Clinical Study of the Acute Effects of Intravenous Nifekalant on the Defibrillation Threshold in Patients With Persistent and Paroxysmal Atrial Fibrillation

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Background Antiarrhythmic agents are considered to have significant effects on the defibrillation energy requirement, so this study investigated the effects of nifekalant on defibrillation. Methods and Results Forty-two patients with persistent atrial fibrillation (AF) underwent electrical cardioversion via intracardiac electrode catheters prior to and after the intravenous administration of nifekalant. The success rate of the defibrillation and change in the defibrillation threshold using sequential incremental defibrillation energy deliveries was investigated. In addition, the parameters that could predict the beneficial effects of nifekalant were also assessed. Nifekalant significantly decreased the defibrillation energy requirement in 13 of the 42 cases, and nifekalant also converted AF to sinus rhythm with an identical energy to that of the last unsuccessful defibrillation in 21 of 42 cases. The success of defibrillation seemed to be dependent on significant prolongation of the intracardiac atrial electrogram intervals during AF by the nifekalant. Conclusions Intravenous nifekalant significantly improved the electrical defibrillation efficacy in patients with persistent AF that was resistant to defibrillation, without any serious adverse effects. (Circ J 2008; 72: 76 - 80)