When the CHADS2 Score = 1: Will Aspirin Do or Is Warfarin Indicated?

The CHADS₂ risk score is used to determine whether anticoagulation or antiplatelet therapy is indicated in patients at risk for thrombotic complications of atrial fibrillation (AF). The score, from 0 to 6, is based on the presence/absence of 5 risk factors: Congestive heart failure, Hypertension, Age ≥ 75 years, Diabetes, and Stroke/TIA (2 points). When the risk score is moderate or high, the choice is clear and warfarin is the guideline-recommended therapy. When the score is low, however, the risk/benefit calculation-warfarin-induced bleeding versus avoidance of ischemic stroke-is not as straightforward.

Coppens et al,¹ writing in The European Heart Journal  in January 2013, selected from the AVERROES^a and ACTIVE^b trials only those patients in whom antithrombotic treatment recommendations were uncertain (ie, those with a CHADS₂ of 0-1) to determine whether they would be reclassified on the basis of a modified version of the CHADS₂ called the CHA₂DS₂-VASc score.¹  

The CHA₂DS₂-VASc score improves risk determination by incorporating 3 more risk factors: age 65 to 74 years, female sex, and history of vascular disease. (It also incorporates another point for being age 75 years or older.) Past evaluations of the CHA₂DS₂-VASc score have included AF patients from the full spectrum of risk and so have included patients in whom there was no potential for improving stratification because they would already benefit from anticoagulation (eg, CHADS₂ score ≥2). All patients selected for the Coppens study had a CHADS₂ score of 1 and were treated with only antiplatelet therapy–aspirin, with or without clopidogrel. Of the 4670 patients, three-quarters (74%) had a CHA₂DS₂-VASs score of ≥ 2, and approximately one-quarter (26%) had a score of 1. The annual rates of stroke and systemic emboli in these patients with 11,414 patient-years of follow-up were 2.1% and 0.9%, respectively. This advanced risk score significantly improved the C-statistic (score 0.59; 95% CI, 0.55-0.62) and age 65 to <75 was the strongest of the new risk factors.

This study provides contemporary evidence that use of the more comprehensive CHA₂DS₂-VASc risk score improves risk stratification in patients with AF receiving oral antiplatelet therapies and identifies a subset of very low–risk patients with an annual incidence of 1% of stroke and systemic emboli who may not need oral anticoagulation.

Reference:                                                                                                                                                                       
1. Coppens M, Eikelboom JW, Hart RG, et al. The ChA₂DS₂-Vasc score identifies those patients with atrial fibrillation and a CHADS₂ score of 1 who are unlikely to benefit from oral anticoagulation therapy. Eur Heart J. 2013;34:170-176.
 

^a AVERROES = Apixaban vs. Acetylsalicylic Acid to Prevent Stroke in Atrial Fibrillation Patients Who Have Failed or Are Unsuitable for Vitamin K Antagonist Treatment. Designed to determine the efficacy and safety of apixaban compared with ASA for the treatment of patients with AF for whom VKA therapy was considered unsuitable.
 

^b ACTIVE = Atrial Fibrillation Clopidogrel Trial with Irbesartan for Prevention of Vascular Events. Two trials were initiated to evaluate the role of clopidogrel plus ASA for the prevention of stroke and other vascular events in patients with AF.

     ACTIVE-W compared clopidogrel plus ASA with VKA therapy.


     ACTIVE-A compared clopidogrel plus ASA with ASA alone in patients for whom therapy with a VKA was considered unsuitable.

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