What are the anticoagulation recommendations for a patient with paroxysmal atrial fibrillation (AFib) and 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 for Paroxysmal Atrial Fibrillation with CHA₂DS₂-VASc Score of 1

For a patient with paroxysmal atrial fibrillation and a CHA₂DS₂-VASc score of 1, oral anticoagulation with a direct oral anticoagulant (DOAC) is recommended over aspirin or no therapy, as this score indicates the presence of one non-sex stroke risk factor which warrants stroke prevention therapy. 1

Critical Distinction: Sex as a Risk Factor

The key nuance here is whether the score of 1 is from female sex alone or from an actual stroke risk factor:

• If the score is 1 in a female patient due to sex alone (no other risk factors): This represents truly low risk, and no antithrombotic therapy is recommended 1, 2

• If the score is 1 from a non-sex risk factor (e.g., hypertension, diabetes, age 65-74, vascular disease, heart failure): Oral anticoagulation is strongly recommended 1, 3, 2

Evidence Supporting Anticoagulation at CHA₂DS₂-VASc = 1

The 2018 CHEST Guidelines explicitly state that stroke prevention should be offered to patients with 1 or more non-sex CHA₂DS₂-VASc stroke risk factors. 1 This represents a strong recommendation with moderate quality evidence.

Real-world data demonstrates that patients with one additional stroke risk factor (beyond sex) have a stroke rate of 1.55 per 100 person-years compared to 0.49 per 100 person-years in truly low-risk patients—representing a significant 3.01-fold increase in stroke risk. 4 More importantly, mortality increased 3.12-fold in these patients when not anticoagulated. 4

A large observational study of over 1,000 patients with AF and CHADS₂ score of 1 found that oral anticoagulation was independently associated with a 58% reduction in the combined risk of death or stroke (relative risk 0.42,95% CI 0.29-0.60, p<0.0001), while antiplatelet therapy showed no significant benefit. 5

Preferred Anticoagulation Strategy

Direct oral anticoagulants (DOACs) are preferred over warfarin for patients with non-valvular atrial fibrillation requiring anticoagulation. 3, 2, 6 Options include:

• Apixaban
• Rivaroxaban
• Edoxaban
• Dabigatran 3, 2

DOACs demonstrate lower rates of intracranial hemorrhage compared to warfarin while maintaining similar or superior efficacy for stroke prevention. 3, 2 Anticoagulation with DOACs or warfarin reduces stroke risk by 60-80% compared to placebo. 6

Why Aspirin is Not Recommended

Aspirin should not be used for stroke prevention in atrial fibrillation, regardless of stroke risk. 1, 3 The evidence is clear:

• Oral anticoagulation reduces stroke risk by 62%, while aspirin provides only 22% risk reduction 3, 7
• Aspirin carries a similar bleeding risk to well-managed warfarin (INR 2.0-3.0) but with substantially less efficacy 7
• The 2018 CHEST Guidelines provide a strong recommendation against antiplatelet therapy alone for stroke prevention in AF 1

The 2014 AHA/ACC/HRS Guidelines suggest that for CHA₂DS₂-VASc score of 1, "no antithrombotic therapy or treatment with an oral anticoagulant or aspirin may be considered," but this represents only a Class IIb recommendation (weak evidence). 1 This conflicts with the more recent and definitive 2018 CHEST Guidelines, which should take precedence.

Warfarin as an Alternative

If a DOAC is contraindicated or unavailable, warfarin is an acceptable alternative with target INR 2.0-3.0. 8 Warfarin is specifically required for:

• Mechanical heart valves
• Moderate-to-severe mitral stenosis
• End-stage renal disease or dialysis patients 3, 2, 8

For warfarin therapy, INR should be monitored weekly during initiation, then monthly when stable. 1, 3, 2

Bleeding Risk Assessment

Bleeding risk assessment must be performed but should focus on modifiable risk factors rather than being used as a reason to withhold anticoagulation. 1 The HAS-BLED score should be used to identify and address modifiable bleeding risks: 1

• Uncontrolled blood pressure
• Labile INRs (if on warfarin)
• Alcohol excess
• Concomitant NSAIDs or aspirin use
• Bleeding predisposition (treat ulcers, optimize renal/liver function) 1

A high HAS-BLED score (≥3) is rarely a reason to avoid anticoagulation but rather indicates the need for more frequent monitoring and aggressive management of modifiable risk factors. 1

Common Pitfalls to Avoid

• Do not use aspirin instead of oral anticoagulation when a non-sex stroke risk factor is present—aspirin provides inadequate stroke protection with similar bleeding risk 3, 7, 9

• Do not discontinue anticoagulation after cardioversion or ablation if stroke risk factors persist, as the CHA₂DS₂-VASc score remains unchanged 3, 2

• Do not overestimate bleeding risk as a justification for withholding appropriate anticoagulation—the mortality benefit of anticoagulation in patients with stroke risk factors outweighs bleeding concerns 3, 5, 4

• Paroxysmal AF carries the same stroke risk as persistent or permanent AF—the pattern of atrial fibrillation does not change anticoagulation recommendations 2, 8

Monitoring and Reassessment

For DOAC therapy, assess renal function before initiation and at least annually thereafter, with dose adjustments based on renal function. 1, 3

The need for anticoagulation should be reevaluated at regular intervals as stroke risk factors may change over time. 1, 3, 2