[Effect of pilsicainide hydrochloride on atrial fibrillation threshold]

To inventigate the electrophysiologic effects of pilsicainide hydrochloride on atrial fibrillation, we compared atrial fibrillation threshold (AFT), right atrial effective refractory period (RAERP), and inter-atrial conduction time (Inter-ACT) before and after the administration of pilsicainide in 12 patients with lone paroxysmal atrial fibrillation. The following electrophysiologic study was performed before and after the administration of the drug as the paced cycle length of 500msec. First, RAERP was measured. Secondly, Inter-ACT from the stimulating artifact to the initial deflection in the elecrocardiograms of the coronary sinus was measured. Thirdly, high-frequency (50Hz) stimulation was given at right atrial appendage continuously for one second just after the eighth basic paced beat. The stimulation current was increased by 1mA in a stepwise fashion from 2mA until atrial fibrillation ensued. AFT was defined as the lowest intensity of the current that induced atrial fibrillation or flutter of more than 30 seconds. Pilsicanide significantly increased AFT and Inter-ACT, but did not change RAERP. In conclusion, it is suggested that pilsicainide might decrease atrial vulnerability mainly by its effect on inter-atrial conduction delay and by the resulting increase in AFT.