Warfarin related to low rate of residual stroke in patients with atrial fibrillation

A review of clinical trials comparing warfarin with other medications for stroke prevention suggests that warfarin was associated with a low risk of stroke or non-central nervous system embolism in patients with nonvalvular atrial fibrillation (rapid, irregular heart beat), according to a study published Online First by Archives of Internal Medicine.

Novel (new) antithrombotic medications (which interfere with blood clots) have been developed as alternatives to warfarin and clinical trials have suggested that some are superior, easier to administer and lack interaction with other medications and food, the authors write in their study background. However, the use of these new medications may be hampered by cost, so the authors comment that they expect warfarin treatment to continue as the dominant therapy for patients with atrial fibrillation (AF) despite some inadequacies and the need for close laboratory supervision.

Shikhar Agarwal, M.D., M.P.H., C.P.H., and colleagues with the Cleveland Clinic, Ohio, searched the medical literature and compiled eight randomized controlled trials with 32,053 patients for their meta-analysis comparing warfarin with other medications.

The authors report that the pooled annual incidence rate of stroke or non-CNS (central nervous system) embolism was estimated to be 1.66 percent, which was lower than the 2.09 percent in a previous meta-analysis.

The risk of stroke was higher in elderly patients, women, patients who had had a previous stroke or TIA (transient ischemic attack or mini-stroke) and those patients reporting no previous exposure to vitamin K antagonists, the review indicated.

"Thus, despite the development of newer antithrombotic agents with increased ease of administration that are superior or noninferior to warfarin, most patients with nonvalvular AF will probably continue to be treated with warfarin in the near future owing to cost considerations," the authors comment. "Indeed, warfarin will likely continue to be widely used as the drug of choice in several countries around the world."

In an invited commentary, Daniel E. Singer, M.D., of Massachusetts General Hospital, Boston, and Alan S. Go, M.D., of Kaiser Permanente Northern California, Oakland, write: "It is beyond the scope of this commentary to provide detailed guidance as to which patients with AF should be taking a novel agent. However, patients who are comfortable with warfarin therapy and whose TTR (time in the standard therapeutic range) is above 75 percent should be in no hurry to switch. They may forgo a small reduction in risk of intracranial hemorrhage, but they should benefit as we gain more experience with the novel agents."

"We have begun a new, very promising era in preventing stroke in AF. The novel anticoagulants appear to constitute a positive disruptive technology. However, warfarin management has also evolved, allowing safe, effective and inexpensive anticoagulation for many patients with AF, likely slowing the ultimate transition to modern anticoagulant agents," they conclude.