Toolbox - the CHA2DS2VASc risk tool
Dr Kathryn Griffith, GP and GPSI in cardiology in York, explains the nuts and bolts of this risk assessment tool and describes when it should be used
The original CHADS2 tool was developed to identify those patients with AF at high risk of having an AF-related stroke.1 The new 2013-14 QOF uses CHADS2 in an indicator requiring that all patients with AF should have an annual risk score where 1 point is given for each of the risk factors and 2 for a previous stroke.
When the score is 2 or more the patient is at high risk of stroke and an oral anticoagulant should be considered (QOF indicator AF004). When the score is 1 then the risk is moderate with an annual stroke rate of 2.8%, and patients should discuss the option of anticoagulation (AF003). A score of 0 does not necessarily infer a low risk, as the mean annual risk is 1.9%. There are other risk factors which have been identified which help to identify those people at lowest risk and they are included in the CHA2DS2VASc tool.2
CHADS2 scoring system for non-valvular AF1
|C||Congestive heart failure||1 point||0|
|H||Hypertension (160/90)||1 point||0|
|A||Age >75||1 point||0|
|S2||Stroke or TIA||2 points||0|
CHADS2 score and stroke1
|CHADS2 score||Adjusted annual stroke rate (%)||NNT 1 year warfarin|
When to use the new tool
The CHADS2 tool is easy to remember and if the patient scores 1 or more then they should be considered at moderate or high stroke risk.
In those who score less than 2 then the CHA2DS2VASc tool will help identify the truly low risk and enable all other patients with AF to be considered for anticoagulation.
This is important for women, those over 65 and people who have existing vascular disease other than stroke - all have an increased risk in addition to the factors included in the original CHADS2 score.
A recent study3 followed up patients with a CHADS2 score of 0 and found that at one year there was a thromboembolism rate of 1.67%, but when patients were scored using CHA2DS2VASc those with a score of 0 had an annual thromboembolism rate of 0.78%, highlighting the value of the tool.
CHA2DS2VASc to identify the truly low risk (score=0)
|C||Congestive heart failure||1 point|
|H||Hypertension (160/90)||1 point|
|A2||Age >75||2 points|
|S2||Stroke or TIA||2 points|
|V||Vascular disease, PAD, aortic plaque||1 point|
|A||Age 65-74||1 point|
|Sc||Sex category female (important over 65)||1 point|
|Score 2 or more, high risk =>20% 10 year|
This means that a lady of 72 who has had a previous MI will have an additional three risk factors and that her score will have been increased by 3 and her annual stroke risk increase from 1.9% to 3.2%, requiring a discussion about the benefits of oral anticoagulation for stroke prevention.
Comparison of the two scores
|CHADS2||Annual stroke risk (%)||CHA2DS2VASc||Annual stroke risk (%)|
Why has this become important?
GPs are much more aware of the high risk of thrombotic stroke associated with AF and the benefits of anticoagulation. There is a large evidence base for the benefits of well-controlled warfarin with patients at low bleeding risk when INR is within the pre-specified ranges. There is also the option to use other effective oral agents which may be considered more suitable for some patients, in particular for those in whom anticoagulation within the target ranges was difficult to achieve.
GPs are more confident at discussing the risks and benefits of anticoagulation in those at lower risk who are now clearly identified using the CHA2DS2VASc tool.
It is now clear that those at intermediate risk do not benefit from antiplatelet therapy and aspirin is not included in the updated ESC Guidelines from 2012.4 Where the choice is anticoagulation or no antithrombotic therapy it is extremely important to assess risk as accurately as possible and offer our patients the best treatment.
Dr Kathryn Griffith is GP and GPSI in cardiology in York
- Gage BF, Waterman AD, Shannon W, et al Validation of Clinical Classification Schemes for Predicting Stroke. JAMA, 2001; 285: 2864-2870
- Lip GYH, Nieuwlaat R, Pisters R, et al Refining Clinical Risk Stratification for Predicting Stroke and Thromboembolism in Atrial Fibrillation using a Novel Risk Factor-Based Approach. CHEST 2010; 137 (2) :263-272
- Olesen JB, Lip GYH,Hansen ML, et al. Validation of risk stratification schemes for predicting stroke and thromboembolism in patients with atrial fibrillation: nationwide cohort study.BMJ; 2011; 342:d124
- Camm AJ et al for ESC Taskforce. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation. European Heart Journal ( 2012) 33, 2719-2747