Background Anticoagulation with warfarin is an important therapy for preventing strokes in patients with atrial fibrillation (AF). Physicians often combine warfarin with aspirin despite evidence for increased bleeding. We investigated the hemorrhagic outcomes related to the differential management of AF with warfarin alone versus combination therapy.
Methods and Results This retrospective cohort study of 695 patients enrolled at a university hospital-based anticoagulation clinic includes patients who received anticoagulation with warfarin or warfarin and aspirin between June 1, 2007 and September 30, 2008. All patients were ≥45 years old, had AF as the indication for anticoagulation, and did not have mechanical heart valves. Hemorrhages were classified as major if they caused death, involved critical sites, or required hospitalization with transfusion of ≥2 units of blood. All other bleeds were classified as minor. Of the 695 patients 307(44.2%) received combination therapy. Hemorrhage rates in the warfarin and the combination cohorts were 5.2% and 7.0% per 100-people years (p=0.29), respectively. There were 17 (3.4%) patients with major hemorrhages in the warfarin only group and 9 (2.8%) in the combination group (p=0.62). On average, patients on combination therapy had lower international normalized ratio (INR) values circa presentation (4.27 vs 3.13 p=0.049). In either group, any history of hemorrhage was associated with a 3.8 (95% CI, 1.79-8.13) times higher risk of hemorrhaging compared to patients without such a history.
Conclusions This study highlights the high incidence of combination therapy and suggests that patients on combination therapy may bleed at lower INR levels. However, hemorrhagic outcomes did not differ significantly
