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) = α[PVA (mmHg.ml.beat^-1)] + b, where a = 1.64 (±0.12 SE) x 10^-5 (ml O₂/beat)/(mmHg.ml.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.