Abstract
AIMS: The two main symptoms referred by chronic heart failure (HF) patients as the causes of exercise termination during maximal cardiopulmonary exercise testing (CPET) are muscular fatigue and dyspnoea. So far, a physiological explanation why some HF patients end exercise because of dyspnoea and others because of fatigue is not available. We assessed whether patients referring dyspnoea or muscular fatigue may be distinguished by different ventilator or haemodynamic behaviours during exercise. METHODS AND RESULTS: We analysed exercise data of 170 consecutive HF patients with reduced left ventricular ejection fraction in stable clinical condition. All patients underwent maximal CPET and a second maximal CPET with measurement of cardiac output by inert gas rebreathing at peak exercise. Thirty-eight (age 65.0 ± 11.1 years) and 132 (65.1 ± 11.4 years) patients terminated CPET because of dyspnoea and fatigue, respectively. Haemodynamic and cardiorespiratory parameters were the same in fatigue and dyspnoea patients. VO(2) was 10.4 ± 3.2 and 10.5 ± 3.3 mL/min/kg at the anaerobic threshold and 15.5 ± 4.8 and 15.4 ± 4.3 at peak, in fatigue and dyspnoea patients, respectively. In fatigue and dyspnoea patients, peak heart rate was 110 ± 22 and 114 ± 22 beats/min, and VE/VCO(2) and VO(2) /work relationship slopes were 31.2 ± 6.8 and 30.6 ± 8.2 and 10.6 ± 4.2 and 11.4 ± 5.5 L/min/W, respectively. Peak cardiac output was 6.68 ± 2.51 and 6.21 ± 2.55 L/min (P = NS for all). CONCLUSIONS: In chronic HF patients in stable clinical condition, fatigue and dyspnoea as reasons of exercise termination do not highlight different ventilatory or haemodynamic patterns during effort.