Thirteenth Bowditch lecture. The determinants of myocardial oxygen consumption.

Abstract

Elucidation of the determinants of myocardial oxygen consumption has been the object of extensive research for more than one-half cen-tury. The heart is an aerobic organ and can develop only a small oxy-gen debt. Therefore, in a steady state, determination of the heart’s oxygen consumption provides a precise measurement of this organ’s total metabolism. It has been known for many years that the total metabolism of the arrested, quiescent heart is only a small fraction of that of the working organ. Thus, while the oxygen consumption of the beating heart ranges from 3 to 15 ml/min/lOO Gm. of left ventricle, the oxygen consumption of the heart arrested with excess potassium is only 1.2 to 1.4 ml/min/lOO Gm. The major purpose of the investiga-tive efforts, to be reviewed herein, has involved the identification of those aspects of cardiac activity which are responsible for the differ-ence between these basal levels and those occurring during activity. The contractile process is a complex one and is initiated by electri-