Stephenson 1980.

Methods	Quasi‐randomized trial, parallel design
Participants	Total number of analysed participants: 223 (number of randomized participants not clearly reported) Inclusion criteria: scheduled for CABG surgery without additional cardiac surgical procedures Exclusion criteria: cardiac arrhythmias in immediate 18 h postoperative period; bradycardia requiring a pacemaker; low cardiac output requiring catecholamine support Type of surgery: elective CABG Baseline characteristics Intervention group (propranolol) Age, mean: 54 years Gender, M/F: 80/7 Preoperative use of beta‐blockers, n: 63 Control group (standard care) Age, mean: 56 years Gender, M/F: 122/14 Preoperative use of beta‐blockers, n: 86 Country: USA Setting: single centre; hospital
Interventions	Intervention group (propranolol) Randomized, n = unclear; losses = at least 4 (2 because of wrong dose; 2 because of bradycardia; number of other losses was not reported); analysed, n = 91 for cardiac arrhythmias (we re‐included 4 excluded participants because study authors reported no cardiac arrhythmias amongst excluded participants) (ITT analysis not used) Details: 10 mg propranolol every 6 h starting on 1st postoperative day Control group (standard care) Randomized, n = 136; losses = we assumed no losses; analysed, n = 136 Details: no details
Outcomes	Outcomes measured/reported by study authors: postoperative cardiac arrhythmias (supraventricular and ventricular) Outcomes relevant to the review: postoperative ventricular arrhythmias; MI; bradycardia (see notes below)
Notes	Funding/declarations of interest: not reported Study dates: not reported Note: although study authors reported data for bradycardia (as a reason for excluding 2 participants in the propranolol group), we did not include these data in analysis because we could not be certain of incidences of bradycardia in the control group
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quasi‐randomized ‐ randomization by date of birth
Allocation concealment (selection bias)	High risk	See above
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	High risk	Number of randomized participants was unclearly reported with an unspecified number of exclusions in the propranolol group. We re‐included data for 4 excluded participants in the propranolol group for arrhythmia data
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	Low risk	Not detected