Effects of milrinone on left ventricular remodeling after acute myocardial infarction.

BACKGROUND Left ventricular remodeling after an acute myocardial infarction may result in progressive left ventricular dilation that may be associated with increased mortality. We studied the effects of the phosphodiesterase inhibitor milrinone on left ventricular remodeling after acute myocardial infarction. METHODS AND RESULTS Rats (n = 90) were randomized to undergo either left coronary artery ligation or sham operation. Three weeks after surgery, rats received either no treatment or milrinone, which was continued until 2 days before the rats were killed. Ninety days after the initial surgery, hemodynamic measurements were made before and after volume loading. The rats were killed, the hearts were removed, and passive pressure-volume curves were obtained. The hearts were fixed at a constant pressure and analyzed morphometrically. Compared with untreated infarcted rats, milrinone-treated infarcted rats had a lower left ventricular end-diastolic pressure (1.7 +/- 0.4 versus 4.3 +/- 1.4 mm Hg, p less than 0.05), a lower left ventricular volume (1.25 +/- 0.20 versus 2.37 +/- 0.30 ml/kg, p less than 0.001) and a lower left ventricular wall stress index (1.3 +/- 0.2 versus 1.7 +/- 0.1, p less than 0.05). Left ventricular chamber stiffness was higher in milrinone-treated infarcted rats than in untreated infarcted rats. Milrinone had no cardiac effect on uninfarcted animals. CONCLUSION Chronic milrinone therapy after acute myocardial infarction improves cardiac hemodynamic indexes and attenuates progressive left ventricular dilation.