| 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. |
