Connolly 2003.

Methods	RCT, parallel design
Participants	Total number of randomized participants: 1000 Inclusion criteria: scheduled for heart surgery with CABG, residing at home before hospital admission Exclusion criteria: emergency surgery, previous adverse reaction to beta‐blockers, COPD, junctional rhythm or 2nd‐ or 3rd‐degree atrioventricular block, long‐term preoperative amiodarone therapy. Additional postoperative exclusion criteria: sinus bradycardia; cardiac index < 2.3 L/min/m²; need for IV inotropic agent; evidence of bronchospasm Type of surgery: elective heart surgery (CABG) Baseline characteristics Intervention group (metoprolol) Age, mean (SD): 63 (± 10) years Gender, M/F: 390/110 Preoperative use of beta‐blockers, %: 82 Control group (placebo) Age, mean (SD): 62 (± 10) Gender, M/F: 400/100 Preoperative use of beta‐blockers, %: 79 Country: Canada Setting: single centre; hospital Mean age: 62.5 years Percentage of female participants: 21
Interventions	Intervention group (metoprolol) Randomized, n = 500; losses = 0; analysed, n = 500 (use of ITT analysis not reported) Details: 50 mg metoprolol starting immediately after surgery every 12 h, using nasogastric tube. Continued for 14 days or until hospital discharge (whichever occurred sooner) Control group (placebo) Randomized, n = 500; losses = 0; analysed, n = 500 Details: given same as intervention group
Outcomes	Outcomes measured/reported by study authors: length of stay, arrhythmias (supraventricular and ventricular arrhythmias), MI, cost of care, stroke, death, haemodynamic parameters Outcomes relevant to the review: length of hospital stay, arrhythmias (AF and ventricular arrhythmias), MI, stroke, death
Notes	Funding/declarations of interest: supported by a grant from Canadian Institutes for Health Research Study dates: January 1997‐September 1999 Notes: after enrolment of 411 participants, dose of metoprolol was increased to 50 mg every 8 h for participants with a cardiac index of > 2.3 L/min/m². study also known as BLOS study
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	Low risk	Randomized, placebo‐controlled, double‐blind trial
Blinding of outcome assessors (detection bias) All outcomes	Unclear risk	Not specified
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses
Selective reporting (reporting bias)	Unclear risk	Study authors did not report prospective clinical trial registration or publication of a protocol. It was not feasible to effectively assess risk of reporting bias
Other bias	High risk	Non‐study beta‐blockers were given to 146 participants in the intervention group, and 199 participants in the placebo group (main indication for this was to treat postoperative AF). This may influence outcome data