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

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Abstract
Left ventricular systolic pressure volume area (PVA) has been reported to be a reliable predictor of cardiac O2 consumption rate per beat (VO2) in a given heart with a stable inotropic background. PVA has been defined as the specific area in the pressure-volume (P-V) plane bounded by the end-systolic and end-diastolic P-V relationship lines and the systolic segment of the P-V loop trajectory. In this study, PVA was separated into 2 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 end-systolic 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. An optimal weighting coefficient K of PE was sought for the best correlation between VO2 and PVAW = EW + K .cntdot. PE, changing K from 0 to infinity. Results in 7 canine excised cross-circulated hearts showed that PVAW correlated best with VO2 at K = 1.03 .+-. 0.03 (SE). Since PVAW at K = 1 is identical with the original PVA, PVA could serve as a reliable predictor of VO2. PVA is physiologically significant in the coupling between cardiac mechanics and energetics.

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