Relationship of atrial fibrillation and stroke after coronary artery bypass graft surgery: When is anticoagulation indicated?

Background. Atrial fibrillation (AF) is considered as a risk factor for stroke after coronary artery bypass grafting operations. Methods. A retrospective search in our hospital's medical record database was done to identify patients with postoperative strokes who underwent coronary artery bypass grafting operations from January 1, 1993, until December 31, 2004. All cases were individually reviewed, and the temporal relationship between neurologic event and postoperative episodes of AF was determined. During the study period it was our consistent policy to use only Coumadin anticoagulation limited to patients who had persistent AF or were to be discharged in AF. Results. Of the 2,964 coronary artery bypass grafting operations, 576 patients (19.4%) had AF and 32 patients (1.1%) suffered stroke. Seventeen stroke patients maintained normal sinus rhythm during their hospital stay. Of the remaining 15 patients, 9 presented with neurologic deficit before the first episode of AF, with 5 having intraoperative and 4 having postoperative stroke. Of the 6 patients with AF before neurologic event, three strokes occurred within 1 week after spontaneous conversion to normal sinus rhythm. One patient with preoperative and also with intraoperative AF who underwent emergency coronary artery bypass grafting woke up with stroke. In the remaining two cases, the AF or atrial flutter episodes lasted less than 6 hours each before the neurologic event. More aggressive anticoagulation as suggested in the published guidelines could not have prevented strokes in any of these 6 patients. Conclusions. This retrospective analysis does not support the use of aggressive anticoagulation, particularly full intravenous heparinization as a bridging therapy to decrease the already low incidence of postoperative strokes after routine coronary artery bypass grafting surgery.