De Azevedo Lúcio 2003.

Methods	RCT, parallel design
Participants	Total number of randomized participants: 200 Inclusion criteria: participants underwent isolated CABG surgery Exclusion criteria: history of bronchospasm, left ventricular ejection fraction < 35% in preoperative period, implantable cardiac pacemaker, chronic AF, history of supraventricular arrhythmias, using amiodarone, congestive heart failure, low cardiac output, dependence on inotropic drugs, bradyarrhythmias Type of surgery: elective CABG Baseline characteristics Intervention group (metoprolol) Age, mean (SD): 59 (± 10) years Gender, M/F: 72/28 History of MI, %: 42 History of hypertension, %: 59 Ejection fraction, > 0.50: 85%; 0.35 to 0.50: 15% Preoperative use of beta‐blockers, %: 65 Control group (standard care) Age, mean (SD): 62 (± 11) Gender, M/F: 74/26 History of MI, %: 42 History of hypertension, %: 63 Ejection fraction > 0.50: 82%; 0.35 to 0.50: 17% Preoperative use of beta‐blockers, %: 63 Country: Brazil Setting: single centre; hospital
Interventions	Intervention group (metoprolol) Randomized, n = 100; losses = 0; analysed, n = 100 (ITT analysis) Details: initiated at 12 h postoperatively, orally or with nasogastric tube, doses range from 100 mg/day to 300 mg/day, given 2 or 3 times a day, and adjusted to maintain HR between 60‐90 bpm. Continuation until day 7 postoperatively or until discharge (whichever occurred first) Control group (standard care) Randomized, n = 100; losses = 0; analysed, n = 100 Details: participants did not receive metoprolol
Outcomes	Outcomes measured/reported by study authors: AF/flutter, death, MI (group affiliation not specified), stroke (group affiliation not specified) Outcomes relevant to the review: AF/flutter, death, MI (group affiliation not specified ‐ see notes below), stroke (group affiliation not specified ‐ see notes below)
Notes	Funding/declarations of interest: not reported Study dates: February 1997‐October 1998 Note: 8 study participants suffered from a MI, and 5 suffered from a stroke. Study group allocation of these participants was not specified
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not specified
Allocation concealment (selection bias)	Unclear risk	Not specified
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label trial
Blinding of outcome assessors (detection bias) All outcomes	High risk	Open‐label trial
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses
Selective reporting (reporting bias)	High risk	We noted that study group allocation of participants with certain adverse events (AMI, stroke) remained unclear; we considered this to demonstrate evidence of selective reporting
Other bias	Low risk	Not detected