Exercise capacity: the prognostic variable that doesn't get enough respect.

Clinicians have long been aware that patients capable of high levels of physical exertion have a better prognosis than those with limited exercise capacity. Although the initial clinical encounter usually suffices to gain a qualitative appreciation of functional capacity, more precision can be obtained from formal graded exercise testing. In both asymptomatic subjects and patients with clinical coronary artery disease (CAD), exercise-based measures of functional capacity repeatedly have been shown to provide powerful independent prognostic information.1,2 Yet when decisions are made about the role and value of exercise testing in clinical cardiology, the focus is inevitably on measures believed to reflect the state of the coronary arterial circulation and the potential need for angiography and revascularization. The widespread tendency to ignore exercise capacity in clinical management seems to be a function of a general uncertainty about its therapeutic implications. Stress-induced ischemia may be less important prognostically, but its message seems clear: Fix the plumbing. See p 1554 In symptomatic CAD patients, exercise capacity typically is used to provide the context in which ischemic responses are interpreted.3 Thus, ischemia in the setting of poor exercise capacity means high risk, whereas in the setting of good exercise capacity, ischemia (even when measured with nuclear perfusion techniques) has little prognostic impact.4 In asymptomatic subjects, in whom evidence of ischemia is quite infrequent, the utility of exercise capacity has been more of a puzzle. In the American College of Cardiology/American Heart Association Exercise Testing Guidelines,5 exercise testing for routine screening of asymptomatic men and women was rated a Class III indication (ie, not useful). The use of exercise testing in asymptomatic persons with multiple risk factors as a guide to risk reduction therapy was rated a Class IIb indication (ie, usefulness not well established).6 These recommendations reflect concerns about …