Early recovery of oxygen kinetics after submaximal exercise test predicts functional capacity in patients with chronic heart failure

Background: Oxygen (O-2) uptake at peak exercise (Vo(2) peak) is an objective measurement of functional capacity in patients with chronic heart failure (CHF) The significance of recovery O-2 kinetics parameters in predicting exercise capacity, and the parameters of submaximal exercise testing have not been thoroughly examined. Methods and results. Thirty-six patients (mean age = 48 +/- 14 years) with CHF and New York Heart Association functional class I [12], II [17], or III [7], and eight healthy volunteers (mean age = 39 +/- 13 years) were studied with maximal and submaximal cardiopulmonary exercise testing (CPET). The first degree slope of O-2 uptake decay during early recovery from maximal (Vo(2)/t-slope), and submaximal exercise (Vo(2)/t-slope)(sub), were calculated, along with Vo(2) half-time (T(1/2)Vo(2)). Patients with CHF had a longer recovery of O-2 uptake after exercise than healthy volunteers, expressed by a lower Vo(2)/t-slope (0.616 +/- 0.317 vs. 0.956 +/- 0.347 l min(-1) min(-1), P = 0.029) and greater T(1/2)Vo(2) (1.28 +/- 0.30 vs. 1.05 +/- 0.15 min, P = 0.005). Vo(2)/t-slope correlated with the Vo(2) peak (r = 0.84, P < 0.001), anaerobic threshold (r = 0.79, P < 0.001), and T(1/2)Vo(2), a previously established estimate of recovery O-2 kinetics (r = -0.59, P < 0.001). (Vo(2)/t-slope)(sub) was highly correlated with Vo(2)/t-slope after maximal exercise (r = 0.87, P < 0.001), with the Vo(2) peak (r = 0.87, P < 0.001) and with T(1/2)Vo(2) after maximal exercise (r = -0.62, P < 0.001). Vo(2)/t-slope after maximal and submaximal exercise was reduced in patients with severe exercise intolerance (F = 9.3, P < 0.001 and F = 12.8, P < 0.001, respectively). Conclusions: Early recovery O-2 kinetics parameters after maximal and submaximal exercise correlate closely with established indices of exercise capacity in patients with CHF and in healthy volunteers. These findings support the use of early recovery O-2 kinetics after submaximal exercise testing as an index of functional capacity in patients with CHF. (C) 2001 European Society of Cardiology. All rights reserved.