CHADS2 Score - Stroke Risk Assessment, and Antithrombotic Therapy

Stroke Risk Assessment, and Antithrombotic Therapy

According to the findings of the initial validation study, the risk of stroke as a percentage per year for the CHADS₂ score is shown in the table.

The CHADS₂ score does not include some common stroke risk factors and its various pros/cons have been carefully discussed. Nonetheless, this score is simple and thus it has become widely used.

To complement the CHADS₂ score, by the inclusion of additional 'stroke risk modifier' risk factors, the CHA₂DS₂-VASc score has been proposed. These additional non-major stroke risk factors include age 65-74, female gender and vascular disease. In the CHA₂DS₂-VASc score score, 'age 75 and above' also has extra weight, with 2 points.

The CHA₂DS₂-VASc score has been used in the new European Society of Cardiology guidelines for the management of atrial fibrillation.

The European Society of Cardiology (ESC) guidelines recommend that if the patient has a CHADS₂ score of 2 and above, oral anticoagulation therapy (OAC) such as warfarin (target INR of 2-3) or one of the new OAC drugs (such as dabigatran) should be prescribed.

If the CHADS₂ score is 0-1, other stroke risk modifiers could be considered: (i) If there are 2 or more risk factors (essentially a CHA₂DS₂-VASc score score of 2 or more), OAC is recommended; and (ii) If there is 1 risk factor (essentially a CHA₂DS₂-VASc score score=1), antithrombotic therapy with OAC or aspirin (OAC preferred) is recommended, and patient values and preferences should be considered.

A CHA₂DS₂-VASc score score=0 corresponds to a 'truly low risk,’ and thus the recommendation is to prescribe either aspirin or no antithrombotic therapy, but 'no antithrombotic therapy' is preferred.

Stroke risk assessment should always include an assessment of bleeding risk. This can be done using validated bleeding risk scores, such as the HEMORR₂HAGES or HAS-BLED scores. The latter is recommended in the ESC and Canadian guidelines. If the patient is taking warfarin, then knowledge of INR control is needed to assess the 'labile INR' criterion in HAS-BLED; otherwise for a non-warfarin patient, this scores zero.