Comparison of the Effects of Na+ and K+ Channel Blockers on the Electrophysiological Properties of the Pulmonary Veins in Patients with Atrial Fibrillation

Abstract

Introduction: We assessed the effects of pilsicainide, a pure Na+ channel blocker, and nifekalant, a pure rapid delayed rectifier potassium current (IKr) blocker, on the electrophysiological characteristics within the pulmonary vein (PV) and at the PV-left atrial (LA) junction. Methods and Results: We used a basket catheter for PV mapping in 38 patients with paroxysmal atrial fibrillation (AF). Programmed stimulation was performed in the distal PV and PV-LA junction before and after the infusion of pilsicainide (1 mg/kg; n = 24) or nifekalant (0.3 mg/kg; n = 14). Both drugs significantly prolonged the effective refractory period (ERP) of the distal PV and PV-LA junction. Pilsicainide significantly decreased the ERP heterogeneity of the PV and PV-LA junction (36 ± 43 vs. 9 ± 60 ms, P < 0:05). In contrast, nifekalant significantly increased the ERP heterogeneity of the PV and PV-LA junction (from 38 ± 34 to 60 ± 46 ms, P < 0:01). Pilsicainide significantly prolonged the conduction time (S1-A1) from the distal PV to the PV-LA junction (from 42 ± 12 to 63 ± 26 ms, P < 0:001), whereas this did not change with nifekalant. Conclusions: In AF patients, pilsicainide has antiarrhythmic effects mainly on the distal PV by modifying the ERP and conduction properties. In contrast, nifekalant has antiarrhythmic effects mainly on the PV-LA junction by modifying the ERP.

Keywords

• Nifekalant
• Pulmonary vein
• Atrial fibrillation
• Pilsicainide
• Electrophysiology