CHADS₂ Score for Atrial Fibrillation Stroke Risk

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.