© 2001 European Society of Cardiology
Early recovery of oxygen kinetics after submaximal exercise test predicts functional capacity in patients with chronic heart failure
a Pulmonary & Critical Care Medicine Department, National and Kapodestrian University Papadiamantopoulou 20, Athens 115 28, Greece
b Clinical Therapeutics Department, National and Kapodestrian University Papadiamantopoulou 20, Athens 115 28, Greece
* Corresponding author. Tel.: +30-1-7236743; fax: +30-1-7242785. E-mail address: snanas{at}cc.uoa.gr (S. Nanas).
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Abstract |
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Background: Oxygen (O2) uptake at peak exercise (VO2 peak) is an objective measurement of functional capacity in patients with chronic heart failure (CHF). The significance of recovery O2 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 O2 uptake decay during early recovery from maximal (VO2/t-slope), and submaximal exercise (VO2/t-slope)sub, were calculated, along with VO2 half-time (T1/2VO2). Patients with CHF had a longer recovery of O2 uptake after exercise than healthy volunteers, expressed by a lower VO2/t-slope (0.616±0.317 vs. 0.956±0.347 l min–1 min–1, P=0.029) and greater T1/2VO2 (1.28±0.30 vs. 1.05±0.15 min, P=0.005). VO2/t-slope correlated with the VO2 peak (r=0.84, P<0.001), anaerobic threshold (r=0.79, P<0.001), and T1/2VO2, a previously established estimate of recovery O2 kinetics (r=–0.59, P<0.001). (VO2/t-slope)sub was highly correlated with VO2/t-slope after maximal exercise (r=0.87, P<0.001), with the VO2 peak (r=0.87, P<0.001) and with T1/2VO2 after maximal exercise (r=–0.62, P<0.001). VO2/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 O2 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 O2 kinetics after submaximal exercise testing as an index of functional capacity in patients with CHF.
Key Words: Exercise recovery • Cardiopulmonary exercise testing • Heart failure • Functional capacity • Risk stratification
Received February 23, 2001; Revised April 17, 2001; Accepted July 18, 2001
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