br Conclusion br Funding br Conflict of interest
Conflict of interest
Introduction Ventricular tachyarrhythmias (VTs) are life-threatening events that result in hemodynamic compromise; therefore, patients often require immediate treatment such as electrical cardioversion. Despite appropriate management of ventricular arrhythmias, recurrence is common and may worsen the clinical course of the patients. The American Heart Association (AHA) guideline on cardiopulmonary resuscitation (CPR) and emergency cardiovascular care states that when ventricular arrhythmias are refractory to defibrillation, antiarrhythmic agents, such as amiodarone, lidocaine, and magnesium sulfate, can be used [1,2]. Lidocaine has been used empirically for the prevention of ventricular arrhythmias. However, when compared to amiodarone, it guanidine hydrochloride has not been demonstrated to improve the return of spontaneous circulation (ROSC) or survival to hospital discharge. Some studies suggested that amiodarone was superior to lidocaine for the management of ventricular arrhythmias [3,4]. However, its antiarrhythmic effect has a late onset, and a large dose is needed to terminate ventricular arrhythmias in emergent settings. Furthermore, bradycardia and hypotension may occur after resuscitation as a result of its β-adrenergic blocking effect and vasoactive effect of the excipients, polysorbate 80 and benzyl alcohol . Nifekalant, a pure potassium channel blocker, was clinically approved and is currently used only in Japan. Although some reports suggested that nifekalant was efficient for the treatment of refractory ventricular arrhythmias, only a small number of studies have directly compared class III drugs because it is difficult to carry out a randomized study in an emergent and critical care setting [6–11].
Material and methods
Discussion In management of ventricular arrhythmias, amiodarone plays a pivotal role in clinical practice, and current guidelines have recommended it as the first choice for intravenous infusion in cases of ventricular arrhythmias refractory to defibrillation. For a decade, nifekalant has been the only approved class III agent in Japan. It was demonstrated to suppress ventricular re-entry by prolonging the action׳s potential duration and effective refractory period without evidencing a negative inotropic effect [12–16]. Furthermore, this agent causes dose-dependent QT prolongation and torsade de pointes. In other countries, intravenous amiodarone has already been used for a few decades and has been established as a mainstay drug for various types of arrhythmias. After the clinical introduction of intravenous amiodarone in Japan, we could not determine which agent was superior for fetal ventricular arrhythmias treatment because there were a small number of clinical studies directly comparing these agents. One study reported that nifekalant was not inferior to amiodarone for the treatment of out-of-hospital cardiac arrest due to shock-resistant ventricular fibrillation . Since most VTs are life threatening, one cannot afford to spare time to obtain appropriate informed consent or to randomly choose antiarrhythmic drugs. A cluster randomization method may be a practical and promising solution to meet this need. According to our registry, three antiarrhythmic agents were used. These are amiodarone, lidocaine, and nifekalant. Lidocaine was conventionally used as first-line therapy, but several observational studies and a meta-analysis showed that lidocaine administration resulted in poor prognosis or no benefit in patients with acute myocardial infarction, therefore its routine use is not generally recommended by the current guidelines [18–20]. In contrast, another study demonstrated that prophylactic administration of lidocaine was associated with a decreased number of recurrent ventricular arrhythmias in post resuscitation periods . There is insufficient data evaluating the prophylactic uses of other antiarrhythmic drugs, and 2015 AHA guidelines stated that there was insufficient evidence on the routine administration of antiarrhythmic drugs after resuscitation; however, lidocaine might be considered [1,2].