AbstractOBJECTIVESData on prognostic implications of new-onset postoperative atrial fibrillation (POAF) after surgical aortic valve replacement (SAVR) is limited. We sought to explore associations between POAF, early initiated oral anticoagulation (OAC) and long-term outcome after SAVR and combined SAVR + coronary artery bypass grafting (CABG).METHODSThis is a retrospective, population-based study including all isolated SAVR (n= 7038) and combined SAVR and CABG patients (n= 3854) without a history of preoperative atrial fibrillation (AF) in Sweden 2007–2017. Individual patient data were merged from 4 nationwide registries. Inverse probability of treatment weighting-adjusted Cox regression models were employed separately in SAVR and SAVR + CABG patients. The median follow-up time was 4.7 years (range 0–10 years).RESULTSPOAF occurred in 44.5% and 50.7% of SAVR and SAVR + CABG patients, respectively. In SAVR patients, POAF was associated with increased long-term risk of death [adjusted hazard ratio (aHR) 1.21 (95% confidence interval 1.06–1.37)], ischaemic stroke [aHR 1.32 (1.08–1.59)], any thromboembolism, heart failure hospitalization and recurrent AF. In SAVR + CABG, POAF was associated with death [aHR 1.31 (1.14–1.51)], recurrent AF and heart failure, but not with ischaemic stroke [aHR 1.04 (0.84–1.29)] or thromboembolism. OAC was dispensed within 30 days after discharge to 67.0% and 65.9%, respectively, of SAVR and SAVR + CABG patients with POAF. Early initiated OAC was not associated with reduced risk of death, ischaemic stroke or thromboembolism in any group of patients.CONCLUSIONSPOAF after SAVR is associated with an increased risk of long-term mortality and morbidity. Further studies are warranted to clarify the role of OAC in SAVR patients with POAF.