Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting Surgery

Postoperative atrial fibrillation (PoAF) is the most common arrhythmia following cardiac surgery, which increase the patient's morbidity and mortality.

The aim of this study was to evaluate new onset of atrial fibrillation (AF) after isolated coronary artery bypass grafting (CABG) surgery, its clinical and surgical predictors, and its impact in immediate and long-term outcomes.

Retrospective study including all CABG surgeries performed in a tertiary centre, between 2004 and 2011. Patients with documented episodes of AF or pacing rhythm before cardiac surgery were excluded. Preoperative, surgical and postoperative data were collected through clinical files and informatics databases. Qui-square tests and independent t-tests were used to compare categorical and continuous data, respectively, between patients with and without PoAF. A multivariate logistic regression model was used to identify independent risk factors of PoAF. To determine the effect of PoAF in long-term survival, we used Kaplan-Meier curves, Log Rank test and multivariate Cox regression (maximum follow-up time: 13 years).

We included 2511 patients, mean age of 63±10 years, 78.7% being male. PoAF occurred in 450 patients (18.0%), 3±3 days after surgery, the majority pharmacologically cardioverted with amiodarone (96.2%). These patients were older (67±9 vs. 62±10 years, p<0.001), more frequently obese (27.8% vs. 22.9%, p=0.026), hypertensive (76.7% vs. 69.7%, p=0.003) and had lower preoperative creatinine clearance (CC) values (73.2±27.4 vs. 81.4±28.3 ml/min, p<0.001), longer cardiopulmonary bypass time (60.0% vs. 54.8%, p=0.043) compared with patients without PoAF. In multivariate analysis, older age (OR: 1.035, 95% CI: 1.015-1.056, p=0.001), lower preoperative CC values (OR: 0.992, 95% CI: 0.985-0.999, p=0.032) and larger left atrial diameter (OR: 1.058, 95% CI: 1.024-1.093, p=0.001) were determined as independent predictors of PoAF. These patients also revealed longer hospitalization time (8 [4 to 193] vs. 6 [4 to 114] days, p<0.001) and higher hospital mortality (2.9% vs. 0.8%, p<0.001). Regarding long-term survival, patients with PoAF showed lower cumulative survival than patients without AF events (52% vs. 66%, p<0.001). PoAF was also found as an independent predictor of mortality in multivariate Cox regression (HR: 1.394, 95% CI: 1.147- 1.695, p=0.001).

PoAF incidence after CABG surgery was 18%. Older age, lower CC values and larger left atrial diameter were settled as PoAF independent predictors. Additionally, the occurrence of this arrhythmia was independently associated with lower long-term survival, after CABG surgery.