What is the indication for anticoagulation in Atrial Fibrillation (AFib) with a CHA2DS2-VASc (Congestive heart failure, Hypertension, Age ≥ 75 years, Diabetes, Stroke or transient ischemic attack, Vascular disease, Age 65-74 years, Sex category) score of 1?

Anticoagulation in Atrial Fibrillation with CHA₂DS₂-VASc Score of 1

For patients with atrial fibrillation and a CHA₂DS₂-VASc score of 1, oral anticoagulation should be considered rather than aspirin or no therapy, with NOACs being the preferred option over vitamin K antagonists when eligible. 1

Risk Assessment for Patients with CHA₂DS₂-VASc Score of 1

The risk of stroke in patients with AF and a CHA₂DS₂-VASc score of 1 is not negligible:

• Annual stroke rates range from 1.96% to 3.50% depending on the specific risk factor 2
• Age 65-74 years carries the highest risk (3.50%/year) among all single risk factors 2
• The presence of 1 additional stroke risk factor increases stroke rate to 1.55 per 100 person-years, representing a significant 3.01-fold increase compared to patients with a score of 0 3

Current Guideline Recommendations

The most recent guidelines from the European Society of Cardiology (2024) state:

• A CHA₂DS₂-VASc score of 1 should be considered an indicator of elevated thromboembolic risk for decisions on initiating oral anticoagulation (Class IIa, Level C) 1
• Antiplatelet therapy is not recommended as an alternative to anticoagulation in patients with AF to prevent ischemic stroke and thromboembolism (Class III, Level A) 1

Earlier guidelines from 2016 indicated that for patients with a CHA₂DS₂-VASc score of 1, "no therapy, aspirin, or OAC therapy may be considered" (Class IIa, Level of Evidence B) 1. However, more recent evidence has shifted recommendations toward oral anticoagulation.

Anticoagulation Options

When oral anticoagulation is chosen for patients with AF and CHA₂DS₂-VASc score of 1:

1. Direct Oral Anticoagulants (DOACs) are preferred over vitamin K antagonists due to:

   • Similar or superior efficacy compared to warfarin
   • Lower rates of intracranial hemorrhage
   • No need for routine coagulation monitoring 1, 4

2. Warfarin can be used when DOACs are contraindicated:

   • Target INR of 2.0-3.0
   • Regular monitoring required to maintain therapeutic range
   • Time in therapeutic range (TTR) should be ≥65-70% for optimal outcomes 1, 5

Risk Factor Considerations

Not all CHA₂DS₂-VASc components carry equal risk. For patients with a score of 1, the specific risk factor matters:

• Age 65-74 years: highest stroke risk (3.50%/year for men, 3.34%/year for women) 2
• Vascular disease: lowest stroke risk (1.96%/year) 2
• No statistically significant difference was identified between subgroups of CHA₂DS₂-VASc 1 in a recent nationwide study 6

Bleeding Risk Assessment

Before initiating anticoagulation, bleeding risk should be assessed using the HAS-BLED score:

• Score ≥3 indicates high bleeding risk requiring caution and regular review 1, 4
• Modifiable bleeding risk factors should be addressed when possible
• Bleeding risk should not automatically exclude patients from anticoagulation but should inform monitoring frequency and patient education 4

Common Pitfalls and Caveats

1. Underestimating stroke risk: Patients with a CHA₂DS₂-VASc score of 1 have a significant stroke risk that should not be dismissed.

2. Overreliance on aspirin: Current guidelines clearly state that antiplatelet therapy is not recommended as an alternative to anticoagulation for stroke prevention in AF 1.

3. Failure to reassess risk: CHA₂DS₂-VASc scores can change over time as patients develop additional risk factors. Regular reassessment is essential 4.

4. Inadequate monitoring: For patients on warfarin, maintaining a TTR >65% is crucial for optimal outcomes 1.

5. Sex category consideration: Female sex alone (CHA₂DS₂-VASc score of 1) is not considered sufficient to recommend anticoagulation without other risk factors 1.

Algorithm for Decision-Making in AF with CHA₂DS₂-VASc Score of 1

1. Confirm the CHA₂DS₂-VASc score of 1 is not due to female sex alone

   • Female sex alone is not sufficient for anticoagulation recommendation

2. Evaluate the specific risk factor contributing to the score

   • Age 65-74 years carries the highest risk and strongest indication for OAC

3. Assess bleeding risk using HAS-BLED score

   • Score ≥3 requires caution but does not contraindicate anticoagulation

4. Select appropriate anticoagulation

   • DOAC preferred (if eligible)
   • Warfarin if DOAC contraindicated (target INR 2.0-3.0)

5. Establish monitoring plan

   • Regular assessment of adherence and side effects
   • Periodic reassessment of stroke and bleeding risk

By following this evidence-based approach, clinicians can provide optimal stroke prevention for patients with atrial fibrillation and a CHA₂DS₂-VASc score of 1, potentially preventing significant morbidity and mortality.