Anti-arrhythmic effects of prazosin and propranolol during coronary artery occlusion and re-perfusion in dogs and pigs.

Open-chest dogs and pigs anaesthetized with pentobarbitone were used to evaluate the anti-arrhythmic effect of prazosin and propranolol during a 30 min period of occlusion of the left anterior descending coronary artery followed by 15 min of re-perfusion. In dogs, both prazosin and propranolol reduced the incidence of ventricular premature depolarizations and ventricular tachycardia during the occlusion period. During the 45 min period of occlusion and re-perfusion, the incidence of ventricular fibrillation was significantly reduced in the prazosin-treated and propranolol-treated dogs. In pigs prazosin reduced the incidence of ventricular premature depolarizations during occlusion and propranolol reduced the incidence of both ventricular premature depolarizations and ventricular tachycardia during occlusion, but the incidence of ventricular fibrillation was not significantly reduced in the prazosin- and propranolol-treated pigs. Prazosin reduced arterial pressure and propranolol lowered heart rate in both dogs and pigs, but a comparison of mean arterial pressure and heart rate in animals surviving and those not surviving the 30 min of coronary artery occlusion and 15 min of re-perfusion showed no significant difference.