A predictor of aerobic threshold for patients with heart failure with reduced ejection fraction.

[Purpose] The initial cardiopulmonary response to exercise is hypothesized to be a useful predictor of aerobic threshold in patients with heart failure. This study aimed to evaluate the correlation between aerobic threshold and cardiopulmonary responses to exercise onset by comparing patients with heart failure using preserved (≥50%) and reduced (<50%) left ventricular ejection fractions. [Participants and Methods] Twenty-eight males (age, 36-82 years; 12 with preserved and 16 with reduced left ventricular ejection fractions) underwent a progressive submaximal cardiopulmonary exercise test using a cycle ergometer. The aerobic threshold, time constant, and area under the oxygen uptake curve for the first 4 min (V̇O2 AUC) were determined. [Results] A significant association was observed between aerobic threshold and V̇O2 AUC in the reduced group but not in the preserved group. No significant correlations were found between time constant and V̇O2 AUC or between aerobic threshold and time constant in either group. [Conclusion] The results suggest that V̇O2 AUC measured from exercise onset to an initial 4-min period could provide an easily and safely obtained predictor to assess aerobic capacity in people with reduced left ventricular ejection fractions.