Clinical significance of positive inotropic action of digoxin in patients with left ventricular disease.

Oral digoxin was administered for io days to 9 patients with aortic Starr-Edwards prostheses. Its effect on the initial phase of left ventricular ejection was measured using a phonocardiographic method reflecting the initial acceleration of blood into the ascending aorta, and was correlated with plasma levels of the drug. A positive inotropic effect was present, maximum 4 to 6 hours after first administration. The response was not correlated with the plasma levels which reached a peak at 2 to 3 hours. The magnitude of the effect was approximately one-third of that produced by mild supine exercise, and in individual patients there was close correlation between the effects of the two positive inotropic stimuli, suggesting variation in responsiveness from one patient to another. No significant positive inotropic effect attributable to digoxin could be demonstrated later in the study though plasma levels of the drug were within the therapeutic range throughout. It was concluded that the positive inotropic effect of digoxin in these patients with left ventricular disease