Background: New-onset postoperative atrial fibrillation (POAF) after coronary artery bypass grafting (CABG) increases ischaemic stroke risk, yet factors influencing this risk remain unclear. We sought to identify factors associated with 1-year ischaemic stroke risk, compare the CHA2DS2-VASc (Congestive heart failure, Hypertension, Age ≥75 years, Diabetes, previous Stroke/transient ischaemic attack (TIA), Vascular disease, Age 65-74 years, Sex category) and ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation) scores' predictive abilities for ischaemic stroke, and assess oral anticoagulation (OAC) dispensing at discharge in patients with POAF.
Methods: This nationwide cohort study used prospectively collected data from four mandatory Swedish national registries. All first-time isolated CABG patients who developed POAF during 2007-2020 were included. Multivariable logistic models were used to identify ischaemic stroke predictors and C-statistics to assess the predictive abilities of the CHA2DS2-VASc and ATRIA scores in patients without OAC. OAC dispensing patterns were described based on stroke-associated factors.
Results: In total, 10 435 patients with POAF were identified. Out of those not receiving OAC (n=6903), 3.1% experienced an ischaemic stroke within 1 year. Advancing age (adjusted OR (aOR) 1.86 per 10-year increase, 95% CI 1.45 to 2.38), prior ischaemic stroke (aOR 18.56, 95% CI 10.05 to 34.28 at 60 years, aOR 5.95, 95% CI 3.78 to 9.37 at 80 years, interaction p<0.001), myocardial infarction (aOR 1.55, 95% CI 1.14 to 2.10) and heart failure (aOR 1.53, 95% CI 1.06 to 2.21) were independently associated with ischaemic stroke. The area under the receiver-operating characteristic curve was 0.72 (0.69-0.76) and 0.74 (0.70-0.78) for CHA2DS2-VASc and ATRIA, respectively (p=0.021). Altogether, 71.0% of patients with a stroke risk >2%/year, according to the CHA2DS2-VASc score, were not discharged on OAC.
Conclusions: Prior ischaemic stroke, advancing age, history of heart failure and myocardial infarction were associated with 1-year ischaemic stroke risk in patients with POAF after CABG. CHA2DS2-VASc and ATRIA scores predicted stroke risk with similar accuracy as in non-surgical atrial fibrillation cohorts. OAC dispense at discharge does not seem to reflect individual stroke risk.
Keywords: Atrial Fibrillation; Cohort Studies; Coronary Artery Bypass; Stroke.
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