Risk Versus Benefit of Combined Aspirin and Warfarin Therapy in Patients With Atrial Fibrillation

Purpose: Guidelines have differing recommendations for aspirin use in patients with an indication for anticoagulation. The purpose of this study was to evaluate the incidence of major bleeding and thromboembolic events (TEs) in patients with atrial fibrillation (AF) receiving warfarin alone (monotherapy group) versus warfarin plus aspirin (combination therapy group). Methods: This was a retrospective, cohort study including patients from a pharmacist-run anticoagulation clinic. Inclusion criteria were patients with AF receiving anticoagulation between January 2013 and January 2014 observed over 5 years. Results: One hundred forty-two patients were included in the combination group versus 89 in monotherapy group. In the combination group, 60 (42.3%) patients were on aspirin for no apparent indication, 19 (13.4%) had stable coronary artery disease and diabetes, and 26 (18.3%) had diabetes alone. Major bleeding occurred in 21 (14.9%) patients in the combination group versus 7 (7.9%) patients in the monotherapy group (odds ratio [OR] = 2.02, 95% confidence interval [CI]: 0.78-5.91; P = .17). TE occurred in 10 (7%) patients in the combination group versus 4 (4.5%) in the monotherapy group (OR = 1.61, 95% CI: 0.44-7.24; P = .57). There was no significant difference in bleeding (P = .85) or TE (P = .37) rates between aspirin indications in the combination group. Conclusion: Combination therapy versus monotherapy may increase bleeding risk with little benefit in decreasing AF-related stroke or cardiovascular events.