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    CHADS₂ Score for Atrial Fibrillation Stroke Risk

    Estimates stroke risk in patients with atrial fibrillation.
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    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
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    Advice

    • 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.
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    Dr. Brian Gage
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