction to either the sedative or the local anesthesia used.
The ability of Doppler echocardiography to provide unique noninvasive information with minimal discomfort or risk without using contrast material or ionizing radiation, coupled with its portability, immediate availability, and repeatability, accounts for its use in virtually all categories of cardiovascular disease. However, two-dimensional Doppler echocardiography is best used after a careful history, physical examination, appropriate electrocardiogram (ECG), and chest radiograph have been obtained so that the appropriate questions can be asked. Indiscriminate use of echocardiography or its use for "screening" is not indicated for two principal reasons. First, the cost of echocardiography is not trivial. Second, the current Doppler echocardiographic techniques reveal details of structure and function such as filamentous strands on valves, valvular prolapse, and jet velocities representing minimal and at times transient valvular insufficiency that could generate unnecessary further testing or inappropriate and potentially detrimental therapy.
These guidelines contain recommendations concerning not only indications for the use of these techniques but also specific circumstances when Doppler echocardiography adds little or nothing to the care of the patient and is therefore not indicated. An example is the evaluation of the patient with a clearly innocent murmur in the opinion of a qualified, knowledgeable examining physician. Another example is the use of echocardiography in diagnosing mitral valve prolapse (MVP) in a patient with chest pain or premature ventricular contractions in the absence of clinical findings consistent with MVP. Because there is no evidence that such patients have an increased risk of endocarditis beyond the general population which does not have "echo-only" MVP, echocardiography is generally not indicated in this situation.
An echocardiographic study is not indicated when the pathology and/or systolic ventricular function have been adequately defined by other techniques, making the echocardiographic study redundant. Furthermore, echocardiography should be performed by laboratories with adequately trained physicians and cardiac sonographers where patient volume recommendations are met as previously described.3
These guidelines also address recommendations about the frequency with which a Doppler echocardiographic study is repeated. If the frequency with which studies are repeated could be decreased without adversely affecting the quality of care, the economic savings realized would likely be significant. With a noninvasive diagnostic study and no known complications, the potential for repeating the study unnecessarily exists. It is easier to state when a repeat echocardiogram is not needed then when and how often it should be repeated, since no studies in the literature address this question. An adult patient with hemodynamically insignificant aortic regurgitation almost certainly does not need a repeat echocardiogram unless there is a change in the clinical picture. The asymptomatic patient with hemodynamically severe aortic regurgitation probably needs repeat echocardiography to monitor left ventricular function. How often this should be done depends on the individual patient and must be left to the judgment of the physician until evidence-based data addressing this issue are available.
The use of two-dimensional Doppler echocardiography in establishing cardiac diagnoses and making therapeutic decisions is well established. Examples include the demonstration of an acquired ventricular septal defect in a patient with an acute myocardial infarction. In the past this diagnosis required catheterization; now the definitive diagnosis can be made in most cases with Doppler echocardiography. At times the Doppler echocardiogram can enable cardiac surgery to proceed without a comprehensive catheterization. Examples of this are the finding of severe aortic stenosis or mitral or aortic regurgitation in the symptomatic young patient or the finding of a left atrial myxoma.
The use of repeated Doppler echocardiographic studies in following patients is illustrated in adult patients with moderate aortic stenosis who have a change in symptoms. Similarly the follow-up evaluation of ventricular function in the patient with chronic aortic or mitral valvular insufficiency lesions can help determine the timing of valvular surgery.
This document assumes that Doppler echocardiographic studies are performed and interpreted in accordance with the statements for clinical competence in echocardiography set forth by the Joint Task Force of the American College of Physicians/American College of Cardiology/American Heart Association. Optimal training for such studies is set forth by the American Society of Echocardiography, the American College of Cardiology, and the Society of Pediatric Echocardiography.
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II. Murmurs and Valvular Heart Disease |
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Echocardiography is extremely useful in the assessment of cardiac murmurs, stenosis and regurgitation of all four cardiac valves, prosthetic valve function, and patients with infective endocarditis. Echocardiography provides valuable information regarding diagnosis, valvular morphology, etiology of valve disease, identification and quantification of lesions, detection and evaluation of associated abnormalities, delineation of cardiac size and function, and assessment of the adequacy of ventricular compensation. Echocardiography readily detects structural abnormalities such as fibrosis, calcification, thrombus, or vegetation, and abnormalities of valvular motion such as immobility, flail or prolapsing leaflets, or prosthetic valve dehiscence. A full echocardiographic evaluation should provide prognostic as well as diagnostic information, allow for risk stratification, establish baseline data for subsequent examinations, and help guide and evaluate the therapeutic approach.
Echocardiography often provides a definitive diagnosis and may obviate the need for catheterization in selected patients. Patients' acceptance of this noninvasive technique for initial and reevaluation observation is high.6 7 8 MRI has the capability to detect the presence of stenotic and regurgitant lesions9 10 and has several advantages. However, MRI instrumentation is substantially more expensive and not as widely available.
Murmurs
Cardiac auscultation remains the most widely used method of
screening for heart disease. Heart murmurs are produced by turbulent
blood flow and are often signs of stenotic or regurgitant valve disease
or acquired or congenital cardiovascular defects. In valvular and
congenital forms of heart disease, a murmur is usually the major
evidence of the abnormality, although some hemodynamically significant
regurgitant lesions may be silent.11 12 However, many
murmurs in asymptomatic people are innocent and of no functional
significance. Such murmurs are defined as having the following
characteristics: a systolic murmur of short duration, grade 1 or 2
intensity at the left sternal border, a systolic ejection pattern, a
normal S2, no other abnormal sounds or murmurs, no evidence
of ventricular hypertrophy or dilation, no thrills, and the absence of
an increase in intensity with the Valsalva maneuver. Such murmurs are
especially common in high-output states such as
pregnancy.13 14 When the characteristic findings of an
individual murmur are considered together with other patient
information and clinical data from the physical examination, the
correct diagnosis can usually be established.15 In
patients with ambiguous clinical findings, the echocardiogram may be
the preferred test because it can provide a definitive diagnosis,
rendering a chest radiograph and/or ECG unnecessary. In some patients
the Doppler echocardiogram is the only noninvasive method capable of
identifying the cause of a heart murmur.12 16
In the evaluation of heart murmurs, the purposes of performing a Doppler echocardiogram are to
- Define the primary lesion and its etiology and judge its severity.
- Define hemodynamics.
- Detect coexisting abnormalities.
- Detect lesions secondary to the primary lesion.
- Evaluate cardiac size and function.
- Establish a reference point for future observations.
- Reevaluate the patient after an intervention.
As valuable as echocardiography may be, the basic cardiovascular
evaluation is still the most appropriate method to screen for cardiac
disease and will establish many clinical diagnoses.17
Echocardiography should not be used to replace the cardiovascular
examination but can be helpful in determining the etiology and judging
the severity of lesions, particularly in pediatric and elderly
patients.15 17 18 19
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Native Valvular Stenosis
Two-dimensional and Doppler echocardiography reliably identify and
quantitate the severity of stenotic lesions of both native and
prosthetic valves. Mitral stenosis is accurately quantified by
planimetry of transthoracic or transesophageal two-dimensional images,
Doppler measurement of transvalvular gradients, and estimation of valve
area by the pressure half-time or continuity methods.20 21 22 23
Prognostic information is obtained from assessment of the hemodynamic
response to exercise24 and/or delineation of morphological
characteristics,25 which in turn help guide the selection
of therapeutic interventions.26
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TEE has also been useful in guiding balloon valvuloplasty procedures.27
Although tricuspid stenosis is readily detected and assessed hemodynamically, the accuracy of Doppler echocardiographic determinations is less well validated but still preferred over other methods.28
Aortic stenosis is accurately quantified by Doppler measurements of instantaneous and mean transvalvular gradients, estimation of valve area by the continuity method, or determination of aortic valve resistance.29 30 31 In patients with reduced LV function, gradient measurements may appear falsely low, while valve area and resistance measurements will more reliably predict the severity of stenosis. Dobutamine perturbation with Doppler assessment of gradients may also be of use.32 Pulmonic valve gradients are similarly quantified. While still experimental, contrast injection may allow more accurate recording of stenotic jet velocities and therefore transvalvular gradients.33
Native Valvular Regurgitation
Doppler echocardiography is the most sensitive technique available
for detection of native valve regurgitation; care must be taken to
distinguish physiological phenomena from pathological lesions. Mild
retrograde flow disturbances are frequently detected in normal
subjects34 35 and if trivial should be identified as being
within the expected normal range and not suggestive of the presence of
valvular heart disease. On the other hand, significant regurgitation
may be silent on auscultation, most often, but not always, in unstable
symptomatic patients.36 Because the finding of clinically
silent valvular regurgitation in an asymptomatic patient carries an
unknown significance, performance of Doppler echocardiography to
exclude valvular heart disease in an asymptomatic patient with a normal
physical examination is not indicated.
Precise assessment of the severity of regurgitant valvular lesions is difficult using any invasive or noninvasive technique, and no gold standard is available to judge relative accuracy.7 Doppler methods for detection of regurgitation are similar for all four native valves and prosthetic valves. Methods include assessment of regurgitant jet characteristics (length, height, area, and width at the vena contracta), effective regurgitant orifice area, and measurement of regurgitant flow volume using the proximal isovelocity surface area.7 37 38 39 40 41 42 43 44 45 The severity of semilunar valve regurgitation is also assessed by the rate of decline in regurgitant gradient as measured by the slope of diastolic flow velocity envelope.46 47 The severity of atrioventricular regurgitation is also reflected by reduction or reversal of the systolic components of venous inflow.48 Finally, in isolated valve disease, regurgitant fraction may be assessed by comparison of stroke volumes at the regurgitant valve and an uninvolved valve.
Doppler echocardiography is also the test of choice in the reevaluation
of regurgitant lesions and in determination of the timing of operative
intervention.49 50 51 Echocardiographically obtainable
information about the severity of regurgitation and associated
structural and functional changes are all important to this therapeutic
decision. The choice between mitral valve repair and replacement is
greatly aided by TTE and TEE; intraoperative assessment of valve repair
is essential to optimal surgical practice, while intraoperative
determination of prosthetic valve seating and function is also
useful.52
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Repeated Studies in Valvular Heart
Disease
A routine follow-up echocardiographic examination is not indicated
after an initial finding of minimal or mild abnormalities in the
absence of a change in clinical signs or symptoms. Patients with more
significant abnormalities on the initial study may be followed
echocardiographically even in the absence of such changes, with the
frequency determined by the hemodynamic severity of the lesion and the
extent of ventricular compensation noted on initial and subsequent
studies. Marked changes in the echocardiographic findings, which may
indicate an alteration in management even in the absence of changes in
clinical signs and symptoms, should be confirmed by reevaluation at a
shorter interval. (See "Indications for Echocardiography in Valvular
Stenosis," "Indications for Echocardiography in Native Valvular
Regurgitation," and "Indications for Echocardiography in
Interventions for Valvular Heart Disease and Prosthetic
Valves.")
Mitral Valve Prolapse
The physical examination remains the optimal method of diagnosing
MVP, because echocardiography may detect systolic billowing of the
leaflets not representing clinically relevant disease. The etiology of
the auscultatory finding of systolic clicks may be defined (as valvular
or chordal), valvular thickening assessed, and the presence, timing,
and severity of regurgitation determined.49 53 In patients
with a nonejection click and/or murmur, an echocardiogram is useful for
diagnosis and risk stratification, particularly by identifying leaflet
thickening and LV dilation (Table 2).54 55 56 57 58 59
Routine repeated studies are of little value unless there is
significant (nontrivial) mitral regurgitation or a change in symptoms
or physical findings.
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Echocardiography to diagnose MVP is of no use in the absence of
physical findings unless there is supportive clinical evidence of
structural heart disease or a family history of myxomatous valve
disease.
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Infective Endocarditis: Native
Valves
Echocardiography is useful for the detection and characterization
of the hemodynamic and pathological consequences of infection,
including valvular vegetations, regurgitant lesions, ventricular
function, and associated abnormalities such as abscesses, shunts, and
ruptured chordae.60 TTE is less sensitive in detecting
vegetations than TEE.61 62 Because of the possibility of a
false-negative examination (or the absence of a vegetation) or a
false-positive study (Lambl's excrecenses, noninfective vegetations,
thrombi), echocardiography should not supplant clinical and
microbiological diagnosis. Echocardiography may be useful in the case
of culture-negative endocarditis63 or in the diagnosis of
a persistent bacteremia whose source remains unidentified after
appropriate evaluation.
Controversy remains as to whether the echocardiographic characteristics
of vegetations are of use in predicting embolization,64 65
although vegetation size and mobility, identification of the involved
valve(s), and especially diagnosis of myocardial involvement are
important for risk stratification and prognosis (Table 3).66 67 68 These features, along with
clinical characteristics such as persistent fever, infecting organism,
etc, may help guide decision making regarding repeated studies and even
valve replacement.
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In most cases TEE is not indicated as the initial examination in the
diagnosis of native valve endocarditis. When the valvular structure or
pathology is well visualized by TTE, there is no indication to perform
TEE. Indications for routine TEE in established endocarditis are
unclear because the clinical importance of the possible additional
information obtained is unproved.69 However, TEE should be
performed when specific questions are not adequately addressed by the
initial TTE examination or in cases where TEE is clearly superior to
TTE. Clinical situations in which TEE is indicated include instances
when the TTE is diagnostically inadequate due to poor quality or
limited echocardiographic windows, when the TTE is negative despite
high clinical suspicion, when a prosthetic valve is involved, when
there is high suspicion such as staphylococcus bacteremia, or in an
elderly patient with valvular abnormalities that make diagnosis
difficult.70
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Prosthetic Valves
Valve replacement is a palliative procedure that carries a
subsequent risk of valve degeneration, development of regurgitation or
stenotic lesions, thrombosis, and endocarditis. Different prostheses
carry different risks for these events so that subsequent evaluations
must be tailored to the patient's clinical situation and type of
prosthesis.
Because the evaluation of prosthetic valves is difficult even in the
best of circumstances, obtaining baseline postoperative studies can be
useful for comparison with future evaluations and assessment of changes
in ventricular function and hemodynamics in response to surgery.
However, the need for routine follow-up echocardiography in the patient
with unchanged clinical signs and symptoms is controversial. In some
patients with known prosthetic valve dysfunction, reevaluation is
indicated even in the absence of a changing clinical situation, as in
some cases reoperation may be dictated by echocardiographic findings
alone.
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Prosthetic Valve Dysfunction and
Endocarditis
Echocardiography is the preferred modality for definition of
abnormalities of poppet motion, annular motion, the presence of
thrombus or fibrin, or prosthetic leaks or stenoses. Because TEE is
often necessary to provide adequate visualization,77 the
necessity for previous performance of a transthoracic study has been
questioned. However, because a great deal of additional information can
be obtained regarding cardiac function and hemodynamics by TTE that may
not be otherwise available and/or may help guide the transesophageal
examination, sequential examinations, starting with TTE, are the
preferred approach.
Assessment of prosthetic valve stenosis is best performed by a combined echocardiography-Doppler technique. However, the Doppler examination may be problematic because eccentric jets may cause recording of falsely low velocities, especially in valves with central occluders. On the other hand, elevated transvalvular velocities may be seen in some prosthetic valves due to pressure recovery and may not accurately represent the hemodynamic gradient. Transvalvular gradients will vary with valve type and size even in the normally functioning prosthesis; individual valve flow characteristics must be considered in the diagnosis of obstruction.78 Reevaluation may be particularly useful in the individual patient.
Determination of prosthetic valve regurgitation is often hampered by prosthetic shadowing, particularly in the mitral position. The transesophageal approach may be particularly useful in this case. Care must be taken to differentiate between the normal, central regurgitation of many mechanical prostheses and pathological paravalvular leaks.79 80 Contrast injection may enhance the spectral recording of both right-sided regurgitant velocities as well as the extent of the regurgitant jet.81 82
Diagnosis of prosthetic valve endocarditis by the transthoracic technique is more difficult than diagnosis of endocarditis of native valves because of the reverberations, attenuation, and other image artifacts related to both mechanical valves and bioprosthesis. Particularly in the case of a mechanical valve, TTE may be helpful only when there is a large or mobile vegetation or significant regurgitation. Thus, the technique cannot be used to exclude the presence of small vegetations. These limitations are diminished with the use of transesophageal recording techniques because of the superior imaging quality and posterior transducer position. Thus, transesophageal techniques have enhanced echocardiographic assessment of prosthetic valve infective endocarditis, especially of the mitral valve and of both mitral and aortic annular areas for abscesses.
Doppler techniques offer important information about the functional
consequences of endocarditis of prosthetic valves, such as the
existence of paravalvular leaks. It should be noted, however, that
paravalvular leaks are not specific for endocarditis. Importantly,
echocardiography may identify vegetations on native valves in patients
with suspected prosthetic endocarditis.
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III. Chest Pain |
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Chest pain can result from many cardiac and noncardiac causes. In mature adults the most common clinical cardiac disorder presenting as chest pain is coronary artery disease (see section IV, "Ischemic Heart Disease"). Other cardiovascular abnormalities that frequently cause chest pain, including hypertrophic cardiomyopathy, valvular aortic stenosis, aortic dissection, pericarditis, MVP, and acute pulmonary embolism, produce distinctive and diagnostic echocardiographic findings (see sections II, IV through VI, VIII, and IX).
In patients with chest pain known to be of noncardiac origin,
further cardiac testing is usually unnecessary. In patients for whom
the character of chest pain or the presence of risk factors raises
concern about possible coronary artery disease, the role of
echocardiography has grown over the last 5 years. Echocardiography can
be performed when possible during chest pain in the emergency room; the
presence of regional systolic wall motion abnormalities in a patient
without known coronary artery disease is a moderately accurate
indicator of an increased likelihood of acute myocardial ischemia or
infarction by pooled data with a positive predictive accuracy of about
50%. The absence of regional wall motion abnormalities identifies a
subset of patients unlikely to have an acute
infarction83 84 85 with a pooled negative predictive accuracy
of about 95%. In a patient with previous myocardial infarction (either
clinically evident or silent), the resting echocardiogram can confirm
that event and evaluate its functional significance.
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IV. Ischemic Heart Disease |
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Echocardiography has become an established and powerful tool for diagnosing the presence of coronary artery disease and defining its consequences in patients with acute ischemic syndromes and those with chronic coronary atherosclerosis. Transthoracic imaging and Doppler techniques are generally sufficient for evaluating patients with suspected or documented ischemic heart disease. However, TEE may be needed in some patients, particularly those with serious hemodynamic compromise but nondiagnostic TTE studies. In these circumstances TEE can distinguish among extensive infarction with pump failure, mechanical complications of infarction, or hypovolemia and can guide prompt therapy.86 87 88 89 Stress echocardiography is useful for evaluating the presence, location, and severity of inducible myocardial ischemia as well as risk stratification and prognostication.
Acute Ischemic Syndromes (Acute Myocardial Infarction and
Unstable Angina)
Echocardiography can be used to rapidly diagnose the presence of
regional contraction abnormality resulting from acute myocardial
infarction, evaluate the extent of associated regional dysfunction,
stratify patients into high- or low-risk categories, document serial
changes in ventricular function, and diagnose important complications.
Some patients with acute chest pain have unstable angina; in these
individuals, echocardiography can also be helpful in diagnosis and risk
assessment.
Diagnosis
The use of echocardiography for diagnosis of acute myocardial
infarction is most helpful when the clinical history and ECG findings
are nondiagnostic.
Segmental LV wall motion abnormalities are characteristic of myocardial
infarction. Their location correlates well with the distribution of
coronary artery disease and pathological evidence of
infarction.83 90 91 92 93 94 95 96 97 However, regional wall motion
abnormalities also can be seen in patients with transient myocardial
ischemia, chronic ischemia (hibernating myocardium), or myocardial
scar. Segmental wall motion abnormalities can also occur in some
patients with myocarditis or other conditions not associated with
coronary occlusion. Table 4 summarizes the utility of TTE in
the diagnosis of acute myocardial infarction. In patients presenting
with chest pain, segmental LV wall motion abnormalities predict the
presence of coronary artery disease but can diagnose an acute
myocardial infarction with only moderate certainty, because acute
ischemia may not be separable from myocardial infarction or even old
scar.83 84 85 90 98 99 100 101 102 However, the absence of segmental
abnormalities (ie, the presence of either normal wall motion or diffuse
abnormalities) has a high negative predictive value. Although it may
not be easy to distinguish acute ischemia or necrosis from
previous myocardial infarction, preservation of normal wall thickness
and normal reflectivity suggest an acute event. Prompt initiation of
treatment to achieve reperfusion can reduce mortality, morbidity, and
patient care costs.103 104 105 106 Hence, early echocardiography
is particularly useful in patients with a high clinical suspicion of
acute myocardial infarction but a nondiagnostic ECG.
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Significant obstructive coronary artery disease is usually present in patients with unstable angina. These patients generally are identified by clinical history, and reversible ECG abnormalities may be recorded during episodes of chest pain. When the clinical history and ECG are unavailable or not reliable and an adequate echocardiographic study can be performed during an episode of chest pain, documentation of reversible segmental wall motion abnormalities confirms the diagnosis of unstable angina.
Severity of Disease/Risk Assessment/Prognosis
In patients with acute myocardial infarction, segmental wall
motion abnormalities can be seen not only in the zone of acute
infarction but also in regions of prior infarction and areas with
ischemic "stunning" or "hibernation" of myocardium that is
nonfunctional but still viable.90 91 94 107 108 109 The sum of
these segmental abnormalities reflects total ventricular functional
impairment, which may overestimate true anatomic infarct size or
perfusion defect.109 Thus, echocardiographically derived
infarct size90 correlates modestly with thallium 201
perfusion defects,94 peak creatine kinase
levels,91 100 hemodynamic changes,90 findings
on ventriculography95 and coronary
angiography96 and pathological findings.108
However, it does predict the development of early110 and
late111 complications and mortality.90 112 In
a given patient with acute myocardial infarction, global and regional
ventricular function as well as clinical status may improve (especially
after reperfusion therapy) or can occasionally deteriorate. As a
noninvasive technique that can be performed at the patient's bedside,
initial and late follow-up echocardiograms are excellent for evaluating
these changes in patients with a large myocardial infarction.
Table 5 summarizes the prognostic value of segmental wall
motion abnormalities detected early in the course of acute myocardial
infarction. In general, more extensive abnormalities denote an
increased risk of complications, including death, recurrent infarction,
pump failure, and serious ventricular dysrhythmias or heart block, even
in patients who appear well
clinically.83 84 91 98 99 110 113 Patients with more
extensive wall motion abnormalities do not invariably develop
complications but do merit careful observation. Relatively mild and
localized wall motion abnormalities indicate a low risk of
complications.
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Assessment of Complications
Echocardiography can be used to evaluate, at the bedside when
needed, virtually any complication of acute myocardial infarction.
1. Acute mitral regurgitation. Development of acute mitral regurgitation following acute myocardial infarction denotes a significantly worsened prognosis.114 Significant regurgitation can result from acute rupture of a papillary muscle head,115 acute ischemic dysfunction of the papillary muscle and associated free wall,116 late fibrosis and shortening of the papillary muscle apparatus,117 altered mitral closure dynamics due to systolic ventricular impairment,118 or annular dilation. All of these different mechanisms can be identified and regurgitant severity evaluated using echocardiographic imaging and Doppler flow studies.
2. Infarct expansion and LV remodeling. Following acute myocardial infarction, development of infarct expansion commonly precedes myocardial rupture (including ventricular septal defect) and denotes a worsened prognosis.119 A follow-up echocardiogram is excellent for identifying infarct expansion120 in patients with a large myocardial infarction and differentiating it from infarct extension as well as subsequent LV remodeling characterized by progressive chamber dilation and further deterioration in global systolic function.
3. Ventricular septal rupture. Both two-dimensional and color Doppler echocardiography can be used to locate and visualize postinfarction ventricular septal defects121 122 123 and to demonstrate left-to-right shunting. Doppler techniques in particular provide an accurate means of distinguishing a ventricular septal defect from mitral regurgitation121 or tricuspid regurgitation that is either preexisting or the result of RV infarction.
4. Free wall rupture. Antemortem diagnosis of free wall rupture in patients with acute myocardial infarction is relatively infrequent. However, free wall rupture is not inevitably fatal,124 and the diagnosis can be made using echocardiographic imaging and Doppler flow studies. Patients who survive free wall rupture often develop a pseudoaneurysm that has a characteristic echocardiographic appearance.125 126 Echocardiography also can help define the presence or absence of associated tamponade physiology and determine the timing of surgical intervention.
5. Intracardiac thrombus. Echocardiography is the definitive test for detecting intracardiac thrombi.127 128 129 130 131 132 133 LV thrombi are most often detected in patients with anterior and apical infarctions127 131 132 133 ; their presence denotes an increased risk of both embolism128 and death.130 The need for serial echocardiography in patients with ventricular thrombi remains controversial.
6. RV infarction. In approximately one third of patients with inferior myocardial infarction, associated RV infarction also occurs.134 This can have significant hemodynamic consequences and implications for patient treatment. Characteristic echocardiographic features of RV infarction have been described.135
7. Pericardial effusion. Pericardial effusion may accompany transmural infarction; its presence does not necessarily imply free wall rupture. The role of echocardiography in evaluating pericardial effusion is discussed in section VI, "Pericardial Disease."
Assessment of Therapy
Given the frequent use of reperfusion therapy (involving either
thrombolytic agents or primary angioplasty) in patients with acute
myocardial infarction, assessment of myocardial salvage is an important
clinical issue. Serial echocardiographic studies can be used to assess
recovery of regional myocardial function from initial stunning.
In patients with unstable angina who undergo revascularization (by angioplasty or surgery), the completeness of revascularization and the functional significance of residual lesions can be determined using exercise or pharmacological stress echocardiography techniques. These applications in unstable angina patients are similar to those in patients with chronic ischemic heart disease discussed below.
Predischarge Evaluation Using Stress Echocardiography
Graded stress echocardiography using intravenous dobutamine can
help in assessing myocardial viability early after myocardial
infarction.136 137 138 Available data suggest that carefully
performed pharmacological stress echocardiography using a gradual
protocol and beginning at low doses of dobutamine appears to be
feasible and reasonably safe when performed 2 to 10 days after acute
myocardial infarction. Myocardial stunning may occur when acute
ischemia is followed by restoration of adequate blood flow and may last
for days to months. Reperfusion-salvaged, stunned (but not functioning
at rest) myocardium can respond to inotropic
stimulation.139 140 As summarized in Table 6,
wall segments that show hypokinesia or akinesia at rest but
improved function during low-dose dobutamine infusion often recover
function136 137 138 (suggesting that these segments are
"stunned"). However, when segments with hypokinesis or akinesis
at rest show no improvement during dobutamine infusion, functional
recovery is less common (suggesting that most of these segments are
infarcted). Segments with initial improvement during low-dose
dobutamine infusion but deterioration of function with higher doses
frequently are supplied by arteries with significant residual stenoses.
Continuing augmentation of systolic wall thickening with higher doses
of dobutamine denotes preserved viability and implies the lack of
critical stenosis in the infarct-related artery.
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Because echocardiographic images obtained during graded exercise demonstrate the location and approximate size of the ischemic territory, they will provide useful information in identifying high-risk patients after acute myocardial infarction.141 142 143 144 145 146 There are few data on long-term event rates in patients studied by predischarge stress echocardiography after an acute myocardial infarction in both those who have and those who have not undergone thrombolytic or other reperfusion therapy. Prospective natural history studies are difficult to accomplish because many clinicians now perform angiography and recommend revascularization in patients with an ischemic response. Nonetheless, when coronary anatomy is unknown, patients who have had an acute myocardial infarction should undergo predischarge functional testing for risk assessment. In those patients unable to exercise because of deconditioning, neurological, or orthopedic limitations, pharmacological stress echocardiography is a valuable alternative for graded testing.
In patients with unstable angina but no myocardial infarction, echocardiography is most helpful for answering specific unresolved clinical questions. When ECG changes of ischemia are obscured by baseline abnormalities (such as chronic left bundle branch block, ventricular pacing, or chronic repolarization changes), reversible segmental wall motion abnormalities during pain can document not only the presence of transient ischemia but also the coronary territory involved and the size of the area at risk. The sensitivity of echocardiography for detecting transient wall motion abnormalities resulting from acute ischemia diminishes the longer the time between resolution of chest pain and acquisition of echocardiographic images. When myocardial viability is uncertain because of persistent impairment of ventricular function in the absence of chest pain (which could be due to "silent" ischemia, myocardial stunning, prior infarction, or cardiomyopathy), the response to carefully graded dobutamine infusion can be clinically useful. However, large-scale studies of this latter question have not been reported.
The indications for echocardiography in acute myocardial ischemic
syndromes are summarized
below.
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Chronic Ischemic Heart Disease
In patients with chronic ischemic heart disease, echocardiography
is useful for a range of indications, including diagnosis, risk
stratification, and clinical management decisions. Quantitative indexes
of global and regional systolic function (including fractional
shortening, fractional area change, ejection fraction, and wall motion
score) are valuable in describing LV function, determining prognosis,
and evaluating the results of therapy. Doppler techniques are also
extremely valuable for evaluating both systolic and diastolic
ventricular function in patients with chronic ischemic heart disease
(see section V, "Cardiomyopathy and Assessment of Left Ventricular
Function").
Diagnostic Accuracy of Echocardiographic Techniques in Chronic
Coronary Artery Disease
1. TTE (at rest). Chronic ischemic heart disease often
results in impaired systolic LV function. The extent and severity of
regional and global abnormalities are important considerations in
choosing appropriate medical or surgical therapy. Abnormal diastolic
ventricular function, which frequently accompanies impaired systolic
function but may also occur when global systolic function is normal,
also can be evaluated (see section V, "Cardiomyopathy and Assessment
of Left Ventricular Function").
Other structural and functional alterations can complicate chronic ischemic heart disease. Mitral regurgitation may result from global LV systolic dysfunction,118 regional papillary muscle dysfunction,116 scarring and shortening of the submitral chords,117 papillary muscle rupture,115 or other causes. The presence, severity, and mechanism of mitral regurgitation can be detected reliably using transthoracic imaging and Doppler echocardiographic techniques. Potential surgical approaches also can be defined. In patients with heart failure or significant ventricular arrhythmias, the presence or absence of ventricular aneurysm can be established.147 148 When an aneurysm is demonstrated, the function of the nonaneurysmal portion of the left ventricle is an important consideration in choosing medical or surgical therapy.149
2. Stress echocardiography. As currently practiced (with
the aid of digital acquisition and storage of relevant images), stress
echocardiography is both sensitive and specific for detecting inducible
myocardial ischemia in patients with intermediate to high pretest
probability of coronary artery disease. A variety of methods can be
used to induce stress; exercise (treadmill, upright or supine bicycle)
and pharmacological techniques (using either adrenergic stimulating or
vasodilator agents) are most often used. The accuracy of stress
echocardiography is summarized in Tables 7 and 8.
As with other noninvasive methods, sensitivity is
higher in patients with multivessel disease than in those with
one-vessel disease, in those with prior infarction, and those with
>70% stenosis compared with those with more moderate
lesions.150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 Compared with standard treadmill exercise
testing, stress echocardiography is of significant additive clinical
value for detecting and localizing myocardial ischemia.
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In patients with a significant clinical suspicion of coronary artery disease, stress echocardiography is appropriate when standard exercise testing is likely to be nondiagnostic. Examples include conditions likely to reduce the validity of ST-segment analysis, such as the presence of resting ST-T wave abnormalities, left bundle branch block, ventricular paced rhythms, LV hypertrophy/strain, or digitalis treatment. When a noncardiac limitation precludes adequate exercise testing, pharmacological stress echocardiography is an appropriate alternative. Dobutamine stress echocardiography has substantially higher sensitivity than vasodilator stress echocardiography for detecting coronary stenoses.150 183 184 Treadmill stress echocardiography may have lowered sensitivity if there is a significant delay from the end of exercise to the acquisition of postexercise images.152 164 Sensitivity can also be diminished if all myocardial segments are not adequately visualized.160 This shortcoming occurs quite variably but is not insignificant. In an asymptomatic patient with prior infarction, stress echocardiography may be helpful in assessing the presence, distribution, and severity of inducible myocardial ischemia and thereby determining the need for cardiac catheterization. However, in certain circumstances it may be difficult to detect residual ischemia within a zone of infarction that exhibits akinetic wall motion.161
Special Issues With Regard to Stress Echocardiography for the
Diagnosis of Coronary Artery Disease
1. The influence of Bayes' theorem. In using any
testing method, it is important to consider the pretest likelihood of
the disorder being sought. With specific regard to stress
echocardiography, the diagnostic value is greatest in patients in whom
the pretest probability of clinical coronary artery disease is
intermediate. Subsets of patients with an intermediate pretest
likelihood would include symptomatic middle-aged women with typical
angina, patients with coronary risk factors and abnormal ECG findings
at baseline, and patients with risk factors and atypical angina
pectoris. In such patients, stress echocardiography would be expected
to have the greatest value in increasing (based on a positive result)
or lowering (based on a negative result) the likelihood of coronary
artery disease. In patients with a very low pretest likelihood for
coronary artery disease (such as patients with no risk factors or those
with highly atypical or nonanginal chest pain), positive stress
echocardiography results may often be false-positive. In patients with
a very high pretest likelihood of coronary artery disease (such as
middle-aged or elderly men with multiple coronary risk factors and
classic angina pectoris), negative stress echocardiography results are
often false-negative.
Notwithstanding these concerns, the results of stress echocardiography
may have important prognostic value (even if the test is less valuable
for diagnostic purposes). A positive stress echocardiographic study can
be helpful in determining the location and severity of inducible
myocardial ischemia, even in a patient with a high pretest likelihood
that disease is present. A negative stress echocardiographic evaluation
may also be prognostically helpful because it predicts a low risk for
future cardiovascular events.185 186 187 188 189 190 191 192 193 Table 9
summarizes the prognostic value of stress echocardiography. Additional
prognostic studies are desirable.
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2. Pharmacological stress echocardiography. Pharmacological agents can be used to increase cardiac workload in lieu of treadmill or bicycle exercise or cause coronary arterial or vasodilation and increased coronary blood flow; these are generally adrenergic-stimulating (such as dobutamine or arbutamine) or vasodilating agents (such as dipyridamole or adenosine). Adrenergic-stimulating agents increase myocardial oxygen demand by increasing contractility, blood pressure, and heart rate. They can be given in graded doses to titrate myocardial workload in a manner akin to standard exercise testing. Vasodilator agents, in contrast, cause heterogenous myocardial perfusion, which in some patients is sufficient to cause functional myocardial ischemia.
These considerations suggest that pharmacological stress echocardiography might best be accomplished using adrenergic stimulants, since they enhance myocardial contractile performance, which can be evaluated directly by echocardiography. Vasodilator agents could cause heterogeneity of myocardial perfusion without actually altering workload (or wall motion) directly. Indeed, comparative studies have suggested a somewhat lower sensitivity for stress echocardiography using adenosine compared with dobutamine.150 183 184 However, in several studies pharmacological stress echocardiography using vasodilator agents does appear to be valuable in detecting inducible myocardial ischemia and in determining prognosis.141 145 153 188 189
3. Detection of coronary artery disease in asymptomatic patients. Stress echocardiography is not recommended for screening in asymptomatic patients without known coronary artery disease because of the low pretest likelihood of disease. However, if a false-positive result is suspected in an asymptomatic patient with a positive exercise treadmill test, a negative stress echocardiographic study may be helpful by lowering the likelihood of coronary artery disease.
4. Stress echocardiography for preoperative evaluation. This topic is discussed in another ACC/AHA guideline.4
Diagnosis of Myocardial Viability in Chronic Coronary Artery
Disease
In patients with chronic stable coronary artery disease,
myocardial contractile function can be impaired because of irreversible
myocardial necrosis or as a result of hibernating
myocardium.194 Myocardial hibernation is thought to be due
to chronic reduction in myocardial perfusion to levels inadequate to
support normal myocardial contractile performance but sufficient to
preserve viability. Since this condition is potentially reversible,
identifying it accurately has important clinical value;
revascularization of hibernating myocardium can lead to functional
recovery and presumably improved long-range outlook. In patients with
multivessel coronary artery disease and depressed LV function,
improvement in regional LV function during dobutamine stress
echocardiography is considered to indicate contractile reserve and to
be predictive of improved ventricular function after
revascularization.195 196 197 198 199 200 The lack of contractile reserve
during dobutamine infusion denotes a low likelihood of improvement
after bypass surgery. Table 6
summarizes the role of dobutamine stress
echocardiography for evaluating hibernating myocardium. Larger studies
in patients with chronic ischemic LV dysfunction are needed to confirm
the accuracy of this approach.
Assessment of Disease Severity/Risk Stratification/ Prognosis in
Chronic Coronary Artery Disease
Echocardiographic techniques, at rest and particularly coupled
with stress, can be helpful in clinical decision making regarding
medical therapies and clinical interventional therapies, in evaluating
the results of therapy, in prognostication, and clinical follow-up of
patients with known coronary artery disease and new or changing
symptoms.
In patients with chronic ischemic heart disease, LV ejection fraction measured at rest has an important influence on long-term prognosis201 ; as LV ejection fraction declines, mortality increases. Ejection fraction is an important consideration in choosing appropriate medical or surgical therapies and in making recommendations about activity levels. In patients with clinical signs and symptoms of congestive heart failure, echocardiography is also helpful in establishing pathophysiological mechanisms and guiding therapy. For example, after a myocardial infarction, a patient with congestive heart failure might have systolic LV dysfunction, predominant diastolic dysfunction, mitral regurgitation, some combination of these abnormalities, or a noncardiac cause for heart failure symptoms. How best to treat the patient can be planned more rationally knowing the state of LV systolic and diastolic function, valvular function, and right-heart hemodynamics. These indications are discussed in section II, "Murmurs and Valvular Heart Disease," and section V, "Cardiomyopathy and Assessment of Left Ventricular Function."
As summarized in Table 9, the presence or absence of inducible
myocardial ischemia has useful prognostic value in patients undergoing
exercise or pharmacological stress echocardiography. A negative stress
echocardiographic study denotes a low cardiovascular event rate during
follow-up.185 186 187 188 189 190 191 192 193 Compared with standard treadmill
testing, stress echocardiography is more specific for identifying
patients with inducible myocardial ischemia. In general, patients with
a positive electrocardiographic response to treadmill stress test but
no inducible wall motion abnormality on stress echocardiogram have a
very low rate of adverse cardiovascular events during
follow-up,185 186 albeit higher than patients with a
completely negative test result.
The prognosis is not benign in patients with a positive stress
echocardiographic study. In this subset, morbid or fatal cardiovascular
events are more likely, but the overall event rates are rather
variable. Hence, the cost-effectiveness of using routine stress
echocardiography testing to establish prognosis is uncertain.
Nonetheless, a number of studies indicate that the risk of future
cardiac events can be stratified based on the presence or absence of
inducible ischemia on stress echocardiography testing (Table 9).
Echocardiographic Assessment Before and After
Revascularization
Echocardiographic studies may help in planning revascularization
procedures by demonstrating the functional significance of a given
coronary stenosis. This may be of particular value in determining the
need for percutaneous transluminal coronary angioplasty, particularly
when the degree of angiographic stenosis is of uncertain physiological
significance or when multiple lesions are present. Moreover, because
restenosis is a common complication, stress echocardiography is useful
in evaluating patients after coronary angioplasty.151
Reassessment roughly 1 month after angioplasty is a reasonable time
frame within which to assess the functional results of angioplasty.
However, in an asymptomatic stable patient, routine stress testing
(with or without an imaging modality) does not appear to be
cost-effective. In a symptomatic patient or when there are other
clinical indications, an evaluation can be performed using either
treadmill, bicycle, or pharmacological methods to induce stress,
depending on the patient's physical capabilities. Compared with the
preangioplasty evaluation, improvement in wall motion on stress
echocardiography evaluation after angioplasty confirms a successful
result; persistent evidence of inducible ischemia after angioplasty
indicates an inadequate result or restenosis. More extensive studies
are needed to document the value of stress echocardiography in
assessing the results of percutaneous revascularization.
In patients with heart failure due to ischemic LV dysfunction, evaluation of myocardial viability by stress echocardiography can help determine the potential benefit of revascularization. The demonstration of significant hibernating myocardium, suggesting a high likelihood of improved function after revascularization,195 196 197 198 199 200 can help in choosing revascularization rather than heart transplantation.
After successful bypass surgery, routine follow-up testing generally is not necessary in the asymptomatic individual. Improvement in patient outcomes by identifying asymptomatic residual inducible ischemia has not been demonstrated, hence routine testing cannot be recommended. However, when symptoms persist or recur after coronary bypass surgery, stress echocardiography testing can be helpful. After cardiac surgery many patients have abnormal baseline ECG findings, and early after bypass surgery some demonstrate abnormal ECG responses on standard treadmill testing.202 When the possibility of incomplete revascularization is of clinical concern, stress echocardiography studies may be helpful in evaluating the location and severity of residual ischemia. When an initial postoperative stress echocardiographic study is negative for inducible ischemia, but a subsequent test is positive, the likelihood of graft closure or development of new obstructive lesions can be inferred.
The indications for echocardiography in chronic ischemic
heart disease are summarized below.
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V. Cardiomyopathy and Assessment of Left Ventricular Function: Echocardiographic Parameters |
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Of all the indications for echocardiography, the evaluation of ventricular systolic function is perhaps the most common. In the recent prospective study by Krumholz et al,203 evaluation of LV systolic function was the primary indication for TTE in 26% of inpatients studied, a frequency at least twice that of the next most common indication. Current echocardiographic techniques permit a comprehensive assessment of LV size and function. LV cavity measurements and wall thickness at end diastole and end systole and shortening fraction may be obtained with precision by M-mode echocardiography; conventions for obtaining these measurements204 205 and reference normal values have been published. Two-dimensional echocardiography, because of its superior spatial resolution, is used to guide appropriate positioning of the M-mode beam and is used for direct measurements of ventricular size204 as well as LV volumes and ejection fraction. An advantage of two-dimensional (compared with M-mode) echocardiography is that the myocardial mass, chamber volumes, and ejection fraction of an abnormally shaped ventricle can be measured. Therefore, in most laboratories two-dimensional echocardiography is the principal noninvasive method used for quantitating LV volumes and assessing global and regional systolic function. LV mass and volume quantitation by echocardiography requires high-quality images, meticulous attention to proper beam orientation, and the use of geometric models to approximate LV shape.206
Assessment of Ejection Fraction
M-mode echocardiographic methods can be used to define many
indexes of global LV function; the most widely used parameters are
ejection phase indexes, including fractional shortening of the minor
axis and velocity of circumferential fiber shortening. However,
ejection fraction, a more widely used index, must either be derived
using algorithms developed for volume determination from M-mode linear
dimensions,206 207 visually estimated from two-dimensional
echocardiographic images,208 or obtained by quantitative
analysis of two-dimensional echocardiographic
images.209 210 The algorithms vary considerably in
complexity. In general, although all are suitable for assessing
performance of a normally shaped, normally contracting left ventricle,
more complex approaches are required to assess deformed ventricles with
regional wall motion abnormalities. Simplified approaches combining
measurements and visual assessment of the function of the apex have
been proposed,209 but these also have limited
applicability in distorted ventricles.
In clinical practice the visual estimation of ejection fraction from two-dimensional echocardiography is common.208 211 Ejection fraction may be reported quantitatively or qualitatively as increased; normal; mildly, moderately, or severely reduced; or it may be quantitated. When performed by skilled observers, visual estimation has been reported to yield ejection fractions that correspond closely to those obtained by angiography207 or gated blood pool scanning.208 However, because of its subjective nature, a visual estimate of ejection fraction may be less reproducible than quantitative methods. Optimally, its use should be restricted to those practitioners with considerable experience in clinical echocardiography who can periodically compare their visual estimates to those obtained with a nonechocardiographic method. Alternative approaches such as LV angiography and nuclear methods are often used to obtain a quantitative ejection fraction. However, in the absence of an interval change in patient status or another indication for testing, duplicate estimates of ejection fraction with multiple modalities should be discouraged.
All ejection phase indexes of myocardial contractile performance are limited by their load dependence. Load-independent indexes, including end-systolic pressure-volume relations,210 preload recruitable stroke work, and end-systolic stress-length relations,212 can be derived echocardiographically. Although these indexes may be used in the clinical setting, practically speaking, their use is limited by the need for simultaneous LV pressure and difficult mathematical calculations.
Although Doppler analysis of aortic outflow spectra may be used to derive systolic time intervals, peak aortic flow velocity, and acceleration, these measurements are not generally used clinically. The determination of cardiac output is a potentially more useful Doppler application,213 214 but clinically, thermodilution methods are usually used for this purpose.
Edema and Dyspnea
The causes of peripheral edema, both cardiac and noncardiac, are
numerous. Cardiac causes include any abnormality that results in
elevated central venous pressure and thus encompasses the full spectrum
of myocardial, valvular, and pericardial disease. Echocardiography
provides the diagnosis in most instances. In some instances, however,
the overlapping features of constrictive pericarditis and restrictive
cardiomyopathy make definitive diagnosis by ultrasound difficult (see
section VI, "Pericardial Disease"). Echocardiography is not
recommended in patients with edema when the clinically determined
jugular venous pressure is definitely not elevated.
Dyspnea, either at rest or with exertion, is one of the cardinal symptoms of heart disease. When present in patients with heart failure, dyspnea usually denotes pulmonary venous hypertension. It can be difficult to distinguish among the various etiologies of dyspnea, which include primary cardiac or respiratory abnormalities, deconditioning, anemia, difficulties with peripheral circulation, or anxiety. Certain features of the history help establish that dyspnea is of cardiac origin, such as a progressive decrease in the intensity of exertion necessary to produce symptoms. Certainly dyspnea accompanying obvious signs of heart disease strongly suggests a cardiac etiology. When the etiology is in doubt, echocardiography can elucidate the origin of dyspnea by documenting or ruling out the common cardiac causes of pulmonary congestion: left-sided valvular disease, depressed systolic function, diastolic function, and cardiomyopathy. In this regard, echocardiography may be the preferred initial diagnostic test when the history, physical examination, and routine laboratory tests suggest or cannot eliminate cardiac disease.
Regional Left Ventricular Function
Echocardiography is well suited for the assessment of regional LV
contractile function in view of its high spatial and temporal
resolution and its ability to define regional wall thickening and
endocardial excursion. Controversy still surrounds the optimal method
for assessing regional LV function; however, virtually all carefully
tested methods have yielded useful data.210
Ventricular Dysfunction
Clinically most instances of systolic dysfunction are due to
ischemic heart disease, hypertensive disease, or valvular heart
disease. However, primary disorders of the heart muscle are often
encountered and are usually of unknown etiology. These disorders are
often categorized as dilated/congestive, hypertrophic, and
restrictive.215 Ultrasound techniques permit a
comprehensive assessment of morphology and function and often allow
assessment of hemodynamic status regardless of etiology. TEE extends
the capability of ultrasound techniques to the acutely ill patient in
the intensive care unit, a setting where routine transthoracic imaging
may be of limited value (see section XIII, "Echocardiography in the
Critically Ill"). For these reasons, echocardiography often provides
important insight into the etiology of congestive heart failure signs
and symptoms. In a retrospective analysis of 50 consecutive patients
with the principal diagnosis of congestive heart failure who underwent
M-mode and two-dimensional echocardiography, Echeverria216
reported that echocardiography often furnished unexpected information;
in 40% of patients with reduced systolic function, the ejection
fraction was worse than expected, and 20 of the 50 patients
(unexpectedly) had normal systolic function. In the study population as
a whole, echocardiography was associated with a change in management in
29 of 50 (or 58%) of patients. The utility of echocardiography was
greatest in the subgroup of 20 patients in whom echocardiography
revealed normal systolic function; this information led to a change in
diagnosis and management in 18 (90%) of these patients.
These observations concerning the utility of echocardiography in patients with congestive heart failure were extended by Aguirre,217 who prospectively studied 151 consecutive patients undergoing Doppler echocardiography who had a clinical diagnosis of congestive heart failure; a normal ejection fraction (>55%) was observed in 34% of patients.
Dilated Cardiomyopathy
Echocardiography demonstrates dilation of ventricular
chambers, usually without increased wall thickness. Systolic function
is depressed to varying degrees, with diffusely abnormal wall motion.
Doppler techniques are used to evaluate the presence and extent of
associated valvular regurgitation, to estimate pulmonary pressures, and
to gain insight into diastolic function of the left
ventricle.218 Echocardiography also permits reevaluation
of ventricular size and function so that disease progression and
response to therapy may be monitored noninvasively. Doppler mitral
inflow abnormalities ("restrictive" pattern) correlate strongly
with congestive symptoms.219 A short deceleration time
(<115 ms) is an independent predictor of poor outcome or need for
transplantation.220 In view of the established benefits of
angiotensin converting enzyme inhibitors221 222 in
patients with ventricular dysfunction, echocardiography is also used to
evaluate the appropriateness of such therapy.
Chemotherapy with doxorubicin produces a dose-dependent degenerative cardiomyopathy.223 It is therefore recommended that cumulative doses of doxorubicin be kept to <450 to 500 mg/m2.224 In fact, subtle abnormalities of systolic function (increases in wall stress) are evident in 17% of patients receiving only one dose of doxorubicin; most patients who receive at least 228 mg/m2 show either increased wall stress or evidence of reduced contractility by stress-shortening analysis.223 For this reason, reevaluation monitoring of ejection fraction throughout the course of chemotherapy appears to be important in that further administration of doxorubicin appears safe if resting ejection fraction remains in the normal range and, conversely, further treatment may be dangerous if ejection fraction is abnormally low. It has been hypothesized that Doppler mitral inflow abnormalities suggestive of impaired relaxation might precede reductions in ejection fraction in patients receiving serial doses of doxorubicin.225 Abnormalities in diastolic filling, either by Doppler or radionuclide techniques, in patients with normal systolic function have been demonstrated in patients receiving 200 to 300 mg/m2 of doxorubicin.226 227
Hypertrophic Cardiomyopathy
Echocardiography provides a definitive diagnosis of hypertrophic
cardiomyopathy, revealing ventricular hypertrophy in patients without
other primary causes. Echocardiographic imaging also permits a
comprehensive assessment of the distribution of
hypertrophy.228 Doppler techniques may be used to localize
and quantitate intraventricular gradients at rest and with provocative
maneuvers, evaluate diastolic filling, and quantitate associated mitral
regurgitation.229 When coronary disease is not strongly
suspected, comprehensive Doppler echocardiographic examination may
obviate the need for catheterization. Echocardiography may also be used
to evaluate the response to therapeutic interventions, such as
dual-chamber pacing.230
Restrictive Cardiomyopathy
Echocardiography generally demonstrates normal ventricular size
and systolic function but atrial enlargement in patients with
restrictive cardiomyopathy. Doppler studies have demonstrated
characteristic ventricular inflow velocity profiles that consist of
elevated peak early flow velocity, rapid deceleration, and reduced flow
velocity associated with atrial contraction.231 232
Frequently isovolumic relaxation time is shortened, and pulmonary
venous flow velocities demonstrate significant diastolic flow
reversal.233 234 The subject of myocardial tissue
characterization by echocardiography is still being investigated.
However, the intense echocardiography reflectance that gives the
myocardium a characteristic stippled appearance in some cases of
amyloidosis is clinically useful in identifying the etiology of one
type of restrictive cardiomyopathy.
Heart Failure With Normal Systolic Function
(Diastolic Dysfunction)
Diastolic dysfunction is thought to be present when a patient with
heart failure has a systolic ejection fraction
>40%.80 217 218 235 There are other, subtler
manifestations of diastolic dysfunction, including failure to augment
cardiac output with exercise.236 Given that the prognosis
and optimal management for the patient with diastolic dysfunction is
likely to be quite different from the heart failure patient with
systolic dysfunction, it is critical that the proper diagnosis be made.
A large number of indexes of diastolic function based on information
from M-mode and two-dimensional echocardiography (and more recently
Doppler mitral and pulmonary flow profiles) have been investigated.
However, experience and theoretic considerations have tempered early
enthusiasm that simple Doppler indexes could adequately describe as
complex a phenomenon as diastolic function. This is due to several
factors, including
- Load and heart rate dependence of the commonly described echocardiographic variables237 238
- The broad overlap in diastolic filling parameters for normal and abnormal subjects
- The inability to apply most methods in atrial fibrillation and other rhythm and conduction disturbances
For these reasons, echocardiographic indexes of diastolic function are most useful in the reevaluation examination of a given patient or in characterizing large groups of subjects. Nonetheless, when these indexes are interpreted in the context of clinical variables with the recognition of all the potentially confounding influences, they may provide valuable information in individual subjects.
Evaluation of the Right Ventricle
Approaches to obtaining quantitative determinations of RV
size204 and volume239 have been proposed but
are more problematic than comparable measurements of the left
ventricle. This is due both to the complex shape of this chamber with
its heavy trabecular pattern as well as difficulty in obtaining
standardized imaging planes. Thus, the assessment of RV size is often
performed in a qualitative fashion. Similarly, although global RV
systolic function in adults is difficult to quantitate by
echocardiography, useful qualitative information may be obtained. In
children, useful quantitative measures of RV systolic function may be
made. Echocardiographic methods of evaluating RV diastolic function
have not been reported.
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VI. Pericardial Disease |
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One of the earliest clinical applications of echocardiography was in the detection of pericardial effusion,240 and it remains the procedure of choice for evaluating this condition. The pericardium usually responds to disease or injury by inflammation, which may result in pericardial thickening, the formation of an exudate, or both, which in turn is manifested in the clinical picture of pericardial effusion with or without tamponade or constriction. Pericarditis can occur after cardiac surgery (postpericardiotomy syndrome). The anatomic evidence of pericardial disease and its functional effects on cardiovascular physiology can often be seen on M-mode, two-dimensional, and Doppler echocardiograms.
Pericardial Effusion
Echocardiography provides a semiquantitative assessment of
pericardial effusion and a qualitative description of its distribution.
Differentiation among types of pericardial fluid (blood, exudate,
transudate, and others) cannot be made, but fibrous strands, tumor
masses, and blood clots can often be distinguished. It should be
remembered that all "echo-free" spaces adjacent to the heart are
not the result of pericardial effusion.241 Focal
epicardial fat must be distinguished from small to medium localized
effusions.
Most pericardial effusions that require pericardiocentesis are located both anteriorly and posteriorly, but loculated effusions may occur, particularly after cardiac surgery. In such cases, echocardiography can define the distribution of the fluid so that the safest and most effective approach can be planned for the pericardiocentesis. TEE may be used in those with technically unsuitable surface studies and in early postoperative cases, in whom it is often difficult to obtain a surface echocardiogram of diagnostic quality. Postoperative loculated effusions may be difficult to detect, and typical echocardiographic signs of tamponade may not be present, but small chamber size and elevated filling pressures should suggest the correct diagnosis.
Cardiac Tamponade
Enlarging pericardial effusions may cause cardiac tamponade.
Although the diagnosis of cardiac tamponade is based on established
clinical criteria, an accurate and early diagnosis of tamponade can
often be made using echocardiography. The elevated intrapericardial
pressure in tamponade decreases the transmural pressure gradient
between the pericardium and right atrium and ventricle and increases
the distending force necessary for ventricular filling.
Echocardiographic evidence of right atrial invagination (collapse) at
onset of systole with the X descent and RV collapse in diastole are
signs of hemodynamic compromise.242 243 244 245 Right atrial
collapse is a sensitive sign of increased intrapericardial pressure;
however, diastolic RV collapse is more specific for tamponade.
Distension of the inferior vena cava that does not diminish on deep
inspiration may also be seen and indicates an elevation of central
venous pressure.246 The respiratory changes in mitral
valve motion and ventricular dimensions were correlated with
paradoxical pulse.247 Doppler flow studies have shown
marked respiratory variation in transvalvular flow velocities, LV
ejection, and LV isovolumetric times in patients with pericardial
tamponade.248 249 These echocardiographic findings often
precede the clinical signs of tamponade and may provide an opportunity
for early therapeutic intervention.
Increased Pericardial Thickness
Increased echocardiographic density behind the posterior wall
suggests pericardial thickening, but echocardiographic measurement of
the precise pericardial thickness may be inaccurate.250
The causes of such thickening include fibrosis, calcification, and
neoplasms, although it is usually not possible to differentiate the
specific cause by echocardiography. Improved resolution by TEE provides
a more accurate assessment of pericardial thickness, especially if
fluid accumulation is also present.251
Pericardial Tumors and Cysts
Tumor in the pericardium is usually metastatic from the breast or
lung, but other types occasionally occur.252 The clinical
findings are typically a sizable pericardial effusion, at times leading
to tamponade, but tumor may also present as single or multiple
epicardial tumor nodules, as effusive-constrictive pericarditis, or
even as constrictive pericarditis.253 The effects of
radiation therapy on the tumor may further affect the pericardium,
resulting in inflammation, effusion, or fibrosis.
Pericardial cysts are rare and are usually located at the right costophrenic angle. They are readily visualized by echocardiography, and their cystic nature can be differentiated from that of a solid mass.254
Constrictive Pericarditis
In constrictive pericarditis there are such prominent
pathological and physiological changes that echocardiographic
abnormalities are always present, and in most cases there are multiple
abnormalities. However, no single echocardiographic sign is diagnostic
of constrictive pericarditis. Some frequently seen findings are
pericardial thickening, mild atrial enlargement with a normal-sized
left ventricle, dilation of the vena cava, flattening of LV endocardial
motion in mid and late diastole, various abnormalities of septal
motion, and premature opening of the pulmonary valve.
The Doppler findings of respiratory variations in flow velocities across the atrioventricular valves as well as across the LV outflow and pulmonary venous flow are often highly characteristic and provide additional supportive evidence favoring constriction. A combination of echocardiographic255 256 257 258 and Doppler flow data232 259 in an appropriate clinical context usually indicates the diagnosis of pericardial constriction.
The pericardial thickness may also be assessed, often more accurately by computed tomography or MRI.
Congenital Absence of the Pericardium and Pericardial
Disease After Open-Heart Surgery
In both total and partial absence of the pericardium, there are
echocardiographic findings that are helpful in establishing the
diagnosis.260 261 Pericardial disease occurs in patients
after open-heart surgery; early postoperative bleeding may result in
localized accumulation of blood clots, especially posteriorly. This
situation is often difficult to diagnose except by TEE.
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VII. Cardiac Masses and Tumors |
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TTE and TEE are accurate, high-resolution techniques for identifying masses within any of the four cardiac chambers. Masses that can be identified by echocardiographic techniques include primary tumors of the heart, such as atrial myxoma, metastatic disease from extracardiac primary sites, thrombi within any of the four chambers, and vegetations (infectious or noninfectious) on any of the four cardiac valves. Atrial myxoma is the most common primary tumor of the heart, and two-dimensional echocardiography is the primary method for diagnosis.
Intracardiac masses should be suspected in the context of the clinical presentation. Examples of this include suspicion of vegetative lesions in patients with underlying connective tissue diseases and new or varying murmurs and obviously in patients with signs and symptoms suggesting infective endocarditis. Intracardiac thrombi should be suspected in several clinical situations. These include a suspicion of LV thrombi in patients after extensive anterior myocardial infarction and left atrial thrombi in patients with atrial fibrillation, especially in association with rheumatic heart disease. Patients with signs and symptoms of peripheral embolic phenomenon (neurological events as well as non-neurological) should be suspected of having intracardiac masses if another embolic source is not identified.
In addition to detection and localization, echocardiographic techniques can play a role in stratifying the embolic risk of a cardiac mass. Sessile, laminar thrombi represent less of a potential embolic risk than do pedunculated and mobile thrombi.
Identifying patients who are appropriate candidates for
echocardiographic screening for intracardiac masses represents a
greater clinical dilemma than actual detection of the mass. Patients
for whom echocardiography may be appropriate include those in whom
there is a high clinical suspicion that a cardiac mass is present. An
intracardiac mass should be suspected in patients with one or more
embolic peripheral or neurological events or in those who have
hemodynamic or auscultatory findings suggesting intermittent
obstruction to intracardiac flow. Patients in whom a mass may be
suspected because of a predisposing condition include those with
rheumatic heart disease, dilated cardiomyopathy, and atrial
fibrillation, as well as following anteroapical myocardial infarction.
Patients with malignancies known to have a high incidence of
cardiovascular involvement may be appropriate targets for screening.
This includes individuals with hypernephroma as well as those with
metastatic melanoma or metastatic disease with known primary tumors of
intrathoracic organs. Clinical suspicion of disease entities such as
endocarditis in which a mass is known to develop would also fall into
the latter category. Special considerations referable to pediatric
populations are found in the section on congenital heart disease.
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VIII. Diseases of the Great Vessels |
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Echocardiography can be effectively used to visualize the entire thoracic aorta in most adults. Complete aortic visualization by combined transthoracic imaging (left and right parasternal, suprasternal, supraclavicular, and subcostal windows) frequently can be achieved. Biplane or multiplane TEE provides high-resolution images of the aortic root, the ascending aorta, and the descending thoracic and upper abdominal aorta. The only portion of the aorta that cannot be visualized is a small segment of upper ascending portion adjacent to the tracheobronchial tree. Using transthoracic imaging, good visualization of the main pulmonary artery segment and the proximal right and left pulmonary arteries can also be achieved in most children and the majority of adults. Visualization of the proximal portion of the innominate veins along with the superior vena cava can be achieved in nearly all patients with the use of the right supra- clavicular fossa and suprasternal notch approaches. Similarly the proximal inferior vena cava and hepatic (subcostal) and pulmonary veins (apical and transesophageal) can be visualized in many patients.
Aortic Dissection
Acute aortic dissection is a life-threatening emergency, and an
early and prompt diagnosis is mandatory for appropriate patient care.
Although TTE may visualize the intimal flap in patients with aortic
dissection, TEE has proved to be a far more sensitive diagnostic
procedure.262 263 Since time is of the essence in the
prompt diagnosis of dissection, only a brief transthoracic study should
precede TEE. Biplane or multiplane TEE should be used for a
comprehensive and accurate visualization of the thoracic aorta. In
addition to establishing the diagnosis and extent of aortic dissection,
echocardiography is useful in delineating any associated complications,
such as pericardial effusion with or without tamponade and the degree
and mechanism of aortic regurgitation and pleural effusion, as well as
evaluating LV size and function. TEE is also suited for postoperative
evaluation of patients with aortic dissection.264
Aortic Aneurysm
Aneurysms of the ascending aorta can be characterized by TTE. The
aneurysm may be localized to one of the sinuses of Valsalva. With
Doppler color flow imaging, rupture of an aneurysm in the sinus of
Valsalva can be diagnosed, and its communication with the receiving
cardiac chamber can be documented. Annuloaortic ectasia as well as
localized atherosclerotic aneurysms of the ascending aorta can be well
visualized with the use of the left as well as the right parasternal
windows. Echocardiography is particularly well suited for the
reevaluation of patients with ascending aortic aneurysms (especially in
patients with Marfan syndrome) for determining increase in the size of
the aneurysm. Descending thoracic aortic aneurysms are difficult to
visualize with the transthoracic approach. TEE is particularly suited
for complete characterization of these aneurysms.265
Aortic Rupture and Thoracic Aortic Degenerative
Disease
TEE has provided diagnostic information in traumatic and
other causes of aortic rupture. Although large tears are easily
visualized, it is possible to overlook small tears, which may also have
dire prognostic implications.266
The use of TEE has made it possible to detect atheromatous debris,
clots, and other lesions capable of producing embolic occlusions
downstream.
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The Great Veins
Echocardiography is a useful technique for visualizing the
superior vena cava and diagnosing various congenital and acquired
abnormalities. A persistent left superior vena cava often can be imaged
directly from the left supraclavicular fossa. Its connection, which is
frequently to the coronary sinus, can be seen from a parasternal window
as dilation of that structure. In some cases the connection to the
coronary sinus can be better delineated with contrast echocardiography
with injection of a contrast into a left arm vein. Other abnormalities,
such as vena caval thrombosis, can also be diagnosed with combined use
of echocardiographic and Doppler techniques. The proximal inferior vena
cava can be readily visualized in nearly all patients, and vena caval
dilation and thrombosis or extension of tumors from the inferior vena
cava to the right-heart chambers have been visualized. The hepatic
veins, their size, connection, and flow dynamics can be characterized
with combined use of two-dimensional and Doppler echocardiography.
Although visualization of all four pulmonary veins is not feasible with
the transthoracic approach in the majority of adult patients, TEE
permits clear visualization of the pulmonary vein connections.
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IX. Pulmonary Disease |
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As a general rule, patients who have primary pulmonary disease are not ideal subjects for echocardiographic examinations because the hyperinflated lung is a poor conductor of ultrasound. Despite these technical limitations, TTE can still be very informative in some patients with primary lung disease. The usual precordial or parasternal windows are frequently unavailable in patients with hyperinflated lungs. However, in these same patients the diaphragms are frequently lower than normal. Thus, the subcostal or subxiphoid transducer position can offer a useful window for echocardiographic examinations. For those few patients in whom transthoracic and subcostal echocardiographic windows are totally unavailable, the transesophageal approach provides an unobstructed view of the heart in patients with lung disease. As a result, with use of one examining technique or another, almost all patients with primary lung disease can be studied echocardiographically.
If lung disease does not result in anatomic or physiological alteration of cardiac structure or function, the findings on the echocardiogram will be normal. Although a normal result on echocardiography does not indicate a diagnosis of lung disease, the differential diagnosis of cardiac versus pulmonary symptoms can often be made on the basis of the echocardiogram. When shortness of breath can be due to either a lung or heart condition, normal findings on the echocardiogram can be extremely helpful in such a differential diagnosis.
In those patients whose lung disease affects cardiac function, the echocardiogram can be of significant value. Pulmonary hypertension is one of the most common complications of primary lung disease, and echocardiography is helpful in evaluating its presence and severity. The right ventricle commonly dilates, which can be detected on both the M-mode and two-dimensional echocardiogram. With marked systolic or diastolic overload of the right ventricle, the shape or motion, or both, of the interventricular septum is distorted, with abnormal diastolic bulging toward the left ventricle. In patients with increased pulmonary vascular resistance, the M-mode recording of the pulmonary valve shows a distinctive early to mid-systolic notch with loss of its A wave. A somewhat similar pulmonary artery velocity flow pattern is seen on the Doppler recording in such patients.
Any valvular regurgitation resulting from pulmonary hypertension can be detected with Doppler techniques. If adequate tricuspid and pulmonary valve regurgitation signals are obtained (as is the case in nearly 70% of all subjects), Doppler techniques can be used to accurately calculate RV systolic pressure.267 268 The tricuspid regurgitation signal is especially suited for saline contrast enhancement. The pulmonary artery diastolic pressure may also be estimated. This type of determination can be made in a high percentage of patients with significant pulmonary hypertension.
Pulmonary Thromboembolism
Echocardiography has aided a diagnosis of central pulmonary artery
thromboembolic disorders, especially in patients with severe or massive
pulmonary embolism. However, echocardiography has low sensitivity and
specificity for detecting pulmonary emboli.269
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X. Systemic Hypertension |
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Echocardiography is the noninvasive procedure of choice in evaluating the cardiac effects of systemic hypertension, the most common cause of LV hypertrophy and congestive heart failure in adults.270 M-mode and two-dimensional echocardiographic estimates of LV mass are more sensitive and specific than either the ECG or chest radiograph in diagnosing LV hypertrophy or concentric remodeling,271 272 273 274 and these estimates have been shown to correlate accurately with LV mass at necropsy.275 276 These techniques have been used to evaluate the relation of LV mass to rest and exercise blood pressure as well as multiple other physiological variables.277 Newer diagnostic techniques such as MRI are arguably more accurate but are often more expensive and less readily available.278 Assessment of hypertrophy is relevant because several cohorts have shown that the risks of cardiac morbidity and mortality are increased in hypertensive patients with electrocardiographic or echocardiographic criteria of LV hypertrophy and are independent of traditional coronary risk factors.272 279 280 281 Moreover, even in those patients without increased LV mass, concentric remodeling, or an increased wall thickness relative to cavity size carries a poor prognosis.272 For these reasons, in patients with borderline hypertension a decision to initiate therapy may be based on the presence of hypertrophy or concentric remodeling. In borderline hypertensive patients without evidence of LV hypertrophy by ECG, a goal-directed echocardiogram to evaluate LV hypertrophy may be indicated.
Echocardiography can also be used to evaluate systolic and diastolic properties of the left ventricle, such as the speed and extent of contraction, end-systolic wall stress, and the rate of ventricular filling throughout diastole,275 and to evaluate related coronary artery disease and degenerative valve disease, especially in the elderly. Stress echocardiography is indicated in the diagnosis and assessment of the functional severity of concomitant coronary artery disease. The usefulness of echocardiography in an individual patient with hypertension without suspected concomitant heart disease depends on the clinical relevance of the assessment of LV mass or function in that patient. Thus, not every patient with hypertension should have resting LV function assessed (Class I), but if such an assessment is relevant, echocardiography is a well-documented and accepted method by which to achieve it.
The value of repeated studies in asymptomatic hypertensive patients
with normal LV function is not clearly established. A decrease in LV
mass in hypertensive patients through control of blood pressure or
weight loss has been demonstrated by many regimens in several
studies.282 283 284 285 While data suggest that LV hypertrophy
regression improves LV filling,282 the impact on patient
morbidity and mortality is unknown, as is the potential effectiveness
of echocardiography in guiding therapy aimed at reducing LV
mass.272 286 Despite this, a possible indication for
reevaluation quantitation of LV mass in assessing drug therapy for
hypertension is evaluation of regression of LV hypertrophy after
adequate blood pressure control.282 More study is required
to prove that regression of LV hypertrophy alters cardiac morbidity and
mortality and that echocardiography is a cost-effective method for both
detection of hypertrophy and follow-up evaluation of the large number
of patients with hypertension. Until these studies are available,
following LV hypertrophy by echocardiography cannot be supported.
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XI. Neurological Disease and Other Cardioembolic Disease |
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Acute interruption of blood flow to the cerebral vasculature or a peripheral artery results in an identifiable clinical syndrome such as transient ischemic attack, cerebrovascular accident, acute limb ischemia, or mesenteric or renal artery insufficiency. The above clinical scenarios can be the result of intrinsic local vascular disease, atheromatous emboli from proximal vessels, or emboli of cardiac origin. Cardioembolic disease refers to the heart as the origin of an occlusive embolus with subsequent migration to a target organ. Depending on the target organ, the age of the patient, and the likelihood of underlying primary vascular disease, the prevalence of a cardioembolic etiology is highly variable. Most studies have documented that a substantial proportion of patients with embolic events, even in those with vascular disease, also have a potential cardiac source of embolus (Table 10
). Proving cause and effect between the
clinical event and a potential embolic source has been more elusive for
many entities. Exceptions include the obvious link between embolic
events and bacterial endocarditis and embolic phenomena occurring in
patients with prosthetic valves.
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The level of evidence for deriving a relation between potential cardiac sources of embolus and neurological events is relatively low. Virtually all studies published to date rely on data from nonrandomized trials and frequently nonconsecutive patients compared with either historical or concurrent control populations. No large-scale prospective studies are available from which a definite cause and effect between cardiac source of embolus and subsequent neurological events can be derived. The available data are all concordant, however, in suggesting a high prevalence of potential cardiac sources of embolus and other neurological embolic events.
Many studies have evaluated the frequency of a cardioembolic source of
an acute neurological syndrome. The definition of cardioembolic events
can be characterized either from the reference of a potential source of
embolus or the reference of the end-organ event. Both definitions have
been used in the literature, and sufficient exceptions to any given
stratification scheme occur. The Cerebal Embolism Task Force has
previously defined a cardioembolic neurological event as "presence
of a potential cardioembolic source in the absence of cerebrovascular
disease in a patient with nonlacunar stroke."287 This
definition obviously implies cause and effect when a potential cardiac
source of embolus is noted in an individual with a neurological event.
Historically several types of neurological events have been thought to
be more likely embolic than due to intrinsic cerebrovascular disease.
The neurological findings traditionally thought to suggest an embolic
source are sudden onset, middle or anterior circulation defects, and
multiple events in peripheral territories. Conversely, classic lacunar
strokes or hemorrhagic strokes have been thought more likely due to
intrinsic cerebrovascular disease. Recent data have called into
question the classification of the latter. At this time there are no
highly specific types of neurological events that should exclude the
possibility of a cardioembolic source. Clinical studies have suggested
that up to 20% of acute neurological events may be attributable to a
cardioembolic source,288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 with an additional 40%
classified as cryptogenic. Recently it has been suggested that a
substantial proportion of the latter may also be attributed to a
cardiac etiology (Table 11). This prevalence is obviously
age dependent, with some studies suggesting a prevalence of
cardioembolic disease >50% for younger persons.303 As
such, the use of echocardiographic techniques in patients with acute
embolic events should be placed in the context of the clinical
presentation and the likelihood of other responsible pathology.
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Additionally, a decision to use echocardiographic techniques must
take into account the presence of underlying cardiac disease. Clearly
the presence of rheumatic heart disease or atrial fibrillation
predisposes a patient to atrial thrombus formation and the likelihood
of an embolic event. Other cardiac diseases that may predispose to
thrombus formation and subsequent embolization include cardiomyopathy,
nonrheumatic atrial fibrillation, mitral annular calcification, and
anterior myocardial infarction with aneurysm formation. Several studies
have demonstrated that the prevalence of potential embolic sources is
greater in persons with clinically apparent organic heart disease than
in those without clinically apparent heart disease (Table 12).
This relatively high prevalence of clinically unsuspected
cardiovascular disease (presumably of embolic potential) suggests that
echocardiographic screening may be applicable to a broader range of
patients than only those persons with clinically suspected disease.
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Two-dimensional echocardiography is the only technique that is easily
applied and widely available for evaluation of potential cardioembolic
source. Rapid intravenous injection of agitated saline floods the right
heart with microbubbles and can detect right-to-left shunting across a
patent foramen ovale. Examinations can be performed either from a
transthoracic or transesophageal approach. Comparative studies between
the two approaches have suggested a higher yield for potential cardiac
source of embolus when TEE is used compared with
TTE.299 300 Table 13 outlines the relation
between TEE and TTE in a wide range of potential cardioembolic sources.
Entities such as mitral stenosis, cardiomyopathy, and LV mural thrombus
are equally well identified with either technique, and once identified
by TTE, the additive cost, inconvenience, and risk of TEE is probably
not warranted. Conversely, TEE is uniquely suited for detection of left
atrial spontaneous contrast,302 304 305 left atrial
thrombi, atrial septal aneurysm,306 307 right-to-left
shunting through a patent foramen ovale, and atheroma of the aortic
arch308 309 310 311 312 313 as well as several other more recently
described anomalies.
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In a similar fashion, the issues of age and presence or absence of atrial fibrillation have been addressed in several of the published series. While in each series the prevalence of potential cardiovascular abnormalities is greater in older patients and those with atrial fibrillation, a clinically pertinent proportion of patients without either risk factor (age or atrial fibrillation) will have cardiovascular pathology that places them at risk for arterial embolization. Traditionally, it has been assumed that there is an inverse relation between age and the prevalence of potential cardiac sources of embolus in patients with neurological events. Recent studies, however, have clearly demonstrated an almost equal prevalence of potential cardiac sources of embolus in older patients when compared with younger cohorts. Younger patients typically have a higher likelihood that the potential cardiac source of embolus is the only identifiable abnormality, whereas older patients are more likely to have identifiable concurrent cerebrovascular disease. The definition of "younger" and "older" patients has been variable. It should be recognized that there is a gradation of age and prevalence of potential cardiac source of embolus rather than distinct age cutoffs. From a standpoint of data analysis, most studies have assumed an age break at approximately 45 years; however, it should be understood that this does not represent a distinct break. Clearly there is a range of likelihood of finding potential cardioembolic sources, with the likelihood of an exclusive cardioembolic source being greater in younger patients and progressively less in older.
Few published series have investigated recurrence rates of neurological events in relation to specific cardiovascular abnormalities. It appears that lesions such as mitral stenosis, left atrial spontaneous contrast, patent foramen ovale with right-to-left shunting, and atrial septal aneurysm represent relatively higher risk entities with respect to recurrent cerebrovascular events. Presumably more aggressive therapy should be directed at these patients.
In addition to the presence or absence of a specific disease
that impacts the likelihood of an embolic event, the nature of the
occlusive event also has implications for the necessity of further
evaluation. Clearly, younger persons with cerebrovascular events are
more likely to have had an event with an embolic basis than are elderly
patients with intrinsic cerebrovascular disease. Likewise, in persons
with events in multiple cerebrovascular territories it is more likely
for the event to be embolic. Additionally, occlusion of a large
peripheral vessel such as a femoral or renal artery is far more likely
to represent a cardioembolic event. The heart represents the only
source for a mass of sufficient size to cause total occlusion of an
otherwise normal large-caliber vessel. In individuals with an abrupt
occlusion of a large vessel, cardioembolic disease should be suspected.
Several recently published studies have evaluated the link between
specific entities of embolic potential and neurological events. These
include atrial septal aneurysm,303 306 307 patent foramen
ovale,303 314 315 316 317 left atrial spontaneous
contrast,302 304 305 and aortic
atheroma.308 309 310 311 312 313 In each case a statistically significant
increase in the prevalence of these entities has been demonstrated in
individuals with neurological events. Tables
14 through 17 outline
results of studies that have evaluated these phenomena. In each case
there is a greater likelihood of finding one or more of these entities
in patients with neurological events than in control populations
without neurological events.
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XII. Arrhythmias and Palpitation |
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Arrhythmias can occur as primary electrophysiological abnormalities or as a complication of or in association with structural heart disease. The spectrum of heart disease associated with arrhythmias is broad, including congenital abnormalities as well as acquired diseases of the myocardium, valves, pericardium, and coronary arteries. While some arrhythmias may be life-threatening or carry significant morbidity, others are considered benign.
In the setting of arrhythmias, the utility of echocardiography lies primarily in the identification of associated heart disease, the knowledge of which will influence treatment of the arrhythmia or provide prognostic information. In this regard, echocardiographic examination is frequently performed to assess patients with atrial fibrillation or flutter, reentrant tachycardias, ventricular tachycardia, or ventricular fibrillation. Echocardiography detects an underlying cardiac disorder in approximately 10% of patients with atrial fibrillation who have no other clinically suspected cardiac disease319 320 and in 60% of those with equivocal indicators of other heart disease.319 Ventricular arrhythmias of RV origin should alert the physician to a diagnosis of RV abnormalities, including RV dysplasia,321 322 323 while ventricular tachycardias of LV origin are frequently associated with reduced LV function.
A large group of patients have benign arrhythmias such as atrial or ventricular premature beats. Although, in general, echocardiographic evaluation should be reserved for those for whom there is a clinical suspicion of structural heart disease, there may be a therapeutic role for cardiac ultrasound by reassuring the anxious patient that the heart is structurally normal. Unless there are other indications for testing, echocardiography need not be performed in a subject with palpitation for which an arrhythmic basis has been ruled out.
Although echocardiography has provided useful insights into the effects of arrhythmias on cardiac function,324 there is no indication for repeated clinical testing for this purpose unless there has been a change in clinical status or the result might impact a therapeutic decision. One situation where treatment might be impacted is in the selection of appropriate settings for DDD pacing where Doppler studies can be used to determine stroke volume at various settings to provide optimum cardiac output.325 However, it appears that for most patients, similar settings provide optimum output. Thus, this application of echocardiography might be limited to those in whom the usual settings do not appear to convey favorable hemodynamics. Similarly, while there have been reports that echocardiography may assist in identification of an arrhythmia when a surface ECG is nondiagnostic326 327 328 or allow accurate localization of the bypass tract in patients with Wolff-Parkinson-White syndrome,329 cardiac ultrasound is rarely used for these purposes.
In this era of interventional electrophysiology, an expanded role for echocardiography has been suggested. Thus, TEE has been reported to be helpful in guiding transseptal catheterization during radiofrequency ablative procedures.329 Early studies also proposed routine postprocedural evaluation of patients undergoing ablation. However, the yield was low enough in laboratories with established ablative programs that the test is no longer recommended in uncomplicated cases.
For a discussion of the role of echocardiography in the assessment of
children with arrhythmias, see the corresponding section in section XV,
"Echocardiography in the Pediatric Patient."
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Cardioversion of Patients With Atrial
Fibrillation
Recent studies have supported a role for echocardiography in
patients with atrial fibrillation undergoing cardioversion.
Echocardiography may help identify subjects who are most likely to
undergo cardioversion successfully and maintain sinus rhythm after
conversion. LV dysfunction argues against long-term success. The
relation between atrial size and successful conversion is more
controversial330 331 332 333 334 335 (Table 18).
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The issue of performing TEE before elective cardioversion from atrial fibrillation has recently been addressed in patients with atrial fibrillation of >48 hours' duration.337 338 Historical data suggest a 5% to 7% incidence rate of cardioembolic events associated with electrical cardioversion from atrial fibrillation in patients who have not undergone anticoagulation. The presumed mechanism is dislodgment of previously existing atrial thrombi after cardioversion to atrial fibrillation. Recently it has been demonstrated that transient left atrial mechanical dysfunction and spontaneous echocardiography contrast may occur after cardioversion to sinus rhythm, potentially explaining the mechanism of delayed cardioembolic events.339
In subjects undergoing cardioversion it has been reported that exclusion of intra-atrial thrombus with TEE can obviate the need for extended precardioversion anticoagulation.337 However, the authors emphasize the importance of anticoagulation from the time of study until the time of cardioversion and subsequently until atrial mechanical function has returned after conversion. Others, however, have reported that in a group of patients not routinely given anticoagulation in the pericardioversion period, there was a 2.4% incidence of embolic events despite the absence of thrombus at the time of precardioversion TEE.338 Large multicenter trials are under way to address this issue. Thus, at present, although there is controversy concerning the routine use of TEE to identify patients to undergo cardioversion without prolonged anticoagulation, there is agreement that periconversion and postconversion anticoagulation is indicated. For individuals in whom anticoagulation confers more than a minimal risk, further stratification into subgroups at high and low risk for embolic events with TEE may be warranted.
There is less information available about the risk of thrombus and pericardioversion embolism in patients with atrial fibrillation of recent onset. It has been the recommendation of the American College of Chest Physicians Consensus Conference on Antithrombotic Therapy340 that anticoagulation is not necessary before cardioversion of patients with atrial fibrillation of <48 hours' duration. This assumes that thrombus formation does not occur in this time interval. However, a recent TEE study has reported left atrial appendage thrombus in 14% of patients with acute-onset atrial fibrillation.341 These results argue that guidelines for anticoagulation and TEE in patients undergoing cardioversion of atrial fibrillation should not differentiate between those with recent versus chronic fibrillation.
The prevalence of thrombus in patients with atrial flutter appears to
be lower than that for those with atrial fibrillation or
fibrillation/flutter.342 However, no studies have
addressed the role of pericardioversion anticoagulation and TEE in
these patients.
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Syncope
Syncope is a common clinical problem with multiple causes. The
role of echocardiography in the diagnostic evaluation of patients with
syncope relates to its ability to diagnose and quantitate obstructive
lesions and identify abnormalities such as LV dysfunction that provide
a substrate for malignant arrhythmias. The abnormality identified may
be solely causative or one of several combining to cause syncope.
Whether the use of echocardiography can be justified as a routine
component of a syncopal workup is controversial. Only retrospective
studies published in abstract form are available on the
subject,343 344 345 and the conclusions differ. While two
studies reported no diagnostic yield from echocardiography in patients
in whom history, physical examination, and ECG failed to indicate a
cause,343 344 a third study reported that echocardiography
identified what was ultimately determined to be the sole cause in 8%
of subjects with syncope referred for echocardiographic
evaluation.345 However, it is impossible to determine the
true yield of echocardiography in this setting, including its ability
to rule out as well as rule in clinically suspected abnormalities in a
retrospective study. Thus, there is a strong need for a large
prospective study in this area.
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Screening
If screening asymptomatic individuals for cardiac abnormalities is
to be recommended, several criteria must be met. First, the test used
must be accurate, free of complications, widely available, and
inexpensive. Second, the abnormalities sought should occur with
reasonable frequency in the population to be screened and, if present,
should convey risk to the affected individual. Third, recognition of
the abnormality should ideally lead to initiation of a management plan
that will favorably affect long-term outcome or prevent initiation of a
potentially detrimental plan. At minimum, identification of the disease
should provide prognostic information that will influence the
patient's life decisions.
As a testing modality, echocardiography is a safe, widely available, and accurate method for identifying most structural heart disease. Its cost varies, depending in part on which components are included in the examination. In general, its cost is higher than that of a physical examination, ECG, or a conventional stress test but lower than that of cardiac imaging with computerized axial tomography, MRI, or nuclear methods. Thus, echocardiography has several properties that promote its use as a screening tool. However, of the many conditions that echocardiography is capable of identifying, few meet the criteria enumerated above.
Among those that meet these criteria are heritable diseases of the heart and great vessels when the target group for screening is the family members of an affected individual. The most common diseases that fall into this category are hypertrophic cardiomyopathy and Marfan syndrome.
The inheritance pattern of hypertrophic cardiomyopathy is variable, with familial occurrence reported in 56% and sporadic occurrence in 44%.346 In a large-scale screening study,346 the proportion of first-degree relatives of probands with hypertrophic cardiomyopathy also found to have the disease was 22%. Of relevance to the screening process is the fact that in an affected individual, the hypertrophy may develop de novo or increase dramatically during childhood and adolescence.347 These observations provide justification for more than one screening examination of subjects in this age group. In contrast, one study has suggested that hypertrophy does not progress in adulthood.348 However, emerging data demonstrating the genetic heterogeneity and variable expression of hypertrophic cardiomyopathy raise the possibility that patterns of disease progression may be similarly variable. Thus, repeat screening of adults may also be justifiable, particularly in those whose kindred have malignant forms of the disease.
Marfan syndrome is transmitted as an autosomal dominant with
spontaneous mutation occurring in up to 30% of subjects. The diagnosis
is made using a multidisciplinary set of major and minor diagnostic
criteria that include abnormalities of the skeleton, eye,
cardiovascular system, pulmonary system, skin, and central nervous
system, and take into consideration the family history (Table 19).
Because the primary method of diagnosing cardiovascular
abnormalities is echocardiography, this tool is an essential element of
screening for Marfan syndrome. When screening is performed, it is
essential to use normal values corrected for body size and age. In
adult cases where a thorough multifaceted evaluation excludes
diagnosis, no subsequent screening is necessary. However, in borderline
cases and young children of a clearly affected parent, repeat
evaluation in 12 months is appropriate as skeletal, aortic, and ocular
abnormalities may evolve.
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The current approach to screening for Marfan syndrome and to guiding treatment of patients diagnosed with this disorder is echocardiographic assessment of the aorta. Improved medical and surgical therapy has increased life expectancy in these patients.350
Other heritable conditions of the heart include other connective tissue disorders and tuberous sclerosis. A single report has suggested that one of five patients with dilated cardiomyopathy has a familial form of the disease, thus proposing a role for echocardiographic screening in this setting as well.351 However, no other study has confirmed this observation.
Another accepted indication for echocardiographic screening is in the evaluation of potential donor hearts for transplantation.352 In patients in whom transthoracic imaging is inadequate, TEE provides an alternative approach.353 The overall yield for conditions that eliminate the heart as a donor is approximately one of four patients.
Noninvasive screening of LV function before the initiation of chemotherapy with cardiotoxic agents is also accepted clinical practice. Both echocardiography and nuclear gated blood pool scanning have been used for this purpose. Similarly, either modality may be used to monitor ventricular function serially during treatment. In this regard it is notable that two small prospective studies have reported Doppler-defined abnormalities of diastolic function that preceded detectable changes in systolic performance in patients with doxorubicin cardiotoxicity.225 226
Although a number of systemic diseases have the potential to involve the heart, there appears to be little role and generally few options for treatment of asymptomatic cardiac disease in this setting. Thus, the role of echocardiographic screening of these subjects is debatable.
In contrast to its utility in screening selected relatively
high-risk populations, echocardiographic testing cannot be justified
when asymptomatic cardiovascular disease is sought in larger lower-risk
groups. For example, in two large screening studies the prevalence of
echocardiographically manifest hypertrophic cardiomyopathy in an adult
population was reported to be 0.2%,354 355 with the
majority of individuals thus identified having mild manifestations of
the disease. Similarly, although there is considerable public awareness
of athletes dying from unrecognized heart disease,
studies356 357 358 have shown that the prevalence of these and
other conditions appears to be too low to justify widespread screening
(Table 20).
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XIII. Echocardiography in the Critically Ill |
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Numerous applications of TTE and TEE to clinical conditions discussed elsewhere in these guidelines also apply to the hemodynamically unstable patient who is evaluated in either the emergency department or critical care unit. Chest pain, hypotension, or shock of unknown cause may not have the usual clinical findings that clearly define the diagnosis. Among the specific conditions detectable in the acutely ill patient are acute myocardial infarction and its complications, cardiac tamponade, aortic dissection, mechanical or infective complications of native or prosthetic valves, and source of embolism.359 360 In the critically ill patient there are significant differences in the relative value of TEE versus TTE.
The critically ill patient in the emergency department or intensive care unit is often managed by intubation and mechanical ventilation frequently utilizing positive end-expiratory pressure (PEEP). Up to one half of such patients cannot be adequately imaged by TTE, especially those requiring >10 cm PEEP.361 Furthermore, many patients in intensive care units cannot be appropriately positioned, have sustained chest injury, or are postoperative with dressings and tubes preventing adequate TTE. Because of these considerations, TEE is often required to make the diagnosis.
In the critically ill patient without myocardial infarction, significant left-sided valve or ventricular disease, or known pulmonary disease, the finding of RV dilation or hypokinesis on TTE indicates a high probability of pulmonary embolism. The presence of RV hypokinesis identifies patients with 30% or more of the lung nonperfused who may receive significant benefit from thrombolysis.362
The majority of studies of echocardiography in the clinically ill have
been retrospective analyses. In most, both TTE and TEE results were
available, allowing a comparison between the two. In some of the
studies both the critically ill and injured were evaluated, and in
others only postoperative patients were included. These studies total
735 patients. In general, there is an improved yield of critical
findings by TEE in patients in whom the standard two-dimensional
Doppler TTE study provided inadequate information. TEE often resulted
in a change in treatment or surgery86 88 363 364 365 366 367 368 369 370 (Table 21). Recently the first prospective but
nonrandomized trial comparing the value of TTE and TEE for evaluating
unexplained hypotension found that 64% of 45 TTE studies were
inadequate, compared with 3% of 61 TEE studies. Transesophageal
studies contributed new clinically significant diagnoses (not seen by
TTE) in 17 patients (28%), leading to operation in 12
(20%).86
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TTE or TEE may help to define pathophysiological abnormalities in patients even when there is constant invasive monitoring of pulmonary artery pressures by the Swan-Ganz technique. In several series echocardiography was found to be more reliable than Swan-Ganz catheter pressure in determining the cause of hypotension.86 371 372 373 Although the measurement of cardiac output by TEE and Doppler using special views appears to be feasible,374 375 376 clinical use on a continuous basis is not yet available. It is not a realistic expectation at this point that echocardiography and Doppler measurements will replace thermodilution-determined cardiac output or pulmonary artery catheter monitoring.5 Other measurements of function can be obtained using TEE and Doppler, including pulmonary venous flow determination, which may assist in separating various cardiovascular conditions responsible for hemodynamic instability.87
TEE is valuable in the hypotensive postoperative cardiac surgery patient to detect treatable conditions.372 373 Other potential advantages of TEE in the surgical patient are addressed in practice guidelines for perioperative TEE.377
Although no fatal and few serious complications of TEE were reported in the studies cited, there are significant special technical considerations that must be taken into account in these critically ill patients.87 378
Echocardiography in the Trauma Patient
Both TTE or TEE methods have been found to be useful in the
severely injured patient in whom cardiac, pericardial, mediastinal, or
major intrathoracic vascular injury has occurred. Myocardial contusion
or rupture, pericardial effusion, tamponade, major vascular disruption,
septal defects or fistulae, and valvular regurgitation may all result
from either blunt or penetrating trauma. Assessment of the patient's
volume status and detection of significant underlying heart disease,
especially in the elderly patient, is possible through standard Doppler
echocardiography techniques.
These patients represent a diagnostic challenge as they often present with serious multisystem trauma or major chest injury and are hemodynamically unstable. The ECG is helpful but often nonspecific, and serum enzymes have not been found reliable. TTE has been used since the early 1980s to evaluate cardiac trauma.379 380 In both blunt and penetrating chest trauma, 87% of patients could be imaged satisfactorily by TTE, with significant abnormalities found in 50%, the most common of which was pericardial effusion (27%).381 In a prospective study of 336 patients over 6 years, young patients with minor blunt thoracic trauma and a normal or minimally abnormal ECG have a good prognosis, and further diagnostic studies and monitoring are seldom necessary.382 Others have proposed a similar triage scheme for blunt cardiac trauma using both TTE and TEE.383 384 385
Blunt cardiac injury may result in cardiac contusion significant enough to produce serious dysrhythmias,386 cardiac dysfunction, or tamponade. The majority of serious injuries result in death from rupture of the ventricle or aorta before the patient can be transported.387 In patients with serious blunt trauma who reach the hospital, even if in profound shock or cardiac arrest, survival is possible if the injury is recognized and immediate surgery undertaken, even in cardiac rupture.388 In certain cases, TTE done emergently in the emergency department may assist in the diagnosis and result in salvage. The sequelae of blunt cardiac trauma may not be immediately evident and require close follow-up. The diagnosis may eventually be made by various means, including cardiac echocardiography.389
It is often difficult to image patients with severe blunt trauma with TTE. Most studies have found that TEE was valuable when TTE images were suboptimal and when aortic injury was suspected.390 391 392 In one study of intubated multiple injury patients not confined to blunt chest trauma, TEE evaluation detected unsuspected myocardial contusion, pericardial effusion, and aortic injury.393
Thoracic aortic disruption usually occurs in a sudden deceleration injury or serious blunt trauma in which torsion forces are brought to bear upon the aorta, resulting in tears in the intima or transection of the aorta. The most common sites of rupture or partial rupture in those patients surviving to reach the hospital are the descending aorta just distal to the left subclavian artery (aortic isthmus) and the ascending aorta just proximal to the origin of the brachiocephalic vessels. Of the 20% who survive to reach the emergency room, 40% die within the first 24 hours. Radiological signs in these patients include widening of the mediastinum on chest radiograph, fracture of first and second ribs with an apical cap, or multiple types of thoracic trauma. Occasional patients with multisystem trauma without evidence of chest trauma sustain rupture.
While aortography has been the gold standard, computed tomography and MRI have also been used in an attempt to differentiate patients with trauma and a widened mediastinum. TEE is becoming the first approach in many centers because of the utility and speed with which it can be accomplished and because of its superiority in evaluating aortic disease such as dissection. This is especially so with the widespread use of biplane and multiplane TEE.384 391 392 Obviously, the value of TEE depends on its availability in a timely manner and the expertise of the operators to perform a comprehensive evaluation of the aorta without serious complications in the traumatized patient.394 395 Several series of patients undergoing TEE have been reported in which most patients have had aortography or surgery to confirm the diagnosis.266 390 392 396 397 The use of TEE as a primary diagnostic modality in traumatic aortic rupture appears to be rapid, safe, and accurate as a bedside method. Although widespread use of TEE has not been documented in large series from many different institutions, aortography may be avoided except in those patients in whom TEE results are equivocal, when TEE is not tolerated or contraindicated, or when other vascular injuries of arch vessels or lower portions of the descending aorta are suspected. TEE, aortography, computed tomography, and MRI are reviewed in a recent publication.398
Penetrating chest trauma, whether by gunshot, stabbing, or other means, has usually required surgical exploration using a subxiphoid pericardial approach to exclude cardiac injury. The subxiphoid exploration, however, carries a negative exploration rate of 80%. TTE, when compared to subxiphoid pericardiotomy, is 96% accurate, 97% specific, and 90% sensitive in detecting pericardial fluid in juxtacardiac penetrating chest wounds.399 Thus, TTE may prevent unnecessary exploratory thoracotomy or subxiphoid pericardiotomy.400 In a report in which TTE was used in the emergency department of a large metropolitan hospital, survival in the group who had TTE was 100%; for the nonechocardiography group, survival was 57.1%.401 In another series of patients with penetrating chest injury, TTE had an accuracy of 99.2% and positive and negative predictive values of 100% and 98%.402 Others, however, have reported that a normal echocardiogram (TTE) does not always exclude major intrapericardial injury, and that even small effusions in penetrating chest trauma may be associated with significant injury.403 When hemothorax is associated with penetrating injury, cardiac echocardiography does not have adequate sensitivity and specificity to avoid the necessity of subxiphoid exploration.404
Late sequelae of penetrating injuries are not uncommon, and thus routine TTE is recommended in all patients with penetrating cardiac injuries.405 406 The detection and location of bullet fragments is also possible with TEE and Doppler.407 While no large series of penetrating cardiac wounds studied by TEE and Doppler has been reported, initial reports support its routine use in the perioperative period.408
Iatrogenic penetrating cardiac injury in the catheterization laboratory is rare, occurring in 0.12% of procedures. Whether by guidewires, pacemaker catheters, balloon valvulotomy, PTCA, or pericardiocentesis, tamponade is the result in many of these, recognizable by fluoroscopy at the time and confirmed by cardiac echocardiography in the lab or at the bedside. Pericardiocentesis is the definitive treatment in most, and surgery is rarely necessary.409
In summary, echocardiography and Doppler techniques are
extremely valuable in delineating pathology and hemodynamics in the
critically ill or injured patient and in certain perioperative
situations. TEE appears to have a distinct advantage in certain
settings and conditions.
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Because of the highly variable nature of these
patients, the differing clinical circumstances in reported series, and
the evolving utilization of either TTE or TEE and Doppler techniques,
the relative merit and recommendations may vary among institutions.
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XIV. Two-Dimensional Doppler Echocardiography in the Adult Patient With Congenital Heart Disease |
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The adult patient with congenital heart disease is seen either because the problem was not discovered in childhood or more often because the patient was previously diagnosed as having inoperable congenital heart disease or has had one or more palliative or corrective surgical procedures.
As a general rule, all patients with congenital heart disease must be followed indefinitely, even those who have had "corrective" procedures to return them to physiologically normal status. The only potential cures are in repaired patent ductus arteriosus and in some patients a repaired atrial septal defect. Adult patients with congenital heart disease are seen by the cardiologist because they
- Have been undiagnosed in the past.
- Have recognized congenital heart disease that is presently inoperable, eg, hypoplastic pulmonary arteries or systemic level pulmonary hypertension and severe pulmonary vascular disease and –Progressive clinical deterioration, such as ventricular dysfunction or arrhythmias due to the natural history of the disease. –Become pregnant or have other stresses such as noncardiac surgery or infection, including infective endocarditis.
- Have residual defects after a palliative or corrective operation.
- Develop arrhythmias (including ventricular tachycardia, atrial flutter, or atrial fibrillation) that may result in syncope or sudden death.
- Have progressive deterioration of ventricular function with congestive heart failure.
- Have progressive hypoxemia because of inadequacy of palliative shunt or development of pulmonary vascular disease.
- Require monitoring and prospective management to maintain ventricular or valvar function and/or to prevent arrhythmic or thrombotic complications.
Table 22 lists the late complications
that occur in patients with surgically treated congenital heart
disease.
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Of special importance is the recognition that congenital heart disease is relatively infrequent in the practice of the cardiologist who sees adults. Most cardiologists and echocardiographic technicians have insufficient experience with the wide variety of congenital heart disease lesions that exist. It is likely that they will recognize that something is abnormal but not recognize the specifics of the congenital heart lesion. For this reason, it is necessary that both the cardiac sonographer and interpreting cardiologist have special competencies in congenital heart disease or refer the patient to a cardiologist (adult or pediatric) experienced in the area.
Two-dimensional Doppler echocardiography is useful in
- Demonstrating chamber size.
- Evaluating RV and LV function.
- Defining the presence, site, and relative magnitude of intracardiac and/or systemic-to-pulmonary artery shunts.
- Defining the presence, magnitude, and site of LV and RV outflow tract and valvular obstruction.
- Evaluating valvar regurgitation.
- Estimating pulmonary artery pressure.
- Defining the relation of veins, atria, ventricles, and arteries.
- Visualizing coarctation of the aorta and estimated degree of obstruction.
- Using contrast echocardiography and color Doppler to define the presence, site, and relative magnitude of intracardiac or vascular shunts.
- Demonstrating intracardiac and/or central vascular mural thrombi as well as coronary fistulas.
- Assessment of atrioventricular valve anatomy and function.
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XV. Echocardiography in the Pediatric Patient |
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Congenital structural heart disease is the most common type of cardiovascular disease in the pediatric population. However, acquired heart disease also contributes to the cardiovascular morbidity of this population. Historically identified with rheumatic fever and endocarditis, acquired pediatric heart disease now includes Kawasaki disease, human immunodeficiency virus (HIV) and other viral-related cardiac disease, dilated cardiomyopathy with or without acute-onset congestive heart failure, hypertrophic cardiomyopathy, and an increasing pediatric and young adult population with clinical cardiovascular issues related to surgical palliation/correction of structural heart disease.
Doppler echocardiography has become the definitive diagnostic method for the recognition and assessment of congenital and acquired heart disease in the pediatric population. Its use has eliminated the need for invasive or other noninvasive studies in some and decreased the frequency and improved the timing and performance of invasive studies in other patients.410 411 412 413 414 415 Echocardiographic reevaluation in some candidates improves medical or surgical management. For the child with insignificant cardiac disease, an echocardiographic evaluation provides reassurance to the family. For those patients with significant cardiac abnormality, early and accurate echocardiographic evaluation improves clinical outcome.
Reevaluation echocardiographic examinations are frequently used to monitor cardiovascular adaptation to surgical repair or palliation and identify recurrence of abnormalities. Such longitudinal follow-up facilitates proactive surgical and/or medical intervention. 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 For these reasons, echocardiography provides improved outcome and lowers healthcare costs by streamlining the use of medical resources, guiding management decisions, and providing early education and support for the family.
Resource Utilization and Age
Guidelines for pediatric echocardiography utilization must be
stratified by age to accommodate the unique cardiovascular physiology
of the neonate. Such guidelines must recognize the newborn's
transitional circulation and the frequent coexistence of confounding
pulmonary disease. The transitional circulation in the perinatal age
group may obscure hemodynamically important, even critical,
cardiovascular abnormalities. Due to the rapid changes in pulmonary
vascular resistance and the patency of the ductus arteriosus,
reevaluation echocardiographic examinations of the critically ill
neonate are often required. Newborns with primary pulmonary
hypertension (persistent fetal circulation) will require repeated
echocardiographic evaluation of the cardiovascular response to medical
interventions modulating pulmonary artery pressure. Those undergoing
extracorporeal cardiopulmonary therapy require echocardiographic
monitoring of ventricular function432 and surveillance for
intracardiac thrombus formation. Newborn infants with noncardiac
anomalies requiring urgent surgical intervention undergo
preoperative echocardiographic screening, even in the absence of
clinically manifest cardiovascular disease, to exclude associated
cardiovascular anomalies. This knowledge facilitates perioperative
treatment of these patients and focuses both on noncardiac and cardiac
therapy. For neonates with multiple congenital abnormalities and severe
anatomic and/or functional neurological impairment, echocardiographic
identification of cardiac anomalies will better define survivability
and help guide difficult management decisions regarding life support
and palliation.433
Congenital Cardiovascular Disease in the
Neonate
Structural Congenital Cardiovascular Disease
Two-dimensional echocardiography provides essential structural
information in all forms of cardiac and great vessel disease in
pediatric patients. Doppler echocardiography provides important
physiological information that, when combined with anatomic data, helps
guide therapeutic management in some diagnostic categories.
Reevaluation examinations allow tracking of hemodynamic changes such as
those occurring during the transition phase from fetal to newborn and
infancy periods.434 Echocardiography provides clinical
information to guide medical or surgical intervention and provide
prognostic information. It is also valuable to track evolutionary
changes in the cardiovascular system and to determine management
subsequent to medical or surgical intervention.
Perinatal physiological changes often mask or obscure the presence of hemodynamically important cardiovascular lesions. Echocardiography allows early recognition of lesions in the neonate with presumed sepsis or pulmonary disease in which either the pulmonary or the systemic circulation depends on the patency of the ductus arteriosus.435 436 437 Definitive diagnosis in these lesions before ductal closure may prevent severe morbidity or death. Infants with a loud murmur, signs of congestive heart failure, cyanosis, or failure to thrive have a high probability of significant heart disease and along with a general examination by a qualified pediatric cardiologist should undergo immediate echocardiographic evaluation under his/her supervision. These evaluations should not be performed in the field.
The common categories of structural congenital cardiovascular disease encountered in the neonate and information provided by echocardiography are summarized as follows:
- Intracardiac shunts: location, morphology and size of defect, direction of flow and gradient across defect, pulmonary/systemic flow profile, ventricular compensation, associated lesions438 439
- Obstructive lesions: location, morphology, pressure gradient, ventricular compensation, associated lesions437 440 441 442 443
- Regurgitant lesions: valve morphology, assessment of severity, atrial/ventricular dilation, ventricular compensation, associated lesions420 444 445 446
- Anomalous venous connections: location and connections of proximal systemic and pulmonary veins, assessment of left-to-right and right-to-left shunts, presence of venous obstruction, and associated lesions424 447 448 449
- Conotruncal abnormalities: position of great arteries, ventriculoarterial connections, spatial and hemodynamic relation of great arteries to coexisting ventricular septal defect, nature of subarterial obstruction, great artery anatomy, associated lesions, ventricular compensation450 451 452 453 454
- Coronary anomalies: origin, size and flow in coronary arteries, presence of abnormal coronary artery/ventricular fistulae, ventricular compensation455 456 457
- Complex lesions: cardiac segmental analysis of situs and connections, size and location of all cardiac chambers, atrioventricular valve morphology and function, subarterial and arterial obstruction, interatrial and interventricular communications, venous and great artery anatomy, ventricular compensation
Cardiopulmonary Disease
The transition from fetal to extrauterine hemodynamics influences
clinical expression of cardiovascular and pulmonary disease in the
neonate. Premature infants may have respiratory failure based on a
combination of processes: lung immaturity, hyaline membrane disease,
persistence of the ductus arteriosus, inflammatory disease, or
congenital heart disease. Echocardiography indicates the patency of the
ductus arteriosus, direction and degree of shunting at the ductal
level, and estimation of pulmonary artery pressure and its
consequences. Echocardiography identifies coexisting ductal-dependent
cardiovascular lesions before pharmacological or surgical closure of a
patent ductus arteriosus is planned.
Neonates with primary pulmonary hypertension (persistent fetal circulation) may present with or without perinatally acquired pulmonary parenchymal disease. Differentiation of this entity from cyanotic heart disease can be accomplished by echocardiography. In addition to excluding structural abnormalities, Doppler echocardiography provides additional information about atrial and ductal shunting, pulmonary artery pressure, and ventricular function. Reevaluation studies are useful for monitoring the efficacy of therapeutic interventions. In patients with severe disease progressing to extracorporeal membrane oxygenation, this information is useful in assessing the contribution of extracorporeal circulation to ventricular output, alteration in myocardial function, and changes in ductus arteriosus flow.432
Arrhythmias
Electrophysiological anomalies may be present in the newborn
period. Arrhythmias may occur as an isolated clinical problem; however,
some neonatal rhythm abnormalities are associated with structural
cardiac or systemic disease. Intracardiac tumors, particularly the
rhabdomyomas of tuberous sclerosis,458 can present
with supraventricular or ventricular tachyarrhythmias. Neonatal
arrhythmia may present as acute-onset congestive heart failure or
findings of nonimmune fetal hydrops. Echocardiography is integrated
into the treatment of these patients to identify the hemodynamic
sequelae of the dysrhythmia and coexisting systemic disease.
Myocardial Disease in the Neonate
Myocardial abnormalities in the neonate are most commonly related
to transplacentally acquired pathogens, metabolic abnormalities,
structural congenital heart disease, maternal systemic disease, or
peripartum injury.459 460 Echocardiography is used to
identify reversible structural anomalies contributing to myocardial
dysfunction, monitor the response of the myocardium to medical
intervention, and document recovery from peripartum injury. Premature
infants receiving steroids for pulmonary disease should undergo
echocardiography at intervals to screen for the appearance of
hypertrophic cardiomyopathy.
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Congenital Cardiovascular Disease in the Infant,
Child, and Adolescent
Cardiovascular disease in the infant, child, and adolescent
includes anomalies of cardiac anatomy, function, morphogenesis, and
rhythm. While these problems often present as an asymptomatic heart
murmur, the cardiac murmurs of this age group are more commonly
functional than pathological. History and physical examination by a
skilled observer are usually sufficient to distinguish functional from
pathological murmurs and are more cost-effective than referral for an
echocardiogram.461 However, in the presence of ambiguous
clinical findings, echocardiography can demonstrate the presence or
absence of abnormalities such as an interatrial septal defect, bicuspid
aortic valve, mildly obstructive subaortic stenosis, MVP, or
functionally occult cardiomyopathy. Such determination clarifies the
need for further evaluation or endocarditis prophylaxis, or both. For
patients with clinical findings of hemodynamically significant heart
disease, anatomic and physiological data provided by reevaluation and
two-dimensional Doppler echocardiography may provide a definitive
diagnosis and allow the most efficient selection of adjuvant diagnostic
procedures or medical/invasive intervention. Referral for cardiac
ultrasound must provide the pediatric cardiologist and the sonographer
with relevant diagnostic data and the clinical objective for the
examination.
Structural Cardiovascular Disease
The categories of structural cardiovascular disease in the infant,
child, or adolescent are identical to those encountered in the neonate
(see previous section). The presence of heart disease is more likely to
be recognized in the older population because of an abnormal clinical
finding. Therefore, echocardiography plays a less important role in
screening for heart disease than it does in the neonatal period. The
more important role for echocardiography in the infant, child, and
adolescent is in fully characterizing a cardiac lesion once an
abnormality is suspected. It also provides essential information
concerning the natural history of the abnormality and responses to
medical and surgical management. Contributing to the successful
management of these children is the early recognition and prevention of
secondary functional changes in the cardiovascular system, and
echocardiography is often the most direct and cost-effective way to
acquire this information.
Echocardiography also provides important information in patients
with systemic connective tissue disorders, eg, Marfan syndrome or
Ehlers-Danlos syndrome. Reevaluation examination of patients with these
disorders identifies acute and chronic changes in great artery size,
semilunar and atrioventricular valve function, and ventricular
compensation.462 463 464 Functional murmurs are commonly
encountered in this pediatric population. The contribution of
echocardiography to the evaluation of an asymptomatic patient with this
finding on routine examination by an experienced clinician is limited.
Such murmurs can usually be diagnosed by an experienced clinician
without the need for echocardiography. Referral of infants, children,
and adolescents with functional murmurs for echocardiographic
examination should be guided by evidence of coexisting congenital or
acquired cardiovascular disease.
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Arrhythmias/Conduction Disturbances
Frequent, sustained, or complex rhythm abnormalities in the
pediatric population may be associated with Ebstein's anomaly of the
tricuspid valve, cardiac tumor, cardiomyopathy, MVP, glycogen storage
disease, or stimulation from migrated central venous catheters. Thus,
exclusion of these lesions by echocardiography is an important
component in evaluation. Mild rhythm disturbances, such as sinus
arrhythmias and low-grade supraventricular ectopic beats or brief and
infrequent runs of supraventricular tachycardia, are rarely associated
with cardiac pathology. Therefore, echocardiography is generally
indicated only when abnormal findings are also present. Occasionally,
echocardiography aids in the characterization of an arrhythmia when
surface ECG findings are ambiguous.
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Acquired Cardiovascular Disease
Acquired cardiovascular disease occurs with systemic disease
processes associated with inflammation, renal disease and related
systemic hypertension, cardiotoxic drug therapy, pulmonary parenchymal
disease, and after heart transplantation. Patients receiving
anthracycline or other cardiotoxic agents should have baseline and
reevaluation follow-up studies. Echocardiographic assessment of
patients with renal disease provides guidance in management of
hemodialysis and hypertensive medications.
Echocardiography provides information for the common categories of acquired pediatric heart disease regarding acute and chronic changes in ventricular size, ventricular wall thickness, ventricular wall motion, ventricular systolic and diastolic function, ventricular wall stress, atrioventricular and semilunar valve anatomy and function, pericardial anatomy, and the presence of intracardiac masses.
The common categories of pediatric acquired heart disease are summarized as follows:
- Kawasaki disease can result in abnormalities in the proximal or distal coronary circulation, myocarditis, pericarditis, and myocardial infarction. Baseline and reevaluations by echocardiography are recommended in all patients with clinical stigmata of this disease to guide management decisions.465 466 467 468 469 Since long-term abnormalities of the coronary arteries have been noted after resolution of initial aneurysms, these patients may require lifelong follow-up studies.470
- Endocarditis is encountered in the pediatric population with and without structural congenital heart disease. The increased use of central venous catheters for hemodynamic monitoring, parenteral alimentation, and chemotherapy expands the population at risk for endocarditis. Echocardiography identifies intracardiac masses and valve regurgitation associated with infectious valvulitis. Echocardiography offers supportive evidence for bacterial or rickettsial endocarditis but does not necessarily confirm or exclude the diagnosis. Children with suspected bacterial and rickettsial diseases associated with myocardial depression should have echocardiographic assessment of ventricular size and function, particularly because the acutely ill presentation of these disorders may mask the contribution of myocardial dysfunction to low cardiac output.
- Rheumatic fever is a persistent cause of acquired pediatric cardiac disease in the United States. Newer diagnostic criteria include echocardiographic assessment of mitral valve function, ventricular function, and pericarditis. Echocardiography is an important component of the diagnostic and sequential evaluation of children with fever, new cardiac murmur, migratory polyarthritis, and chorea.471
- In children, HIV infection acquired during the fetal or newborn period is aggressive with early and prominent myocardial involvement. Therefore, a baseline study and reevaluation follow-up studies should be done as indicated by the appearance of tachycardia, congestive heart failure, and respiratory distress.470 472
- Dilated cardiomyopathy with or without acute-onset congestive heart failure occurs in association with metabolic disorders after viral myopericarditis473 474 or cardiotoxic chemotherapy. Frequently no etiology is identified to account for an occult dilated cardiomyopathy.475 476 Echocardiography identifies pericardial disease and myocardial dysfunction and permits surveillance of ventricular function during acute and convalescent phases of myocarditis. Identification of occult ventricular and atrial mural thrombi allows prompt anticoagulation therapy, possibly reducing further systemic morbidity. Echocardiographic follow-up of patients receiving cardiotoxic chemotherapy identifies at-risk subjects and helps guide subsequent therapy.477 478
- Echocardiography is useful in detecting hypertrophic cardiomyopathy and determining the presence and nature of subaortic and subpulmonary obstruction, mitral insufficiency, and diastolic compliance abnormalities. Echocardiography is useful in screening family members for all types of cardiomyopathy associated with a dominant or recessive pattern of inheritance, eg, isolated noncompaction of the myocardium,479 and in screening patients with multisystem disorders associated with cardiomyopathy, eg, muscular dystrophy and Friedreich's ataxia.480 481 Reevaluation studies measuring septal and ventricular wall thickness as well as systolic and diastolic function are required to monitor the sequelae of hypertrophic or dilated cardiomyopathies in the pediatric population. Hypertrophic cardiomyopathy also occurs in response to systemic hypertension482 secondary to chronic renal disease, the Noonan syndrome, and obliterative arteriopathies and after cardiac transplantation.483 484 Echocardiographic surveillance of LV wall thickness, systolic function, and diastolic function permits appropriate adjustments in medical therapy. Reevaluation studies identify changes in cardiac allograft ventricular function and wall motion in a population at risk for small-vessel coronary artery disease.
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Pulmonary Diseases in Pediatric Acquired
Cardiovascular Disease
Children with upper airway or chronic lung disease may have
clinical or ECG evidence of pulmonary artery hypertension.
Echocardiography provides indirect documentation of pulmonary artery
hypertension and estimation of severity by the presence of RV dilation
and/or hypertrophy, the presence of tricuspid or pulmonic valvular
regurgitation, and by Doppler estimation of RV systolic pressure.
Follow-up studies reflect response to therapy and are useful in guiding
management.
Disease states in older infants and children with diseases that cause
secondary pulmonary hypertension require documentation of pulmonary
hypertension when there are suggestive clinical, ECG, or radiographic
findings. These include severe scoliosis, central hypoventilation,
diaphragmatic hernia, pulmonary hypoplasia, upper airway obstruction,
and familial pulmonary artery hypertension.
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Thrombus/Tumor
Stroke and other manifestations of thromboembolism that
occur in childhood may result from intracardiac thrombus, tumor, or
vegetation. In some groups of patients, long-term indwelling catheters
in the central veins or atria may predispose to thrombus formation or
infection. Because children have a lower incidence of distal vascular
disease as a cause of stroke or loss of pulse, the yield of
echocardiography in finding an intracardiac cause may be somewhat
higher than for adults. Situations in which there is a high suspicion
of intracardiac thrombus include late-onset arrhythmias after Fontan
palliation of congenital heart disease,485 severe dilated
cardiomyopathy or other causes of severely reduced ventricular
function, noncompaction of the myocardium, and patients on
cardiac-assist or extracorporeal cardiopulmonary membrane oxygenation
devices or with reduced systolic function of any cause. In addition,
the presence of aortic thrombus should be sought in neonates with
indwelling aortic catheters and the appearance of hypertension, low
cardiac output, or renal failure.
Patients with longstanding indwelling catheters and evidence for sepsis, cyanosis, or right-heart failure should be screened for the presence of thrombus or vegetation on the catheter. The patient with intracardiac right-to-left shunting and indwelling catheter should be evaluated by echocardiography when there are suggestive symptoms or findings of systemic embolization.
Echocardiographic screening for cardiac tumor is indicated in the
fetus, newborn, or child with clinical evidence or familial history of
tuberous sclerosis. Screening in the second and third trimester of
gestation as well as during infancy and again in childhood is warranted
because this lesion may appear at any of these times. Older children
and adolescents with evidence of peripheral embolization should be
screened for the presence of myxoma.
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Transesophageal Echocardiography
TTE, using high-frequency imaging probes and multiple parasternal,
apical, suprasternal, and subcostal projections offers excellent
resolution of intracardiac and paracardiac structures in the infant and
young child. TEE, however, adds important clinical information
regarding these structures in the older pediatric patient and in
subjects of all ages during or after thoracic instrumentation. Because
the potential for airway compromise and coexistence of complex
gastroesophageal anomalies is increased in smaller patients, the
procedure should only be performed by persons skilled in TEE and
trained in the care of infants and children.
TEE may be used in concert with cardiac catheterization to limit the quantity of radiographic contrast material. This is indicated in the presence of significant pulmonary artery hypertension or in complex cases when an unsafe amount of radiographic contrast material would be required for adequate documentation of the lesion. For neonates requiring urgent balloon atrial septostomy, performance of this procedure under TTE or TEE guidance in the neonatal intensive care unit may be lifesaving.
The placement of intracardiac and intravascular devices can be aided by echocardiographic guidance. Likewise, placement of catheters for radiofrequency ablation of arrhythmogenic pathways can be facilitated by TEE when there are intracardiac abnormalities.
Intraoperative echocardiography has been used to provide timely
information about the success of septal defect closure and valve
palliation.486 487 488 489 490 491 492 493 In some lesions the ability to scan the
heart by TEE or direct transducer placement on the heart surface allows
the patient to undergo surgical repair without previous cardiac
catheterization.
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Fetal Echocardiography
Widespread use of general fetal ultrasound examinations
among women receiving prenatal care has resulted in increased referrals
for specific cardiac analysis. Definition of fetal cardiac structures
is currently possible at 10 to 12 weeks of gestation with the use of
vaginal probes with high-resolution transducers. By 16 to 18 weeks,
accurate segmental analysis of cardiac structure is possible with a
conventional transabdominal approach at the current state of
technology.494 495 In the coming years such studies are
likely to be performed even earlier than 16 to 18 weeks. Doppler
examination provides important information about blood flow across the
cardiac valves, great arteries, ductus arteriosus, and umbilical
arteries.496 A general fetal ultrasound examination
usually includes a four-chamber or inflow view of the fetal
heart.497 This view is sensitive to abnormalities of
the inflow portions of the heart but is insensitive to some septal
defects, outflow lesions, and conotruncal
abnormalities.498 Patients are referred for specific
fetal echo-cardiographic examination because of an abnormality of
structure or rhythm noted on ultrasound examination or because the
patient is in a high-risk group for fetal heart
disease.499 500 501 502 Early recognition of fetal heart disease
allows the opportunity for transplacental therapy, as in the case
of arrhythmias.503 504 505 When a potentially life-threatening
cardiac anomaly is found,506 507 508 the delivery can be
planned at a tertiary care center where supportive measures can be
instituted before severe hypoxia, shock, or acidosis
ensues.509 Education of the parents can be initiated early
so that complex therapeutic choices can be reviewed and informed
consent obtained.510 511 512 If the fetal heart appears
normal, the family may be reassured.
Diagnostic difficulties may arise because of modulation of the anatomic and physiological presentation of certain lesions by the fetal circulation and dramatic changes in the heart and great vessels that may occur throughout gestation. As an example, the severity of pulmonary stenosis cannot be assessed by quantitation of valve gradient because of the variability in RV output and the patency of the ductus arteriosus. The outcome of fetal heart disease is often suggested only after reevaluation studies to determine growth of cardiac chambers and vascular structures and changes in blood flow patterns. The spectrum of congenital cardiac lesions is broader than that seen in neonates and infants because of the presence of nonviable subcategories of disease. A knowledge of prenatal maternal history513 is as necessary as good imaging in providing proper care for these patients. An additional degree of difficulty is imposed by the inability to see the fetus for orientation reference and the inability to examine the fetus for clinical findings that might guide the performance and interpretation of the echocardiogram.
In skilled hands the diagnostic accuracy of fetal echocardiography may
reach the high sensitivity and specificity of echocardiography in the
neonate; however, not all pediatric cardiology centers have specially
trained fetal echocardiographers.514 Such experts may be
pediatric cardiologists, obstetricians, or radiologists with special
training or experience in fetal ultrasound imaging and a comprehensive
knowledge of congenital heart disease, fetal cardiac anatomy and
physiology, and arrhythmias. When specific expertise in fetal
echocardiography does not exist, close collaboration between a
pediatric cardiologist/echocardiographer and a fetal ultrasonographer
may produce similar results once a learning curve has been completed.
The collaboration of a multidisciplinary perinatal team provides
support for diagnostic and therapeutic decisions .
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Staff |
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American College of Cardiology
- David J. Feild, Executive Vice President
- Grace D. Ronan, Assistant Director, Clinical Practice and Guidelines
- Nelle H. Stewart, Document/Guidelines Coordinator, Clinical Practice and Guidelines
- Helene B. Goldstein, MLS, Director, Griffith Resource Library
- Gwen C. Pigman, MLS, Assistant Director, Griffith Resource Library
American Heart Association
- Office of Science and Medicine
- Rodman D. Starke, MD, FACC, Senior Vice President
- Kathryn A. Taubert, PhD, Senior Science Consultant
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Footnotes |
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"ACC/AHA Guidelines for the Clinical Application of Echocardiography" was approved by the American College of Cardiology Board of Trustees in October 1996 and by the American Heart Association Science Advisory and Coordinating Committee in December 1996.
When citing this document, the American College of Cardiology and the American Heart Association request that the following citation format be used: Cheitlin MD, Alpert JS, Armstrong WF, Aurigemma GP, Beller GA, Bierman FZ, Davidson TW, Davis JL, Douglas PS, Gillam LD, Lewis RP, Pearlman AS, Philbrick JT, Shah PM, Williams RG. ACC/AHA guidelines for the clinical application of echocardiography: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Clinical Application of Echocardiography). Circulation. 1997;95:1686-1744.
A single reprint of the full text of "ACC/AHA Guidelines for the Clinical Application of Echocardiography" is available by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Avenue, Dallas, TX 75231-4596. Ask for reprint No. 71-0102. To obtain a reprint of the executive summary and recommendations published in the March 15, 1997, issue of the Journal of the American College of Cardiology, ask for reprint No. 71-0103. To purchase additional reprints: up to 999 copies, call 800-611-6083 (US only) or fax 413-665-2671; 1000 or more copies, call 214-706-1466, fax 214-691-6342, or
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