Anticoagulation for stroke prevention in new atrial fibrillation after coronary artery bypass graft surgery

BACKGROUND: The benefit of early anticoagulation for stroke prophylaxis in atrial fibrillation after coronary artery bypass graft (CABG) surgery is uncertain. We therefore studied what proportion of ischemic strokes in patients with atrial fibrillation early after CABG surgery were potentially preventable by anticoagulation with warfarin. METHODS: We reviewed medical records from 2264 patients with isolated CABG performed during a period when our institution had no policy on anticoagulation for postoperative atrial fibrillation. The outcome was ischemic stroke within 30days postoperatively and verified with computed tomography (CT) in patients with new postoperative atrial fibrillation for more than 48h. RESULTS: New, postoperative atrial fibrillation occurred in 403 (17.8%) of the patients and 191 of those (47.4%) were not started on warfarin at 48hours. Eight patients developed CT-verified ischemic stroke, which occurred on postoperative day 1-3 in 4 patients and in 3 patients was of the lacunar type. In two patients (stroke day 25 and day 30) warfarin could have been preventive. In another patient with onset of neurological symptoms on postoperative day 8 (4days from onset of the arrhythmia), systemic anticoagulation might have limited the severity of the stroke but warfarin therapy would not likely have reached therapeutic levels within 2days. CONCLUSION: The preventive effect of warfarin on early stroke associated with new atrial fibrillation after CABG seems limited. Treatment with warfarin during the hospitalization has to take the risk of bleeding, particularly into the pericardium, as reported in the literature, into account.