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

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Abstract

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.

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