Metoprolol good for preventing AF following cardiac surgery

Prophylactic use of the beta blocker metoprolol in patients undergoing open heart surgery is effective, leading to a lower incidence of postoperative atrial fibrillation (POAF) compared with placebo, according to a systematic review and meta-analysis.

However, the drug does not prove superior to class III antiarrhythmic drugs, such as sotalol and amiodarone, as well as carvedilol, which is another beta blocker, the investigators said.

“Currently, there are no definitive preventive strategies for AF following heart surgery. There were a few meta-analyses for the evaluation of metoprolol for prophylaxis of POAF; following which, new trials were included in this review,” they added. [Int Cardiovasc Res J 2014;8:111-115; Am J Cardiol 2014;113:565-569; Egypt Heart J 2016;68:89-96]

There were nine trials involving 1,570 arrhythmia-free patients who underwent cardiac surgery, including coronary artery bypass surgery and valvular heart surgery, in total. All trials evaluated the occurrence of AF in the postoperative period with continuous ECG monitoring. The period of POAF monitoring ranged from immediately after surgery until 7 days postoperation or discharge from hospital.

Metoprolol was pitted against placebo in three trials, against sotalol in two trials, amiodarone in two trials, and carvedilol in four trials. The beta blocker was given orally and/or intravenously, with doses ranging from 100–200 mg per day. The other drugs were administered in the same fashion, and the doses were titrated based on the patients’ heart rates and tolerance levels.  

Pooled data showed that the beta blocker reduced the incidence of POAF compared with placebo (n=416; risk ratio [RR], 0.46, 95 percent confidence interval [CI], 0.33–0.66; I², 21 percent; risk difference [RD], –0.19, 95 percent CI, –0.28 to –0.10). [BMJ Open 2020;10:e038364]

However, relative to carvedilol, metoprolol was associated with a higher incidence of POAF (n=159; RR, 1.59, 95 percent CI, 1.20–2.12; I², 4 percent; RD, 0.13, 95 percent CI, 0.06–0.20). No significant differences emerged in comparisons of sotalol and amiodarone.

“Side effects, such as hypotension and bradycardia, was not found to be significant in this study; thus, we can say that metoprolol is relatively safe for POAF prophylaxis,” the investigators said.

Quality of evidence in the trials for the primary outcome varied, ranging from moderate to high. Furthermore, there were unclear and high risk of bias in some assessments, but the investigators believe that such risks are not significant for the review.

The most important type of secondary AF, POAF is a potentially lethal and morbid complication after open heart surgery. The frequency of this complication, however, has been shown to significantly decrease with beta blockers. [Nat Rev Cardiol 2019;16:417-436]

“One meta-analysis found that carvedilol is better than metoprolol in reducing POAF after cardiac surgery, and one review agreed ... in this regard,” the investigators noted. [Am J Cardiol 2014;113:565-569; Egypt Heart J 2016;68:89-96]

“A physician or cardiothoracic surgeon should be aware of the various beta blockers available in their clinical practice. The selection should be based on the evidence available; for example, studies showed that carvedilol is still superior but in cases when it is not available, then other beta blockers would be of choice,” they added.