MYOCARDIAL OXYGEN-CONSUMPTION AND THE LEFT-VENTRICULAR PRESSURE VOLUME AREA IN NORMAL AND HYPERTROPHIC CANINE HEARTS

Background. To assess and compare the energy demands of normal and hypertrophic hearts, we defined the relation between myocardial oxygen consumption (MVo2, an index of the energy consumed by contraction) and the left ventricular pressure-volume area (PVA, an index of the total mechanical energy generated by contraction) in eight normal and eight hypertrophic (aortic band model) dog hearts; MVo2 was also measured in the nonworking (empty beating) and basal (potassium arrest) states. Methods and Results. The hearts were studied in an isolated, blood-perfused heart apparatus. The slope of the MVo2-PVA relation (the inverse of which reflects myofibrillar efficiency) was similar in normal and hypertrophic hearts (3.89 +/- 1.91 and 4.19 +/- 1.25 ml O2/mm Hg . ml . 10(5), p = NS). The MVo2 in empty beating (0.038 +/- 0.006 and 0.041 +/- 0.015 ml/beat/100 g, p = NS) and potassium-arrested (1.95 +/- 0.06 and 1.98 +/- 0.20 ml/min/100 g, p = NS) hearts was likewise similar in the two groups. Conclusions. Basal and nonworking energy demands and working efficiencies of hypertrophic hearts are equivalent to those of normal hearts.