New-onset atrial fibrillation at discharge in patients after coronary artery bypass surgery: short- and long-term morbidity and mortality

OBJECTIVES: Atrial fibrillation (AF) after coronary artery bypass surgery is often considered a non-harmful and self-terminating condition. We studied the mortality and morbidity in patients with new-onset AF (NOAF) present at the time of hospital discharge. METHODS: We conducted a retrospective follow-up study of 138 patients discharged in NOAF (NOAF group) and a propensity score-matched control group of 138 patients who were in sinus rhythm (SR) at the time of discharge (SR group). Follow-up data were obtained from the hospitals' records, from the national registry of hospital discharge diagnoses and death records from the Finnish Statistical Bureau. RESULTS: At 3 and 12 months after surgery, AF was present in 20.3 and 23.2% of patients in the NOAF group, respectively, but in none of the patients in the SR group (P < 0.001). At the end of follow-up (8.5 +/- 2.8 years), 28.3 and 5.1% of the patients who survived in the NOAF and SR groups, respectively, were in chronic AF (P < 0.001). All-cause mortality (33.3 vs 18.8%, P = 0.002) and cardiac mortality (15.2 vs 4.3%, P = 0.001) were higher in the NOAF group when compared with the SR group. The incidence of cerebrovascular disorders in the NOAF and SR groups did not differ from each other (13.8 vs 10.9%, P = NS). Independent risk factors for all-cause death were NOAF [P = 0.024, hazard ratio (HR) 1.828, 95% CI 0.547-3.09], age (P = 0.0025, HR 1.074, 95% CI 1.026-1.13), diabetes (P = 0.015, HR 1.965, 95% CI 1.142-3.38) and prolonged respiratory support (P = 0.00024, HR 3.394, 95% CI 1.767-6.52). In addition, patients in the NOAF group had more hospitalizations due to heart failure (7.2 vs 0.7%, P < 0.001) and had a higher rate of implantation of permanent pacemakers (6.5 vs 0.4%, P < 0.001). CONCLUSIONS: A majority of NOAF patients revert to SR during the first months after surgery. On the other hand, 20-25% of NOAF patients develop chronic AF during long-term follow-up. Almost half of the NOAF patients were hospitalized during follow-up due to cardiovascular causes. Similarly, NOAF was associated with increased mortality due to cardiac causes, but not increased risk of stroke. This highlights the need for proper oral anticoagulation therapy in these patients.