Use of metoprolol CR/XL to maintain sinus rhythm after conversion from persistent atrial fibrillation - A randomized, double-blind, placebo-controlled study

OBJECTIVES The primary objective of the present study was to assess the eff icacy of metoprolol CR/XL to reduce the risk of relapse after cardioversion of persistent atrial fibrillation to sinus rhythm. BACKGROUND Indirect data from studies with d,l sotalol provide evidence tha t the beta-blocking effects of the compound are important in maintaining si nus rhythm after cardioversion of atrial fibrillation. METHODS After successful conversion to sinus rhythm, 394 patients with a hi story of persistent atrial fibrillation were randomly assigned to treatment with metoprolol CR/XL or placebo. The two treatment groups were similar wi th respect to ail pretreatment characteristics. Patients were seen on an ou tpatient basis for recording of resting electrocardiogram (ECG) after one w eek, one, three and six months of follow-up or whenever they felt that they had a relapse into atrial fibrillation or experienced an adverse event. RESULTS In the metoprolol CR/XL group, 96 patients (48.7%) had a relapse in to atrial fibrillation compared with 118 patients (59.9%) in the placebo gr oup (p = 0.005). Heart rate in patients after a relapse into atrial fibrill ation was significantly lower in the metoprolol group (98 +/- 23 beats/min) than in the placebo group (107 +/- 27 beats/min). The rate of adverse even ts reported was similar in both groups when the difference in follow-up tim e was taken into account. CONCLUSIONS The results of this double-blind, placebo-controlled study in p atients after cardioversion of persistent atrial fibrillation showed that m etoprolol CR/XL was effective in preventing relapse into atrial fibrillatio n or flutter. (C) 2000 by the American College of Cardiology.