Ventricular systolic pressure-volume area as predictor of cardiac oxygen consumption

We scrutinized the recently reported correlation between the canine left ventricular systolic pressure-volume area (PVA) and cardiac oxygen consumption rate per beat (Vo2) by use of an improved method of Vo2 assessment. PVA is the specific area in the pressure-volume (PV) plane bounded by the end-systolic and end-diastolic PV lines and the systolic segment of the PV loop. Different from the previous study in which Vo2-PVA data from isovolumic and ejecting contractions were pooled for analyses, we analyzed Vo2-PVA data from the two different modes separately to examine whether there was any difference of Vo2-PVA relationship between them. The results indicated that the linear regressions of Vo2 on PVA were virtually the same for isovolumic and ejecting contractions. The regression line was Vo2 (ml O2/beat) = a[PVA (mmHg x ml x beat-1)] + b, where a = 1.64 (+/- 0.12 SE) X 10(-5) (ml O2/beat)/(mmHg x ml x beat-1) and b = 0.015 +/- 0.002 ml O2/beat in 10 hearts. We conclude that PVA serves as a reliable predictor of Vo2 regardless of the mode of contraction in a given left ventricle with a stable inotropic background.