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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 β-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 ms1/2, respectively; p

Nifekalant hydrochloride is a novel class III antiarrythmic agent used especially for malignant VT/VF, which is resistant to electrical defibrillation and lidocaine. We previously reported that this agent restored the sinus rhythm from ventricular fibrillation more successfully than lidocaine. A 60-year-old female was transferred to the Emergency Medical Center of Tokai University Hospital because of cardiac arrest due to ventricular fibrillation. After several unsuccessful attempts at electrical defibrillation at the scene and the emergency room, we administrated nifekalant hydrochloride before lidocaine. With the infusion of nifekalant, the patient was successfully defibrillated. A 57-year-old female also admitted to our hospital with recurrent ventricular fibrillation that was resistant to electrical defibrillation. In situations of VT/VF resistance to electrical defibrillation, lidocaine has been used prior to nifekalant. However, we selected nifekalant first, with which the patient was successfully defibrillated. After the infusion of nifekalant hydrochloride, the sinus rhythm was restored. We concluded that nifekalant hydrochloride is especially effective for recurrent ventricular fibrillation and it should be administrated as early as possible.

We report two cases that the combination of amiodarone and nifekalant hydrochloride (NIF) is useful against electrical storm (ES). The first patient is 81-year-old man with CRT-D because of ischemic cardiomyopathy (ICM). He was admitted to add class III antiarrhythmic agent due to frequent ICD therapy. On admission day he felt palpitation followed by strong shock. Electrocardiogram showed frequent sustained VT accompanying ICD therapy. The injection of amiodarone followed by continuous intravenous injection (CIV) reduced the frequency of VT, but not suppressed completely. After additional CIV of NIF the patient no longer experienced the VT. During the ES 60 times of antitachycardia pacing, 13 times of 15 J cardioversion, and nine times of 35 J direct current were recorded in no more than 19 minutes. The second one is 56-year-old man with chronic heart failure due to ICM. He was admitted to control heart failure (HF). In spite of the treatment for HF, he had sustained VT with circulatory collapse and CRT-D was implanted. After the implantation, even taking oral amiodarone, he had ES and underwent the treatment with ICD shocks. Also in this case, additional CIV of NIF suppressed the VT and reduced ICD shock dramatically.