Major hemorrhage and tolerability of warfarin in the first year of therapy among elderly patients with atrial fibrillation.

BACKGROUND

Warfarin is effective in the prevention of stroke in atrial fibrillation but is under used in clinical care. Concerns exist that published rates of hemorrhage may not reflect real-world practice. Few patients > or = 80 years of age were enrolled in trials, and studies of prevalent use largely reflect a warfarin-tolerant subset. We sought to define the tolerability of warfarin among an elderly inception cohort with atrial fibrillation.

METHODS AND RESULTS

Consecutive patients who started warfarin were identified from January 2001 to June 2003 and followed for 1 year. Patients had to be > or = 65 years of age, have established care at the study institution, and have their warfarin managed on-site. Outcomes included major hemorrhage, time to termination of warfarin, and reason for discontinuation. Of 472 patients, 32% were > or = 80 years of age, and 91% had > or = 1 stroke risk factor. The cumulative incidence of major hemorrhage for patients > or = 80 years of age was 13.1 per 100 person-years and 4.7 for those < 80 years of age (P=0.009). The first 90 days of warfarin, age > or = 80 years, and international normalized ratio (INR) > or = 4.0 were associated with increased risk despite trial-level anticoagulation control. Within the first year, 26% of patients > or = 80 years of age stopped taking warfarin. Perceived safety issues accounted for 81% of them. Rates of major hemorrhage and warfarin termination were highest among patients with CHADS2 scores (an acronym for congestive heart failure, hypertension, age > or = 75, diabetes mellitus, and prior stroke or transient ischemic attack) of > or = 3.

CONCLUSIONS

Rates of hemorrhage derived from younger noninception cohorts underestimate the bleeding that occurs in practice. This finding coupled with the short-term tolerability of warfarin likely contributes to its underutilization. Stroke prevention among elderly patients with atrial fibrillation remains a challenging and pressing health concern.