EFFECTS OF PROPAFENONE ON SINUS NODE FUNCTION IN THE RABBIT HEART

Propafenone is a type 1C antiarrhythmic drug with efficacy for both ventricular and supraventricular arrhythmias. We investigated the effects of propafenone on properties of sinus node function in an in vitro preparation of rabbit sinus node and surrounding atrium. Spontaneous sinus cycle length (SCL), atriosinus conduction time (ASCT), and sinus node effective refractory period (SNERP) at multiple pacing cycling lengths were measured in the control state and during superfusion with propafenone (2.3 μM). SNERP prolonged from 175 ± 25 ms in the control state to 220 ± 45 ms (p < 0.001) with propafenone. ASCT also prolonged significantly (p < 0.01) from 50 ± 20 ms to 65 ± 20 ms whereas SCL did not change. In four experiments, multiple concentrations of propafenone were utilized and there appeared to be a dose-dependent prolongation of SNERP. Thus, propafenone has a significant effect on SNERP and ASCT in an isolated rabbit sinus node preparation.