Improvements in warfarin therapy reduce stroke rate, study shows

Current use of warfarin as a stroke prevention therapy in patients with nonvalvular atrial fibrillation (AF) is associated with a lower rate of residual stroke or systemic embolism compared with previous data, according to a recent study.

The meta-analysis, published in the April 23 issue of the Archives of Internal Medicine, found significant improvements in the use of warfarin for anticoagulation therapy.

AF is associated with a 5-fold increase in the risk of ischemic stroke and has been implicated as a causal factor in as many as 15% to 20% of all ischemic strokes, said Shikhar Agarwal, MD, Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, and colleagues.

Although several new antithrombotic agents have been developed for stroke prevention in patients with AF, the authors predict that many physicians will continue to treat patients with warfarin because of cost considerations and a limited amount of safety data for the newer agents.

The researchers evaluated the safety and efficacy of warfarin treatment by searching the MEDLINE, EMBASE, and Cochrane databases for relevant randomized clinical trials that compared warfarin with an alternative thromboprophylaxis strategy. Their meta-analysis included 8 randomized clinical trials with 55,789 patient-years of warfarin therapy follow-up.

Agarwal and colleagues found an estimated annual incidence of stroke or non-central nervous system embolism of 1.66% in patients with AF taking warfarin, 0.76% for myocardial infarction, and 3.83% for all-cause mortality. Rates of major bleeding ranged from 1.40% to 3.40% per year. Patients aged 75 years and older (2.27%), female patients (2.12%), patients with a history of stroke (2.64%), and patients reporting no previous exposure to vitamin K antagonists (1.96%) had a significantly higher annual risk of stroke.

The authors also noted a significant increase in the annual incidence of stroke in patients with increasing CHADS2 (congestive heart failure, hypertension, age, diabetes, and prior stroke) score.

“Faced with these newer choices, it is imperative that physicians precisely estimate the inherent bleeding risk accompanying warfarin treatment in eligible candidates with nonvalvular AF using current data over historical rates obtained in the previous decade,” the authors stated.

“These results could potentially aid the decision process for warfarin therapy for individual physicians and allow health systems to evaluate the cost efficacy of adopting newer agents universally or in specific high-risk clinical subsets.”