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.

研究目的：慢性心力衰竭（chronic heart failure, HF）患者在极量心肺运动试验（maximal cardiopulmonary exercise test, CPET）中因运动终止所自述的两大主要症状为肌肉疲劳与呼吸困难。截至目前，尚缺乏针对部分HF患者因呼吸困难终止运动、另一部分则因肌肉疲劳终止运动的生理学解释。本研究旨在探究，自述呼吸困难或肌肉疲劳的患者，在运动过程中是否可通过不同的通气或血流动力学特征加以区分。

研究方法与结果：本研究纳入170例病情稳定的射血分数降低型慢性心力衰竭连续患者，对其运动数据进行分析。所有患者均接受极量CPET检查，其中另有一次极量CPET检查，在运动峰值阶段通过惰性气体复吸法测定心输出量（CPET-CO）。
其中38例患者（年龄65.0±11.1岁）因呼吸困难终止CPET，132例患者（年龄65.1±11.4岁）因肌肉疲劳终止CPET。两类患者的血流动力学与心肺参数均无显著差异。疲劳组患者在无氧阈时的氧摄取量（VO₂）为10.4±3.2 ml/min/kg，呼吸困难组为10.5±3.3 ml/min/kg；两组运动峰值时的VO₂分别为15.5±4.8 ml/min/kg与15.4±4.3 ml/min/kg。疲劳组与呼吸困难组患者的运动峰值心率分别为110±22次/分钟与114±22次/分钟；两组的VE/VCO₂斜率分别为31.2±6.8与30.6±8.2，氧摄取量-做功量关系斜率分别为10.6±4.2与11.4±5.5 L/min/瓦。峰值心输出量分别为6.68±2.51 L/min与6.21±2.55 L/min（所有比较的P值均无统计学意义）。

结论：对于病情稳定的慢性HF患者，以肌肉疲劳或呼吸困难作为运动终止诱因时，其运动过程中的通气或血流动力学模式并无显著差异。