Dabigatran and warfarin in vitamin K antagonist-naive and -experienced cohorts with atrial fibrillation.

BACKGROUND The comparison of anticoagulants dabigatran and warfarin might be most equitable in vitamin K antagonist (VKA)-naive patients. METHODS AND RESULTS Warfarin and 2 doses of dabigatran-110 mg BID (D110) and 150 mg BID (D150)-were compared in a balanced population of VKA-naive (≤62 days of lifetime VKA exposure, with 33% never prescribed a VKA) and VKA-experienced patients with atrial fibrillation (n=18 113). For VKA-naive and -experienced patients assigned warfarin, the time in therapeutic range (international normalized ratio 2.0 to 3.0) was 62% and 67%, respectively, and 61% and 66% for those never and ever prescribed a VKA. In VKA-naive patients, stroke and systemic embolism rates were 1.57%, 1.07%, and 1.69% per year for D110, D150, and warfarin, respectively. D110 was similar to warfarin (P=0.65); D150 was superior (P=0.005). Major bleeding rates were 3.11%, 3.34%, and 3.57% per year, respectively. D110 and D150 were similar to warfarin (P=0.19 and P=0.55). Intracranial bleeding rates were 0.19%, 0.33%, and 0.73% per year, respectively. D110 and D150 were lower than warfarin (P<0.001 and P=0.005). In VKA-experienced patients, stroke and systemic embolism rates were 1.51%, 1.15%, and 1.74% per year for D110, D150, and warfarin, respectively. D110 was similar to warfarin (P=0.32); D150 was superior (P=0.007). Major bleeding rates were 2.66%, 3.30%, and 3.57% per year, respectively. D110 was lower than warfarin (P=0.003); D150 was similar (P=0.41). Intracranial bleeding rates were 0.26%, 0.32%, and 0.79% per year, respectively. D110 and D150 were lower than warfarin (P<0.001 for both). Results were similar for patients never on a VKA. CONCLUSIONS Previous VKA exposure does not influence the benefits of dabigatran at either dose compared with warfarin. CLINICAL TRIAL REGISTRATION http://www.clinicaltrials.gov. Unique identifier: NCT00262600.