Dabigatran Use in a Postoperative Coronary Artery Bypass Surgery Patient with Nonvalvular Atrial Fibrillation and Heparin-PF4 Antibodies

Abstract

To present a case of dabigatran use for nonvalvular atrial fibrillation in a patient from a population for whom it has not been studied. Postoperative coronary artery bypass patients have significant bleeding risk and potential to develop heparin-induced thrombocytopenia (HIT). A 70-year-old male with a history of paroxysmal atrial fibrillation in sinus rhythm prior to surgery developed atrial fibrillation on postoperative day 2 after coronary artery bypass surgery. Because of thrombocytopenia, anticoagulation to decrease stroke risk with atrial fibrillation was initiated with dabigatran 150 mg orally twice daily beginning on postoperative day 4. Later on postoperative day 4, after dabigatran was administered, the patient's HIT screening test was positive for heparin/PF4 antibodies; however, he was not clinically diagnosed with HIT. Heparin was not used postoperatively and transition dosing from dabigatran to warfarin was started on postoperative day 8, the day of discharge. At the time of the outpatient follow-up appointment, the patient had no signs of thrombosis or bleeding complications. Dabigatran is a direct thrombin inhibitor approved for nonvalvular atrial fibrillation. In this case, the physician ordered dabigatran for an approved use, according to manufacturer labeling. However, patients with this diagnosis would have been excluded from the RE-LY (Randomized Evaluation of Long-term Anticoagulant Therapy) trial, on which Food and Drug Administration approval was based. Our patient had thrombocytopenia with a low pretest probability for HIT but was positive for heparin/PF4 antibodies, based on enzyme immunoassay testing. Dabigatran was continued for atrial fibrillation and not switched to any other direct thrombin inhibitor, such as argatroban, lepirudin, or bivalirudin, which are listed in the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines, 8th edition, for the Treatment and Prevention of Heparin Induced Thrombocytopenia. Further research on the use of dabigatran in patients with recent coronary bypass surgery and heparin/PF4 antibodies is needed before any recommendations can be made.