Stroke Risk Tool CHA2DS2-VASc Better Than CHADS2 for Certain Atrial Fibrillation Patients

By Christine Welniak

February 22, 2011 — New research on the CHA2DS2-VASc stroke risk tool provides insight into stroke risk factors related to atrial fibrillation and could help assess which patients should be placed on anticoagulant medication. These findings are particularly important for afib patients who are deemed to have intermediate stroke risk based on CHADS2, the most widely used stroke risk scoring system.

The CHADS2 Conundrum

CHADS2 is a mnemonic device that allows doctors to quickly recall the major stroke risk factors. CHADS2 assigns one point each for congestive heart failure (C), high blood pressure (H), age 75 or older (A), and diabetes (D), and two points for a previous stroke (S2) or transient ischemic attack, called a mini-stroke.

Medical guidelines recommend that patients with a CHADS2 score of two or more be placed on anticoagulant medication, such as warfarin (Coumadin) or dabigatran (Pradaxa). Patients on anticoagulants have an increased risk for bleeding, which is one of the reasons that not all patients with atrial fibrillation are automatically placed on anticoagulation medications.

The conundrum with CHADS2 relates to patients who have a score of one, which is intermediate risk for stroke. Should they be anticoagulated? Is their stroke risk low enough so that they don’t have to be put on Coumadin or Pradaxa?

Enhanced Stroke Risk Scoring System

The recently updated European Society of Cardiology afib guidelines recommend doctors apply the CHA2DS2-VASc scoring system to patients who fall in the intermediate risk category. Similar to CHADS2, CHA2DS2-VASc assigns points to additional risk factors, such as female gender, age 65–75, and vascular disease.

New research demonstrates that CHA2DS2-VASc is better than CHADS2 in assessing stroke risk. Researchers in Denmark used data from their national hospital registry to identify patients with atrial fibrillation who were treated in 1997-2006. They excluded patients who had mitral or aortic valve disease from their analysis along with patients who were taking anticoagulants. In total, 73,538 Danish patients were included in the analysis.

The researchers compared patients’ stroke risk scores, as determined by CHADS2 and CHA2DS2-VASc. CHADS2 categorized 23,730 patients (32.3% of total) as having intermediate stroke risk, whereas CHA2DS2-VASc showed nearly all of these patients (92.7%) were actually at high risk for stroke. Based on CHA2DS2-VASc, only 11.2% of patients had intermediate stroke risk.

Similarly, CHADS2 categorized 16,406 (22.3% of total) patients at low risk of stroke. Researchers found 39.5% of these patients actually had intermediate risk and 21.7% had high risk, based on CHA2DS2-VASc, and only 8.7% of patients were actually at low risk of stroke using this tool.

The data showed that CHA2DS2-VASc provides a more accurate assessment of stroke risk. Patients defined as intermediate risk by CHADS2 were more likely to have a thromboembolic event (stroke) than those defined as intermediate-risk by CHA2DS2-VASc. Specifically, CHADS2 intermediate-risk patients had 4.75 thromboembolic events per 100 person years at one year compared to 2.01 for CHA2DS2-VASc intermediate-risk patients. At five years, CHADS2 intermediate-risk patients had 3.70 thromboembolic events per 100 person years compared to only 1.51 for those defined as intermediate risk by CHA2DS2-VASc.

The researchers also found that some risk factors carry more weight than others. Diabetes and age (65-75 years) were associated with higher thromboembolic events for patients with CHA2DS2-VASc scores of one. In other words, even if the patient had one only stroke risk factor, if that risk factor was diabetes or being aged 65-75, they were more likely to have a stroke than other patients with only one risk factor, such as congestive heart failure. In addition, female gender increased stroke risk at one year and vascular disease increased stroke risk at five and 10 years.

Comment: CHA2DS2-VASc is still relatively new and is not used by all doctors. U.S. medical guidelines for the management of atrial fibrillation were last updated in 2006, prior to the development of CHA2DS2-VASc. In general, recommendations in guidelines reflect data from clinical trials or from studies of large patient populations, so the recently published Danish analysis could form the basis for including CHA2DS2-VASc in the next update to U.S. medical guidelines. This likely needs to happen for CHA2DS2-VASc to be widely adopted around the globe.

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Disclaimer: Patients come first at, and we do not compromise on that. For transparency, we note that Dr. Gregory YH Lip, who was integral to the development of CHA2DS2-VASc, is on the medical advisory board. However, he did not contribute to, or review, this article prior to publication.