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.