Results of an open-label, prospective study of anticoagulant therapy for atrial fibrillation in an outpatient anticoagulation clinic

Ahmed H Abdelhafiz, Nigel M Wheeldon
Clinical Therapeutics 2004, 26 (9): 1470-8

OBJECTIVE: The goal of this study was to investigate the complications and control of warfarin treatment in patients with nonvalvular atrial fibrillation (NVAF) newly referred to an outpatient anticoagulation clinic.

METHODS: This study included new patients with NVAF who were referred to an anticoagulation clinic for warfarin therapy over a recruitment period of 21 months. To reflect real-world clinical practice, patient selection for anticoagulation and patient management were left to the referring physicians, who were blinded to their patients' participation in the study. Patients were interviewed in person at the first clinic visit and then by telephone every 4 to 6 weeks. They were questioned about any bleeding or thromboembolic events.

RESULTS: A total of 402 patients were included (100% of all new referrals over 21 months). The mean (SD) age was 72.3 (10.3) years, and 224 (56%) patients were men. The mean (SD) international normalized ratio (INR) was 2.4 (0.31). Patients were followed up for a mean (SD) of 19 (8.1) months (range, 1.0-31.0 months). They spent a mean (SD) 66% (18.3) of time in the target range of INR (ie, 2.0-3.0). Annual event rates were 1.7% (95% CI, 0.4%-3.0%) for major bleeding, 16.6% (95% CI, 13.0%-20.2%) for minor bleeding, 1.2% (95% CI, 0.1%-2.3%) for ischemic stroke, and 0.3% (95% CI, 0.2%-0.8%) for transient ischemic attacks. There were no cases of hemorrhagic stroke or fatal bleeding. Variability of INR and number of medications were identified as risk factors for bleeding (P = 0.03 and P = 0.001, respectively). There was no significant association between age and bleeding.

CONCLUSIONS: Based on this analysis, the risks of long-term oral anticoagulation therapy in an outpatient anticoagulation clinic appear to reflect the results of clinical trials. Rates of ischemic stroke, major bleeding, and anticoagulation control were comparable. There was no age-related risk of complications.

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