Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting and Its Association with Length of Stay, Discharge Disposition, and 90-Day Outcomes

Background: Postoperative atrial fibrillation (POAF) is a frequent complication following coronary artery bypass grafting (CABG) and is associated with increased acute morbidity and resource utilization. However, its independent role in driving post-discharge adverse events in contemporary practice remains debated. Objective: To evaluate the association between POAF and short-term outcomes after CABG, and to utilize empirical Bayesian risk updating to stratify 90-day post-discharge vulnerabilities. Methods: A retrospective cohort analysis of 4,684 adult patients who underwent isolated CABG in Florida between January 1, 2021, and June 30, 2024, was conducted, excluding those with documented preoperative AFib. We employed multivariable negative binomial and logistic regression models to assess length of stay (LOS), discharge disposition, 90-day readmission, and 90-day composite complications. Additionally, a Bayesian Beta-Binomial conjugate model with an objective Jeffreys Prior was utilized to estimate the posterior probabilities of adverse outcomes across key clinical phenotypes. Results: POAF occurred in 355 patients (7.58%). Multivariable analysis demonstrated a 30% relative increase in expected LOS (IRR 1.30, 95% CI [1.23 - 1.36], P < .001) and 33% higher odds of facility discharge (OR 1.33, 95% CI [1.03 - 1.72], P = .030) for patients with POAF. However, POAF was not independently associated with 90-day readmission (OR 1.25, P = .063) or composite complications (OR 1.20, P = .118). Chronic heart failure (CHF) emerged as the dominant predictor. Bayesian risk updating revealed that while the baseline posterior probability for a 90-day complication was 27.2%, the synergistic presence of both POAF and CHF radically shifted this posterior risk to 42.6% (Probability of Direction > 0.999 vs. baseline). Conclusions: POAF prolongs hospitalization and drives non-home discharges, but it does not independently dictate 90-day morbidity. Bayesian stratification demonstrates that post-discharge outcomes are predominantly driven by underlying chronic conditions. Effective reduction of readmissions requires robust transition-of-care frameworks, empowering primary care clinicians to aggressively optimize heart failure and metabolic disease rather than focusing solely on the acute surgical arrhythmic event.