HARTFORD, CONNECTICUT. A group of Austrian researchers recently reported that pre-injection of magnesium sulfate considerably improves the efficacy of pharmaceutical conversion with ibutilide (Corvert). In a group of 65 patients with typical right atrial flutter the conversion effectiveness with magnesium was 85% as compared to 59% with placebo.

Now physicians at the Hartford Hospital report that pre-injecting magnesium sulfate also improves the cardioversion efficacy of dofetilide (Tikosyn) when used in patients with atrial fibrillation. Their clinical trial involved 150 patients with AF and 10 with atrial flutter. The average age was 67 years and the majority of participants had pretty severe health problems including heart failure (38%) and hypertension (54%), and the average left ventricular ejection fraction in the group was a very low 36%. All patients had normal serum levels of magnesium at baseline – average value of 2.1 mg/dL vs. normal range of 1.7 - 2.6 mg/dL. The patients were evaluated in two groups – one group of 100 patients received the standard dofetilide protocol (6 doses over 3 days), while the remaining 50 patients also received intravenous magnesium sulfate (average of 3 grams) on the first day of dofetilide administration and another 3 grams (average) over the next 2 days. This corresponds to a total average intake of elemental magnesium of 1200 mg over the 3-day hospital stay.

The overall conversion rate was 41.9%; however, the rate of successful conversion was substantially higher in the magnesium group (50%) than in the no magnesium group (38.2%). The increase in cardioversion efficiency was only statistically significant in the afib group – here patients who had received magnesium + dofetilide were more than twice as likely to be successfully converted than were those who received dofetilide only. The Hartford group speculates that the beneficial effects associated with magnesium is due to its role in maintaining high intracellular potassium concentrations and in its ability to regulate intracellular calcium concentration or directly oppose the actions of calcium.

Steinwender, C, et al. Pre-injection of magnesium sulfate enhances the efficacy of ibutilide for the conversion of typical but no of atypical persistent atrial flutter. International Journal of Cardiology, 2009 [Epub ahead of print]
Coleman, CI, et al. Intravenous magnesium sulfate enhances the ability of dofetilide to successfully cardiovert atrial fibrillation or flutter. Europace, April 6, 2009 [Epub ahead of print]

Editor's comment: This study again shows that patients can have normal serum levels of magnesium and yet receive substantial benefits from a magnesium injection. It would certainly seem advisable for patients contemplating cardioversion with dofetilide (Tikosyn) to ask for a pre-procedure magnesium sulfate injection.