Mechanisms of the preventive effect of pilsicainide on atrial fibrillation originating from the pulmonary vein.

Background: It has been shown that pilsicainide terminates atrial fibrillation (AF) by pharmacologic pulmonary vein (PV) isolation. However, whether it can prevent AF induction originating from the PV by the same mechanism is still uncertain.

Methods And Results: Rapid pacing from the left superior PV (LSPV) and the right atrial free wall (RAF) was performed to induce AF during electrical stimulation of both cervical vagal nerves in 6 anesthetized dogs and during the infusion of acetylcholine (ACh) in 8 isolated atria. Rapid pacing induced AF in all dogs, regardless of the pacing site, before pilsicainide. Pilsicainide (1 mg/kg) prevented AF during rapid pacing from the LSPV, with an impulse conduction block between the LSPV and the left atrial free wall (LAF). However, the same dose of pilsicainide did not prevent AF when pacing was performed from the RAF. Pilsicainide partially restored the action potential duration shortened by ACh infusion and prevented AF with an impulse conduction block at the LSPV-left atrial junction in all isolated preparations tested.

Conclusion: The results suggest that (1) impulse conduction block at the LSPV-LA junction is the underlying mechanism of pilsicainide-induced prevention of vagally-induced AF originating from the LSPV and (2) pilsicainide is more effective at preventing AF originating from the LSPV than that from the RA.