Recent AF Guidelines Would Significantly Expand OAC Use

March 03, 2015

DURHAM, NC — An update of the guidelines for the management of patients with atrial fibrillation (AF)—one that saw a shift from the CHADS2 score to the CHA2DS2-VASc score for stroke risk assessment—significantly increases the number of patients eligible for oral anticoagulant therapy, according to the results of a new analysis[1].

Using data from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF), the researchers found that the overall proportion of patients recommended for oral anticoagulation increased from 71.8% under the 2011 American Heart Association (AHA)/American College of Cardiology (ACC)/Heart Rhythm Society (HRS) guidelines to 90.8% with the 2014 AHA/ACC/HRS clinical recommendations.

Using the new CHA2DS2-VASc score, researchers say that nearly every AF patient older than 65 years of age and nearly every woman with AF would be eligible for oral anticoagulation. In fact, with the 2014 recommendations guiding the management of AF, 98.5% of patients 65 years of age and older and 97.7% of women would receive a definitive recommendation for oral anticoagulant therapy.

The analysis, which was led by Dr Emily O'Brien (Duke Clinical Research Institute, Durham, NC) and reported March 2, 2015 in JAMA: Internal Medicine, suggests that nearly one million more Americans would be eligible for anticoagulation based on the newer 2014 guidelines.

Estimated Change in the Number of US Patients Eligible for Oral Anticoagulation

Variable 2011 2014 Change from 2011 to 2014
Overall 3 734 100 4 722 600 988 500
Men 2 046 400 2 572 300 525 900
Women 1 687 800 2 150 400 462 600
Age <65 years 452 700 636 500 183 800
Age >65 years 3 281 300 4 086 300 805 000

In an editorial[2], however, Dr Margaret Fang (University of California, San Francisco) argues that while stroke rates have declined to historically low levels, there is no evidence that shifting from CHADS2 to CHA2DS2-VASc improves net clinical outcomes. Fang states that the newer risk score primarily affects people at the lower end of the stroke-risk spectrum, whereas the largest benefit of anticoagulation occurs mostly in patients at the highest risk of stroke.

What is needed, she writes, are clinical trials directly comparing the bleeding risks and stroke-prevention benefits associated with anticoagulation using the different risk-scoring systems.

"It is possible that the new guideline, which recommends anticoagulation for a wider swath of the population, will result in lower stroke rates," writes Fang. "However, more widespread anticoagulation will also increase the number of bleeding complications. Before we can be sure that adopting one risk scheme over another is really a good thing, it is necessary to consider what the actual net clinical benefit of such a change will be, accounting for strokes prevented and bleeds induced."

The CHA2DS2-VASc score differs from CHADS2 in that female sex, the presence of vascular disease, and ages 65 to 74 years are now risk factors for stroke. In addition, CHA2DS2-VASc increases the risk score from 1 to 2 for AF patients 75 years and older. Among the patients newly recommended for oral anticoagulation in ORBIT-AF, 44% were reclassified because of a single risk factor. For those reclassified by a single risk factor, 21% were reclassified because of sex, 64% because of age, and 15.5% because of vascular disease.

The ORBIT-AF registry is sponsored by Janssen. O'Brien has reported receiving research support from Janssen Pharmaceuticals and serving as a consultant and on the advisory board for Modest and Portola Pharmaceuticals; disclosures for the coauthors are listed in the article. Fang reports no relevant financial relationships.

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