Background: Most large studies of magnesium sulfate for assistance with rate control in AF occurred in the postoperative setting. This study compared rate control in the ED using magnesium sulfate at high (9 g) and low (4.5 g) doses vs. placebo in combination with usual treatment with atrioventricular nodal-blocking agents.
Study design: Double-blind, prospective, randomized, controlled trial.
Setting: Three tertiary Tunisian EDs.
Synopsis: This trial in Tunisian EDs enrolled 450 patients who presented with AF with rapid ventricular response and were divided into three groups: placebo, low-dose magnesium, and high-dose magnesium. Each patient’s trial medication was given as a 100-cc infusion. Patients were then treated with AV nodal-blocking agents at the discretion of the ED physician. The primary outcome was 20% reduction in rate or heart rate of less than 90 beats per minute. Notable exclusion criteria included hypotension, altered consciousness, decompensated heart failure, MI, and renal failure.
Rate control was achieved at 4 hours in 64% of patients with low-dose magnesium, 59% with high-dose magnesium, and 43% with placebo. At 24 hours, reduction in rate was controlled for 97% of patients on the low dose, 94% on the high dose, and 83% on placebo. Adverse events were mostly flushing, which occurred more frequently with the high dose than the low dose. Major limitations of the study included a lack of statistical assessment regarding baseline similarity between the two groups and that generalizability was limited by a preference for digoxin as the AV nodal agent.
Bottom line: This trial demonstrated that 4.5 g of magnesium sulfate was a useful addition to AV nodal blockers in achieving faster rate control for atrial fibrillation with rapid ventricular response in selected ED patients.
Citation: Bouida W et al. Low-dose magnesium sulfate versus high dose in the early management of rapid atrial fibrillation: Randomized controlled double blind study. Acad Emerg Med. 2018 Jul 19. doi: 10.1111/acem.13522.
Dr. Scott is an assistant professor in the division of hospital medicine, University of New Mexico.