Patients with AF, CHA2DS2-VASc score of 1 may be at low risk for ischemic stroke

Issue: March 2015

Patients with atrial fibrillation and a CHA₂DS₂-VASc score of 1 may be at lower risk for ischemic stroke than previously thought, according to the results of a retrospective study.

These findings call into question whether this patient population benefits from anticoagulation, the researchers wrote.

The CHA₂DS₂-VASc score assesses risk for stroke among patients with AF, who receive 1 point for being aged 65 to 74 years, 2 points for being aged 75 years or older, 1 point for being a woman, 1 point for having a history of congestive HF, 1 point for having a history of hypertension, 2 points for having a history of stroke, transient ischemic attack or thromboembolism, 1 point for having a history of vascular disease and 1 point for having diabetes.

According to the study background, a score of 1 is considered low risk, but previous studies have differed greatly in the risk for stroke associated with a score of 1.

Leif Friberg, MD, PhD, and colleagues evaluated 140,420 patients with nonvalvular AF without documented exposure to warfarin in Swedish nationwide health registries to assess risk for AF-related stroke in patients without oral anticoagulation treatment and a CHA₂DS₂-VASc score of 1.

Based on a 4-week quarantine period, the overall ischemic stroke event rate was 2.8%, but this increased to 4.5% if thromboembolism (including unspecified stroke, systemic embolism and pulmonary embolism) was included, and it increased to 5.2% if TIA and thromboembolism were included, the researchers found.

Stroke rates low

For patients with a CHA₂DS₂-VASc score of 1, the ischemic stroke event rate was 0.5%, but this climbed to 0.9% if TIA and thromboembolism were included, Friberg and colleagues wrote. Women with a CHA₂DS₂-VASc score of 1 had an annual ischemic stroke rate between 0.1% and 0.2%, compared with 0.5% to 0.7% for men with a CHA₂DS₂-VASc score of 1.

“The risk of ischemic stroke among patients with AF and a CHA₂DS₂-VASc score of 1 seems to be lower than previous studies have indicated,” Friberg, from Karolinska Institute and Danderyd Hospital, Stockholm, and colleagues wrote. “This earlier finding may have led to unnecessary, and potentially harmful, [oral anticoagulation] treatment of low-risk patients.”

Predictive performance mediocre

In a related editorial, Daniel E. Singer, MD, from the division of general internal medicine at Massachusetts General Hospital and Harvard Medical School, and Michael D. Ezekowitz, MBChB, DPhil, from Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, wrote that determining whether a CHA₂DS₂-VASc score of 1, 2 or 3 should be the threshold for treatment with oral anticoagulation poses a challenge. The threshold is 2 in US guidelines, but in European guidelines, it is 1, although female sex is not considered a standalone risk factor, they wrote.

The problem, they wrote, is that the score is “based on informal selection and weighting of risk factors reported in previous studies, not on formal statistical risk models,” and thus its overall predictive performance has been “mediocre.”

“Going forward, guideline writers should be aware of the drawbacks of the CHA₂DS₂-VASc score,” they wrote. “However, given the current state of knowledge, AF patients [younger than] 65 years of age but with a CHA₂DS₂-VASc score of 1 are unlikely to benefit from anticoagulation therapy.”

For more information:

Friberg L. J Am Coll Cardiol. 2015;65:225-232.

Singer DE. J Am Coll Cardiol. 2015;65:233-235.

Disclosure: The study was supported by the Swedish Heart and Lung Foundation, the Stockholm City Council, the Swedish Society of Medicine and the Board of Benevolence of the Swedish Order of Freemasons. The researchers report financial ties with AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Sanofi and St. Jude Medical. See the full editorial for a list of Singer’s and Ezekowitz’ relevant financial disclosures.