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

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 (O₂) was higher in the dilated group, while the slope relating carbon dioxide production and ventilation (E/CO₂ 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 peak O₂ and age (peak O₂ = 33.9 − 0.267*age; r = 0.36; p < 0.001). After correcting for age, the peak achieved O₂ 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.

Keywords: exercise performance;  heart failure;  ischaemic heart disease;  dilated cardiomyopathy