Abstract 2850: Inappropriate Use of Warfarin Among Patients With Atrial Fibrillation
Background: Warfarin reduces the risk of stroke and thromboembolic events in patients with atrial fibrillation (AF). However, this benefit is offset by the increased risk of bleeding. The purpose of this study was to determine the appropriateness of warfarin use based on the most recent 2006 ACC/AHA guidelines in a large cohort of patients with nonrheumatic AF.
Hypothesis: We hypothesized that warfarin is inappropriately overused in patients at low risk of stroke.
Methods: Individual CHADS2 score, associated comorbidities and anticoagulant therapy were determined in 2223 consecutive patients with nonrheumatic AF at a single academic center between 2006 and 2008. The decision for anticoagulation was at the discretion of the primary physician and no intervention to guide anticoagulant therapy was made.
Results: Among the 2223 patients (mean age=72±13 years), the CHADS2 score was 0 in 261(12%), 1 in 636 (29%), and ≥2 in 1326 (59%) patients. There were 363 (16%) patients with a prior TIA or stroke. Warfarin was prescribed in 106/261 (41%) patients with a CHADS2 score of 0, 483/636 (76%) with a CHADS2 of 1, and 1119/1324 (84%) with a CHADS2 of ≥2. In patients with a CHADS2 of 1, independent predictors of warfarin use were LV dysfunction (OR 3.26, p=.004), coronary artery and other vascular disease (OR 2.39, p=.002), and male gender (OR 1.53, p=.041). Age, hypertension, and diabetes were not predictors of warfarin use. Among the 205 patients not on warfarin with CHADS2≥2, 71 (35%) were not taking warfarin due to prior hemorrhagic event or risk of fall, 23 (11%) refused warfarin, while the remaining 111 (54%) patients had no documented contraindication. Of the 363 patients with a prior stroke or thromboembolic event, 314 (87%) were taking warfarin while 49 were not on warfarin (13%) due to major bleed or risk of fall (21/49, 43%), or patient refusal (6/49, 12%).
Conclusion: In an academic, university based health system, most low risk patients with a CHADS2 score of 1 are taking warfarin while many very low risk patients with a CHADS2 of 0 are taking warfarin. Recent ACC/AHA guidelines for the management of atrial fibrillation have not been quickly adopted in this setting. Warfarin for nonrheumatic atrial fibrillation might be inappropriately overused for patients at low risk of stroke.