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Benefit of anticoagulation for atrial fibrillation varies across patient populations

When using current guideline recommendations, the clinical net benefit of starting oral anticoagulation varied widely among patients with atrial fibrillation, according to findings published in Annals of Internal Medicine.

Using anticoagulation in a patient with a CHA₂DS₂-VASc (congestive heart failure, hypertension, age, diabetes, stroke and vascular disease) score of 2 or higher is currently recommended by guidelines, according to Sachin J. Shah, MD, MPH, from the University of California, San Francisco, and colleagues.

However, “stroke rates in patients with nonvalvular atrial fibrillation who are not receiving anticoagulant therapy vary widely across published studies; the resulting effect on the net clinical benefit of anticoagulation in atrial fibrillation is unknown,” they wrote.

To address this gap in knowledge, Shah and colleagues performed a Markov model decision analysis to investigate the effect of variation in four published studies on atrial fibrillation stroke rates.

The cohorts assessed included the ATRIA (AnTicoagulation and Risk Factors In Atrial Fibrillation) study, the Danish National Patient Registry cohort, the Swedish Atrial Fibrillation cohort study and the SPORTIF (Stroke Prevention using ORal Thrombin Inhibitor in atrial Fibrillation) study. The studies included 33,434 community-dwelling adults with incident atrial fibrillation.

The researchers found that among participants with a CHA₂DS₂-VASc score of 2 or greater (n = 27,179) the population benefit of warfarin anticoagulation varied across the different studies with the ATRIA study demonstrating the least benefit on stroke rates (6,290 quality-adjusted life-years [QALYs]) and the Danish National Patient Registry demonstrating the greatest (24,110 QALYs).

The optimal CHA₂DS₂-VASc score threshold for anticoagulation also varied across the studies. The optimal threshold was 3 or more when using stroke rates from ATRIA, 2 or more using those from the Swedish Atrial Fibrillation cohort study, 1 or more using those from the SPORTIF study and 0 or more using those from the Danish National Patient Registry, according to the researchers.

There was a decrease in optimal CHA₂DS₂-VASc score thresholds when the researchers accounted for lower rates of non–vitamin K antagonist oral anticoagulants-associated intracranial hemorrhage. However, there was still a wide variation among these thresholds.

“Our findings ... indicate that the current guidelines based on CHA₂DS₂-VASc score may need to be revised in favor of more accurate, individualized assessments of risk for both ischemic stroke and major bleeding,” Shah and colleagues concluded. “Until such time, guidelines should better reflect the uncertainty of the current approach in which a patient’s CHA₂DS₂-VASc score is used as the primary basis for recommending oral anticoagulants.”

In an accompanying editorial, Jennifer M. Wright, MD, and Craig T. January, MD, PhD, both from the University of Wisconsin School of Medicine and Public Health Madison, wrote that the findings by Shah and colleagues call into question the optimal CHA₂DS₂-VASc threshold for initiating anticoagulation in a specific population or even patient.

“Thus, this report by Shah and colleagues demonstrates one of the ways in which treatment of patients with [atrial fibrillation] cannot be assumed to be equal across different populations and shows that the CHA₂DS₂-VASc score threshold for anticoagulation may be not a “one-size fits-all” approach but rather a starting point for a more tailored assessment,” they concluded. – by Alaina Tedesco

Disclosures: January reports being Chairperson for the 2014 AHA/ACC/HRS Atrial Fibrillation Guidelines. Shah reports no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures. Wright reports no relevant financial disclosures.