Scales for Evaluating Risk of Atrial Fibrillation
The CHA₂DS₂-VASc score is the recommended scale for evaluating stroke risk in patients with atrial fibrillation, as endorsed by the American College of Cardiology, American Heart Association, and European Society of Cardiology guidelines. 1, 2
CHA₂DS₂-VASc Score Components
The CHA₂DS₂-VASc score assigns points for the following risk factors:
| Risk Factor | Points |
|---|---|
| Congestive heart failure | 1 |
| Hypertension | 1 |
| Age ≥75 years | 2 |
| Diabetes mellitus | 1 |
| Stroke/TIA/thromboembolism (previous) | 2 |
| Vascular disease (prior MI, PAD, aortic plaque) | 1 |
| Age 65-74 years | 1 |
| Sex category (female) | 1 |
Total possible score ranges from 0-9 points, with higher scores indicating greater stroke risk.
Clinical Application of CHA₂DS₂-VASc
- The CHA₂DS₂-VASc score has replaced the older CHADS₂ score in current guidelines due to its superior ability to identify truly low-risk patients 1
- According to the 2023 ACC/AHA guidelines, the CHA₂DS₂-VASc score should be documented for all patients with atrial fibrillation 1
- The score helps determine which patients would benefit from anticoagulation therapy:
- Score of 0 in males or 1 in females: Low risk, no anticoagulation recommended
- Score of 1 in males or 2 in females: Consider oral anticoagulation
- Score ≥2 in males or ≥3 in females: Oral anticoagulation strongly recommended 2
Stroke Risk Stratification Based on CHA₂DS₂-VASc Score
Annual stroke risk increases with higher CHA₂DS₂-VASc scores:
- Score of 0: 0.04-0.3% annual stroke risk
- Score of 1: 0.5-1.3% annual stroke risk
- Score of 2: 0.8-2.2% annual stroke risk
- Score of 3: 1.7-3.7% annual stroke risk
- Score of 4: 2.8-4.0% annual stroke risk
- Score of 5: 4.0-6.7% annual stroke risk
- Score ≥6: 4.8-8.4% annual stroke risk 1, 2
Complementary Risk Assessment: HAS-BLED Score
When evaluating patients with atrial fibrillation, the HAS-BLED score should also be calculated to assess bleeding risk:
| Risk Factor | Points |
|---|---|
| Hypertension (>160 mmHg) | 1 |
| Abnormal renal or liver function | 1 or 2 |
| Previous stroke | 1 |
| Bleeding predisposition | 1 |
| Labile INR | 1 |
| Age >65 years | 1 |
| Medications or alcohol | 1 or 2 |
A HAS-BLED score ≥3 indicates high bleeding risk requiring caution and regular review 2.
Limitations and Considerations
- The CHA₂DS₂-VASc score has modest predictive accuracy with C-statistics typically between 0.64-0.70 1, 3
- There is significant heterogeneity in stroke risk predictions across different populations and clinical settings 3
- Hospital-based studies tend to show higher stroke risks for each score point compared to community-based studies 3
- The score should be reassessed periodically as risk factors may develop over time 2
Additional Risk Factors Not Included in CHA₂DS₂-VASc
Several factors may increase stroke risk but are not included in the CHA₂DS₂-VASc score:
- Higher AF burden/longer duration
- Persistent/permanent AF versus paroxysmal
- Obesity (BMI ≥30 kg/m²)
- Hypertrophic cardiomyopathy
- Poorly controlled hypertension
- Reduced renal function (eGFR <45 mL/h)
- Proteinuria
- Enlarged left atrial volume 1
The CHA₂DS₂-VASc score has also shown utility in predicting new-onset atrial fibrillation in patients without pre-existing AF, with a hazard ratio of 1.57 for each 1-point increase in score 4.