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Is ventilatory classification preferable to peak oxygen consumption for risk stratification in heart failure?

Since the 1980s, cardiopulmonary exercise testing has been applied to patients with congestive heart failure (CHF) to objectively assess exercise capacity, to risk stratify patients, and to assess the response to therapeutic interventions.1 Subsequently, peak oxygen consumption (Vo2) was reported to be a reliable prognostic index and to be particularly useful for the timing of cardiac transplantation in patients with advanced CHF caused by left ventricular systolic dysfunction.2 As peak Vo2 is derived from the Fick equation and as most patients achieve comparable arterial-venous oxygen differences when they give maximal effort, peak Vo2 has provided a noninvasive marker for peak cardiac output response and thus cardiac reserve. However, peak Vo2 is affected not only by the cardiac output response to exercise as observed in healthy subjects but also by limited skeletal muscle mass and perfusion in patients with advanced CHF. Thus the usefulness of peak Vo2 to predict prognosis in patients with CHF also results from an objective quantification of the derangements that the failing heart causes in the periphery. Not unexpectedly, CHF patients with severe skeletal muscle wasting and low peak Vo2 have a worse prognosis than patients with little or no muscle wasting and moderately reduced peak Vo2. Numerous studies before and after the advent of β-blocker therapy have repeatedly demonstrated the effectiveness of peak Vo2 to predict outcome in patients with heart failure.3–5 The prognostic power of ancillary data collected during cardiopulmonary testing, such as Vo2 at anaerobic threshold, percentage predicted …