Use of the frank-starling mechanism during exercise is linked to exercise-induced changes in arterial load

Effective arterial elastance(E _A) is a measure of the net arterial load imposed on the heart that integrates the effects of heart rate(HR), peripheral vascular resistan-ce(PVR), and total arterial compliance(TAC) and is a modulator of cardiac performance. To what extent the change in Ea during exercise impacts on cardiac performance and aerobic capacity is unknown. We examined E _A and its relationship with cardiovascular performance in 352 healthy subjects. Subjects underwent rest and exercise gated scans to measure cardiac volumes and to derive EA[end-systolic pressure/ stroke volume index(SV)], PVR[MAP/(SV*HR)], and TAC(SV/pulse pressure). Ea varied with exercise intensity: the AEa between rest and peak exercise along with its determinants, differed among individuals and ranged from -44% to +149%, and was independent of age and sex. Individuals were separated into 3 groups based on their AEaI. Individuals with the largest increase in AEA(group 3;AEa^0.98 mmHg.m ²/ml) had the smallest reduction in PVR, the greatest reduction in TAC and a similar increase in HR vs. group 1(AEa<0.22 mmHg.m ²/ml). Furthermore, group 3 had a reduction in end-diastolic volume, and a blunted increase in SV(80%), and cardiac output(27%), during exercise vs. group 1. Despite limitations in the Frank-Starling mechanism and cardiac function, peak aerobic capacity did not differ by group because arterial-venous oxygen difference was greater in group 3 vs. 1. Thus the change in arterial load during exercise has important effects on the Frank-Starling mechanism and cardiac performance but not on exercise capacity. These findings provide interesting insights into the dynamic cardiovascular alterations during exercise.