CHADS₂ Score for Atrial Fibrillation Stroke Risk

What is the CHADS₂ Score?

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. The name is an acronym of the risk factors it includes:

• C: Congestive heart failure (1 point)
• H: Hypertension: blood pressure consistently above 140/90 mmHg (or treated hypertension on medication) (1 point)
• A: Age ≥75 years (1 point)
• D: Diabetes mellitus (1 point)
• S₂: Prior Stroke or TIA or thromboembolism (2 points)

How to Use the Calculator

Using the CHADS₂ Score Calculator is straightforward. Simply check the boxes for each risk factor that applies to the patient:

1. Select whether the patient has congestive heart failure
2. Indicate if the patient has hypertension
3. Check if the patient is 75 years of age or older
4. Select whether the patient has diabetes mellitus
5. Indicate if the patient has a history of stroke or transient ischemic attack (TIA)
6. Click "Calculate CHADS₂ Score" to see the results

The calculator will add up the points for each risk factor present and provide a total score ranging from 0 to 6.

Interpreting the Results

The CHADS₂ score ranges from 0 to 6, with higher scores indicating a greater risk of stroke:

• Score 0: Low risk (1.9% annual stroke risk)
• Score 1-2: Moderate risk (2.8-4.0% annual stroke risk)
• Score 3-4: High risk (5.9-8.5% annual stroke risk)
• Score 5-6: Very high risk (12.5-18.2% annual stroke risk)

Based on the CHADS₂ score, clinicians can make recommendations regarding anticoagulation therapy:

• Score 0: Aspirin 81-325 mg daily or no antithrombotic therapy
• Score 1: Aspirin 81-325 mg daily or oral anticoagulation (e.g., warfarin)
• Score ≥2: Oral anticoagulation (e.g., warfarin) with target INR 2.0-3.0

Clinical Significance

The CHADS₂ score is widely used in clinical practice to guide antithrombotic therapy in patients with atrial fibrillation. It helps clinicians balance the risk of stroke against the risk of bleeding associated with anticoagulation therapy.

While the CHADS₂ score is valuable, it has been largely superseded by the CHA₂DS₂-VASc score, which includes additional risk factors and provides better risk stratification, especially for patients previously classified as "low risk" by CHADS₂.

Limitations

The CHADS₂ score has several limitations:

• It does not include some important risk factors for stroke, such as vascular disease
• It may underestimate stroke risk in patients with a score of 0, who may still have significant risk factors not captured by the score
• It does not account for the severity or duration of risk factors (e.g., well-controlled vs. poorly controlled hypertension)
• It does not consider bleeding risk, which is an important consideration when prescribing anticoagulation

Due to these limitations, many clinicians now prefer the CHA₂DS₂-VASc score, which addresses some of these issues.

References

1. Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA. 2001;285(22):2864-2870.
2. Lip GY, Nieuwlaat R, Pisters R, Lane DA, Crijns HJ. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the euro heart survey on atrial fibrillation. Chest. 2010;137(2):263-272.
3. January CT, Wann LS, Calkins H, et al. 2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation. Circulation. 2019;140(2):e125-e151.