The effect and safety of the antithrombotic therapies in patients with atrial fibrillation and CHADS₂ Score 1

Background: The revised ACC/AHA/ESC 2006 guideline recommends either aspirin or warfarin for the prevention of ischemic stroke in patients with atrial fibrillation (AF) in CHADS₂ score 1. We hypothesized that warfarin is superior to aspirin therapy for the prevention of stroke without increasing bleeding complication in AF patients with CHADS₂ score 1. Methods and Results: Among 1,502 patients (mean 62.4 ± 13.8 years old, male 65.4%) who were treated for nonvalvular AF without previous stroke, the number of patients with CHADS₂ score 1 was 422 (62.9 ± 10.7 years old, male 290 [68.7%]) and their antithrombotic therapies were as follows: warfarin (n = 143), aspirin (n = 124), other antiplatelet (n = 45), and no antithrombosis (none: n = 110). We reviewed the incidences of ischemic stroke, mortality, and bleeding complications during the follow-up period. Results were: (1) during 22.3 ± 17.8 months of follow-up, the incidence of ischemic stroke was significantly lower in warfarin (6 patients, 4.2%, mean international normalized ratio [INR] 2.0 ± 0.5 IU) than in aspirin (16 patients, 12.9%, P = 0.008) than none (23 patients, 20.9%, P < 0.001) without differences in all-cause mortality. (2) The incidence of major bleeding (decrease in hemoglobin ≥2 g/dL, requiring hospitalization or red blood cell transfusion ≥2 pints) was not different between warfarin (2.1%) and aspirin (0.8%, P = NS), but minor bleeding was more common in warfarin (10.5%) than in aspirin (2.4%, P = 0.007). Conclusion: In AF patients with CHADS₂ score 1, warfarin was better to prevent ischemic stroke than aspirin without increasing the incidence of major bleeding complications. However, the incidence of minor bleeding was higher in the warfarin group than the aspirin group.