(Circulation. 1997;95:2241-2243.)
© 1997 American Heart Association, Inc.
Articles |
Timing of Valve Replacement in Aortic Stenosis
Moving Closer to Perfection
From the Cardiology Division, Department of Medicine, and the Gazes Cardiac Research Institute, Medical University of South Carolina, and the Ralph H. Johnson Department of Veterans Affairs, Charleston, SC.
Correspondence to Blase A. Carabello, MD, Charles Ezra Daniel Professor of Cardiology, Cardiology Division, Medical University of South Carolina, 171 Ashley Ave, Charleston, SC 29425-2221.
Key Words: • Editorials • valves • aorta • stenosis
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Introduction |
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 Top Introduction Analogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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The current results of aortic valve replacement for acquired aortic stenosis represent a medical triumph. Age-corrected survival after aortic valve replacement is excellent for patients over the age of 65 years and is similar to that of the normal population of that age.1 In the absence of extracardiac co-morbidity and in the absence of coronary artery disease, aortic valve replacement can be performed at a 2% to 3% operative mortality with an 85% age-corrected 10-year survival.1 This excellent outcome can be attributed to a variety of factors including the universal use of intraoperative cardiac protection, the insertion of hemodynamically excellent and durable valve prostheses, and the proper timing of aortic valve replacement.
Currently, timing in most cases is predicated upon the absence or presence of symptoms. In the absence of cardiac symptoms, survival is excellent without surgery.2 3 4 5 Since there is always some risk of operative death and some risk of prosthetic valve–related complications, the risk-benefit ratio does not favor operating on the asymptomatic patient. However, studies that have examined the "natural" history of aortic stenosis in the modern era consistently report a few subjects who progress from the asymptomatic state to the development of symptoms and then to sudden death in a very short period of time.3 4 In two echocardiographic studies of asymptomatic patients in whom aortic stenosis was quantified by Doppler interrogation as at least moderate, 5 of 195 patients with aortic stenosis suffered this rapid and unfortunate progression.3 4 Thus, the guidelines for timing aortic valve replacement are not yet perfect. An obvious question is, "How do we recognize and protect this small at-risk minority of patients with aortic stenosis?" It is clear that prophylactic surgery (surgery before symptoms develop) is not the answer, since the whole population of patients with aortic stenosis would have to be exposed to the risks of surgery and to the complications of a valve prosthesis in order to protect a tiny minority. In fact, in the study by Pellikka et al,4 mortality was slightly higher in the asymptomatic group that received "prophylactic" valve replacement than in patients not operated on until symptoms developed.4
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Analogy to the Timing of Surgery in Aortic Regurgitation |
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TopIntroductionAnalogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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In the past 15 years, the surgical outcome for patients with aortic regurgitation has also improved dramatically. As with aortic stenosis, improved surgical techniques and better valve prostheses are in part responsible for this improvement. However, in my view, a major contribution to improved prognosis is the adoption of the "55 rule" for asymptomatic patients with aortic regurgitation.6 7 If the patient with aortic regurgitation has an echocardiographic left ventricular end-systolic dimension of
55 mm, symptoms are imminent
and long-term survival is reduced. An ejection fraction <55% also
confirms a poor prognosis. Thus, there is a persuasive argument to
operate on patients with aortic regurgitation even if
they are asymptomatic when these thresholds are
approached. |
Where We Are Headed |
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TopIntroductionAnalogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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If similarly prognostic noninvasive parameters could be developed for aortic stenosis, surgery in asymptomatic patients could be contemplated. The study by Otto and colleagues8 presented in this issue provides data that are a step in this direction. Two findings from this study stand out. First, of 123 patients with an initial average mean gradient of 30 mm Hg followed for 21/2 years, there were no sudden cardiac deaths. Second, of those patients who entered the study with a peak aortic jet velocity >4 m/s, only 21% were alive and free of valve replacement after 2 years of follow-up.
In light of Otto's study, should we now recommend
prophylactic aortic valve replacement for
asymptomatic patients with aortic stenosis whose
peak outflow velocity exceeds 4 m/s? The argument in support of this
position would be that since such patients are likely to become
symptomatic within the next 2 years anyway, why not proceed
with surgery to avoid the potential risks of further delay, which
include unexpected sudden death? The answer to this rhetorical question
is yes and no. If every patient could receive a pulmonary
autograft (transfer of the native pulmonary valve into aortic
position, ie, the Ross procedure) or a durable homograft and the
operative risk was 
1.0%, then the answer would be yes; early surgery
in asymptomatic patients predicted to soon become
symptomatic (jet velocity >4.0 m/s) would be justified
because the complications of prostheses could be avoided at low
operative risk. Unfortunately, the Ross procedure is difficult for some
to perform and is not universally practiced, and the durability of
homografts is not known with certainty. Furthermore, the current study
was not designed to answer questions about reducing mortality, so we
cannot know whether the prophylactic approach would save
lives. Thus, for the most part the answer is no, we are not yet ready
for "prophylactic" surgery. Nonetheless, the current
data are provocative and point to a time in the future when
such surgery might be advisable.
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The Dreaded Stress Test |
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TopIntroductionAnalogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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Other important information regarding the timing of surgery comes from Otto et al8 about exercise testing in patients with aortic stenosis. While it was of interest that the patients with an end point (surgery or death) had a smaller increase in valve area during exercise, this factor was not useful as a multivariate predictor of outcome. More important in my opinion is the fact that a large number of patients with relatively severe but asymptomatic aortic stenosis underwent exercise testing without incident. While a large experience in Europe is similar to that of the current study,9 the general practice in the United States has been not to exercise patients with aortic stenosis for fear that such patients were at high risk for complications during the test.10 While indeed, it is unwise to stress the patient with aortic stenosis who has any of the classic aortic stenosis symptoms (angina, syncope, or heart failure), exercise testing in asymptomatic patients or patients with vague symptoms appears to be safe and useful. Safety is probably predicated in part on the fact that physicians testing such patients avoid the extremes of exercise tolerance in a prudent effort to avoid complications. During exercise testing, the unexpected precipitation of typical symptoms at a low workload support prompt surgery, in my view. On the other hand, it would be difficult to recommend aortic valve replacement in an asymptomatic patient who achieved greater than age-predicted exercise tolerance, even if aortic jet velocity exceeded 4 m/s.
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What Is `Critical' Aortic Stenosis, and How Does Valve Area Help Time Surgery? |
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TopIntroductionAnalogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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My definition of critical aortic stenosis is that valve area small enough to cause the symptoms of aortic stenosis that often presage sudden death: a "critical" situation indicating aortic valve replacement. The current study amplifies the concept that no discrete value for critical valve area exists, but varies from patient to patient. Different cardiac output demands from the valves of different patients, together with problems inherent in the calculation of valve area, cause patients to become symptomatic in a range of valve areas between 0.6 and 0.8 cm2.8 11 12 13 14 Areas of 0.8 to 1.0 cm2 constitute a gray zone into which some cases of critical stenosis also fall. These are usually cases in which the patient is large or in which the cardiac output is high.
For patients with valve areas >1.0 cm2, another source for
symptoms should be sought, especially if the mean transvalvular
gradient is 30 mm Hg. For the patient with clear symptoms whose
valve area is <0.8 cm2 and possibly <1.0 cm2,
aortic valve replacement is indicated.
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Current Timing of Aortic Valve Replacement for Aortic Stenosis |
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TopIntroductionAnalogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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The data from the current study taken with previous investigations suggest a reasonable plan for the timing of aortic valve replacement aortic stenosis as follows.
Asymptomatic Patients
Asymptomatic patients with aortic stenosis
whose initial peak jet velocity is <3 m/s should be followed medically
at yearly intervals with written instructions in layman's terms, which
indicate that upon the onset of angina, syncope, or the symptoms of
heart failure, the patient should alert his or her physician
immediately. Echocardiography should probably be
repeated during the yearly visit to assess the rate of progression of
the disease, a potentially useful datum in following the patient
according to the present study. However, a strong recommendation
regarding the need for additional echocardiograms cannot be made
conclusively since the exact influence of this information on
management is not clear.
For asymptomatic patients with a jet velocity >3 m/s,
follow-up at 6-month intervals, again with written instructions
regarding the onset of symptoms, is recommended. Repeat
echocardiography in patients with an initial jet of
velocity of 4.0 m/s is probably unnecessary until symptoms develop
since such patients have already been identified as at high risk for
rapid progression to aortic valve replacement.
Patients With Vague Symptoms
Patients with symptoms that cannot be directly attributed to
aortic stenosis should have an initial workup that includes a
history, physical examination, and Doppler interrogation of the
aortic valve. If the peak jet velocity exceeds 3.0 m/s, an exercise
test should be performed to assess exercise tolerance and to
investigate objectively for the presence of symptoms more typical of
aortic stenosis. If these symptoms are present, or if
exercise tolerance is subnormal, further workup for aortic valve
replacement is recommended. A cardiac catheterization
to obtain additional data in this murky situation is warranted in my
opinion.
If exercise tolerance is normal and exercise does not elicit symptoms, continued medical follow-up is indicated. It should be noted that ST-segment shifts during exercise do not constitute a positive test in this group of patients with left ventricular hypertrophy.
Symptomatic Patients
For symptomatic patients whose symptoms are
unquestionably attributable to severe aortic stenosis, prompt
surgery is indicated. As Otto and colleagues point out, there is not an
exact definition of what constitutes a critical valve area. Patients
who are symptomatic but have a valve area >1.0
cm2 probably have symptoms based on another
extravalvular problem. Patients with a valve area of <0.8
cm2 who have typical symptoms almost certainly have them on
the basis of aortic valve stenosis, and surgery is indicated.
Patients with areas ranging from 0.8 to 1.0 cm2 are in the
gray zone in which a variety of clinical factors must be taken into
account. In such patients, additional hemodynamic data
obtained during cardiac catheterization are likely to
be helpful in establishing a course of action.
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Footnotes |
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The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association.
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References |
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TopIntroductionAnalogy to the Timing...Where We Are HeadedThe Dreaded Stress TestWhat Is `Critical' Aortic...Current Timing of Aortic...References |
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