We love magnesium in the Emergency Department. It’s been said that magnesium is second-line for everything (kind of like doxycycline). But what about rate/rhythm control in atrial fibrillation (AF)? The 2014 AHA/ACC/HRS guideline for the management of patients with AF don’t mention magnesium at all.1 Dr. Josh Farkas (@PulmCrit) wrote about magnesium infusions for atrial fibrillation and torsade last year. His post looked at its use for cardioversion, rhythm-control, and rate-control in critically-ill patients. Our post will focus specifically on the IV magnesium data for rate-control in ED-related settings.
Over the years, IV magnesium has been studied for the treatment of rapid AF in several clinical situations, most prominently in post-cardiac surgery patients. However, there are also studies in ED and cardiology patients, both as a primary therapy and as an adjunct. In fact, two meta-analyses from 2007 evaluated the data (mostly the same studies).2,3 Both concluded that magnesium is safe and effective in controlling ventricular rate in rapid AF compared to placebo, the latter in patients also receiving digoxin. A closer look at the meta-analyses reveals that the positive rate control effect for magnesium seems to be driven by the placebo-controlled trials.4 Similarly, the positive benefit of magnesium in rhythm control is largely derived from trials versus placebo or traditional rate-control medications (e.g., beta-blockers or calcium channel blockers) rather than amiodarone or other rhythm-control agents. Of the 11 studies cited in the meta-analyses, only five reported rate-control data in ED-related settings.