How is the CHADS2VASc (Cardiac failure, Hypertension, Age >= 75, Diabetes, Stroke, Vascular disease, Age 65-74, Sex category) score used to determine anticoagulation therapy in patients with non-rheumatic atrial fibrillation?

CHADS₂VASc Score for Anticoagulation in Non-Rheumatic Atrial Fibrillation

The CHA₂DS₂-VASc score is the recommended tool for stroke risk assessment in patients with non-rheumatic atrial fibrillation, with oral anticoagulation strongly recommended for men with a score ≥1 and women with a score ≥2. 1

Components of the CHA₂DS₂-VASc Score

The CHA₂DS₂-VASc score includes the following components:

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

Risk Stratification and Anticoagulation Recommendations

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. The score helps stratify patients into risk categories:

1. Low Risk:

   • Men with score = 0
   • Women with score = 1
   • Recommendation: No anticoagulation therapy 2, 1

2. Moderate to High Risk:

   • Men with score ≥1
   • Women with score ≥2
   • Recommendation: Oral anticoagulation therapy 2, 1

The annual stroke risk increases with higher CHA₂DS₂-VASc scores:

• Score 0: 0-0.3% annual stroke risk
• Score 1: 1.3% annual stroke risk
• Score 2: 2.2% annual stroke risk
• Score 3: 3.2% annual stroke risk
• Score 4: 4.0% annual stroke risk
• Score 5: 6.7% annual stroke risk
• Score 6: 9.8% annual stroke risk
• Score 7: 9.6% annual stroke risk
• Score 8: 6.7% annual stroke risk
• Score 9: 15.2% annual stroke risk 2

Anticoagulation Options

When anticoagulation is indicated based on CHA₂DS₂-VASc score:

1. Direct Oral Anticoagulants (DOACs) are preferred over warfarin for eligible patients due to their efficacy and safety profile 1:

   • Apixaban: 5 mg twice daily (or 2.5 mg twice daily in patients with certain characteristics)
   • Rivaroxaban: 20 mg once daily with food (15 mg once daily if CrCl 30-50 mL/min) 3
   • Dabigatran: 150 mg twice daily (75 mg twice daily if CrCl 15-30 mL/min)
   • Edoxaban: 30 mg once daily (for CrCl 15-50 mL/min)

2. Warfarin is recommended for specific patient populations 4:

   • Patients with mechanical heart valves
   • Moderate to severe mitral stenosis
   • End-stage renal disease (CrCl <15 mL/min) or on dialysis
   • Target INR: 2.0-3.0
   • Time in therapeutic range (TTR) goal: >65-70%

Bleeding Risk Assessment

The HAS-BLED score should be calculated alongside the CHA₂DS₂-VASc score to assess bleeding risk 1:

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, but is rarely a reason to avoid anticoagulation 2. Instead, modifiable bleeding risk factors should be addressed.

Clinical Pearls and Pitfalls

1. Do not use antiplatelet therapy (aspirin) as an alternative to oral anticoagulation for stroke prevention in AF patients, regardless of stroke risk 5, 6.

2. Female sex is only a risk factor in patients >65 years or with additional risk factors. Women <65 years with no other risk factors are not at excess stroke risk 2.

3. Stroke risk is dynamic and should be reassessed at every patient contact, as risk factors may develop over time 1.

4. The CHA₂DS₂-VASc score has modest discrimination ability (C-statistic around 0.66-0.67) for predicting stroke, but it remains the recommended tool for clinical decision-making 7.

5. Patients with a single CHA₂DS₂-VASc risk factor are not all equal. Those aged 65-74 years or with diabetes may be at higher risk compared to those with other single risk factors 8.

6. Regular monitoring is essential for all anticoagulants:

   • Renal function should be evaluated before initiating DOACs and at least annually
   • Regular monitoring for adherence, side effects, and drug interactions
   • Periodic reassessment of stroke and bleeding risk 1

By following this evidence-based approach to using the CHA₂DS₂-VASc score, clinicians can make informed decisions about anticoagulation therapy to reduce stroke risk while minimizing bleeding complications in patients with non-rheumatic atrial fibrillation.