Effect of lidocaine on ventricular conduction in acutely ischemic dog hearts

The effect of graded doses of lidocaine (1.25-10 mg/kg) on endocardial Purkinje and transmural conduction at different heart rates as well as during extrasystolic stimulation was studied in dogs, 30 min after ligation of the anterior descending coronary artery. The drug had no effect on endocardial conduction within the ischemic zone except at the highest dose. Transmural conduction time was increased by ischemia in only 50% of dogs. Transmural conduction time was increased further at high heart rates but not by short coupled extrasystoles. Lidocaine slowed conduction further in the ischemic myocardium by a process that was both rate and interval dependent. "Apparent" supernormal transmural conduction was observed during short coupled extrasystoles but not at fast drive rates. This phenomenon was blocked only by administration of high doses of lidocaine.