NEW YORK (Reuters Health) – In high-risk atrial fibrillation patients who are candidates for anticoagulation, stroke usually occurs if warfarin is not used or drug levels are subtherapeutic, the results of a new study reveals. Many patients in the study were receiving no antithrombotic therapy.

“These findings should encourage greater efforts to prescribe and monitor appropriate antithrombotic therapy to prevent stroke in individuals with atrial fibrillation,” lead author Dr. David J. Gladstone, from Sunnybrook Health Sciences Centre, Toronto, and his colleagues emphasize.

As reported in the January issue of Stroke, the research team examined warfarin use in atrial fibrillation patients by analyzing data from the Registry of the Canadian Stroke Network, a prospective database of consecutive stroke patients seen at 12 centers in Ontario from 2003 to 2007.

Included in the study were 597 patients with atrial fibrillation and a first ischemic stroke and 323 with a prior stroke or transient ischemic attack, according to the report.

In the first-time stroke group, 60% of strokes were disabling and 20% were fatal, the authors note. Just 10% of patients had therapeutic levels of warfarin at the time of stroke. Twenty-nine percent of patients had warfarin at subtherapeutic levels. Single antiplatelet therapy was used in 29% of patients, dual antiplatelet therapy in 2%, and no antithrombotics in 29%.

In the prior stroke group, 18% of patients had therapeutic warfarin levels at the time of their current stroke and 39% had subtherapeutic warfarin. Single antiplatelet therapy was used in 25% of patients, dual antiplatelet therapy in 3%, and no antithrombotics in 15%.

In a related editorial, Dr. John Worthington, from Liverpool Health Service, NSW, Australia, and colleagues point out that “too often and for too long we have overstated the inconvenience of warfarin and exaggerated its risks, ignoring convincing evidence of its effectiveness in practice. Gladstone et al. reminds us of the perils of discounting the benefits of warfarin.”

Reference:
Stroke 2009;40:235-240.