CHA₂DS₂-VASc: Stroke Risk Stratification Score for Atrial Fibrillation
CHA₂DS₂-VASc is a validated clinical scoring system used to assess stroke risk in patients with nonvalvular atrial fibrillation, guiding decisions about oral anticoagulation therapy. 1, 2
Score Components and Point Assignment
The acronym represents specific risk factors, each assigned points based on their relative contribution to stroke risk 1, 2:
- C - Congestive heart failure or left ventricular ejection fraction ≤40%: 1 point 1
- H - Hypertension (blood pressure >140/90 mmHg or on antihypertensive treatment): 1 point 1, 2
- A₂ - Age ≥75 years: 2 points (doubled because age is a major stroke risk factor) 1, 2
- D - Diabetes mellitus (fasting glucose ≥126 mg/dL or on hypoglycemic agents): 1 point 1, 2
- S₂ - Prior Stroke, TIA, or thromboembolism: 2 points (doubled due to significantly elevated recurrence risk) 1, 2
- V - Vascular disease (prior MI, peripheral artery disease, or aortic plaque): 1 point 1, 2
- A - Age 65-74 years: 1 point 1, 2
- Sc - Sex category (female): 1 point 1, 2
Maximum possible score: 9 points 1, 2
Clinical Application for Anticoagulation Decisions
Risk Stratification Thresholds
The score directly determines anticoagulation recommendations based on annual stroke risk 1, 2, 3:
- Score 0 (men): Annual stroke risk ~0% - No anticoagulation recommended 2, 3
- Score 1 (men): Annual stroke risk ~1.3% - Individualized decision (consider additional risk factors like biomarkers, left atrial size, or patient preference) 1, 2
- Score ≥2 (men) or ≥3 (women): Annual stroke risk ≥2.2% - Oral anticoagulation strongly recommended 1, 2, 3
Important Sex-Based Consideration
Female sex alone (score of 1 in women) does not mandate anticoagulation; women require ≥3 points total (meaning ≥1 additional risk factor beyond sex) to warrant anticoagulation. 3 This reflects that female sex is a risk modifier rather than an independent high-risk factor.
Superiority Over CHADS₂ Score
CHA₂DS₂-VASc provides more precise risk stratification than the older CHADS₂ score by 1:
- Including vascular disease as a risk factor
- Distinguishing between age 65-74 years (1 point) and ≥75 years (2 points)
- Accounting for female sex
- Better identifying truly low-risk patients (score 0) who do not require anticoagulation 1
Preferred Anticoagulation Options
First-Line Therapy
Direct oral anticoagulants (DOACs) are preferred over warfarin for eligible patients with CHA₂DS₂-VASc ≥2. 3 Options include:
DOACs demonstrate at least non-inferiority and often superiority to warfarin for stroke prevention, with significantly lower intracranial hemorrhage rates (hazard ratio 0.48). 1, 3
Alternative Therapy
Warfarin (target INR 2.0-3.0) remains appropriate for 1, 3:
- Patients with contraindications to DOACs
- Severe renal impairment (creatinine clearance <15 mL/min) or hemodialysis
- Mechanical heart valves or moderate-to-severe mitral stenosis (where DOACs are contraindicated)
INR monitoring should occur weekly during initiation and monthly when stable. 3
Bleeding Risk Assessment
The HAS-BLED score should be calculated to identify modifiable bleeding risk factors, but high bleeding risk alone should NOT exclude patients from anticoagulation. 1, 3 The HAS-BLED components include 1:
- Hypertension (systolic BP >160 mmHg): 1 point
- Abnormal renal/liver function: 1-2 points
- Stroke history: 1 point
- Bleeding history or predisposition: 1 point
- Labile INR (if on warfarin): 1 point
- Elderly (age >65 years): 1 point
- Drugs (NSAIDs, antiplatelet agents) or alcohol: 1-2 points
HAS-BLED ≥3 indicates need for caution and regular monitoring, but should prompt modification of reversible bleeding risks (uncontrolled hypertension, NSAID use, excessive alcohol) rather than withholding anticoagulation. 1
Critical Clinical Pitfalls
Aspirin monotherapy provides inadequate stroke protection in atrial fibrillation and should NOT be used as an alternative to oral anticoagulation in patients with CHA₂DS₂-VASc ≥2. 1 Observational data demonstrate aspirin offers no net benefit compared to anticoagulation in intermediate-risk patients. 1
Renal function must be assessed before initiating DOACs and reassessed at least annually, as DOAC dosing requires adjustment or contraindication with declining renal function. 1, 3
The CHA₂DS₂-VASc score has modest predictive accuracy (C-statistic 0.6-0.7), meaning individual patient risk may vary; consider additional factors like elevated biomarkers (NT-proBNP >1400 ng/L), enlarged left atrium (≥4.7 cm), or low left atrial appendage emptying velocity (<20 cm/s) for refined risk assessment in borderline cases. 1, 2