Date: February 7th, 2019

Reference: Bouida et al. LOw dose MAGnesium sulfate versus HIgh dose in the early management of rapid atrial fibrillation: randomised controlled double-blind study. AEM February 2019.

Guest Skeptic: Dr. Corey Heitz is an emergency physician in Roanoke, Virginia. He is also the CME editor for Academic Emergency Medicine.

Case: You are working in your local freestanding emergency department (ED). This is an ED not physically attached to a hospital, for the non-American listeners. A 64-year-old male patient presents with a feeling of “palpitations” for about one week. His heart rate is 130-140 beats per minute, irregular, and his EKG shows atrial fibrillation with rapid ventricular response (RVR). You want to control his rate and have recently heard some of your colleagues talking about using intravenous magnesium in addition to their typical rate control agents.

Background: Atrial fibrillation is the most frequent cardiac arrhythmia. Patients often present to the ED with increased heart rates, chest pain and weakness among other presentations.

Rate control vs. rhythm control is a debate that has gone on for many years. The management in the USA tends to be rate control while in Canada they tend to do more rhythm control.

In Canada, we tend to cardiovert patients with recent onset of atrial fibrillation (less than 48 hours). There is an aggressive protocol out of Ottawa using procainamide and electricity to rapidly cardiovert and discharge patients with these arrhythmias. A study by Stiell et al showed that the vast majority of patients (97%) were discharged home from the ED with 93% in normal sinus rhythm using this protocol (SGEM#88).

In patients with chronic atrial fibrillation or unknown time of onset and a rapid ventricular response (RVR), rate control and consideration of anticoagulation therapy are the standard ED approach.

Dr. Anand Swaminathan and I reviewed a RCT comparing diltiazem vs. metoprolol in the management of atrial fibrillation or flutter with rapid ventricular rate in the ED (SGEM#133). The SGEM bottom line was that the best available evidence shows that diltiazem will achieve more rapid rate control in patients with atrial fibrillation than metoprolol (NNT 2).

Magnesium has been investigated as an alternative or adjunct for to rate control patients with rapid atrial fibrillation. Prior analyses have suggested that it is a safe and effective alternative strategy, however it has not been well studied in the ED, and the best dosing has been unclear.

Clinical Question: Can IV magnesium sulfate reduce the ventricular rate safely and effectively in ED patients with rapid atrial fibrillation?

Reference:Bouida et al. LOw dose MAGnesium sulfate versus HIgh dose in the early management of rapid atrial fibrillation: randomised controlled double-blind study. AEM February 2019.

* Population: Emergency department patients older than 18 years of age with rapid atrial fibrillation (>120 bpm).

* Exclusions: Hypotension (SBP < 90 mm Hg), impaired consciousness, renal failure (serum creatinine > 180 mmol/L), wide-complex ventricular response, or contraindication to MgSO4, acute myocardial infarction, acute congestive heart failure (New York Heart Association functional class 3 or 4), sick sinus syndrome, or rhythm other than atrial fibrillation.

* Intervention: 9g IV Magnesium sulfate (MgS) infused over 30 minutes.

* Comparison: 5g IV Magnesium sulfate or placebo infused over 30 mi...