Nifekalant for shock-resistant atrial fibrillation.
Introduction: In severely ill patients, the development of atrial fibrillation (AF) may provoke lethal hemodynamic instability requiring immediate electrical defibrillation, which often is unsuccessful. Using the novel potassium channel blocking agent nifekalant, we prospectively assessed the hypothesis that class III antiarrhythmic drugs facilitate electrical cardioversion and suppress the immediate recurrence of hemodynamically deleterious AF.
Methods and results: Among 1896 adults admitted to the intensive care unit for cardiovascular diseases, hemodynamically destabilizing new-onset AF (systolic blood pressure<90 mm Hg) resistant to conventional electrical cardioversion occurred in 27 patients, and of these, 24 patients (70+/-12 years) were enrolled. Twenty-one patients had congestive heart failure and 11 patients had been mechanically ventilated. After three failed transthoracic cardioversions due to failure of conversion to SR (11 patients) or immediate reinitiation (13 patients), nifekalant (0.25+/-0.04 mg/kg) was administered intravenously, and electrical defibrillation was reattempted. In 18 patients (75%), sinus rhythm was restored and maintained after nifekalant infusion (6 patients) or subsequent transthoracic cardioversion (12 patients). Nifekalant administration significantly decreased the heart rate and increased systolic blood pressure during AF (P<0.001), and successful cardioversion rapidly further ameliorated these parameters (P<0.001). Logistic regression analysis showed that atrial defibrillation failure (relative risk [RR] 19.34, P=0.05) and age of >75 years (RR 15.25, P=0.03) were independent predictors of in-hospital death.
Conclusion: Nifekalant renders electrical defibrillation and the prevention of the early recurrence of hemodynamically unstable AF more successful without deteriorating hemodynamics, and successful defibrillation is associated with a more favorable patient outcome. Pretreatment with other class III drugs, e.g., ibutilide or dofetilide, would also be efficacious in patients with failed urgent electrical cardioversion.