Efficacy of Intravenous Magnesium in Facilitating Cardioversion of Atrial Fibrillation

Abstract

P atients with atrial fibrillation (AF) may require electric cardioversion, either because of intolerable symptoms related to AF or as part of a rhythm control strategy. See Editorial by KotechaElectric cardioversion using a biphasic waveform has a procedural success rate of 86% to 94%, sometimes requiring multiple shocks.1-3 The success of electric cardioversion depends on the duration of AF, transthoracic impedance, delivered energy, and the type of electric shock used.1 Pharmacological cardioversion using antiarrhythmic drugs (AADs) has a lower success rate and may take a few hours to days to achieve sinus rhythm.Magnesium (Mg) is an abundant mineral in the body, present in bone, the heart, and the central nervous system. In the heart, Mg modulates potassium (slow-activating delayed rectifier K channel, I Ks ) and calcium channels (L-type) in both the atria and the ventricles. 4,5 Mg has been shown to have membrane-stabilizing properties within the atrium. 4 This membrane-stabilizing property may be particularly helpful in rhythm control of AF. Data from the Framingham offspring and Atherosclerosis Risk in Communities (ARIC) prospective cohorts have linked low serum Mg levels to AF. 6,7 Studies on pharmacological cardioversion have shown increased success of cardioversion when Mg is used along with an AAD. 8,9 A recent study on electric cardioversion showed that the infusion of a K-Mg electrolyte solution was successful in facilitating electric cardioversion of AF.3 On the basis of data suggesting an association of low Mg levels with the incidence of AF and the membrane-stabilizing property of Mg in the atrium with the modulation of I K+ and I Ca2+ currents, we postulated that administration of Mg alone would be useful in increasing the success of cardioversion. The purpose of this study was to investigate the benefit of intravenous © 2016 American Heart Association, Inc. Circ Arrhythm Electrophysiol

Magnesium for Atrial Fibrillation, Myth or Magic?

“…This was demonstrated in another large community cohort where the association of hypomagnesemia with incident AF was identified in long-term follow-up, but not present within the first 90 days. 9 In this issue of Circulation: Arrhythmia and Electro physiology, Rajagopalan et al 10 add to the growing evidencebase on this issue by performing a randomized, double-blind, placebo-controlled trial of intravenous magnesium before electric cardioversion of AF. A total of 261 patients were enrolled with normal magnesium levels at baseline (2.1±0.2 mg/dL; 0.86±0.08 mmol/L).…”

“…The Figure displays trials and meta-analyses that have randomized patients to magnesium in a range of situations, including treatment of acute AF, prevention of AF during cardiac surgery, and facilitation of electric cardioversion. [10][11][12][13][14] Although varying with respect to population and magnesium dosage, they share common features of a small sample size, short follow-up, and disappointing treatment effect.…”

Utility of calcium, magnesium and phosphate testing in the emergency department

“…It has been reported that Mg may have a role in AF prevention in the postoperative cardiothoracic surgery setting . However, there is conflicting evidence regarding the efficacy of Mg in AF treatment in the ED and other settings . As many of these studies had methodological limitations, there is no high‐level evidence to support the use of Mg for the treatment of AF in the ED.…”

Magnesium and Cardiovascular Disease

“…Meta-analysis of studies using magnesium to treat AF did not show any significant effect on restoring sinus rhythm compared to placebo, although magnesium reduced the fast ventricular response, when used as adjunct to digitalis (88), or combinations of magnesium, potassium, insulin and glucose (89). A more recent randomized controlled trial (RCT) of infusing magnesium in patients undergoing electric cardioversion for chronic AF, also did not show any increased rate of successful cardioversion (90). As such, role of magnesium in the treatment of AF remains controversial.…”