New-Onset Atrial Fibrillation After Coronary Artery Bypass Grafting and Long-Term Outcome: A Population-Based Nationwide Study From the SWEDEHEART Registry

Abstract

Background The long-term impact of new-onset postoperative atrial fibrillation (POAF) after coronary artery bypass grafting and the benefit of early-initiated oral anticoagulation (OAC) in patients with POAF are uncertain. Methods and Results All patients who underwent coronary artery bypass grafting without preoperative atrial fibrillation in Sweden from 2007 to 2015 were included in a population-based study using data from 4 national registries: SWEDEHEART (Swedish Web System for Enhancement and Development of Evidence-based Care in Heart Disease Evaluated According to Recommended Therapies), National Patient Registry, Dispensed Drug Registry, and Cause of Death Registry. POAF was defined as any new-onset atrial fibrillation during the first 30 postoperative days. Cox regression models (adjusted for age, sex, comorbidity, and medication) were used to assess long-term outcome in patients with and without POAF, and potential associations between early-initiated OAC and outcome. In a cohort of 24 523 patients with coronary artery bypass grafting, POAF occurred in 7368 patients (30.0%), and 1770 (24.0%) of them were prescribed OAC within 30 days after surgery. During follow-up (median 4.5 years, range 0‒9 years), POAF was associated with increased risk of ischemic stroke (adjusted hazard ratio [aHR] 1.18 [95% CI, 1.05‒1.32]), any thromboembolism (ischemic stroke, transient ischemic attack, or peripheral arterial embolism) (aHR 1.16, 1.05‒1.28), heart failure hospitalization (aHR 1.35, 1.21‒1.51), and recurrent atrial fibrillation (aHR 4.16, 3.76‒4.60), but not with all-cause mortality (aHR 1.08, 0.98‒1.18). Early initiation of OAC was not associated with reduced risk of ischemic stroke or any thromboembolism but with increased risk for major bleeding (aHR 1.40, 1.08‒1.82). Conclusions POAF after coronary artery bypass grafting is associated with negative prognostic impact. The role of early OAC therapy remains unclear. Studies aiming at reducing the occurrence of POAF and its consequences are warranted.

Trial registration: ClinicalTrials.gov NCT04045665.

Keywords: CABG; oral anticoagulation therapy; postoperative atrial fibrillation.

Figure 1. Flow chart of included and excluded patients.

CABG indicates coronary artery bypass grafting; OAC, oral anticoagulant; and POAF, postoperative atrial fibrillation.

Figure 2. The adjusted cumulative incidence of all‐cause mortality, ischemic stroke, recurrent atrial fibrillation and hospitalization for heart failure, in 24 553 patients with CABG with (blue line) and without (red line) new‐onset postoperative atrial fibrillation.

The hazard ratios are adjusted for patient characteristics, comorbidities, CHA2DS2‐VASc score, year of surgery and medications. A detailed list of the variables used for adjustment is shown in Table S3. AF indicates atrial fibrillation; aHR, adjusted hazard ratio; CABG, coronary artery bypass grafting; and POAF, postoperative atrial fibrillation.

Figure 3. The annual proportion of early‐initiated oral anticoagulation during 2007 to 2015 in patients with new‐onset postoperative atrial fibrillation after coronary artery bypass grafting (CABG).

Figure 4. The proportion of patients with new‐onset postoperative atrial fibrillation treated with oral anticoagulation at different time points after coronary artery bypass grafting.

Figure 5. Oral anticoagulation therapy at different time points after discharge in all patients with new‐onset postoperative atrial fibrillation and anticoagulant therapy initiated within 30 days after coronary artery bypass grafting (n=1714 at 30 days).