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    CHADS₂ Score for Atrial Fibrillation Stroke Risk

    Estimates stroke risk in patients with atrial fibrillation.
    When to Use
    Why Use

    The CHADS2 score is one of several risk stratification schema that can help determine the 1 year risk of an ischemic stroke in a non-anticoagulated patient with non-valvular AF.

    MDCalc recommends the CHA2DS2-VASc score over the original CHADS2 score to assess stroke risk in patients with atrial fibrillation. It risk stratifies these patients better than the CHADS2.

    The CHADS2 score can help physicians estimate stroke risk in patients with non-valvular atrial fibrillation and determine which antithrombotic therapy is most appropriate.

    • Studies have found that as the CHADS2 score increases, the annual risk of ischemic stroke increases proportionally.
    • Patients with high CHADS2 scores (>2) are at significant risk for stroke: 5.9% annual risk with a score of 3; up to 18.2% annual stroke risk for patients with a score of 6.
      • It is generally recommended that patients with a score >2 be started on warfarin, as the benefits of ischemic stroke prevention outweigh the bleeding risk.
    • According to some studies, patients with a CHADS2 score of 0 may be at low enough stroke risk (0.8-3.2% annual risk) that they can take aspirin (325mg) rather than warfarin as antithrombotic therapy.

    Points to keep in mind:

    • More recent studies suggest that CHADS2 of 0 points is not necessarily “low-risk” (still 3.2% incidence of stroke per year.)
    • The more recently developed CHA2DS2-VASc score takes into account other stroke risk factors and may be able to accurately identify which patients are at low enough stroke risk to forgo oral anticoagulation.
    • Among patients aged 65-95 years old with non-valvular atrial fibrillation, very few (<7%) will be classified as low risk according to the CHADS2 score.
    • The CHADS2 score does not perform well in the risk stratification of patients with AF who are receiving outpatient elective electric cardioversion.
      • In one study, 10% of patients with a score of zero were found to have left atrial appendage thrombi on transesophageal echocardiography.

    The risk stratification provided by the CHADS2 score may help physicians make more informed and personalized decisions about whether the risks and benefits of initiating antithrombotic therapy.



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    Next Steps
    Creator Insights


    • Consider applying the CHA2DS2-VASc score to patients with a CHADS2 score of 0 in order to further risk stratify these patients.

    Critical Actions

    One recommendation suggests a 0 score is low risk and may not require anticoagulation, however there is literature that suggests that not all patients with a CHADS2 score of 0 are at low risk for ischemic stroke.

    • Consider using the CHA2DS2-VASc score to further risk stratify patients who are identified as low risk by their CHADS2 score.
    • For patients who are identified as moderate (score 1-2) or high risk for ischemic stroke (>3), anticoagulation therapy should be considered.
    • For those patients in whom anticoagulation is considered, bleeding risk scores such as ATRIA, HAS-BLED or HEMORR2HAGES can be used to determine the risk for warfarin-associated hemorrhage.
    • Carefully consider all the risks and benefits prior to initiating anticoagulation in patients with non-valvular AF.


    Addition of the selected points:

    Facts & Figures

    See formula table, below:

    Criteria Value
    Congestive heart failure history +1
    Hypertension history +1
    Age ≥ 75 +1
    Diabetes mellitus history +1
    Stroke or TIA symptoms previously +2

    Evidence Appraisal

    • Although in the initial derivation and validation studies a CHADS2 score of 0 was associated with a low annual stroke risk of 1.9 and 0.8% respectively, subsequent studies have found that patients with a CHADS2 score of 0 may have up to a 3.2% per year risk of ischemic stroke (Gage 2004).
    • The derivation study, published in 2001, was a retrospective review of the National Registry of Atrial Fibrillation involving 1,733 patients and 2,121 patient years (Gage 2004).
      • It compared the performance of the CHADS2 score to two previously established stroke risk(AFI and SPAF III).
      • Found that the CHADS2 was the most accurate at predicting future stroke risk, with risk increasing by a factor of 1.5 for every additional point in a subject’s score.
    • The validation study included 2,580 subjects with non-valvular AF who were started on aspirin and found that the CHADS2 score could successfully risk stratify patients (Gage 2001).
      • A score of 0 translated into a 0.8% annual stroke risk in this cohort, potentially making these patients appropriate for forgoing oral anticoagulation.
      • Patients with a score of 1-2 had a 2.7% annual stroke risk.
      • Patients with a score of 3 or more had a stroke risk of 5.3% up to 18.2% for subjects with a CHADS2 score of 6.
    • A study of the Danish National Patient Registry identified 146,251 patients with non-valvular AF and found that 47,576 had a CHADS2 score of 0 or 1 (Olesen 2012).
      • 19,444 had a CHADS2 score of 0 and the CHA2DS2-VASc score was applied to these patients.
      • Authors found that in patients with a CHADS2 score of 0 but a CHA2DS2-VASc score of 3 (if they had all three risk factors not accounted for by CHADS2) that this cohort was at a 3.2% annual risk of stroke.
      • In contrast, patients with a CHA2DS2-VASc score of 0 was considered to be “truly low risk” with an annual ischemic stroke risk of 0.82%.
    • Among 541 patients with non-valvular AF (of >48 hours duration) who underwent electrical cardioversion, 136 had a CHADS2 score of 0 but 14 of those patients were found to have atrial thrombus on echocardiography, suggesting that the score missed 10% of patients who would have been at a high risk for a thromboembolic stroke after cardioversion (Yarmohammadi H 2012).


    Other References

    Research PaperSinger DE, Albers GW, Dalen JE, Fang MC, Go AS, Halperin JL, Lip GY, Manning WJ; American College of Chest Physicians. Antithrombotic therapy in atrial fibrillation: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008 Jun;133(6 Suppl):546S-592S. doi: 10.1378/chest.08-0678.Research PaperOlesen JB, Torp-Pedersen C, Hansen ML, Lip GY. The value of the CHA2DS2-VASc score for refining stroke risk stratification in patients with atrial fibrillation with a CHADS2 score 0-1: a nationwide cohort study. Thromb Haemost. 2012 Jun;107(6):1172-9. doi: 10.1160/TH12-03-0175.Research PaperYarmohammadi H, Varr BC, Puwanant S, Lieber E, Williams SJ, Klostermann T, Jasper SE, Whitman C, Klein AL. Role of CHADS2 score in evaluation of thromboembolic risk and mortality in patients with atrial fibrillation undergoing direct current cardioversion (from the ACUTE Trial Substudy). Am J Cardiol. 2012 Jul 15;110(2):222-6. doi: 10.1016/j.amjcard.2012.03.017.
    Dr. Brian Gage

    About the Creator

    Brian F. Gage, MD, MSc, is a professor of medicine at Washington University in St. Louis where he teaches Designing Outcomes & Clinical (DOC) Research and practices at Barnes-Jewish Hospital, where he directs the Clinical-Scientist Teaching And Research (C-STAR) program for medical residents. He directs the Washington University Fellowship in General Medical Sciences (GMS). Dr. Gage studies antithrombotic therapy and thrombosis, including cardioembolic stroke.

    To view Dr. Brian Gage's publications, visit PubMed

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    About the Creator
    Dr. Brian Gage
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