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/VCO(2) 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 (VO(2)), the VE/VCO(2) slope and ventilation. Spirometry was used to measure FEV(1) and FVC. Maximal voluntary ventilation (MVV) was calculated as FEV(1)x 35. RESULTS: Peak VO(2) was lower in patients 20.9 (7.5) ml min(-1) kg(-1) vs. 34.5 (10.1); P<0.001 and VE/VCO(2) 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 MVV 110.1 (37.9) l/min vs. 136.2 (53.1); P<0.001, but ventilation at peak as a proportion of MVV was the same in patients 60.0 (19.0)% as controls 65.7 (12.4)%). There was an inverse relation between peak VO(2) and VE/VCO(2) slope (r=-0. 62; P<0.001). Percentage predicted FEV(1) correlated with ventilation at peak (r=0.62; P<0.001) and inversely with VE/VCO(2) slope (r=-0.32; P<0.001). There was no relation between percentage of MVV achieved and peak VO(2), or VE/VCO(2) 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.