Exercise endpoints in patients with chronic heart failure

Background: Peak oxygen consumption ((V) over dot(O2)) is a powerful predictor of outcome in patients with chronic heart failure. This is not a test that is readily clinically available, We therefore sought to establish a method of assessing peak (V) over dot(O2) from non-invasively acquired data. Methods: We analysed the results from incremental treadmill exercise tests in 60 patients [aged 59.0 (S.D. 12.4) years] with chronic heart failure or left ventricular dysfunction [left ventricular ejection fraction (29.6 (15.2)%)] and 52 control subjects [aged 36.7 (12.3)]. Metabolic gas exchange during exercise was measured with a respiratory mass spectrometer. Heart rate and blood pressure were measured. Results: Peak (V) over dot(O2) was lower in patients than controls [19.9 (7.7) ml/kg/min vs. 38.3 (9.0), P<0.001]. Exercise time (r=0.84, P<0.001), heart rate at peak exercise (r=0.63, P<0.0001), change in heart rate (r=0.72, P<0.0001), rate pressure product at peak exercise (r=0.64, P<0.0001) and change in systolic blood pressure (r=0.31, P=0.002) all correlated with peak (V) over dot(O2). In a stepwise regression model, exercise time was the most powerful predictor of peak (V) over dot(O2) (r(2)=0.79). The only additional independent Variable was change in heart rate from rest to peak exercise, which increased r(2) to 0.80. In a survival analysis, measured peak (V) over dot(O2) and the peak (V) over dot(O2) estimated from exercise time and change in heart rate had similar predictive power. Conclusions: In this preliminary study, peak (V) over dot(O2) can be estimated from non-invasively acquired parameters. Estimated peak (V) over dot(O2) and measured peak (V) over dot(O2) have similar predictive power for outcome. Further work is necessary to see if estimated peak (V) over dot(O2) is widely applicable in a clinical setting. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.