Intravenous magnesium sulfate versus diltiazem in paroxysmal atrial fibrillation.

BACKGROUND Drugs currently available for the acute treatment of paroxysmal atrial fibrillation have significant limitations. We assessed the safety and effectiveness of intravenous magnesium sulfate versus diltiazem therapy in patients with prolonged episodes of paroxysmal atrial fibrillation. METHODS In a prospective randomized trial, 46 symptomatic patients presenting with paroxysmal atrial fibrillation were given intravenous magnesium sulfate (n=23) or diltiazem (n=23) therapy. Primary outcome measures were effects on ventricular rate control and proportion of patients restored to sinus rhythm at 6 h after initiation of treatment. RESULTS There were no differences in baseline characteristics between the two groups. Both forms of treatment were well tolerated, with no adverse clinical events. Both drugs had similar efficacy in reducing the ventricular rate at the first hour of treatment (P<0.05) with a tendency toward a further decrease during infusion times of 2 (P<0.01), 3, 4, 5 and 6 h, respectively (P<0.001). However, at the end of the 6-h treatment period, restoration of sinus rhythm was observed in a significantly higher proportion of patients in the magnesium group compared with the diltiazem group [13 of 23 patients, (57%), versus five of 23 patients, (22%), P=0.03]. CONCLUSIONS Magnesium sulfate favorably affects rate control and seems to promote the conversion of long lasting episodes of paroxysmal atrial fibrillation to sinus rhythm, representing a safe, reliable and cost-effective alternative treatment strategy to diltiazem.