Comparison of the effects of pirmenol and lidocaine on intraventricular conduction in canine myocardial infarction

Effects of pirmenol hydrochloride and lidocaine hydrochloride on intraventricular conduction were examined in the infarcted heart of anesthetized dogs. The effects of the drugs on the excitation induced by ventricular stimulations were determined with coupling intervals between 150 and 1,000 ms. Effects of the drugs on the His bundle electrocardiograms were also examined. Pirmenol in doses of 1-5 mg/kg prolonged the conduction time in the infarcted zones over a wide range of coupling intervals. Pirmenol at 5 mg/kg blocked the delayed conduction at a short coupling interval in the infarcted zones. The effect of pirmenol on the conduction time in the normal zone was slight. Lidocaine in doses of 3 and 10 mg/kg prolonged the conduction time in the infarcted zone at a short coupling interval. Pirmenol did not significantly prolong PQ or AH interval. In conclusion, pirmenol selectively depressed the delayed conduction in the infarcted zone, which could result in a reentrant pathway. The effect of pirmenol on delayed conduction was dependent on the coupling interval and was quite different from that of lidocaine.