Chronic Therapy with Nipradilol, a .BETA.-Adrenergic Blocker, Attenuated Left Ventricular Remodeling Following Myocardial Infarction in Rats.

We determined whether chronic treatment with nipradilol, a beta-blocker with vasodilating action, reduces left ventricular cavity dilation (LV remodeling) following myocardial infarction and improves cardiac performance. Myocardial infarction was produced by coronary artery ligation in 16-week-old female rats and then the rats were treated for 3-4 months with nipradilol (10 mg/kg/day) or vehicle (0.5% carboxymethylcellulose). The effect of nipradilol on LV remodeling was evaluated by assessing the left ventricular end-diastolic volume index (LVEDVI) and passive pressure-volume relation curve. Since LVEDVI depends on the infarct size, LVEDVI was compared between the vehicle- and nipradilol-treated rats with similar infarct size (10-40%). At 3-4 months after myocardial infarct production, the left ventricular end-diastolic volume index in the vehicle-treated rats with myocardial infarction was significantly increased, compared with that in the sham-operated rats without infarction. The nipradilol-treated rats had a significantly smaller left ventricular volume index than the vehicle-treated rats (2.04 +/- 0.16 ml/kg in the vehicle-treated group vs 1.36 +/- 0.10 ml/kg in the nipradilol-treated group, P < 0.01). The maximum cardiac index achieved by volume loading as an index of cardiac performance was significantly greater in the nipradilol group than the vehicle group (254.5 +/- 12.6 ml/min kg in the vehicle group vs 347.9 +/- 20.2 ml/min kg in the nipradilol group, P < 0.01). These results suggest that chronic treatment of nipradilol attenuated left ventricular cavity dilation after myocardial infarction and improved cardiac performance.