Emergency Treatment With Nifekalant, a Novel Class III Anti-Arrhythmic Agent, for Life-Threatening Refractory Ventricular Tachyarrhythmias : Post-Marketing Special Investigation

Background Because class I anti-arrhythmic drugs sometimes suppress cardiac function caused by their negative inotropic effects, they are not adequate for use in patients with severe heart failure, even as emergency treatment for life-threatening ventricular tachyarrhythmias (ventricular tachycardia (VT)/ventricular fibrillation (VF)). Methods and Results An objective evaluation committee re-evaluated the effect of nifekalant in 191 patients with refractory VT/VF. The attack termination was achieved in 45 out of 93 patients (48.4%). Nifekalant was administered to 39 patients with direct-current (DC) shock-resistant VT/VF and directly terminated VT/VF in 9 patients. In 15 of the remaining 29 patients (51.7%), VT/VF was successfully cardioverted by additional DC shock after nifekalant administration. Prevention of recurrence was achieved in 60 out of 99 patients (60.6%). Corrected QT interval (QTc) was significantly prolonged after initial administration of nifekalant (0.463±0.056 to 0.504±0.072), and during maintenance infusion (0.470±0.056 to 0.547±0.070). As an adverse reaction, excess prolongation of QTc was noted in 11 patients including 3 patients with torsades de pointes. Hemodynamic parameters tended to improve after maintenance infusion of nifekalant. Conclusion Nifekalant is effective and useful for life-threatening refractory ventricular tachyarrhythmias, although careful observation of the QT interval is required.