The effects of nifekalant hydrochloride on the spatial dispersion of repolarization after direct current defibrillation in patients with oral amiodarone and β-blocker therapy

Background: Although nifekalant hydrochloride (NIF) has been demonstrated to suppress ventricular tachyarrhythmias, especially electrical storms, the mechanism by which it does so is still unclear. We examined the effects of NIF on the spatial dispersion of repolarization (SDR) after implantable cardioverter-defibrillator (ICD) shock.Methods and Results: In 35 patients with oral amiodarone and beta-blocker therapy, and an ICD, we recorded the 87-lead electrocardiogram during sinus rhythm (CONTROL-1 group) under general anesthesia, and just after the termination of induced ventricular fibrillation (VF) by ICD shock, with or without NIF administration. In all recordings, the corrected QT interval (QTc) was measured in each lead. The dispersion of QTc (QTc-D; maximum QTc minus minimum QTc) was also measured. Compared with that in the CONTROL-1 group, the QTc-D exhibited significant deterioration after ICD shock (61+/-14 and 90+/-19 ms(1/2), respectively; p<0.05). However, after the termination of induced VF by ICD shock with NIF administration, the QTc-D did not differ significantly from that in the CONTROL-1 group (63+/-20 and 61+/-14 ms(1/2), respectively).Conclusions: NIF suppressed the deterioration of the SDR after ICD shock. This might be one of the mechanisms by which NIF suppresses recurrence of ventricular tachyarrhythmia just after ICD shock in patients with oral amiodarone and beta-blocker therapy. (C) 2013 Japanese Heart Rhythm Society. Published by Elsevier B.V. All rights reserved.