The Effect of Digitalis on Ventricular Ejection in Normal Human Subjects.

W HILE animal studies have demonstrated that digitalis enhances the force of contraction of the nonfailing heart,'X the effects of this agent on ventricular contractility of the normal human heart are as yet unsettled. In the absence of clinical heart failure, digitalis administration is associated with either a slight decrease -9 or no significant change in cardiac output.10-'4 Such observations have led to a widely held clinical impression that digitalis exerts its salutary effects only in the failing human heart 15, 16 and may even exert an adverse influence on the contractility of the normal heart.17 In contrast, Braunwald, Bloodwell, Goldberg, and Morrow,18 employing direct measures of ventricular tension during thoracotomy in individuals without heart failure, have offered strong evidence favoring the stimulatory effect of digitalis on the nonfailing heart. In 1927, in their studies on the cardiodynamic actions of digitalis and g-strophanthidin, Wiggers and Stimson 19 demonstrated that the increased myocardial systolic force induced by digitalis is associated with a shortening in the duration of mechanical systole. A similar decrease in the duration of mechanical systole accompanying the positive inotropic effect of digitalis has been observed by Cotten and Bay,3 who noted a linear relationship between the myocardial force and the decrease in the duration of the isometric pressure gradient.