Differentiation of the Electrophysiological Effects on the Atrial Myocardium Between the Pure Na Channel Blocker, Pilsicainide, and Flecainide

The purpose of this study was to identify the difference between the pure Na channel blocker, pilsicainide and Ic-antiarrhythmic drug, flecainide, on the atrial electrophysiological characteristics. METHODS: The subjects consisted of 24 patients (48 +/- 12 years-old: P-group) in whom pilsicainide was administrated intravenously (1 mg/kg/10 min) and 31 patients (47 +/- 15 years-old: F-group) in whom flecainide was administrated intravenously (2 mg/kg/10 min). The atrial effective refractory period (ERP-A), intra-atrial conduction time (CT), max intra-atrial conduction delay (Max CD), repetitive atrial firing zone (RAFZ), fragmented atrial activity zone (FAZ) and intra-atrial conduction delay zone (CDZ) were measured before and after the drugs. RESULTS: Pilsicainide and flecainide significantly prolonged the ERP-A (211 +/- 27 msec to 246 +/- 39 msec; p < 0.001, 217 +/- 25 msec to 244 +/- 33 msec; p < 0.001, respectively) and CT (121 +/- 33 msec to 149 +/- 43 msec; p < 0.001, 122 +/- 22 msec to 153 +/- 27 msec; p < 0.001, respectively) to the same degree. However, the Max CD was shortened by pilsicainide, but not by flecainide. The RAFZ, FAZ and CDZ decreased in the P-group (21 +/- 25 msec to 4 +/- 10 msec; p < 0.01, 24 +/- 24 msec to 14 +/- 18 msec; p < 0.05, 56 +/- 29 msec to 43 +/- 32 msec, p < 0.05, respectively), but not in the F-group. CONCLUSIONS: The effects of atrial conduction delays may differ between pilsicainide and flecainide. Further examination will be needed to explain this mechanism.