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-blocke r with vasodilating action, reduces left ventricular cavity dilation ( LV remodeling) following myocardial infarction and improves cardiac pe rformance. Myocardial infarction was produced by coronary artery ligat ion 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% carboxymethylce llulose). The effect of nipradilol on LV remodeling was evaluated by a ssessing the left ventricular end-diastolic volume index (LVEDVI) and passive pressure-volume relation curve. Since LVEDVI depends on the in farct size, LVEDVI was compared between the vehicle- and nipradilol-tr eated rats with similar infarct size (10-40%). At 3-4 months after myo cardial infarct production, the left ventricular end-diastolic volume index in the vehicle-treated rats with myocardial infarction was signi ficantly increased, compared with that in the sham-operated rats witho ut 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 nip radilol-treated group, P<0.01). The maximum cardiac index achieved by volume loading as an index of cardiac performance was significantly gr eater 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 nipradilo l group, P<0.01). These results suggest that chronic treatment of nipr adilol attenuated left ventricular cavity dilation after myocardial in farction and improved cardiac performance.