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(Circulation. 1998;97:1651-1653.)
© 1998 American Heart Association, Inc.

Correspondence

Prospective Study of Asymptomatic Aortic Stenosis

John B. Barlow, Hon DSc (Med), MD, FRCP; ; David Jankelow, FCP(SA)

Division of Cardiology, Johannesburg Hospital, Parktown, South Africa

To the Editor:

Relevant points were raised in the study of Otto et al¹ on 123 adults with asymptomatic aortic stenosis and in the editorial by Caraballo.² We wish to endorse the crucial but neglected role of exercise testing in the management of patients with "asymptomatic" hemodynamically significant aortic stenosis. Stress testing is particularly pertinent before a decision is made to postpone surgical treatment. It is not only in the United States, as stated by Carabello,² but also in the United Kingdom and in our own environment that there is some reluctance "to exercise patients with aortic stenosis for fear that such patients were at high risk for complications during the test." That philosophy is illogical when it is realized that such patients will inevitably exert themselves during their everyday lives, such as when late for an appointment or running for a bus. It is surely much safer to risk "complications" during or after a supervised treadmill test when adverse events can immediately be managed by experts and with appropriate facilities available. Several years ago we were referred an elderly colleague with tight calcific aortic stenosis who insisted that he regularly played 18 holes of golf without a golf cart. Exercise was stopped early on the treadmill because of depressed ST segments. Three minutes after effort, the heart rate decreased dramatically, the ST segments were depressed 6 mm, and the blood pressure was unrecordable. Elevation of his legs, administration of intravenous isoproterenol, and other measures reversed his parlous state. What would have happened on the golf course? This is anecdotal, but anecdotes remain instructive.

In the study of Otto et al,¹ exercise testing was stopped in 60% of the "asymptomatic" patients because of "fatigue or shortness of breath." The inference is that in at least some of these patients, the stress test should be judged to be abnormal. In a much smaller number, the definite abnormality of a drop in systolic pressure was detected. Exercise tests should be assessed not only for ST-T changes but also so-called "exercise variables."³ Carabello² stated that "ST-segment shifts during exercise do not constitute a positive test... ," but "positive" for what? As further stated by Carabello,² it is well known that many patients with tight aortic stenosis, left ventricular hypertrophy, and ST-T changes caused or exaggerated by exercise and who may or may not complain of angina have anatomically normal coronary arteries. This does not exclude the probability, however, that myocardial ischemia, whatever the mechanism for the inadequate coronary flow, is reflected in some instances by the ST-segment shifts.⁴

Although any prognostic implication of these ST-T changes has not yet been clarified, we submit that it is their absence that has crucial significance in at least one important context. Children or young adults with tight aortic stenosis, invariably congenital (but occasionally rheumatic in our practice, where rheumatic valve disease remains highly prevalent⁵ ), may be nearly asymptomatic, but there is always the consideration of sudden death.⁴ There is currently no operation, including the much-vaunted Ross procedure,^{2 4 6} that will last for 30 years, and surgery should clearly be postponed provided the patient's life is not jeopardized. Such patients should be subjected to frequent maximal stress testing and, if ST segments remain normal or have minimal changes, there is to our knowledge no case documented in which sudden death occurred. The findings of Kveselis et al⁷ are in accord with this philosophy.

Provided frequent exercise testing is undertaken, we agree with the overall conclusions of Otto et al¹ and Carabello² that surgical management may be delayed justifiably in a number of patients with asymptomatic, or mildly symptomatic, aortic stenosis. We have several concerns with that policy, however. First, unduly rapid progression^{1 8} of the aortic stenosis must be carefully sought in all patients.⁴ Second, any one of us may suffer a vasovagal syncopal episode, and it is possible that this would be fatal in a patient with concomitant aortic stenosis. The presenting symptom in several of our patients with tight aortic stenosis was a near-fatal vasovagal episode. We can only speculate on how many elderly, previously asymptomatic patients with aortic stenosis die that way. Third, the onset of atrial fibrillation, albeit uncommon, often causes acute left ventricular decompensation because of the tachycardia and loss of the atrial boost.⁴

Somewhat contrary to the conservative approach of Otto et al,¹ we currently have an aggressive policy regarding "prophylactic" aortic valve surgery⁹ in patients with mild to moderate aortic stenosis undergoing coronary artery bypass surgery. Aortic valve replacement undertaken after coronary artery bypass surgery, especially when an internal mammary graft had been inserted, probably carries a twofold increase in operative mortality rates.^{4 10}

Last, Carabello² correctly concluded that "prompt surgery is indicated" in symptomatic patients with severe aortic stenosis. We wish he had added "irrespective of the extent of left ventricular dysfunction" because, unlike some cases of aortic regurgitation,^{2 4} the postoperative result will always reflect some, and usually considerable, improvement.⁴

References

1. Otto CM, Burwash IG, Legget ME, Munt BI, Fujioka M, Healy NL, Kraft CD, Miyake-Hull CY, Schwaegler RG. Prospective study of asymptomatic valvular aortic stenosis. Circulation. 1997;95:2262–2270.[Abstract/Free Full Text]
   
2. Carabello BA. Timing of valve replacement in aortic stenosis. Circulation. 1997;95:2241–2243.[Free Full Text]
   
3. Barlow JB. The `false positive' exercise electrocardiogram: value of time course patterns in assessment of depressed ST segments and inverted T waves. Am Heart J. 1985;110:1328–1336.[Medline] [Order article via Infotrieve]
   
4. Barlow JB. Cardiological aspects of aortic valve surgery: Who? When? What? Isr J Med Sci. 1996;32:821–831.[Medline] [Order article via Infotrieve]
   
5. Marcus RH, Sareli P, Pocock WA, Barlow JB. The spectrum of severe rheumatic mitral valve disease in a developing country. Ann Intern Med. 1994;120:177–183.[Abstract/Free Full Text]
   
6. Joyce F, Tingleff J, Pettersson G. Expanding indications for the Ross operation. J Heart Valve Dis. 1995;4:352–363.[Medline] [Order article via Infotrieve]
   
7. Kveselis DA, Rocchini AP, Rosenthal A, Crowley DC, Dick M, Snider AR, Moorehead C. Hemodynamic determinants of exercise-induced ST-segment depression in children with valvar aortic stenosis. Am J Cardiol. 1985;55:1133–1139.[Medline] [Order article via Infotrieve]
   
8. Wagner S, Selzer A. Patterns of progression of aortic stenosis: a longitudinal hemodynamic study. Circulation. 1982;65:709–712.[Free Full Text]
   
9. Antunes MJ. Coronary artery bypass surgery and minor aortic stenosis: to replace or not to replace? An alternative: to repair. J Heart Valve Dis. 1994;3:235.[Medline] [Order article via Infotrieve]
   
10. Fiore AC, Swartz MT, Naunheim KS, Moroney DA, Canvasser DA, McBride LR, Peigh PS, Kaiser GC, Willman VL. Management of asymptomatic mild aortic stenosis during coronary artery operations. Ann Thorac Surg. 1996;61:1693–1698.[Abstract/Free Full Text]
    

Response

Blase A. Carabello, MD

Division of Cardiology, Medical University of South Carolina, Charleston, SC

I wish to thank Drs Barlow and Jankelow for their comments regarding my Editorial on "The Timing of Aortic Valve Surgery for Aortic Stenosis."¹ They point out that it is far more logical to exercise the patient with aortic stenosis under a physician's supervision than to assume that a patient's normal daily activities, which may involve considerable exertion, can be performed without risk. I entirely concur.

The issue of the meaning of S-T segment depression in aortic stenosis remains problematic. Many patients with left ventricular hypertrophy have S-T segment depression ("strain") at rest. This occurs at a time when left ventricular function is normal and when coronary vasodilator reserve is not exhausted, suggesting that such depression does not indicate ischemia. Exactly what S-T depression means in aortic stenosis when it only occurs with exercise is also unresolved. While I concur with their assertion that the absence of S-T segment depression is reassuring, it is unclear to me that a totally asymptomatic patient who previously had no S-T segment depression during exercise but now has S-T depression on a repeat test should undergo valve replacement.

I certainly concur and have long espoused that patients with left ventricular dysfunction caused by aortic stenosis normally derive great benefit from surgery.² However, I would not agree with Drs Barlow and Jankelow that all patients should undergo surgery irrespective of the degree of left ventricular dysfunction. I believe that there remains a small group of patients with aortic stenosis with such severe left ventricular dysfunction manifested by very small transvalvular gradients, low cardiac output, and severely depressed ejection fraction who do not benefit from surgery.

References

1. Carabello BA. Timing of valve replacement in aortic stenosis. Circulation. 1997;95:2241–2243.
   
2. Carabello BA, Green LH, Grossman W, Cohn LH, Koster JK, Collins JJ. Hemodynamic determinants of prognosis of aortic valve replacement in critical aortic stenosis and advanced congestive heart failure. Circulation. 1980;62:42–48.[Free Full Text]
   

Response

Catherine M. Otto, MD

Division of Cardiology, University of Washington, Seattle, Wash

Drs Barlow and Jankelow raise several interesting points, specifically the potential prognostic implications of ST-wave segment changes, the role of exercise testing in adults with asymptomatic aortic stenosis, and the optimal timing of surgery in patients with mild to moderate aortic stenosis undergoing coronary artery bypass grafting. In our prospective study of 123 adults with asymptomatic valvular aortic stenosis,^R1 the presence and severity of ST-segment depression during exercise testing did not correlate with clinical outcome, the presence or absence of coronary artery disease, or the severity of aortic stenosis. Even patients with mild aortic stenosis often had significant ST depression with exercise. However, the cause of ST depression in adults with only mild to moderate aortic stenosis remains unclear, and I share the concern of Drs Barlow and Jankelow that these abnormalities may represent subclinical myocardial ischemia.

The role of exercise testing also remains controversial. Although the exercise changes in cardiac output, stroke volume, systolic blood pressure, and valve area were all univariate predictors of clinical outcome in this patient population, the only multivariate predictors of outcome were aortic stenosis severity, the rate of change in aortic stenosis severity, and the patient's functional status. In my view, because exercise testing does not add additional information regarding prognosis, it is difficult to justify routine exercise testing in adults with asymptomatic aortic stenosis. Also, it should be noted that although exercise testing can be performed safely in asymptomatic patients when monitored closely, we were careful to review possible symptoms with each patient immediately before the test and deferred exercise testing if any symptoms were present. Clinicians should be aware that the exercise test should be stopped promptly if blood pressure fails to rise appropriately because exertional hypotension may lead to serious complications, even with "asymptomatic" aortic stenosis.

The clinical decision regarding the optimal timing of surgery in adults with valvular aortic stenosis must consider the risks of surgery and a prosthetic valve as well as the natural history of the disease. It should be noted that there were no sudden deaths in our population, and cardiac deaths only occurred in patients with concurrent coronary disease and left ventricular dysfunction or those who refused aortic valve replacement. Thus we continue to defer valve replacement for aortic stenosis in adults until symptoms are present. However, it must be emphasized that a careful and detailed history is needed to elicit symptoms in adult patients. Given the gradual progression of the disease, many patients adjust their lifestyle as the disease progresses and may deny symptoms even when functional status is impaired. A careful discussion of the level of physical activity, comparison to prior levels of physical activity, and discussions with family members often are needed for recognition of the early symptoms of aortic stenosis. Clearly, in patients with severe aortic stenosis and decreased exercise tolerance, surgical intervention should be performed promptly rather than waiting for more severe symptoms.

The issue of aortic valve replacement in patients with mild to moderate aortic stenosis was not directly addressed in our study. I hope that the data on rate of progression will be helpful for physicians and surgeons making this decision in each individual patient.

References

1. Otto CM, Burwash IG, Legget ME, Munt BI, Fujioka M, Healy NL, Kraft CD, Miyake-Hull CY, Schwaegler RG. Prospective study of asymptomatic valvular aortic stenosis: clinical, echocardiographic, and exercise predictors of outcome. Circulation. 1997;95:2262–2270.
   

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