Critical evaluation of left ventricular systolic pressure volume area as predictor of oxygen consumption rate

Left ventricular systolic pressure volume area (PVA) has been reported to be a reliable predictor of cardiac oxygen consumption rate per beat (V_O2) in a given heart with a stable inotropic background. PVA has been defined as the specific area in the pressure-volume (P-V) plane that is bounded by the end-systolic and end-diastolic P-V relationship lines and the systolic segment of the P-V loop trajectory. In the present experimental study, we separated PVA into two parts: EW and PE. EW is the area surrounded by the P-V loop, corresponding to the external mechanical work. PE is the area surrounded by the endsystolic and end-diastolic P-V lines and the relaxation segment of the P-V loop, corresponding to what is considered the end-systolic elastic potential energy in terms of a time-varying elastance model of the ventricle. We attempted to find an optimal weighting coefficient K of PE for the best correlation between V_o2 and PVA_W=EW+K·PE, changing K from 0 to infinity. Results in 7 canine excised cross-circulated hearts showed that PVA_W best correlated with V_O2 at K=1.03±0.03 (SE). Since PVA_W at K=1 is identical with the original PVA, we concluded that PVA could serve as a reliable predictor of V_O2. PVA is concluded to be physiologically significant in the coupling between cardiac mechanics and energetics.