Effect of Flecainide on Longitudinal and Transverse Conduction Velocities in Ventricular Myocardium. An Experimental Study

It is known that the effect of flecainide on longitudinal and transverse ventricular conduction velocities depends on the coupling interval. If this is so, whether the longitudinal or transverse direction is predominantly affected could depend on the magnitude of the coupling interval. In order to investigate this hypothesis, we studied the effect of flecainide, 1 µmol/L, on conduction velocities in excised heart preparations from 11 rabbits using a basal cycle length of 250 ms and inserting 2 extrastimuli at a decreasing coupling interval. Flecainide significantly reduced both conduction velocities. However, the effect increased as the coupling interval decreased for only the longitudinal velocity. At long coupling intervals, flecainide produced a greater reduction in transverse than longitudinal velocity, whereas, at short intervals, both velocities were affected similarly.