HAMBURG, GERMANY. The immediate success rate of electrical cardioversion for persistent atrial fibrillation (AF) varies between 64% and 96%. Unfortunately, of patients successfully converted to normal sinus rhythm (NSR), as few as 25% are still in NSR a year following their conversion. There is evidence that lone afibbers tend to be deficient in magnesium and that being replete in potassium is important in ensuring a successful cardioversion.

Researchers at the University Hospital Hamburg now report that pretreatment with a magnesium/potassium (Mg/K) solution significantly improves the outcome of electrical cardioversion. Their randomized clinical trial comprised 170 patients (71% men) with an average age of 67 years. The participants had persistent AF and the episode for which cardioversion was planned had lasted at least 78 hours. The average pre-procedure (baseline) serum level of potassium and magnesium were both at or below normal ranges.

The study participants were randomized into two groups with one group (86 patients) acting as controls and the other group (84 patients) receiving a Mg/K solution providing 34 mg of elemental magnesium (2.772 mEq) and 108 mg of elemental potassium (2.774 mEq) prior to cardioversion. Successful biphasic cardioversion was achieved in 86% of the control group vs. 96.4% in the Mg/K infusion group. Furthermore, the shock energy required to effect conversion was substantially lower in the Mg/K group. In this group, 51.2% of participants converted at the relatively low energy input of 75 joule as compared to a conversion rate of only 29.1% in the control group.

The authors conclude that pretreatment with intravenous Mg/K significantly reduces the shock energy required to achieve restoration of NSR and also improves the immediate success rate of the cardioversion procedure.

Sultan, A, Willems, St, et al. Intravenous administration of magnesium and potassium solution lowers energy levels and increases success rates electrically cardioverting atrial fibrillation. Journal of Cardiovascular Electrophysiology, Vol. 23, January 2012, pp. 54-59

Editor's comment: This study again confirms that afibbers tend to be low in magnesium. The average baseline serum level of Mg in the 170 patients was 0.85 mg/dL or 0.34 mmol/L. The normal range is 1.5 to 2.3 mg/dL or 0.75 to 0.95 mmol/L. It would have been interesting if the authors had provided follow-up data to see if the longevity of NSR was affected by the Mg/K pretreatment infusion. It would, of course, also have been hugely interesting if the cardioverted participants had been randomly assigned to oral Mg/K supplementation or placebo post-procedure to see if continuous Mg/K supplementation would extend their time in NSR. NOTE: The amount of magnesium infused (34 mg elemental) is very low and hardly likely to have any effect. Also, the baseline level of magnesium is way below normal. I suspect a couple of typos and have contacted the authors for clarification.