The slope of the end-systolic pressure-volume relation with afterload changes was significantly steeper than with preload changes (6.3 vs 4.8 mmHg/ml, p<0.05), demonstrating load dependency.
Does afterload impedance change compared to preload change affect the slope of the end-systolic pressure-volume relation in isolated, ejecting canine hearts?
The slope of the end-systolic pressure-volume relation is load-dependent in ejecting hearts, limiting its utility as a pure index of contractility.
Tasa de eventos absoluta: 6.3% vs 4.8%
valor p: p=<0.05
If characteristic muscle properties such as myocardial viscosity and/or shortening deactivation influence left ventricular ejection in the whole heart, the slope of the left ventricular end-systolic pressure-volume relation should be a function of both the contractile state and the loading mode. Thus, the load dependence of the end-systolic pressure-volume relation was examined using isolated, perfused canine hearts ejecting saline into a hydraulic loading system. The instantaneous left ventricular volume was measured with a plethysmograph. Under constant coronary flow and heart rate, two regression lines for end-systolic pressure-volume relations in two sets of loading modes were obtained: (1) Preload (left ventricular end-diastolic pressure; 4-15 mmHg) changes under fixed afterload impedance (preload changes); (2) Afterload impedance (peripheral resistance; 1.9-9.6 x 10(3) dyn sec cm-5) changes under fixed left ventricular end-diastolic volume (afterload changes). The slope of the end-systolic pressure-volume relation with afterload changes was steeper than that with preload changes (6.3 +/- 0.7 vs 4.8 +/- 0.6 mmHg/ml, p less than 0.05). Accordingly, under constant coronary flow, the slope of the end-systolic pressure-volume relation depended on loading conditions within the physiological range of afterload impedance and preload. This finding supports our hypothesis and implies that the slope change is of limited value as a contractile index in the ejecting heart.
Nishioka et al. (Fri,) conducted a other in Isolated canine hearts (n=13). Afterload impedance changes vs. Preload changes was evaluated on Slope of the end-systolic pressure-volume relation (ESPVR) (p=<0.05). The slope of the end-systolic pressure-volume relation with afterload changes was significantly steeper than with preload changes (6.3 vs 4.8 mmHg/ml, p<0.05), demonstrating load dependency.