Oxygen-saving effect of negative work in dog left ventricle.

We compared left ventricular oxygen consumptions (VO2) of contractions performing negative external work (EW less than 0) and positive external work (EW greater than 0) that developed comparable peak systolic pressures in the excised cross-circulated dog hearts. We changed the polarity of ventricular work with volume servo-pump and measured both left ventricular VO2 and systolic pressure-volume area (PVA). PVA represents the total mechanical energy generated by contraction and is equal to the area circumscribed by the end-systolic and end-diastolic pressure-volume (PV) relation curves and the systolic PV trajectory. For comparable peak systolic pressures of approximately 90 mmHg, contractions performing negative EW of -834 +/- 327 mmHg.ml.100 g left ventricle-1 had 27 +/- 11% smaller VO2 and 62 +/- 12% smaller PVA than those performing positive EW of 851 +/- 329 mmHg.ml.100 g-1. The smaller VO2 for negative EW could be accounted for by the linear VO2-PVA relation regardless of the polarity and magnitude of work. The results indicate that negative work can save VO2 of contractions to develop a given peak systolic pressure.