The safety and adequacy of antithrombotic therapy for atrial fibrillation: a regional cohort study.

BACKGROUND: Atrial fibrillation is a common problem in older people. The evidence base for the safety of warfarin and aspirin in atrial fibrillation is largely derived from selective research studies and secondary care. Further assessment of the safety of warfarin in older people with atrial fibrillation in routine primary care is needed. AIM: To measure the complication rates and adequacy of warfarin control in a cohort of patients with atrial fibrillation managed in primary care and compare them with published data from controlled trials and community patients with atrial fibrillation not receiving warfarin. DESIGN OF STUDY: Retrospective review of regional cohort.
SETTING: Twenty-seven general practices in southwest Scotland.
METHOD: Case note review of 601 patients previously identified as having atrial fibrillation by GPs.
RESULTS: The average age of our cohort was 77 years at recruitment. Two hundred and sixty-four (44%) patients died within 5 years of follow up. Three hundred and nine of the 601 (51%) patients with atrial fibrillation took warfarin at some stage during this study. INR (international normalised ratio) was maintained between 2 and 3 for 68% of the time. Bleeding risk was higher in patients taking warfarin than in those on aspirin or no antithrombotic therapy (warfarin 9.0% per year versus aspirin 4.7% per year versus no therapy 4.6% per year). The annual risk of any bleeding complication on warfarin (9%) was similar to that recorded in randomised trials (9.2%) whereas the annual risk of severe bleeding was approximately double (2.6 versus 1.3%).
CONCLUSION: Adequacy of anticoagulant control was broadly comparable to that reported in clinical trials, whereas the risk of severe bleeding was higher, possibly reflecting the older age and the comorbidities of our unselected cohort.