Condition | Points | |
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C | Congestive heart failure |
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H | Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication) |
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A | Age ≥75 years |
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D | Diabetes mellitus |
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S2 | Prior Stroke or TIA |
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The CHADS2 score is a clinical prediction rule for estimating the risk of stroke in patients with non-rheumatic atrial 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,[1] 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 score is simple and has been validated by many studies.[2]
The CHADS2 scoring table is shown above:[3] adding together the points that correspond to the conditions that are present results in the CHADS2 score, that is used to estimate stroke risk.
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CHADS2 Score | Stroke Risk % | 95% CI |
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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.[4] 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.[5] 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.[6][7]
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,’[8][9] and thus the recommendation is to prescribe either aspirin or no antithrombotic therapy, but 'no antithrombotic therapy' is preferred.[10]
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.[11] 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.
Score | Risk | Anticoagulation Therapy | Considerations |
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0 | Low | None or Aspirin | Aspirin daily |
1 | Moderate | Aspirin or Warfarin | Aspirin daily or raise INR to 2.0-3.0, depending on patient preference |
2 or greater | Moderate or High | Warfarin | Raise INR to 2.0-3.0, unless contraindicated |
Treatment strategies recommended based on the CHADS2 score are shown in the table.[1][2]
How the treatment recommendations based on the CHADS2 score are modified by considering additional 'stroke risk modifier' risk factors using the CHA2DS2-VASc score, see ESC guideline recommendations, which recommend the management as shown in the following table:
Condition | Points | |
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C | Congestive heart failure (or Left ventricular systolic dysfunction) |
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H | Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication) |
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A2 | Age ≥75 years |
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D | Diabetes Mellitus |
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S2 | Prior Stroke or TIA or thromboembolism |
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V | Vascular disease (eg. peripheral artery disease, myocardial infarction, aortic plaque) |
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A | Age 65-74 years |
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Sc | Sex category (i.e. female gender) |
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The CHA2DS2-VASc score is a refinement of CHADS2 score and extends the latter by including additional common stroke risk factors, as discussed below.
The maximum CHADS2 score is 6, whilst the maximum CHA2DS2-VASc score is 9.
Score | Risk | Anticoagulation Therapy | Considerations |
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0 | Low | No antithrombotic therapy (or Aspirin) | No antithrombotic therapy (or Aspirin 75-325mg daily) |
1 | Moderate | Oral anticoagulant (or Aspirin) | Oral anticoagulant, either new oral anticoagulant drug eg dabigatran or well controlled warfarin at INR 2.0-3.0 (or Aspirin 75-325mg daily, depending on factors such as patient preference) |
2 or greater | High | Oral anticoagulant | Oral anticoagulant, using either a new oral anticoagulant drug (eg rivaroxaban or dabigatran) or well controlled warfarin at INR 2.0-3.0 |
Based on the ESC guidelines on Atrial Fibrillation, oral anticoagulation is recommended or preferred for patients with one or more stroke risk factors (ie. a CHA2DS2-VASc score of 1 and above). This is consistent with a recent decision analysis model showing how the 'tipping point' on the decision to anticoagulate has changed with the availability of new 'safer' OAC drugs.[12][13]