Banning A P, Lewis N P, Northridge D B, Elborn J S, Hendersen A H
Department of Cardiology, University of Wales College of Medicine, Cardiff.
Br Heart J. 1995 Jul;74(1):27-33. doi: 10.1136/hrt.74.1.27.
The ventilatory cost of carbon dioxide (CO2) elimination on exercise (VE/VCO2) is increased in chronic heart failure (CHF). This reflects increased physiological dead space ventilation secondary to mismatching between perfusion and ventilation during exercise. The objectives of this study were to investigate the relation of this increased VE/VCO2 slope to the syndrome of CHF or to limitation of the exercise related increase of pulmonary blood flow, or both.
Maximal treadmill exercise tests with respiratory gas analysis were performed in 45 patients with CHF (defined as resting left ventricular ejection fraction < 40% on radionuclide scan); 15 normal controls; 23 patients with coronary artery disease and normal resting left ventricular function; and 13 pacemaker dependent patients (six with and seven without CHF) directly comparing exercise responses in rate responsive and fixed rate mode.
Patients with CHF had a steeper VE/VCO2 slope than normal controls: this was related inversely to peak VO2 below 20 mol/min/kg. In patients with coronary artery disease in whom peak VO2 (at respiratory exchange ratio > 1) was as limited as in the patients with CHF but resting left ventricular function was normal, the VE/VCO2 slope was normal. In pacemaker dependent patients fixed rate pacing resulted in lower exercise capacity and peak VO2 than rate responsive pacing; the VE/VCO2 slope was normal in patients without CHF but steeper than normal in patients with CHF; the VE/VCO2 slope was steeper during fixed rate than during rate responsive pacing in these patients with CHF.
These findings suggest that the perfusion/ventilation mismatch during exercise in CHF is related to the chronic consequences of the syndrome and not directly to limitation of exercise related pulmonary flow. Only when the syndrome of CHF is present can matching between perfusion and ventilation be acutely influenced by changes in pulmonary flow.
慢性心力衰竭（CHF）患者运动时二氧化碳（CO2）排出的通气成本（VE/VCO2）会升高。这反映出运动期间由于灌注与通气不匹配导致生理无效腔通气增加。本研究的目的是探讨这种升高的VE/VCO2斜率与CHF综合征或与运动相关的肺血流量增加受限之间的关系，或两者之间的关系。
对45例CHF患者（定义为放射性核素扫描静息左心室射血分数<40%）、15例正常对照者、23例冠状动脉疾病且静息左心室功能正常的患者以及13例依赖起搏器的患者（6例有CHF，7例无CHF）进行了带有呼吸气体分析的最大运动平板试验；直接比较频率应答模式和固定频率模式下的运动反应。
CHF患者的VE/VCO2斜率比正常对照者更陡：这与低于20 mol/min/kg的峰值VO2呈负相关。在冠状动脉疾病患者中，其峰值VO2（呼吸交换率>1时）与CHF患者一样受限，但静息左心室功能正常，其VE/VCO2斜率正常。在依赖起搏器的患者中，固定频率起搏导致的运动能力和峰值VO2低于频率应答起搏；无CHF患者的VE/VCO2斜率正常，但CHF患者的VE/VCO2斜率比正常者更陡；在这些CHF患者中，固定频率起搏时的VE/VCO2斜率比频率应答起搏时更陡。
这些发现表明，CHF患者运动期间的灌注/通气不匹配与该综合征的慢性后果有关，而不是直接与运动相关的肺血流量受限有关。只有当存在CHF综合征时，灌注与通气的匹配才会受到肺血流量变化的急性影响。
