A Simple yet Enduring Standard
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In this issue of Circulation, Pardaens et al1 examine the prognostic value of cardiopulmonary exercise testing in ambulatory patients with heart failure who are screened for cardiac transplantation. The investigators failed to demonstrate any significant advantage of ventilatory data over peak oxygen uptake (V̇o2). Over the past 10 years, several investigators have attempted to refine the use of peak V̇o2 to improve its prognostic yield. Others have sought methods or equations to estimate peak V̇o2 from submaximal data, such as that collected from 6-minute walk tests or during low-level exercise. Most investigators have concluded that the straightforward measurement of peak V̇o2 provides the best index of prognosis in patients with ambulatory heart failure.
The measurement of oxygen consumption (V̇o2) in patients with heart failure was first described by Weber et al2 as a noninvasive method for characterizing cardiac reserve and functional status in these patients. Its use as a prognostic tool has evolved. Szlachcic et al3 initially described the prognostic use of peak V̇o2 in a group of 27 patients. The 1-year mortality rate was 77% for patients with a peak V̇o2<10 mL · kg−1 · min−1 and 21% for those with a peak V̇o2 of 10 to 18 mL · kg−1 · min−1. Likoff et al4 reported a 36% mortality rate in 201 patients with heart failure who had a peak V̇o2≤13 mL · kg−1 · min−1; the mortality rate was 15% when peak V̇o2 exceeded 13 mL · kg−1 · min−1. Exercise data from the first Veterans Administration Heart Failure Trial (VHeFT)5 also demonstrated that peak V̇o2 …