Williams 1982.

Methods	Quasi‐randomized trial, parallel design
Participants	Total number of randomized participants: 50 Inclusion criteria: scheduled for CABG surgery without additional cardiac procedures Exclusion criteria: heart failure requiring use of intra‐aortic balloon pump Type of surgery: elective CABG Baseline characteristics Intervention group (propranolol) Age, mean: 55.3 years Gender, M/F: 25/3 Preoperative use of beta‐blockers, %: 89.3 Control group (standard care) Age, mean: 55.3 years Gender, M/F: 24/8 Preoperative use of beta‐blockers, %: 84.3 Country: USA Setting: single centre; hospital
Interventions	Intervention group (propranolol) Randomized, n = 28; losses = 0; analysed, n = 28 (we assumed that ITT analysis was not used) Details: propranolol 10 mg every 6 h, started at noon of the participant's 1st postoperative day until hospital discharge Control group (standard care) Randomized, n = 32; losses = 0; analysed, n = 32 (we assumed that ITT analysis was not used) Details: standard care, no details
Outcomes	Outcomes measured/reported by study authors: postoperative arrhythmias (supraventricular and ventricular, to include AF) Outcomes relevant to the review: ventricular arrhythmias, AF
Notes	Funding/declarations of interest: not reported Study dates: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "Patients were randomised by odd or even birthdate" Comment: quasi‐randomization
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	Low risk	5 participants were excluded from analysis because of postoperative heart failure requiring IABP perioperatively, which we assumed to be an a priori exclusion criteria; we have not included these in the overall number of randomized participants
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