Recovery kinetics of oxygen uptake and heart rate in patients with coronary artery disease and heart failure

Abstract

Background: Patients with congestive heart failure exhibit a prolonged period of recovery to baseline levels of oxygen consumption, but the decline of heart rate during recovery from exercise has been shown to be similar to that in healthy subjects, and the results of studies on the response of ventilation in recovery have been mixed. Patients with coronary artery disease have a reduced exercise capacity, but it is unknown whether the patterns of the decline in oxygen uptake (VO2), ventilation, or heart rate are similar to those in patients with heart failure.

Methods: We performed a cardiopulmonary exercise test with a ramping protocol in 18 healthy subjects, 18 patients with coronary artery disease, 19 patients with class A or B congestive heart failure, and 19 patients with class C congestive heart failure, according to the Weber classification. Peak oxygen uptake and the kinetics of oxygen uptake, ventilation, and heart rate were calculated and expressed as the slope of a single exponential relation between VO2 levels and time during the first 3 min of recovery as y(VO2) = y0Ae(-x/t).

Results: A difference in time of recovery of VO2 was found only between healthy subjects and patients with more severe heart failure (class C) (p < 0.05); no significant differences were observed among any of the groups in ventilation or heart rate recovery responses.

Conclusion: VO2 recovery time is prolonged only in the presence of more severe heart failure. The presence and degree of heart disease has no effect on ventilation or heart rate recovery time.