Effectiveness and Safety of Warfarin Initiation in Older Hemodialysis Patients with Incident Atrial Fibrillation

Abstract

Although generally recommended in atrial fibrillation (AF) patients, the effectiveness and safety of oral anticoagulation in dialysis patients with AF is unknown. We assembled a cohort of older hemodialysis patients who initiated dialysis without prior record of AF and who had prescription drug benefits through three state-administered programs. The index event was a first hospitalization with diagnosed AF; patients with any recorded prior warfarin use were excluded. Eligible patients survived ≥30 days from discharge, and new warfarin use was recorded from prescription records during that 30-day window. Propensity-matched warfarin users and nonusers were compared using Cox regression. Outcomes included ischemic stroke, hemorrhagic stroke, and mortality. Among 2313 patients with new AF who survived 30 days from discharge, 249 (10.8%) filled a prescription for warfarin. Comparing 237 warfarin users and 948 propensity-matched nonusers over 2287 person-years of follow-up, the occurrence of ischemic stroke was similar (HR = 0.92; 95% CI, 0.61 to 1.37), whereas warfarin users experienced twice the risk of hemorrhagic stroke (HR = 2.38; 95% CI, 1.15 to 4.96). The risks of stroke, gastrointestinal hemorrhage, and mortality did not differ between groups. As-treated analyses yielded similar findings, as did analyses restricted to patients with CHADS(2) scores ≥2. Although we confirmed association between warfarin use and hemorrhagic stroke in dialysis patients with AF, we found no association between warfarin use and ischemic stroke. Adequately powered randomized trials are required to conclusively determine the risks and benefits of the studied warfarin indication in hemodialysis patients.