Relative effectiveness of three antiarrhythmic agents in the treatment of ventricular arrhythmias in experimental acute myocardial ischemia

Since ventricular arrhythmias complicating acute myocardial infarction in man have an uncetain course, an animal model of acute ischemia was used to compare three commonly used agents—procainamide, lidocaine, and diphenylhydantoin.A total of 150 dogs were divided into “treatment only” and “prophylaxis plus treatment” groups for each of the three agents. Twenty additional dogs served as untreated controls.The arterial branch (left circumflex or anterior descending branch) had no effect on ultimate success in preventing ventricular fibrillation with drug therapy for at least 4 hours. Ninety per cent of untreated controls developed fatal ventricular fibrillation within 4 hours. Among the “treatment only” groups 4 hour survival with procainamide (80 per cent) was significantly higher than with lidocaine (45 per cent) or diphenylhydantoin (56 per cent). Prophylactic administration of drugs following S-T-segment elevation but preceding ventricular arrhythmias did not increase survival rate. Following acute myocardial ischemia in the previously undamaged heart, procainamide appears to afford greater protection against ventricular fibrillation than the other two agents.