Outcomes in Early Postoperative Versus Late New-Onset Atrial Fibrillation After Coronary Artery Bypass Grafting.

Background: It is unclear whether new-onset postoperative atrial fibrillation (POAF) early after coronary artery bypass grafting (CABG) is associated with a similar risk of adverse outcomes as new-onset atrial fibrillation occurring later after CABG.

Methods: All patients treated with CABG in Sweden from 2007 to 2020 were investigated. Individual patient data from SWEDEHEART (Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) registry and 3 other prospective national registries were merged. The adjusted incidences of all-cause mortality, ischemic stroke, any thromboembolism, heart failure hospitalization, and major bleeding within 12 months after debut of POAF (AF occurring before hospital discharge) or Late AF (new-onset AF occurring between 3 months and 3 years after CABG) were compared by multivariable Poisson regression analysis, adjusted for time-updated patient characteristics and comorbidities.

Results: Out of 35 329 patients, 10 609 (30.0%) developed POAF and 628 (2.5%) developed Late AF. The crude mortality rate was lower in patients with POAF than in patients with Late AF (1.88 [95% CI, 1.63-2.17] versus 9.08 [95% CI, 6.92-11.82] per 100 patient-years). The adjusted incidence rate ratios for all-cause mortality (2.91 [95% CI, 2.10-3.95]); ischemic stroke (1.70 [95% CI, 1.15-2.44]); any thromboembolism (1.59 [95% CI, 1.11-2.22]), heart failure hospitalization (1.61 [95% CI, 1.19-2.12]); and major bleeding (1.73 [95% CI, 1.24-2.36]) were higher in patients with Late AF.

Conclusions: POAF was associated with a markedly lower risk for morbidity and mortality than late new-onset AF after CABG. POAF and late new-onset AF after CABG are 2 different clinical entities of AF that may require different treatment strategies.