Efficacy of Pilsicainide After Radiofrequency Ablation of Paroxysmal Atrial Fibrillation

Catheter ablation has become an integral part of the management of atrial fibrillation (AF), when a strategy to preserve normal sinus rhythm is required. However, recurrence of atrial arrhythmias is common after AF ablation. In order to prevent these arrhythmia recurrences, antiarrhythmic drugs (AADs) are often resumed empirically after AF ablation. Previously a prospective randomized trial demonstrated that the treatment with AADs during the first 6-weeks after AF ablation reduced the incidence of clinically significant atrial arrhythmias and need for cardioversion or hospitalization for arrhythmia management.

Pilsicainide is a class IC antiarrhythmic drug originally developed in Japan, which has a pure sodium channel blocking action with slow recovery pharmacokinetics. Its mechanism of action appears to provide new insight into the pharmacological conversion of AF.

In experimental studies, pilsicainide has a potent depressant effect on intra-atrial conduction and a prolonging effect on the atrial effective refractory period (ERP). Theoretically the suppression of conduction velocity minimizes the prolongation of wavelength induced by the increase in the ERP and may thus serve to allow the continuation of multiple re-entrant wavelets. Iwasa et al demonstrated that pilsicainide was more effective at terminating vagally induced AF than propafenone, despite the greater effect of propafenone on wavelength, suggesting that suppression of conduction velocity may play an important role in terminating AF. Moreover, Wijffels et al reported that the pharmacological cardioversion of AF cannot be explained by the prolongation of wavelength.

The effects of a single oral treatment of pilsicainide were compared with that of a disopyramide infusion in a multicentre trial. Seventy two patients with symptomatic paroxysmal AF were randomised to receive either a single oral dose of pilsicainide (100-150mg) or an infusion of disopyramide (2 mg/kg; maximum dose = 100mg). In the pilsicainide group, the cumulative percentage of conversion to sinus rhythm within 120 minutes was high as disopyramide (73% vs 56%). Moreover, the conversion time of pilsicainide is shorter than that of other class IC antiarrhythmics, including flecainide and propafenone, in patients with recent-onset AF. This seems likely to be due to the favorable pharmacokinetics of pilsicainide, including its rapid absorption from the gastrointestinal tract, the absence of changes from a first-pass effect, and a short elimination half-life.

In the case of an unsuccessful ablation for AF, AADs that were ineffective before the ablation are sometimes effective. The effects and mechanisms of hybrid therapy with pilsicainide and PV isolation for AF have been assessed. Seventy four patients with paroxysmal AF in whom pilsicainide was ineffective underwent PV isolation. A second PV isolation was performed in 31 patients among 42 recurred patients (57%). Pilsicainide was re-administered in recurred patients even after the second session. Amng 21 patients with recurrence of AF, pilsicainide and eliminated AF in 11 patients (success with hybrid therapy was 86%).

In patients with paroxysmal AF, pilsicainide significantly prolonged the ERP of the distal pulmonary vein (PV), PV-left atrium (LA) junction and LA, and the conduction time from the distal PV to the PV-LA junction. In some patients, PV-LA conduction block has been observed just before pilsicainide-induced termination of AF; this isolation of the PV may provide a new insight into the mechanism of pharmacological conversion of AF. Hybrid therapy with pilsicainide and PV isolation (by radiofrequency catheter ablation) appears to be an effective therapeutic approach for AF. The pharmacological PV isolation by pilsicainide and its suppression of focal discharges from atrial tissue may prevent the development of AF after unsuccessful ablation. These mechanism makes it suitable for hybrid therapy with catheter ablation of the PVs.

Therefore investigators hypothesized that the use of Pilsicainide after radiofrequency ablation of AF could reduce the incidence of recurrence of atrial arrhythmia during follow up compared with other AADs. Furthermore, we seek to identify whether there are clinical predictors of AF recurrence at 1-year follow-up and the relationship of early recurrence during blanking period and recurrence during 1-year follow up.