A simple in vivo model to evaluate the effects of antiarrhythmic agents.

Antiarrhythmic agents alter cardiac conduction, refractoriness, and action potential duration in a rate dependent fashion. A simple in vivo model was developed to measure these variables over a wide range of cycle lengths. Complete heart block was produced in dogs using an 8 French hexapolar ablation catheter, anterior skin electrode, and radiofrequency current (30 W, 13.6 +/- 2.6 seconds). Ventricular pacing and monophasic action potential recordings were performed using a single combination catheter. QRS and action potential durations were measured at multiple cycle lengths and after an abrupt change in paced cycle length. Ventricular effective refractory periods were also measured at multiple cycle lengths. Data obtained during flecainide and d-Sotalol infusions are presented. This simple model allows detailed in vivo evaluation of the electrophysiological effects of antiarrhythmic agents and combinations.