Regression of cardiac oxygen consumption on ventricular pressure-volume area in dog

Left ventricular systolic pressure-volume area (PVA) has been reported to be a reliable predictor of cardiac oxygen consumption rate per beat (Vo₂) in a given heart with a stable inotropic background. PVA is the specific area in the pressure-volume (PV) diagram, consisting of the area (EW) within the PV loop and the area (PE) bound by the end-systolic and end-diastolic PV lines and the relaxation segment of the PV loop. EW and PE correspond to the external mechanical work and the end-systolic elastic potential energy in the ventricular wall, respectively. We determined the optimal combination of EW and PE for the best prediction of Vo₂, using the linear multiple regression analysis. From EW, PE, and Vo₂, data of many isovolumic and ejecting contractions, the optimal coefficients of EW and PE were 1.67 ± 0.43 (SD; 7 hearts) and 1.74 ± 0.49 (10^-5ml O₂/mmHg.ml), virtually identical to each other, corroborating that PVA, i.e., a simple sum of EW and PE, can reliably predict Vo₂ of a given heart in a stable contractile state.