New-onset atrial fibrillation after coronary surgery and stroke risk: a nationwide cohort study

Abstract

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.

Figure 1. Flow chart of included and excluded patients. AF, atrial fibrillation; CABG, coronary artery bypass grafting; OAC, oral anticoagulation; POAF, postoperative atrial fibrillation.

Figure 2. Incidence of ischaemic stroke during the first postoperative year, by age category and previous ischaemic stroke.

Figure 3. Incidence of ischaemic stroke during the first postoperative year, by (A) CHA₂DS₂-VASc score and (B) ATRIA score. ATRIA, Anticoagulation and Risk Factors in Atrial Fibrillation; CHA₂DS₂-VASc, Congestive heart failure, Hypertension, Age ≥75 years, Diabetes, previous Stroke/transient ischaemic attack–Vascular disease, Age 65–74 years, Sex category.

Figure 4. Rates of oral anticoagulant (OAC) use at discharge in patients with new-onset postoperative atrial fibrillation after coronary artery bypass grafting in relation to (A) CHA₂DS₂-VASc score, (B) ATRIA score, (C) prior ischaemic stroke and (D) age. ATRIA, Anticoagulation and Risk Factors in Atrial Fibrillation score; CHA₂DS₂-VASc, Congestive heart failure, Hypertension, Age ≥75 years, Diabetes, previous Stroke/transient ischaemic attack–Vascular disease, Age 65–74 years, Sex category score.