BACKGROUND: OBJECTIVE: DESIGN: Mixed retrospective and prospective cohort study of patients with atrial fibrillation between 1996 and 2003. SETTING: An integrated health care delivery system. PATIENTS: MEASUREMENTS: RESULTS: Patients accumulated more than 66 000 person-years of follow-up. The adjusted net clinical benefit of warfarin for the cohort overall was 0.68% per year (95% CI, 0.34% to 0.87%). Adjusted net clinical benefit was greatest for patients with a history of ischemic stroke (2.48% per year [CI, 0.75% to 4.22%]) and for those 85 years or older (2.34% per year [CI, 1.29% to 3.30%]). The net clinical benefit of warfarin increased from essentially zero in CHADS(2) stroke risk categories 0 and 1 to 2.22% per year (CI, 0.58% to 3.75%) in CHADS(2) categories 4 to 6. The patterns of results were preserved when weighting factors for intracranial hemorrhage of 1.0 and 2.0 were used. LIMITATIONS: Residual confounding is a possibility. Some outcome events were probably missed by the screening algorithm or when medical records were unavailable. CONCLUSION: PRIMARY FUNDING SOURCE: National Institute on Aging; National Heart, Lung, and Blood Institute; and Massachusetts General Hospital.
|