Standardized Ejection Fraction as a Parameter of Overall Ventricular Pump Function

To evaluate the pump function of the ventricle, a parameter which (i) incorporates systolic and diastolic function and (ii) separates the heart from preload and afterload is needed. This study utilized ejection fraction (EF), calculated from the end-systolic (ES) and end-diastolic (ED) pressure-volume relationship (PVR) using an arbitrary set of loading conditions. Ten isolated canine hearts with a balloon placed inside the left ventricle were used to determine the ESPVR and EDPVR. An end-diastolic volume (EDV) at a pressure of 15 mmHg and an end-systolic volume (ESV) at 70 mmHg were obtained from the EDPVR and ESPVR, respectively. EF was calculated as (EDV-ESV)/EDV. With low-dose (8 microg/min) and high-dose (40 microg/min) dobutamine infusion, the EF increased from 0.25+/-0.16 to 0.33+/-0.13 and 0.57+/-0.08 (p<0.01), respectively, in conjunction with increases in end-systolic elastance from 3.11+/-0.83 to 3.48+/-1.08 and 5.38+/-1.91 mmHg/ml (p<0.01). It was thus concluded that because the estimation of EF separates the heart from preload and afterload, this method may facilitate comparing overall pump function of hearts beating under different loading conditions.