Ventilatory capacity and exercise tolerance in patients with chronic stable heart failure

Background: Patients with chronic heart failure complain of breathlessness. This is associated with an increase in the ventilatory response to carbon dioxide production (VE/VCO2, slope), yet a reduction in the maximal ventilation achieved at peak exercise. We analysed ventilatory capacity in heart failure in relation to exercise capacity. Methods: We analysed data from 74 patients with chronic stable heart failure [age (S.D.) 50.6 (8.8) years; left ventricular ejection fraction 30 (15)%] and 36 controls [48.9 (11.5) years]. Subjects undertook maximal incremental exercise testing with metabolic gas exchange measurements to derive peak oxygen consumption (VO2), the VE/VCO2 slope and ventilation. Spirometry was used to measure FEV1 and FVC. Maximal voluntary ventilation (MW) was calculated as FEV1 x 35. Results: Peak VO2 was lower in patients [20.9 (7.5) ml min(-1) kg(-1) vs. 34.5 (10.1); P < 0.001] and VE/VCO2 greater [33.4 (10.7) vs. 26.0 (4.7); P < 0.001]. Ventilation at peak exercise was lower in patients [63.5 (20.4) l/min vs. 86.9 (29.5); P < 0.001], as was MW [110.1 (37.9) l/min vs. 136.2 (53.1); P < 0.001], but ventilation at peak as a proportion of MW was the same in patients [60.0 (19.0)%] as controls [65.7 (12.4)%)]. There was an inverse relation between peak VO2 and VE/VCO2 slope (r = -0.62; P < 0.001). Percentage predicted FEV1 correlated with ventilation at peak (r = 0.62; P < 0.001) and inversely with VE/VCO2 slope (r = - 0.32; P < 0.001). There was no relation between percentage of MW achieved and peak VO2, or VE/VCO2 slope. Conclusions: Although ventilation at peak exercise is lower in patients with heart failure than normal subjects, ventilation is the same proportion of maximal voluntary ventilation. These findings suggest that ventilatory capacity does not limit exercise capacity in heart failure. (C) 2000 European Society of Cardiology. All rights reserved.