The effects of nifekalant hydrochloride on the QT dispersion after direct-current defibrillation.

Background: Although nifekalant hydrochloride (NIFE) has been demonstrated to suppress ventricular tachyarrhythmia, especially electrical storm, the mechanism by which it does so is still unclear. We examined its effects on the spatial dispersion of repolarization (SDR) after implantable cardioverter-defibrillator (ICD) shock.

Methods and results: In twenty five patients with an ICD, we recorded the 87-lead ECG during sinus rhythm (the CONTROL group) under general anesthesia, after NIFE administration alone, and just after termination of induced ventricular fibrillation (VF) by ICD shock with or without NIFE 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 the CONTROL, the QTc-D exhibited significant deterioration after ICD shock (61 +/- 12, 91 +/- 24 ms(1/2), respectively, p < 0.001). However, the QTc-D after NIFE administration either with or without ICD shock did not differ from the CONTROL group (65 +/- 20, 61 +/- 18, and 61 +/- 12 ms(1/2), respectively, p = 0.99).

Conclusions: NIFE suppressed the deterioration of SDR by ICD shock. This might be a mechanism by which NIFE suppresses recurrence of ventricular tachyarrhythmia after ICD shock.