What is the purpose and calculation of the CHA2DS2-VASc (Congestive heart failure, Hypertension, Age, Diabetes, Vascular disease, and female Sex) score in assessing stroke risk in patients with non-rheumatic atrial fibrillation?

CHA₂DS₂-VASc Score: Purpose and Calculation

The CHA₂DS₂-VASc score is a validated risk stratification tool used to identify stroke risk in patients with non-valvular atrial fibrillation, with the primary purpose of determining which patients require oral anticoagulation for stroke prevention. 1, 2

Score Components and Point Assignment

The CHA₂DS₂-VASc acronym represents the following risk factors with their assigned points 1, 2:

• C - Congestive heart failure (signs/symptoms of heart failure with objective cardiac dysfunction): 1 point 2
• H - Hypertension (BP >140/90 mmHg or on antihypertensive treatment): 1 point 2
• A₂ - Age ≥75 years: 2 points 1, 2
• D - Diabetes mellitus (fasting glucose ≥126 mg/dL or on hypoglycemic agents): 1 point 2
• S₂ - Prior Stroke/TIA/thromboembolism: 2 points 1, 2
• V - Vascular disease (prior MI, peripheral artery disease, or aortic plaque): 1 point 2
• A - Age 65-74 years: 1 point 1, 2
• Sc - Female sex: 1 point 1, 2

The maximum possible score is 9 points, with higher scores indicating progressively greater stroke risk 2.

Annual Stroke Risk by Score

The validated annual thromboembolic event rates increase progressively with each point 3:

• Score 0: 0% annual stroke rate 3
• Score 1: 0.6-1.3% annual stroke rate 3
• Score 2: 1.6-2.2% annual stroke rate 3
• Score 3: 3.2% annual stroke rate 3
• Score 4: 4.0% annual stroke rate 3
• Score 5: 6.7% annual stroke rate 3
• Score 6: 9.8% annual stroke rate 3
• Score 9: ≥15.2% annual stroke rate 3

Clinical Decision Algorithm

Step 1: Calculate the CHA₂DS₂-VASc score for all patients with newly diagnosed non-valvular atrial fibrillation, including those with paroxysmal AF. 1, 2

Step 2: Identify truly low-risk patients who do NOT require anticoagulation:

• Men with score = 0 1, 2
• Women with score = 1 (sex alone) 1, 2

These patients have annual stroke rates <1% and should not receive antithrombotic therapy 1.

Step 3: Offer stroke prevention with oral anticoagulation to:

• Men with score ≥1 1, 2
• Women with score ≥2 1, 2

The contemporary guideline approach differentiates by sex because women without other risk factors (score = 1 for sex alone) have truly low risk similar to men with score 0. 2, 3

Advantages Over CHADS₂ Score

The CHA₂DS₂-VASc score replaced the older CHADS₂ score in 2010 ESC guidelines because it demonstrates superior sensitivity, particularly for identifying truly low-risk patients 1, 2. The key improvements include 2:

• Broader score range (0-9 vs 0-6) allowing more refined risk stratification
• Inclusion of additional risk factors (female sex, age 65-74, vascular disease) that CHADS₂ omits
• Better discrimination of stroke risk among patients with low CHADS₂ scores (0-1)
• C-statistic of 0.606-0.67 for CHA₂DS₂-VASc versus 0.561 for CHADS₂

Critical Clinical Considerations

For patients with CHA₂DS₂-VASc score of 1 (men) or 2 (women), there is evidence supporting anticoagulation despite some heterogeneity in the data. 1, 4 The annual stroke rate in this intermediate-risk group ranges from 1.4% (range 0.5-2.9%) without anticoagulation to 0.7% (range 0.1-1.3%) with anticoagulation 3. Net clinical benefit analysis demonstrates positive benefit favoring oral anticoagulation over no therapy or antiplatelet therapy in this group 4.

Not all risk factors within a CHA₂DS₂-VASc score of 1 carry equal risk. 5 Age 65-74 years is associated with the highest risk (hazard ratios 1.9-3.9), while vascular disease tends to show lower event rates, though all demonstrate clinically relevant increased thromboembolic risk 5.

Anticoagulation Recommendations

For patients requiring anticoagulation (score ≥2 in men or ≥3 in women), preferentially use NOACs (dabigatran, apixaban, edoxaban, rivaroxaban) over warfarin. 2 Before initiating anticoagulation, assess bleeding risk using the HAS-BLED score separately, as the CHA₂DS₂-VASc score does not account for bleeding risk 2.

Important Caveats

• The CHA₂DS₂-VASc score has only modest predictive accuracy (C-statistic around 0.6-0.7) 2
• Stroke risk is dynamic and should be reassessed at every patient contact 1
• The score does not include other potential risk factors such as impaired kidney function, cancer, rheumatoid arthritis, obesity, or smoking 1
• For postoperative atrial fibrillation after cardiac surgery, the standard thresholds may not apply, as these patients show lower stroke rates at equivalent scores 6