SOURCE: Butt JH, Xian Y, Peterson ED, et al. Long-term thromboembolic risk in patients with postoperative atrial fibrillation after coronary artery bypass graft surgery and patients with nonvalvular atrial fibrillation. JAMA Cardiol 2018; Mar 28. doi:10.1001/jamacardio.2018.0405. [Epub ahead of print].

New onset of atrial fibrillation in the early postoperative period after coronary artery bypass graft (CABG) surgery is a common occurrence and is reported in between 11% and 40% of cases. The condition is thought to be transient and benign, but evidence is increasing that these patients face a greater risk of postoperative complications and prolonged hospital stay. In addition, it is unclear whether these patients should be treated with anticoagulant therapy in a similar fashion as patients who have nonvalvular atrial fibrillation that occurs spontaneously, and it is unclear what the long-term risk of stroke might be for these patients. Butt et al and other investigators in Denmark performed a retrospective cohort study to try and answer these questions.

The investigators retrieved data from a clinical cardiology surgery database and Danish nationwide registries to identify patients who underwent CABG surgery for the first time and developed atrial fibrillation in the postoperative period, from years 2000 through 2015. The patients were matched for age, sex, CHA2DS2–VASc score, and the year of diagnosis, to a group of patients who had nonsurgical, nonvalvular atrial fibrillation in a 1 to 4 ratio. The major outcomes and measures were 1) the proportion of patients initiating oral anticoagulant therapy within 30 days of hospital discharge, and 2) the rates of thromboembolism.

Investigators identified 2,108 patients who developed atrial fibrillation after CABG surgery, and they were matched with 8,432 patients with nonvalvular atrial fibrillation. In the total population, the median age was 69.2 (63.7-74.7) years, and 82.3% of patients were men. Oral anticoagulation was initiated 30 days postdischarge in 175 patients with postoperative atrial fibrillation (8.4%) and 3,549 patients with nonvalvular atrial fibrillation (42.9%). The risk of thromboembolism was significantly lower in the postoperative atrial fibrillation group than in the nonvalvular atrial fibrillation group (18.3 vs. 29.7 events per 1,000 patient-years; P < 0.001). Anticoagulation therapy during the follow-up was associated with a lower risk of thromboembolism in both groups of patients, compared with patients who did not receive any anticoagulant therapy. Overall, the risk of thromboembolism was not significantly higher in patients with postoperative atrial fibrillation compared with those who did not develop postoperative atrial fibrillation after CABG surgery.

The data from this study do not indicate that new-onset postoperative atrial fibrillation should be regarded as having the same risks as primary nonvalvular atrial fibrillation in terms of long-term thromboembolic risk, and that anticoagulation in this group may not be necessary unless the atrial fibrillation is persistent.