Well-Managed Warfarin as Alternative in Non-Valvular Atrial Fibrillation

MedicalResearch.com Interview with:
Dr. Fredrik Björck, MD
Umea University
Umea, Sweden

MedicalResearch.com: What is the background for this study?

Dr. Björck: Vitamin K antagonist (eg, warfarin) use is nowadays challenged by the non–vitamin K antagonist oral anticoagulants (NOACs) for stroke prevention in non-valvular atrial fibrillation (AF). NOAC studies were however based on comparisons with warfarin arms with times in therapeutic range (TTRs) of 55.2% to 64.9%, making the results less credible in health care systems with higher TTRs. Historically Sweden has had the best international normalized ratio (INR) control in the world. By this study we wanted to evaluate the efficacy and safety of real life well-managed warfarin therapy in patients with non-valvular AF, the risk of complications, especially intracranial bleeding, in patients with concomitant use of aspirin, and the impact of INR control. We therefore performed a retrospective, multicenter cohort study based on Swedish registries, especially AuriculA, a quality register for AF and oral anticoagulation. A total of 40 449 patients starting warfarin therapy owing to non-valvular AF during the study period were monitored until treatment cessation, death, or the end of the study. The study was conducted from January 1, 2006, to December 31, 2011.  By associating complications with risk factors and individual INR control, we evaluated the efficacy and safety of warfarin treatment in patients with concomitant aspirin therapy and those with no additional antiplatelet medications.

MedicalResearch.com: What are the main findings?

Dr. Björck: With the results representing real-life data with no exclusions, warfarin treatment safety seems to be relatively good, with an annual incidence of 2.19% for all-cause mortality and 0.44%for intracranial bleeding—both lower than comparable results in the pivotal NOAC studies. However, patients receiving concomitant aspirin had higher bleeding and thromboembolic rates, and patients with individual times in a therapeutic range (iTTR) of less than 70% or high INR variability had an increased rate of complications. Patients achieving iTTR over 70% had annual all-cause mortality of only 1.29% and, for intracranial bleeding 0.34%. For those patients with iTTR over 70%, the cumulative complication rates were independent of INR variability. Patients with renal failure had more than a 2-fold increased risk of intracranial bleeding.

MedicalResearch.com: What should clinicians and patients take away from your report?

Dr. Björck: Well-managed warfarin treatment is a valid alternative in patients with non-valvular AF who require anticoagulant treatments, with relatively low complication rates and low all-cause mortality. Therapy should be closely monitored in those with renal failure, concomitant aspirin use, and an iTTR less than 70%. The iTTR is a strong indicator of probability for both bleeding and thromboembolic events and should be maintained at 70% or greater.

MedicalResearch.com: What should clinicians and patients take away from your report?

Dr. Björck:  In Sweden, and other nations with well-managed warfarin settings, there is a need for further evaluation of outcomes for warfarin vs. NOACs in clinical reality. Indeed, other features related to good INR control, such as adherence, lack of interruptions, and better health care might contribute to the good results we show for warfarin. Some of these features might enhance outcome for NOACs as well, but further studies are needed, preferably with long-time follow up. The need for monitoring in warfarin might be one of the keys in achieving high long-term adherence to treatment, which is crucial for outcome in AF and anticoagulants. The question is how to achieve, secure and measure high adherence with NOACs?


Fredrik Björck, Henrik Renlund, Gregory Y. H. Lip, Per Wester, Peter J. Svensson, Anders Själander. Outcomes in a Warfarin-Treated Population With Atrial Fibrillation. JAMA Cardiology, 2016; DOI: 10.1001/jamacardio.2016.019

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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Last Updated on April 25, 2016 by Marie Benz MD FAAD