Magnesium Supplements and Heart Health

By Hans R. Larsen MSc ChE –

TORONTO, CANADA. Magnesium is effective in prolonging the atrial and atrioventricular nodal refractory periods. As afib cannot be initiated during refractory periods, this is clearly a good thing and may explain why many afibbers have experienced substantial benefit from magnesium supplementation. Unfortunately, several studies have shown that 50% or more of patients with atrial fibrillation suffer from hypomagnesemia – that is, a lower than normal blood serum magnesium concentration (less than about 0.8 mmol/L). Serum magnesium concentration is a fairly poor indicator of magnesium status since only about 2% of the body’s total magnesium stores are found in the blood. It is thus likely that substantially more than 50% of afibbers are magnesium deficient if intracellular levels are measured.

Researchers at the University of Toronto have just released the results of a meta-analysis of 8 clinical trials involving patients presenting with rapid atrial fibrillation. The trials compared the effect of magnesium infusions with placebo controls and patients given intravenous diltiazem or amiodarone. In the trials 1,200 to 10,000 mg of magnesium (as magnesium sulfate) was infused over a period of 1 to 30 minutes. In four of the studies magnesium infusion was continued for an additional 2 to 6 hours. Adequate rate control (ventricular rate below 100 bpm) was achieved in 61% of patients with magnesium as compared to 35% among controls. Magnesium was found to be as effective as diltiazem and amiodarone in achieving adequate rate control during the first hour. Magnesium was also found to be twice as effective as diltiazem or placebo in restoring sinus rhythm. Overall, the average time to conversion to sinus rhythm was 4 hours for magnesium as compared to 15 hours for placebo. The researchers conclude that magnesium infusions are safe and effective in achieving both rate and rhythm control in patients presenting with rapid atrial fibrillation.

Onalan, O, et al. Meta-analysis of magnesium therapy for the acute management of rapid atrial fibrillation. American Journal of Cardiology, Vol. 99, June 15, 2007, pp. 1726-32

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