The CHADS2score is aclinical prediction rulefor estimating the risk ofstroke in patients withnon-rheumaticatrial fibrillation (AF), a common and serious heart arrhythmia associated with thromboembolic stroke. It is used to determine whether or not treatment is required with anticoagulation therapy or antiplatelet therapy,since AF can cause stasis of blood in the upper heart chambers, leading to the formation of a mural thrombus that can dislodge into the blood flow, reach the brain, cut off supply to the brain, and cause a stroke. A high CHADS2 score corresponds to a greater risk of stroke, while a low CHADS2 score corresponds to a lower risk of stroke.
The CHADS2 scoring table is shown above: adding together the points that correspond to the conditions that are present results in the CHADS2 score, that is used to estimate stroke risk.
In clinical use, the CHADS2 score has been superseded by the CHA2DS2-VASc score that gives a better stratification of low-risk patients.
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.