EFFECT OF EXERCISE ON LEFT-VENTRICULAR MECHANICAL EFFICIENCY IN CONSCIOUS DOGS

Article

关键词: PRESSURE-VOLUME AREA;    CARDIAC OXYGEN-CONSUMPTION;    CONTRACTILE STATE;    AFTERLOAD;    ENERGY;    SUBSTRATE;    AGENTS;    WORK;    FLOW;   

DOI  :  10.1161/01.CIR.90.6.3047

来源: SCIE

【 摘 要 】

Background We studied the effect of exercise (7.2 to 8.0 km/h) on the efficiency of the conversion of metabolic energy to external work or stroke work (SW) by the left ventricle (LV). Methods and Results Energy use was calculated from LV myocardial oxygen consumption per beat (MVo(2)). LV volume was calculated from orthogonal dimensions and coronary flow measured with ultrasonic flow probes. The total mechanical energy of the LV was calculated as the pressure-volume area (PVA). At rest, the MVo(2)-PVA point fell on the MVo(2)-PVA relation determined by steady-state changes in arterial pressure produced by graded infusions of phenylephrine. Exercise increased the slope (E(es)) of LV end-systolic pressure-volume (PV) relation by 29%. During exercise, the MVo(2)-PVA point shifted to the right only slightly above the control MVo(2)-PVA relation by 0.007+/-0.005 mL O-2.beat(-1).100 g LV(-1). Despite the increase in ventricular contractility with exercise, the PVA/MVo(2) ratio was unchanged because of the marked increase in PVA. During exercise, the transmission of total mechanical energy to external work (SW/PVA) increased from 65+/-5% to 72+/-4% (P<.01) as the ratio of the arterial end-systolic elastance to E(es) decreased from 1.1+/-0.2 to 0.8+/-0.1 (P<.05). Thus, LV mechanical efficiency (SW/MVo(2)=SW/PVA.PVA/MVo(2)) improved from 12.9+/-1.5% to 14.3+/-1.1% (P<.05) during exercise. Conclusions Exercise increases the efficiency of conversion of metabolic energy to external work by the LV due to alteration in LV arterial coupling resulting in increased production of mechanical energy and enhanced transmission of mechanical energy to external work, which more than offsets any increased metabolic cost of the enhanced contractility.

【 授权许可】

Free