Laboratory studies suggest that nifekalant has no negative inotropic effects and no effect on cardiac conduction and hemodynamic status, whereas amiodarone has these effects via its β‐blocking action. On the other hand, nifekalant is a pure potassium channel blocker that specifically blocks the rapid component of delayed rectifier potassium currents without blocking sodium or calcium channels. In other words, amiodarone has negative inotropic and vasodilatory effects, which may negatively affect hemodynamic status after ROSC in OHCA patients. Amiodarone has several effects on ion channels, receptors, and sympathetic activity, in addition to blocking the rapid components of delayed rectifier potassium currents, such as sodium and calcium channel‐blocking effects, and α‐ and β‐receptor blocking actions. However, these two class III antiarrhythmic drugs have different pharmacological characteristics. Īmiodarone and nifekalant are both classified as class III antiarrhythmic agents (potassium channel blockers) in the Vaughan‐Williams classification. After the reports of two landmark studies on amiodarone, resuscitation guidelines were revised with preference for amiodarone over lidocaine in the treatment of cardiac arrest patients with persistent VF/pVT. One retrospective study suggested that lidocaine may improve the success rate of resuscitation, contrary to the negative results reported in other studies. Although lidocaine is low‐cost and simple to administer, evidence is not enough to suggest its superiority to other antiarrhythmic drugs or placebo in terms of rate of survival to hospital discharge of OHCA patients with persistent VF/pVT. Lidocaine is classified as a class Ib agent in the Vaughan‐Williams classification. Lidocaine was traditionally used as the drug of choice for the treatment of OHCA in patients with persistent VF/pVT until the early 2000s. reported survival data for patients with OHCA due to initial VF/pVT in the prehospital setting and found that survival rates with amiodarone or lidocaine administration were not significantly higher than with placebo. reported that the rate of survival to admission was significantly higher in the amiodarone group than in the lidocaine group but found no significant difference in the rate of survival to discharge between the two groups. In a trial involving OHCA patients with VF/pVT, Dorian et al. However, as mentioned in the knowledge gap section of the latest resuscitation guidelines, existing evidence is not enough to suggest that amiodarone is superior to lidocaine and/or nifekalant in terms of the critical outcome of survival to discharge. Lidocaine and nifekalant are recommended as alternatives to amiodarone in the treatment of refractory VF/pVT in adult patients. The ILCOR guidelines recommend the use of amiodarone as first‐choice treatment for adult patients with refractory VF/pVT to improve the rate of return of spontaneous circulation (ROSC). Īntiarrhythmic drugs that may be used include amiodarone, lidocaine, and nifekalant ( Table 1). ![]() Refractory VF/pVT is generally defined as failure to terminate VF/pVT with one to three stacked shocks. ![]() Even after three decades of accumulation of evidence, the 2015 International Liaison Committee on Resuscitation (ILCOR) guidelines still recommend immediate defibrillation with CPR as the treatment of choice for VF/pVT in OHCA patients and that antiarrhythmic drugs can be used as advanced life support during cardiac arrest in patients with refractory ventricular dysrhythmias. To overcome this time‐sensitive and severe condition that has a low survival rate, the “chain of survival” concept was first introduced by Newman in the 1980s as follows: (1) early access to emergency medical care (2) early cardiopulmonary resuscitation (CPR) (3) early defibrillation and (4) early advanced cardiac life support. ![]() Among all the presentations of cardiac arrest (asystole, pulseless electrical activity, ventricular fibrillation, and pulseless ventricular tachycardia ), VF and pVT are considered the most treatment responsive, but the rate of survival to hospital discharge after OHCA remains markedly low. ![]() Out‐of‐hospital cardiac arrest (OHCA) affects approximately 300,000 people in the United States, 280,000 people in Europe and 110,000 people in Japan each year.
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