LINEAR END-SYSTOLIC PRESSURE-VOLUME RELATIONSHIP DURING PULSATILE LEFT-VENTRICULAR BYPASS REPRESENTS NATIVE HEART FUNCTION

This study assessed whether the end-systolic pressure-volume relations hip obtained without any interventions during pulsatile left ventricul ar bypass adequately represents native heart function. In 11 anestheti zed Holstein calves, left ventricular pressure was measured with a mic romanometer while left ventricular volume was simultaneously calculate d from orthogonal left ventricular diameters measured with ultrasonic dimension transducers. End-systolic pressure and volume data were subj ected to linear regression analysis to achieve an end-systolic pressur e-volume relationship, Data from both caval occlusions and aortic occl usion were used for the control end-systolic pressure-volume relations hip (median r = 0.941, slope = 7.4 +/- 0.8 mm Hg per milliliter per 10 0 gm left ventricular weight; mean +/- standard error of the mean). Du ring left atrial-aortic bypass with a Pierce-Donachy pneumatic assist pump in the asynchronous mode, the end-systolic pressure-volume relati onships were obtained without interventions to change ventricular load ing conditions. During maximal ventricular unloading during full to em pty pumping, termed 100%, the resulting narrow range of pressure and v olume data did not yield highly linear end-systolic pressure-volume re lationships (median r = 0.669, slope = 4.9 +/- 0.9 mm Hg per millilite r per 100 gm left ventricular weight), However, at reduced rates off p umping, the end-systolic pressure-volume relationships were considerab ly linear (80%, median r = 0.819; 60%, median r = 0.868; 40%, median r = 0.899). Slopes did not significantly differ from control values (80 %, 6.9 +/- 1.1; 60%, 8.2 +/- 1.1; 40%, 7.8 +/- 1.1). The end-systolic pressure-volume relationship obtained without exogenous load changes d uring asynchronous, pulsatile left ventricular bypass represents nativ e left ventricular systolic function.