Flow and power output of right ventricle facing load with variable input impedance

Abstract

The output from the right ventricle (RV) was studied at different load impedances. Isolated cat hearts were perfused with Tyrode solution with erythrocytes. Coronary perfusion pressure and RV end-diastolic pressure were kept constant. The RV pumped into an artificial hydraulic load with independently variable resistance (R) and compliance (C). Mean RV flow (RVO) decreased after R increase or C reduction. For each heart, RVO and mean RV pressure were linearly related. The slope of the regression line is interpreted as an "apparent source resistance" (Rs). Rs was on average 3.4 X 10(3) (dyn.s.cm-5). The static hydraulic power output was maximum at a certain load R (Rm). Rm was C dependent at an average high C of 5 X 10(-5) dyn-1.cm5, Rm was 9.4 X 10(3) dyn.s.cm-5 on average and shifted to 5.4 X 10(3) at low C (avg 0.8 X 10(-5). Theoretical considerations show that Rm/Rs will be equal to total heart period divided by ejection period in the extreme case C leads to infinity, and Rm/Rs leads to 1 when C leads to 0. Experimentally, Rm/Rs was 2.4 (avg) for high C, and approached 1 for low C, which fits the theoretical predictions. The results indicate that high C facilitates the matching between the right heart and the vascular resistance in the lung.