Assessment of patients with clinical congestive heart failure: Ventilatory threshold or aerobic power determination?

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Abstract
We have investigated the relative merits of ventilatory threshold (Vt) and maximal oxygen intake (VO2max) in the functional assessment of 12 patients with heart failure (New York Association class II and III ejection fraction [EF] less than 35%). Subjects performed two cycle ergometer (CE) and two treadmill (TM) tests at 4‐day intervals, according to a Latin square design. The Vt was evaluated by two observers. On an analysis of variance, the Vt showed no significant observer bias and no difference of reliability between observers. In most instances, the two observers defined the Vt to within 1 ml·kg−1·min−1 of each other (95% confidence interval [CI] 0.23 to 2.04 ml·kg−1·min−1). When compared with VO2max, Vt measurements were more reliable and had greater validity relative to the available quantitative external criterion, the resting EF. Neither Vt nor VO2max differed systematically between CE and TM tests. The patients preferred CE to TM, and collection of expired gas was easier on seated patients. The within‐subject variation of Vt was less for CE than for TM. Correlations with EF also tended to be larger for CE (for the first and second tests by this technique, observer 1: Vt = 0.49, 0.48; observer 2: Vt = 0.33, 0.39; VO2max = 0.30, 0.20) than for TM (observer 1: Vt = 0.40, 0.44; observer 2: Vt = 0.36, 0.29; VO2max = 0.30, 0.08). We conclude that although the direct TM measurement of VO2max is the preferred method of assessing cardiorespiratory function in the healthy young adult, the CE determination of Vt provides the better noninvasive method of evaluating the disabled patient with congestive heart failure.