Experiments in the isolated, supported heart preparation were performed in which the influence of graded doses of acetyl strophanthidin on myocardial oxygen consumption and efficiency was determined. Aortic pressure, heart rate and stroke volume, hemodynamic variables which can influence oxygen consumption and efficiency independently of drug action, were held constant or almost so. Under such circumstances, treatment with acetyl strophanthidin produced a marked increase in myocardial contractility without a change of either oxygen consumption or efficiency. When acute left ventricular failure was induced by a maintained restriction of coronary blood flow, acetyl strophanthidin therapy also produced a marked contractility increase, again with no change in oxygen consumption or efficiency. The evidence supporting the position that the digitalis glycosides have a different pharmacologic effect on the normal and failing heart is discussed.
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