Low-Intensity Warfarin Therapy for the Prevention of Stroke in Patients with High-Risk Nonvalvular Atrial Fibrillation

Background: The aim of this study was to determine whether warfarin therapy with the target of INR < 2.0 (low-intensity) could be as effective as that with INR >= 2.0 (conventional-intensity) in stroke prevention for Taiwanese patients with high-risk nonvalvular atrial fibrillation (AF) while simultaneously reducing the risk of bleeding. Methods: We conducted a retrospective study on patients with high-risk nonvalvular AF. The clinical outcomes of patients receiving different antithrombitic therapies and the efficacy and safety of two different intensities of warfarin therapy with a target INR of < 2.0 or a target INR of >= 2.0 were compared. Results: A total of 815 patients were enrolled consecutively, and were followed for an average of 2.5 years. Among them, 226 patients (28%) received warfarin therapy and 512 (63%), antiplatelet therapy whereas, 77 (9%) of the patients received none of the antithrombotic therapy. The overall event rates were 3.6 per 100 person-years with warfarin, 6.0 per 100 person-years with antiplatelet therapy, and 10.1 per 100 person-years with no treatment (p = 0.013). Although there was no significant difference in the frequencies of ischemic stroke between the two different intensities of warfarin therapy, noticeably more bleeding episodes occurred to the conventional-intensity group than the low-intensity one. Conclusion: The results of our study clearly demonstrated how Taiwanese patients with high-risk nonvalvular AF benefited from warfarin therapy in reducing adverse clinical outcomes; however, the low-intensity treatment was proved to be as effective as that of conventional-intensity but less likely to cause any bleeding during the treatment.