Exercise endpoints in patients with chronic heart failure.
BACKGROUND
Peak oxygen consumption (V(O(2))) 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(O(2)) 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(O(2)) 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(O(2)). In a stepwise regression model, exercise time was the most powerful predictor of peak V(O(2)) (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(O(2)) and the peak V(O(2)) estimated from exercise time and change in heart rate had similar predictive power.


CONCLUSIONS
In this preliminary study, peak V(O(2)) can be estimated from non-invasively acquired parameters. Estimated peak V(O(2)) and measured peak V(O(2)) have similar predictive power for outcome. Further work is necessary to see if estimated peak V(O(2)) is widely applicable in a clinical setting.
Clark
A L
AL
Department of Cardiac Medicine, National Heart and Lung Institute, Dovehouse Street, London, UK. c.m.porter@medschool.hull.ac.uk
Coats
A J
AJ
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology*; D006439:Hemodynamics; D006801:Humans; D016014:Linear Models; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology*; D011379:Prognosis; D016019:Survival Analysis; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology*