Studies on digitalis. XVI. Effects on myocardial oxygen consumption.

The effects of cardiac glycosides on myocardial oxygen consumption (MVo2) have been investigated extensively, and although the results of these studies have not been entirely uniform, it is now generally considered that these agents are "the only drugs which increase the force of contraction of the myocardium without at the same time increasing oxygen consumption" (1). The finding in previous investigations that digitalis does not increase MVo2 (2-8) would not appear to be compatible with observations that the glycosides increase the velocity of myocardial fiber shortening (9, 10), since recent studies have suggested that the latter variable is an important determinant of MVo2 (11, 12). These considerations prompted an examination of the effect of acetylstrophanthidin on MVo2 in a preparation that allowed control of hemodynamic variables other than contraction velocity that can significantly influence MVo2.