Effects of lidocaine, disopyramide and verapamil on the in vivo triggered ventricular arrhythmia in digitalized canine heart.

Triggered activity due to delayed after depolarization has been postulated to be one of the generation mechanisms of some arrhythmias, especially that due to digitalis toxicity. The present experiment demonstrates an in vivo canine model of ventricular arrhythmias that were triggered by ventricular stimulation during administration of low doses of ouabain. Ventricular ectopic beats could be induced by stimulation before the occurrence of spontaneous ventricular arrhythmia, and the coupling interval of the first ectopic beat was shortened as the stimulation rate increased. Verapamil (0.2 mg/kg, i.v.) was ineffective in suppressing the occurrence of the triggered ventricular ectopic beats, but lidocaine (1 and 3 mg/kg, i.v.) and disopyramide (0.3 and 1 mg/kg, i.v.) were effective in suppressing these digitalis-induced triggered ventricular ectopic beats in a dose-dependent fashion.