Impact of prophylactic i.v. magnesium on the efficacy of ibutilide for conversion of atrial fibrillation or flutter.

The impact of prophylactic i.v. magnesium on the efficacy of ibutilide for conversion of atrial fibrillation and flutter to normal sinus rhythm was studied. In this multicenter cohort study, all patients in three large, tertiary care centers who received ibutilide for acute chemical conversion of atrial fibrillation or flutter from August 1996 through December 2001 were identified through pharmacy or billing records. Patients who did not receive magnesium before or during ibutilide therapy served as the control group, while those who received magnesium less than two hours before or during ibutilide administration served as the study group. The rate of administration of direct-current cardioversion (DCC) and the occurrence of ventricular arrhythmia were compared between those who did and did not receive magnesium. The rates of successful cardioversion were also assessed. Categorical data were analyzed using chi-square analysis or Fisher's exact test. Demographic data were analyzed using Student's t test. The medical records of 321 patients were analyzed. Successful chemical cardioversion in the study group was approximately 19% higher than in those who did not receive magnesium (p = 0.040). The use of DCC in the group who received magnesium was reduced by approximately 34% (p = 0.045). The conversion rate of atrial fibrillation or flutter with ibutilide was enhanced by magnesium administration (p = 0.040), and the rate of administration of DCC was reduced (p = 0.045) in patients who received magnesium. There was a nonsignificant reduction in the occurrence of ventricular arrhythmias (p = 0.533). The efficacy of ibutilide was enhanced by concomitant administration with intravenous magnesium.