Data Extraction

Two reviewers (A.D. and G.C.) independently extracted quantitative data from the selected studies. Conflicts in extracted data were resolved by a third reviewer (D.C.). The following variables were extracted: study characteristics (ie, sample size, publication year, country, study period, and study design), baseline patient characteristics and comorbidities (ie, age, sex, diabetes, left ventricular ejection fraction, left main disease, number of diseased vessels, and use of the internal thoracic artery in the prior CABG). The risk of bias was assessed using the Newcastle-Ottawa Scale assessment tool for observational studies. The highest possible score is 9 stars: studies with <6 stars were considered of low quality, whereas studies with ≥6 stars were considered of high quality.