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Antiarrhythmic drugs often are used to maintain sinus rhythm in patients who have undergone cardioversion for atrial fibrillation, despite concern that the drugs actually may increase mortality due to proarrhythmia. In this manufacturer-supported, placebo-controlled, double-blind trial, German researchers tested the effect of extended-release metoprolol CR/XL (100 to 200 mg per day) in 394 patients. All patients had undergone successful cardioversion to sinus rhythm for atrial fibrillation that had lasted for at least 3 days but less than 1 year.
Patients were randomized to metoprolol or placebo, and treatment was started after cardioversion. During the next 6 months, relapse to atrial fibrillation or flutter occurred in 49 percent of the me…