Evaluation of the Vasodilator vs Inotropic Effect of Milrinone Using an Animal Model of Left Ventricular Failure: Reversal of Disopyramide Depression of the Myocardium with Milrinone

Abstract

Milrinone (M) has been shown to improve left ventricular (LV) performance in animal and human studies. M has strong vasodilator action, and whether increased LV performance is due primarily to vasodilation or to a direct positive inotropic effect is unclear.

Ten mongrel dogs were studied. Disopyramide caused a significant and sus tained decrease in LV function and was a good model for myocardial depres sion. At equal reduction in systemic vascular resistance (SVR), M reversed this LV depression to a significantly greater degree than nitroprusside (NP) did.

At equal levels of vasodilation, M produced significantly greater improve ment in indices of LV function than NP did in our model of disopyramide- induced LV failure. This suggests that its effect on LV function is not due entirely to afterload reduction, or to reflex sympathetic stimulation, but has a substantial component of direct inotropic stimulation. This study also demon strated a reversal of disopyramide-induced LV dysfunction by M, which may be clinically useful since, as in many antiarrhythmics, myocardial depression may be a limiting factor in its use.

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