Ischemic etiology of heart failure identifies patients with more severely impaired exercise capacity

Background Peak oxygen uptake (peak VO2) and the regression slope of ventilation against CO2 production during exercise (VE/VCO2 slope) are powerful prognostic indicators in patients with chronic heart failure (CHF). Our purpose was to evaluate the influence of CHF etiology on peak VO2 and VE/VCO2 slope, independently of demographic, clinical, Doppler-echocardiographic and neurohormonal factors. Methods Data were collected from 239 CHF patients referred for a cardiopulmonary exercise test as part of their clinical evaluation. Patients were stratified according to their CHF etiology (ischemic versus non-ischemic). Results The etiology of heart failure was ischemic in 143 patients (60%) and non-ischemic in 96 (40%). Patients with ischemic etiology, compared with those with non-ischemic etiology, showed a lower peak VO2 (15.4±4.2 versus 17.8±4.8 ml/kg/min, p<0.0001) and a steeper VE/VCO2 slope (38.1±6.8 versus 34±5.3, p<0.0001). In the univariate model, age (r=−0.36, p<0.0001), female sex (r=−0.21, p=0.001), ischemic CHF etiology (r=−0.26, p<0.0001) and NYHA class (r=−0.52, p<0.0001) correlated with peak VO2. At multivariate analysis, ischemic CHF etiology (β=−0.23, p=0.001) was a predictor of peak VO2 (R2=0.49) independently of age (β=−0.23, p=0.001), female sex (β=−0.25, p=0.0006) and NYHA class (β=−0.31, p<0.0001). Similarly, ischemic etiology (β=0.29, p=0.001) predicted the VE/VCO2 slope (R2=0.38) independently of E/A ratio (β=0.27, p=0.01) and resting heart rate (β=0.22, p=0.01). Conclusions Etiology of heart failure may influence the functional capacity and the ventilatory response to exercise.