HARTFORD, CONNECTICUT. Intravenous ibutilide (Corvert) is often used to chemically convert atrial fibrillation and atrial flutter to normal sinus rhythm. Unfortunately, the procedure only works in about 50% of cases and is accompanied by a 4% risk of developing Torsade de Pointes, a sometimes fatal ventricular arrhythmia. Researchers at the University of Connecticut now report that adding 4 grams of intravenous magnesium sulfate to the ibutilide protocol (2 grams before the first ibutilide dose and 2 grams over half an hour after the final ibutilide dose) will increase the odds of a successful conversion by a factor of 3.
The clinical trial included 229 patients who presented for cardioversion of atrial fibrillation (80%) or atrial flutter. Of these, 88% received ibutilide by itself, 87 patients received between 1 and 3 grams of intravenous magnesium sulfate, and the remaining 54 patients received a total of 4 grams of magnesium sulfate during the administration of ibutilide. The average age of the patients was about 66 years and most had hypertension or underlying heart disease. Only one case of Torsade de Pointes was observed during the trial and that involved a patient who was receiving ibutilide only. The beneficial effect of the addition of 1-3 grams of magnesium was not statistically significant indicating that at least 4 grams is needed.
The researchers speculate that the benefits of concomitant use of magnesium sulfate are related to magnesium's ability to increase intracellular potassium concentrations and regulate intracellular calcium concentrations.
Tercius, AJ, et al. Intravenous magnesium sulfate enhances the ability of intravenous ibutilide to successfully convert atrial fibrillation or flutter. PACE, Vol. 30, November 2007, pp. 1331-35
Editor's comment: Although there were very few lone afibbers in the study group, there is no reason to believe that the addition of magnesium sulfate to the ibutilide protocol would not benefit them as well. Also, if the beneficial effect of magnesium is related to its ability to increase intracellular potassium concentrations and regulate calcium concentrations, then it would seem logical that adding magnesium to cardioversion protocols involving other antiarrhythmics, or even electrical cardioversion, would also be beneficial. Perhaps having a warm bath with plenty of Epsom salt when using the on-demand (pill-in-the-pocket) approach with flecainide or propafenone may improve the odds of a quick conversion.