Thrombus Formation in Left Atrium on Dabigatran Therapy

Dabigatran is a direct thrombin inhibitor, approved in the United States for stroke prevention in nonvalvular atrial fibrillation and prevention and treatment of thromboembolism. It has been also used in patients with documented left atrial thrombus, where treatment with dabigatran effectively led to thrombus resolution. We present a rare case of left atrial thrombus formation in a patient with chronic atrial fibrillation being treated with dabigatran 150 mg twice a day. The patient presented with multiple embolic strokes. There are only three such cases reported in the literature till date, all of whom had thrombus in the left atrium. The possible mechanisms of dabigatran failure include compensatory increase in upstream coagulation factors due to single level downstream blockade of thrombin, lack of inhibition of all available thrombin, and lack of monitoring measures that can be implemented in common clinical laboratories that lead to failure to assess adherence, which in turn can lead to dabigatran failure.