Quality of anticoagulation with warfarin in patients with nonvalvular atrial fibrillation in the community setting.

BACKGROUND: The benefit of oral anticoagulation therapy with warfarin for stroke prevention in atrial fibrillation (AF) is directly dependent on the quality of anticoagulation (QoA), which in the US is provided predominantly in the community setting. With the emergence of new oral anticoagulation agents, the current QoA needs to be assessed. OBJECTIVES: The purpose of our study is to define the QoA with warfarin in patients with nonvalvular AF who are managed exclusively in community practices, and to compare the quality in the community setting with the quality demonstrated in the recent large randomized control trials. In addition, this study will assess the differences in the QoA based on cardiology vs primary care practices. METHODS: This is a retrospective, observational, multi-center study of 392 patients with AF in the community who were initiated on anticoagulation with warfarin for stroke prevention. International Normalized Ratio (INR) values were collected over a one-year period and the QoA was expressed as time in therapeutic range (TTR) calculated by the linear interpolation method. RESULTS: One hundred patients from cardiology practices and 292 patients from primary care were studied. During the one-year period, the overall mean TTR was 56.7%. The TTR in the primary care vs cardiology practices was 55.3% vs. 60.8% (p=0.02). Both practices had similar percent of time below therapeutic range, 29.8% vs. 29.2%. However, the primary care practice patients were above the therapeutic range 15% of the time vs. 10% in cardiology (p<0.001). There were one death secondary to intracranial bleed and one major bleed in the primary care group. There were no strokes during the study period in either group. CONCLUSION: The QoA with warfarin, as assessed by TTR, in the current community setting remains suboptimal, and there has been little to no improvement in current clinical practices. TTR should be considered when assessing the recent comparative studies evaluating novel pharmacologic agents to warfarin for the treatment of AF. SUBJECT AREAS: Arrhythmias, preventive cardiology, anticoagulation, thromboembolism, cardiovascular disease risk factors.