CHADS2 Score for Atrial Fibrillation Stroke Risk Calculator

How does this CHADS2 score for atrial fibrillation stroke risk calculator work?

This is a health tool that stratifies the risk of ischemic events due to thromboembolism in patients with atrial fibrillation. This is the original version of the model but there are also newer versions, such as the CHA2DS2-VASc that aim to estimate risk with better accuracy because of the extra variables they employ.

This CHADS2 score for atrial fibrillation stroke risk calculator allows clinicians to assess stroke risk in patients suffering fromnon-valvular atrial fibrillation and also helps the medical decisions in regard to the most appropriate antithrombotic or antiplatelet therapy.

There are 5 criteria assessed as presented below, each of them on a Yes/No basis with attached points that are summed at the end to provide the overall score.

■ Congestive heart failure history – history of previous inadequacy in the heart pump function can show a progressive disease that impairs the normal function.

■ Hypertension history – personal or family recurrence of high blood pressure, values of systolic blood pressure considered above 140 mmHg puts the patient at risk of ischemic events.

■ Age above 75 – age is a risk factor in both stroke and other heart conditions.

■ Diabetes mellitus history – diabetes is often considered a risk factor in stroke or thromboembolic events.

■ Stroke or TIA symptoms previously – this is the variable that counts twice in the final CHADS2 score and in some cases this occurrence is considered separately as giving an indication of high risk.

CHADS2 interpretation

The score obtained from the above tool corresponds to a group of thromboembolic event risk and is provided along with an annual stroke risk expressed in percentage. This adjusted risk score in the CHADS2 model assumes that there has not been any aspirin intake.

The assessed annual risk increases proportionally with the score and patients with scores above 2 are at significant risk as presented in the table below.

For CHADS2 scores above 2, the preventive anti stroke therapy should be started on warfarin while still monitoring carefully for the bleeding risk. For lower scores of 0 or 1, that are deemed low risk, aspirin should be first choice as antithrombotic therapy. The more precise the assessment is, the better the clinician can opt out of warfarin therapy and choose aspirin in low risk cases.

Often, clinicians should apply the improved version of CHA2DS2-VASc in patients with a CHADS2 score of 0 in order to better stratify risk and to personalize the risks and benefits of antithrombotic therapy in each particular case. However, according to studies, only less than 7% of patients aged between 65 and 95 with non-valvular atrial fibrillation are classed as low risk.

Some physicians respect the risk groups presented in the table below while others consider that if there was an Yes answer to “Stroke or TIA symptoms previously:”, the patient should be in the High risk group regardless of the overall CHADS2 result.

References

1) Gage BF, van Walraven C, Pearce L, Hart RG, Koudstaal PJ, Boode BS, Petersen P. (2004) Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin. Circulation; 110(16):2287-92.

2) Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. (2001) Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA; 285(22):2864-70.