Direct digitalization of the myocardium: Hemodynamic effects

Abstract

Administration of the short-acting digitalis preparation acetyl strophanthidin directly into the left main coronary artery in dogs causes an increase in left ventricular dp/dt and a fall in left ventricular end-diastolic pressure, but no change in aortic mean pressure, heart rate, or cardiac output. With peripheral infusion of acetyl strophanthidin, however, arteriolar vasoconstriction, rise in aortic pressure and increased afterload to contraction occur and result in diminished cardiac output and rise in left ventricular end-diastolic pressure; bradycardia also occurs. Because of these changes in pressure and rate with systemic digitalization, derived hemodynamic variables such as stroke power are unreliable indicators of a change in contractility. The data indicate that digitalis has a direct myocardial positive inotropic effect manifested by an increase in rate of pressure development and improvement in the ventricular function curve of the left ventricle.