CHA2DS2-VASc: A New Score for Stroke Prediction in AF

February 09, 2011

February 9, 2011 (Copenhagen, Denmark)— A new, more sensitive score for assessing the likelihood of stroke in patients with atrial fibrillation (AF), called CHA2DS2-VASc, enables further refinement of risk compared with the traditional CHADS2 score, a group of European researchers say [1]. Dr Jonas Bjerring Olesen (Copenhagen University Hospital, Denmark)and colleagues report their findings online January 31, 2011 in BMJ.

Coauthor Dr Gregory YH Lip (University of Birmingham, UK) told heartwire : "CHA2DS2-VASc improves on stroke risk stratification above CHADS2; the new score is better at predicting those who will get a stroke over 10 years."

The new score is better at predicting those who will get a stroke over 10 years.

In an accompanying editorial [2], Dr Margaret C Fang (University of California, San Francisco), says that CHA2DS2-VASc is also "better than CHADS2 at identifying people at very low risk," those who likely do not need anticoagulation, pointing out that only 8.7% of patients in the cohort studied by Olesen et al were considered low risk by CHA2DS2-VASc compared with 22.3% with the CHADS2 criteria.

But she told heartwire : "I don't think CHA2DS2-VASc should replace CHADS2, because I don’t think the cumulative evidence demonstrates that its performance is superior to CHADS2. However, it might be a viable alternative to CHADS2, and so I would not advocate against using it, either." CHA2DS2-VAScmay ultimately be useful in particular settings, she says, such as "when a clinician is faced with an intermediate-risk patient by CHADS2 criteria (eg, CHADS2 score=1) who also has some of the CHA2DS2-VAScrisk factors (eg, female gender or vascular disease)."

CHA 2 DS 2 -VASc Validated in Largest-Ever Real-World Cohort of AF Patients

In the CHADS2 score, each component--congestive heart failure, hypertension, age over 75, diabetes, and previous stroke--scores one point toward the overall total, except for prior stroke, which scores two points. In the newer CHA2DS2-VASc, age is weighed differently, with two categories (age 65 to 74 and 75 and older), and female sex and a history of vascular disease are added in as risk factors; again, each component in CHA2DS2-VASc scores one point, except for stroke, which scores two, and age >75, which also scores two in CHA2DS2-VASc.

Last year, the first-ever European-specific guidance on AF recommended using CHA2DS2-VASc over CHADS2 as it was deemed to be better at refining stroke risk.

In the current study, Olesen et al used a large nationwide registry of patients admitted to the hospital with AF in Denmark during the period 1997–2006 who were not receiving anticoagulation, representing the "largest real-world cohort of nonanticoagulated patients ever investigated," at almost 75 000 patients, they note. The main outcome measure was stroke and thromboembolism (TE).

In patients with a "low-risk" score (ie, zero), the rate of TE per 100 person-years was 1.67 with CHADS2 and 0.78 with CHA2DS2-VASc at one-year follow-up. In those at "intermediate risk" (score of 1), this rate was 4.75 with CHADS2 and 2.01 with CHA2DS2-VASc, a finding that is "clinically important," they say, "as many of the patients at low risk according to CHADS2 are not truly low risk, and treatment guidelines are not conclusive for those at intermediate risk."

Approach to Thromboprophylaxis in Patients With AF

Risk category

CHA 2 DS 2 VASc score

Recommended anticoagulation

One major risk factor or two or more clinically relevant nonmajor risk factors

>

Oral anticoagulation

One clinically relevant nonmajor risk factor

1

Oral anticoagulation or aspirin 75–325 mg daily

Preferred: Oral anticoagulation rather than aspirin

No risk factors

0

Aspirin 75–325 mg daily or no antithrombotic therapy

Preferred: No antithrombotic therapy

Table adapted from European guidelines on the management of AF [3].

Artificial Categorization Unhelpful; Stroke Is a Continuum

Lip stresses that although there has been a tendency, traditionally, to classify patients into low, intermediate, and high risk, "this is really an artificial categorization of what is essentially a continuum of stroke risk. Essentially a stroke risk factor is a stroke risk factor, and if you have AF plus a stroke risk factor, you stroke, basically." The new score is an attempt to move away from this somewhat simplistic classification system, he explains. 

But Fang points out that in the Danish population studied, CHA2DS2-VASc would classify 80% of the patients as "high" risk, compared with less than half using CHADS2.

To heartwire , she elaborated: "I think these risk schemes are most useful when examined in terms of the absolute stroke risk. For a patient who wants to avoid stroke at all costs, then using CHA2DS2-VASc thresholds for anticoagulation may be reasonable, because it recommends against anticoagulation only for very low-risk patients. However, my personal feeling is that given the risks associated with anticoagulation, by using CHA2DS2-VASc in an entire population, we may be recommending anticoagulation to many people who may still have low stroke risk."

The criteria of vascular disease are vague. . . . Based on this, CHADS 2 is still easier to apply than CHA 2 DS 2 -VASc.

And while some of the newer factors in CHA2DS2-VASc are easy to define, such as female sex and age, vascular disease is not, she says. "Ischemic heart disease may not be the same as peripheral arterial disease or aortic atherosclerosis. Thus the criteria of 'vascular disease' are vague, difficult to apply to general practice, and not well-supported in the literature. Based on this, CHADS2 is still easier to apply than CHA2DS2-VASc."

But Lip says it is almost always pretty obvious to most clinicians who is at high risk of a stroke with AF and who needs anticoagulation, regardless of any score, but it is the "intermediate" patients who are the ones in which "you have to bring into consideration patient values and preferences." 

And Lip and Fang both agree that the advent of newer oral anticoagulants--such as dabigatran (Pradaxa, Boehringer Ingelheim)--which are more convenient than warfarin because they don't require continuous monitoring and are potentially safer, will likely change the landscape for the prevention of stroke in AF.

"We are seeing a whole ballpark change with the availability of new anticoagulants," says Lip. "These new drugs are safer, so some are suggesting that the threshold for starting oral anticoagulation should be as low as 0.9% stroke rate/year."

Fang says more research is needed, however. "An important consideration for future studies is whether the development of alternative treatments . . . should induce clinicians to lower the threshold at which they prescribe anticoagulants. If anticoagulation becomes safer, it might be recommended for use in more patients with AF, particularly those at intermediate or even low risk of stroke. This is an area where consideration must be given to the patient's preference, the balance between absolute benefit and risk, and the cost of care."  

Both the authors and the editorialist report that they have no conflicts of interest.

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