Exercise capacity in chronic heart failure is related to the aetiology of heart disease

Abstract

Objective To assess whether the underlying aetiology of chronic heart failure is a predictor of exercise performance.

Setting Tertiary referral centre for cardiology.

Patients and outcome measures Retrospective study of maximum exercise testing with metabolic gas exchange measurements in 212 patients with chronic heart failure who had undergone coronary angiography. Echocardiography and radionucleide ventriculography were used to determine indices of left ventricular function, and coronary arteriography was used to determine whether the cause of chronic heart failure was ischaemic heart disease (n = 122) or dilated cardiomyopathy (n = 90).

Results The cardiomyopathy group was younger (mean (SD) age 58.45 (11.66) years v 61.49 (7.42); p = 0.02) but there was no difference between the groups in ejection fraction or fractional shortening. Peak oxygen consumption (V˙o ₂) was higher in the dilated group, while the slope relating carbon dioxide production and ventilation (V˙e/V˙co ₂ slope) was the same in both groups. Both groups achieved similar respiratory exchange ratios at peak exercise, suggesting that there was near maximum exertion. There was a relation between peakV˙o ₂ and age (peakV˙o ₂ = 33.9 − 0.267*age; r = 0.36; p < 0.001). After correcting for age, the peak achievedV˙o ₂ was still greater in the cardiomyopathy group than in the ischaemic group (p < 0.002).

Conclusions Exercise performance for a given level of cardiac dysfunction appears to vary with the aetiology of heart failure. Thus the two diagnostic categories should be considered separately in relation to abnormalities of exercise physiology. The difference may in part account for the worse prognosis in ischaemic patients.