The frequency of atrial fibrillation (AF) will be compared between treatment groups by chi square test; this primary analysis will be performed first using an intention to treat model. In post hoc analysis the investigator will explore treatment outcomes after stratification by type of surgery and established clinical risk factors for POAF (age, sex, smoking, obesity, hypertension, diabetes mellitus, myocardial infarction, and BMI). If descriptive analyses suggest imbalance in clinical or demographic characteristics between treatment groups, these will be explored using t tests or their non-parametric equivalent (continuous data) or chi square test (categorical data), as appropriate, and logistic regression will be used to evaluate differences in AF rate between treatment groups, while taking identified covariates into account.