Oral anticoagulant use in patients with atrial fibrillation

OBJECTIVES
Oral anticoagulant therapy has been shown to decrease the risk for vascular complications in patients with atrial fibrillation (AF). We evaluated the frequency of oral anticoagulant use in patients with AF, whether oral anticoagulant use was associated with effective INR values, and the reasons for not including an anticoagulant in the treatment.

STUDY DESIGN
The study included 426 consecutive patients (256 women, 170 men; mean age 66±11 years) who presented with a diagnosis of AF between October 2007 and November 2008. The patients were inquired about whether they were using warfarin and/or aspirin and the reasons for not taking an oral anticoagulant. The INR levels were measured in those receiving warfarin.

RESULTS
Permanent AF was present in 72.8%, and paroxysmal AF was present in 27.2%. Patients ≥75 years of age accounted for 32.4%. The risk for stroke was high in 69.3%, moderate in 21.8%, and low in 8.9%, hypertension being the most frequent risk factor (66.7%). Inquiry about medications showed that 107 patients (25.1%) were taking aspirin and warfarin, 21 patients (4.9%) and 237 patients (55.6%) were taking warfarin and aspirin alone, respectively, while 61 patients (14.3%) used none. The incidence of oral anticoagulant use was 30.1%, being significantly low in patients ≥75 years of age (p=0.0001), and having hypertension (p=0.023) or coronary artery disease (p=0.004). Effective INR values recommended by the guidelines were attained in 47.7% (n=61) of patients receiving warfarin. Sex, age, clinical risk factors, and socioeconomic parameters were not associated with achievement of target INR values. The most frequent reason for not starting anticoagulant treatment was the low tendency of physicians to prescribe the drug (74.3%), followed by the presence of contraindications (9.8%).

CONCLUSION
The most important factor for inadequate oral anticoagulant use especially in patients having a high risk for stroke is the low incidence of prescription of the drug by the physicians, suggesting low influence of the guidelines on the clinical practice.