Newly detected atrial fibrillation and compliance with antithrombotic guidelines

BACKGROUND: Guidelines recommend the use of antithrombotic therapy for stroke prevention in patients with atrial fibrillation (AF), but compliance with such guidelines has not been widely studied among patients with newly detected AF. Our objective was to assess compliance with antithrombotic guidelines and to identify patient characteristics associated with warfarin use. METHODS: A population-based study of newly detected AF (patient age, 30-84 years) was conducted within a large health plan. Cardiovascular disease risk factors, comorbid conditions, medication use, and international normalized ratios were abstracted from the medical record. Patients were stratified by embolic risk according to American College of Chest Physicians (ACCP) criteria. We analyzed the proportion of patients with AF receiving warfarin or aspirin (> or =325 mg/d) during the 6 months following AF. Relative risk regression estimated the association of risk factors and patient characteristics with warfarin use. RESULTS: Overall, 73% of patients (418/572) with newly detected AF had evidence of antithrombotic use after AF onset. Among the 76% (437/572) of patients with AF at high risk for stroke, 59% (257/437) used warfarin, 28% (123/437) used aspirin, and 24% (104/437) used neither. The major predictor of warfarin use was AF classification; intermittent or sustained AF had relative risks for warfarin use of 2.8 (95% confidence interval, 2.2-3.6) and 2.9 (95% confidence interval, 2.2-3.7), respectively, compared with transitory AF. CONCLUSIONS: Three quarters of the patients with newly detected AF received antithrombotic therapy, yet many at high risk of stroke did not receive warfarin. Atrial fibrillation classification, rather than stroke risk factors, was strongly associated with warfarin use.