[Prevention of ventricular fibrillation in animal experiments]

The precursors of ventricular fibrillation and asystole developing after ligation of a branch of the coronary artery and adrenalin injection were studied in 30 albino rats. The comparative efficacy of antiarrhythmic agents (ajmalin, lidocaine, isoptin, visken) in the prevention of ventricular fibrillation induced by electric current was determined in 40 rats. Ventricular extrasystole and tachysystole as well as the block of the bundle of His branch were the most common precursors of ventricular fibrillation. In some experiments fibrillation was preceded by complete atrioventricular block, cardiac fibrillation, sinus bradycardia, nonparoxysmal ventricular tachycardia, and excaped ventricular contractions. Ventricular asystole was most frequently preceded by complete atrioventricular block and the bundle of His branch block. Among the antiarrhythmic agents studied, ajmalin proved most effective in prevention of ventricular fibrillation; it raised the fibrillation threshold in all animals. Lidocaine, which produced a prophylactic effect in 50% of experiments, was second in effectiveness. Changes in the ventricular fibrillation threshold due to the effect of these agents were statistically significant on the average. Isoptin and visken proved to be less effective.