(Circulation. 1995;91:2683-2686.)
© 1995 American Heart Association, Inc.
Articles |
Key Words: electrocardiography arrhythmias myocardial infarction AHA Medical/Scientific Statements
| Introduction |
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This recommendation is one in a series developed to assist in the assessment of physician competence on a procedure-specific basis. The minimal education, training, experience, and cognitive skills necessary for proper interpretation of electrocardiography are specified; whenever possible, these are based on published data linking these factors with competence in certain procedures and, in the absence of such data, on consensus of expert opinion. They are applicable to any practice setting and can accommodate a variety of pathways that physicians might take to attain competence in the performance of specific procedures (see also Guide to the use of ACP statements on clinical competence. Ann Intern Med. 1987;107:588-589.)
| Overview of the Procedure |
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The procedure is safe, there being essentially no risk to the patient; it is simple and reproducible; the record lends itself to serial studies; and the relative cost is minimal. The electrocardiogram (ECG) has the following utilities: It may serve as an independent marker of myocardial disease; it may reflect anatomic, electrophysiologic, metabolic, and hemodynamic alterations; it provides information that is often essential for the proper diagnosis of and therapy for a variety of cardiac disorders; and it is without equal as a method for the diagnosis of arrhythmias. Electrocardiography is the procedure of first choice in patients presenting with chest pain, dizziness, or syncope, symptoms that may be predictive of one or both of the two leading and potentially catastrophic cardiovascular disorderssudden death or myocardial infarction. Electrocardiographic abnormalities also may be the first indicators of life-threatening side effects of drugs and of severe metabolic or electrolyte disturbance and occasionally the only sign of myocardial disease, such as "asymptomatic" myocardial infarction in the aged.1
Appropriate and accurate use of the ECG requires that its sensitivity and specificity be understood and considered in the interpretation of the recording. This is somewhat more complex for the ECG than for many other laboratory tests because the ECG is composed of a number of waveforms, each with its own sensitivity and specificity, and each influenced differently by a variety of pathologic and pathophysiologic factors.
When considering the sensitivity and specificity of the ECG, it is important to recognize that the ECG is a record of electrical activity. Consequently, diagnoses of structural (ie, myocardial infarction, hypertrophy) or pathophysiologic (ie, electrolyte disturbance, effect of drugs) changes are made by inference and are therefore subject to error. The data that allow for a diagnosis by inference were derived from extensive studies correlating the ECG with a variety of clinical pathologic and experimental states.
It is also important to recognize that the same ECG pattern may be recorded with different structural and pathophysiologic states. This explains the frequent low specificity for etiology and anatomy. For example, although ST segment and T wave changes are the most common and most sensitive ECG abnormalities, these changes are at the same time the least specific.2 3 Similarly, different etiologic factors and structural abnormalities may result in an identical form of bundle branch block.
It is obvious from the foregoing that the sensitivity and specificity of the ECG depends to a large extent on the clinical question asked. Although the sensitivity and specificity of the ECG for myocardial disorders vary considerably, depending on the cause, size, and location of the pathologic process, the sensitivity and specificity for arrhythmias are consistently high. The ECG is the only practical method for recording and analyzing abnormalities of cardiac rhythm and conduction.
| Justification for Recommendations |
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Recommendations on maintenance of competence are based on the expert opinion of the ACP/ACC/AHA Task Force on Cardiology of the American College of Physicians' Clinical Privileges Project.
| Indications, Contraindications, and Complications |
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1. For the diagnosis of overt or suspected cardiovascular disease. Follow-up recordings are indicated when there is a change in clinical status.
2. For assessing the results of therapy.
3. In subjects at risk of heart disease, usually >40 years old without evidence of cardiovascular disease but with two or more of the following risk factors: hypercholesterolemia, diabetes, obesity, smoking, or positive family history. In this group frequent follow-up recordings are usually not indicated unless signs or symptoms of heart disease appear.
4. In selected subjects with fewer risk factors whose occupations magnify the consequences of a heart attack or arrhythmia, for example, commercial airline pilots or bus drivers.
5. Before surgical intervention as an aid in the diagnosis and management of preoperative conditions or subsequent postoperative complications. However, it should be emphasized that definitive data regarding the utility of electrocardiography as a routine baseline preoperative procedure are not available.6
6. For assessing cardiac effects of systemic diseases or conditions, such as renal failure, diabetic acidosis and hypothermia, electrolyte abnormalities, and potential cardiotoxic effects of drugs.
Electrocardiography is not cost-effective as a screening procedure for cardiovascular disease or as a baseline study in asymptomatic healthy subjects without symptoms or signs of heart disease, hypertension, or other risk factors for development of heart disease.7 8 9 10 A statement of the indications for electrocardiography was published by the American College of Cardiology and the American Heart Association11 in March 1992.
Although there are no complications resulting from the technique itself, inappropriate interpretation; lack of appreciation of the importance of sensitivity, specificity and predictive value; and failure to correlate the ECG findings with the overall clinical picture may result in serious iatrogenic heart disease. For example, an abnormal T wave is often equated with "ischemia," when in fact the specificity of an abnormal T wave for any one cause (ie, ischemia) is low.2 3 Furthermore, moderate T wave inversion predicts an annual mortality rate of 21% when associated with a history of heart disease, compared with only 3% in the absence of heart disease.12 Thus, a T wave abnormality is of clinical value only when interpreted in light of the total clinical picture and other laboratory results.
| Computer Interpretation of the ECG |
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| Minimal Training Necessary for Competence |
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There are no studies that define the minimal number of ECGs that must be read during the training program to attain competence; however, some survey data are available. The American College of Physicians (ACP) surveys of internal medicine residency program directors, general internists, and cardiologists asked respondents to estimate the number of procedures needed to attain competence. The median number recommended by both program directors and general internists was 100; the median number recommended by cardiologists was 750.13 The recommendation of the 17th Bethesda Conference is that cardiology fellows read 3500 ECGs.4 This task force recommends the interpretation and review of 800 procedures within a 3-year training period under the supervision of an experienced faculty. The ECGs should reflect a wide variety of clinical situations and ECG abnormalities (Appendix).
Although many physicians acquire the cognitive skills needed for proper interpretation of the ECG during a fellowship or a residency program, completion of a fellowship or residency does not guarantee competence. Some training programs do not include structured teaching of electrocardiography. The requirement by the American Board of Internal Medicine Subspecialty Board on Cardiovascular Disease that the candidate successfully pass the ECG component of the examination before being certified implies that those who successfully pass the examination are competent in ECG interpretation.
On occasion, a physician may become competent in the interpretation of ECGs by attending well-designed courses coupled with studies of unknown recordings available in standard texts and by interpreting large numbers of recordings under the supervision of a physician knowledgeable in electrocardiography. Simply attending courses that offer little opportunity for testing individual interpretation of the ECG will not result in competence.
It is evident that although formal teaching of electrocardiography as a part of a fellowship in cardiology or an internal medicine residency is the best approach to becoming competent in reading ECGs, competence can occasionally be attained by routes other than those followed during a residency or fellowship. For this reason, applicants for privileges to read ECGs may have to be evaluated on the basis of their actual cognitive knowledge rather than on the basis of the structure of the training. When the competence of a physician requesting privileges is not clear, monitoring the candidate's interpretations or administration of a test may be appropriate.
| Maintenance of Competence |
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The American College of Cardiology has developed and field-tested a self-assessment program in electrocardiography that is available through the College's office in Bethesda, Md.
| Footnotes |
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Requests for reprints should be sent to the Office of Scientific Affairs, American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231-4596.
1 The 17th Bethesda Conference was recently updated and published as the
first Core Cardiology Training Symposium, which includes Task Force 2:
Electrocardiography, Ambulatory Electrocardiography, and Exercise Testing
(J Am Coll Cardiol. 1994;25:1-34). ![]()
Electrocardiographic Items
Technique
Proper electrode placement
Correct standardization
Proper frequency response
Proper paper speed
Effect of age, weight, and body build
Muscle tremor and other artifacts
Normal electrocardiogram (ECG)
QRS axis, rotation, position
Left-axis deviation (<-30°)
Right-axis deviation (>+100°)
Electrical alternans
Clockwise, counterclockwise rotation
Vertical, horizontal, intermediate position
Sinus node rhythm
Normal
Sinus arrhythmia
Sinus bradycardia
Sinus tachycardia
Sinus pause or arrest
Sinoatrial exit block
Atrial rhythm
Atrial premature complexes
Blocked
Chaotic atrial rhythm
Atrial tachycardia
Atrial tachycardia with atrioventricular (AV) block
Atrial flutter
Atrial fibrillation
Any of the above with aberration
Junctional rhythm
Junctional rhythm (passive)
AV junctional premature complex
AV junctional escape complex or rhythms
Junctional parasystole
AV nonparoxysmal junctional tachycardia
AV node reciprocating tachycardia (reentrant)
Junctional tachycardia with block
AV reciprocating tachycardia (Wolff-Parkinson-White syndrome)
Any of the above with aberration
Supraventricular tachycardia (not otherwise identified)
Wide QRS tachycardia
Supraventricular with aberration
Ventricular
Ventricular rhythm
Ventricular premature complexes
Uniform, with fixed coupling, single or couplets
Multifocal, multiform
R or T wave phenomenon
Interpolated
Ventricular bigeminy
Ventricular parasystole
Ventricular tachycardia
Bidirectional
Accelerated idioventricular rhythm
Ventricular escape complex or rhythm
Ventricular flutter
Ventricular fibrillation
Torsade de pointes
Reciprocal (echo) complexes
Fusion complexes
Capture complexes
AV conduction
AV block
First degree
Second degree
Type I (Wenckebach)
Type II (Mobitz)
High degree
Complete
Paroxysmal
Ventriculoatrial conduction
AV dissociation
Hypertrophy, enlargement
Right atrial enlargement
Left atrial enlargement
Biatrial enlargement
Left ventricular hypertrophy
Voltage only
Voltage and ST-T wave changes
Right ventricular hypertrophy
Combined ventricular hypertrophy (biventricular)
Intraventricular conduction disturbances
Right bundle branch block
Incomplete
Complete
Rate related
Left anterior fascicular block
Left posterior fascicular block
Left bundle branch block
Incomplete
Complete
Rate related
Nonspecific interventricular block
Peri-infarction block
Pre-excitation (Wolff-Parkinson-White syndrome)
Myocardial infarction
Septal
Anteroseptal
Anterior
Lateral
High lateral
Extensive anterior
Inferior
Posterior
Right ventricular
Non-Q wave infarction
Acute injury and/or infarction
Old
Age undetermined
Probable ventricular aneurysm
Atrial infarction
ST, T, QT, U wave changes
Normal variant
Early repolarization
Juvenile T waves
Nonspecific ST and/or T wave changes
ST and/or T wave changes
Suggestive of myocardial ischemia
Suggestive of acute pericarditis
Suggestive of an acute process
Prolonged QT interval
Short QT wave
Prominent U waves
Negative U waves
Pacemaker
Normal function
Abnormal function
ECG patterns suggestive of clinical diagnosis
Hypertrophic cardiomyopathy
Dextrocardia
Long QT syndrome
Mitral stenosis
Cerebrovascular accident
Chronic lung disease
Pericarditis, acute
Pericardial tamponade
Pulmonary embolus
Hyperthermia
Hypothermia
Hypercalcemia
Hypocalcemia
Hyperkalemia
Hypokalemia
Antiarrhythmic drugs
Digitalis effect
| References |
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2. Wilson FN, Finch R. The effect of drinking iced water upon the form of T deflection of the electrocardiogram. Heart. 1923;10:275-278.
3.
Friedberg CK, Zager A. `Nonspecific' ST and T
wave changes. Circulation. 1961;23:655-661.
4. Schlant RC, Adolph RJ, Beller GA, et al. 17th Bethesda Conference: adult cardiology training. J Am Coll Cardiol. 1986;7:1195-1218.
5. Abildskov JA, Dreifus LS, Ariet M, et al. 10th Bethesda Conference: optimal electrocardiography. Am J Cardiol. 1978;41:111-191.
6. Goldberger AL, O'Konski M. Utility of the routine electrocardiogram before surgery and on general hospital admission. Ann Intern Med. 1986;105:552-557.
7. Sox HC Jr, Garber AM, Littenberg B. The resting electrocardiogram as a screening test. Ann Intern Med. 1989;111:489-502.
8. Rubenstein LZ, Greenfield S. The baseline ECG in the evaluation of acute cardiac complaints. JAMA. 1980;24:2536-2539.
9. Moorman JR, Hlatky MA, Eddy DM, Wagner GS. The yield of the routine admission electrocardiogram: a study in a general medical service. Ann Intern Med. 1985;103:590-595.
10. Hoffman JR, Igarashi E. Influence of electrocardiographic findings on admission decisions in patients with acute chest pain. Am J Med. 1985;79:699-707. [Medline] [Order article via Infotrieve]
11. Schlant RC, Adolph RJ, DiMarco JP, et al. ACC/AHA Task Force Report: guidelines for electrocardiography. J Am Coll Cardiol. 1992;19:473-481. [Medline] [Order article via Infotrieve]
12.
Rose G, Baxter PJ, Reid DD, McCartney P.
Prevalence and prognosis of electrocardiographic findings in
middle aged men. Br Heart J. 1978;40:636-643.
13. Wigton RS, Blank L, Nicolas J, Tape T. Procedural skills training in internal medicine residencies. Ann Intern Med. 1989;111:932-938.
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