[Ventriculo-arterial coupling during aerobic and anaerobic exercise in normal subjects]

Physiological differences in aerobic and anaerobic exercise were assessed within the coupling framework between the left ventricle and the arterial system. In 10 normal men, the anaerobic threshold was estimated using sequential breath gas analysis during incremental ergometer tests. Direct arterial pressure and left ventricular echocardiograms were simultaneously recorded as its pressure was changed by phenylephrine or nitroprusside, and the slope (Ees) and volume axis intercept (Vo) of the end-systolic pressure (ESP)-volume relationship were determined. The effective arterial elastance (Ea) was expressed by the slope of the ESP-stroke volume relationship. Assuming that the Vo was unchanged from the resting state, the Ees and Ea were determined during exercise at aerobic and anaerobic work levels for each subject. During aerobic exercise, an increase in left ventricular end-diastolic volume and the tendency to decrease in ESP caused a significant fall in Ea by 30%. There was no significant change in Ees. Consequently, Ea/Ees which correlates inversely with left ventricular pump efficiency, decreased by 35%. During anaerobic exercise, Ea remained the same as during aerobic exercise, but Ees rose substantially by 89%. This caused a further reduction in Ea/Ees (-54%). Thus, ventriculo-arterial coupling during exercise is characterized by a decrease in Ea/Ees, indicating an augmentation of pump efficiency. This is primarily mediated by changes in loading conditions (decrease in Ea) during aerobic exercise, and by enhanced contractility (increase in Ees) during anaerobic exercise.