Exercise performance, haemodynamics, and respiratory pattern do not identify heart failure patients who end exercise with dyspnoea from those with fatigue
Aims: The two main symptoms referred by chronic heart failure (HF) patients as the causes of exercise termination during maximal cardiopulmonary exercise test (CPET) are muscular fatigue and dyspnea. So far, a physiological explanation why some HF patients end exercise because of dyspnea and others because of fatigue is not available. We assessed whether patients referring dyspnea or muscular fatigue may be distinguished by different ventilator or hemodynamic behavior during exercise. Methods and Results: We analyzed exercise data of 170 consecutive HF patients with reduced left ventricular ejection fraction in stable clinical condition. All patients underwent to maximal CPET and to a second maximal CPET with measurement of cardiac output (CPET-CO) by inert gas rebreathing at peak exercise. Thirty-eight (age 65.0±11.1y) and 132 (65.1±11.4y) patients terminated CPET because of dyspnea and fatigue, respectively. Hemodynamic and cardiorespiratory parameters were the same in fatigue and dyspnea patients. VO2 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 dyspnea patients, respectively. In fatigue and dyspnea patients peak heart rate was 110±22 and 114±22 b/min, VE/VCO2 and VO2/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/Watts, respectively. Peak CO 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 dyspnea as reasons of exercise termination do not highlight different ventilatory or hemodynamic patterns during effort.