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Exercise testing, symptoms, and clinical outcome in aortic stenosis
  1. G P McCANN,
  2. D F MUIR,
  1. Cardiovascular & Exercise Medicine
  2. Department of Medicine & Therapeutics
  3. University of Glasgow, Gardiner Institute
  4. Church Street, Glasgow G11 6NT, UK
  1. Dr McCann

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Editor,—We read the recent editorials on aortic stenosis with interest.1 ,2 Otto rightly highlights the importance of classifying patients with aortic stenosis into those at risk of future clinical events. Earlier studies on the natural history of aortic stenosis have shown that patients with symptomatic aortic stenosis have a very poor prognosis.3 The difficulty arises in classifying patients with asymptomatic aortic stenosis as they are generally considered to be at low risk of future events, even in the presence of severe disease. Otto has suggested defining severe aortic stenosis as a peak jet velocity > 4 m/s as “about 80% of asymptomatic patients with a jet velocity > 4 m/s will develop symptoms requiring valve replacement within two years”.1This statement is not strictly correct. Although almost 80% of these patients did indeed have aortic valve replacement carried out within two years, the most common reason for valve replacement was reduced exercise tolerance.3 Having reduced exercise capacity does not mean patients are symptomatic per se and, although it is a fine point, it is of critical importance. We do not know whether reduced exercise capacity in aortic stenosis is an independent predictor of outcome, and Otto's study did not address this question. In a previous study on asymptomatic aortic stenosis it was deemed unethical to withhold exercise testing results from the primary care physicians of the patients concerned, despite the fact there is no evidence in adults to support reduced exercise capacity as a predictor of clinical outcome. In Otto et al's study, of 48 patients undergoing aortic valve replacement, 18 had reduced exercise time stated as the primary reason for surgery.4 This proportion is even higher when patients with severe asymptomatic aortic stenosis and those having incidental valve replacement at the time of coronary artery bypass surgery are excluded. These data clearly show that the primary care physicians were influenced by the results of the exercise tolerance testing and may invalidate Otto's use of a jet velocity of 4 m/s as a predictor of clinical outcome.

Chambers stated that “if chest tightness develops, it is reasonable to prepare for aortic valve replacement”.2 We do not agree that angina confers additional prognostic information compared to other symptoms. In Ross and Braunwald's classic study on aortic stenosis, angina was shown to have a relatively good prognosis compared to symptoms of breathlessness, heart failure, and syncope.3 It is also difficult to distinguish whether chest pain is a result of severe aortic stenosis or underlying coronary artery disease, as approximately 50% of aortic stenosis patients requiring valve replacement will have significant obstructive coronary artery disease.3

We do agree that exercise testing in aortic stenosis confers additional valuable information regarding patients' functional status; however, whether it confers added prognostic significance is not known. Prospective blinded studies on the results of exercise tolerance testing are required before surgery is recommended on this basis in addition to currently accepted echocardiographic and symptomatic variables.