Warfarin for atrial fibrillation in community-based practise.

BACKGROUND

Previous studies of anticoagulation for atrial fibrillation (AF) have predominantly occurred in academic settings or randomized trials, limiting their generalizability.

OBJECTIVE

To describe the management of patients with AF anticoagulated with warfarin in community-based practise.

METHODS

We enrolled 3396 patients from 101 community-based practises in 38 states. Data included demographics, comorbidities, and International Normalized Ratio (INR) values. Outcomes included time in therapeutic INR range (TTR), stroke, and major hemorrhage.

RESULTS

The mean TTR was 66.5%, but varied widely among patients: 37% had TTR above 75%, while 34% had TTR below 60%. The yearly rates of major hemorrhage and stroke were 1.90 per 100 person-years and 1.00 per 100 person-years. Four percent of patients (n = 127) were intentionally targeted to a lower INR, and spent 42.7% of time with an INR below 2.0, compared to 18.8% for patients with a 2.0-3.0 range (P < 0.001). Mean TTR for new warfarin users (57.5%) remained below that of prevalent users through the first six months. Patients with interruptions of warfarin therapy had lower TTR than all others (61.6% vs. 67.2%, P < 0.001), which corrected after deleting low peri-procedural INR values (67.0% vs. 67.4%, P = 0.73).

CONCLUSIONS

Anticoagulation control varies widely among patients taking warfarin for AF. TTR is affected by new warfarin use, procedural interruptions, and INR target range. In this community-based cohort of predominantly prevalent warfarin users, rates of hemorrhage and stroke were low. The risk versus benefit of a lower INR target range to offset bleeding risk remains uncertain.