Mirhosseini 2013.

Methods	Prospective, double‐blind, RCT
Participants	Patients (n = 120) undergoing elective off‐pump coronary artery bypass graft. Mean age: 63.41 ± 10.71 heparin group and 60.80 ± 10.64 heparin plus aspirin group. Male/female: 42/18 and 41/19, respectively
Interventions	Intervention: aspirin (80 mg daily orally) plus heparin (5000 U unfractionated heparin every 8 hours subcutaneously) Control: heparin (5000 U unfractionated heparin every 8 hours subcutaneously) Study treatments were given from admission to discharge
Outcomes	Deep vein thrombosis, bleeding, and pulmonary embolism All participants underwent right and left leg venous ultrasound examination during hospitalisation
Notes	Conflict of interest: none declared
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of sequence generation not reported. Quote: "The patients were randomly assigned into two groups"
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not reported. Quote: "The patients were randomly assigned into two groups"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The nurse (observer) who took the medicine to the patients (participants) and the patients themselves were blinded."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of outcome assessment not reported. Quote: "Ultrasonography was performed by an experienced and expert physician"
Incomplete outcome data (attrition bias) All outcomes	Low risk	From Table 3 (Mirhosseini 2013), it appears that all participants randomised were included in the analysis
Selective reporting (reporting bias)	Unclear risk	Outcomes are not clearly specified in the methods. Quote: "...post‐operation early complications such as bleeding and pulmonary embolism (PE), were recorded."
Other bias	Unclear risk	It is unclear if participants were consecutively included. Risk factors for VTE are poorly reported