What anticoagulation is appropriate for a patient with new atrial fibrillation (AFib)?

Anticoagulation Management for New Atrial Fibrillation

For patients with newly diagnosed atrial fibrillation, oral anticoagulation therapy should be initiated based on stroke risk assessment using the CHA₂DS₂-VASc score, with direct oral anticoagulants (DOACs) recommended as first-line therapy over warfarin for eligible patients due to their superior safety profile and comparable efficacy. 1

Stroke Risk Assessment

• The CHA₂DS₂-VASc score should be used to assess stroke risk in all patients with non-valvular atrial fibrillation 1
• Risk factors include:
  • Congestive heart failure
  • Hypertension
  • Age ≥75 years (doubled)
  • Diabetes mellitus
  • Prior Stroke/TIA (doubled)
  • Vascular disease
  • Age 65-74 years
  • Sex category (female)

Anticoagulation Recommendations Based on Risk

Low Risk (CHA₂DS₂-VASc score = 0)

• No anticoagulation therapy is suggested 1
• For patients who strongly prefer antithrombotic therapy, aspirin (75-325 mg daily) may be considered 1

Intermediate Risk (CHA₂DS₂-VASc score = 1)

• Oral anticoagulation is recommended rather than no therapy 1
• Oral anticoagulation is preferred over aspirin or aspirin plus clopidogrel 1

High Risk (CHA₂DS₂-VASc score ≥ 2)

• Oral anticoagulation is strongly recommended 1
• DOACs are preferred over warfarin in eligible patients 1

Choice of Anticoagulant

Direct Oral Anticoagulants (DOACs)

• Preferred first-line therapy for non-valvular AF in eligible patients 1
• Options include:
  • Apixaban 5 mg twice daily (reduced to 2.5 mg twice daily in patients with ≥2 of: age ≥80 years, weight ≤60 kg, or serum creatinine ≥1.5 mg/dL) 1, 2
  • Dabigatran 150 mg twice daily (110 mg twice daily for patients at high bleeding risk where available) 1
  • Rivaroxaban 20 mg once daily (reduced to 15 mg once daily if CrCl 15-50 mL/min) 1
  • Edoxaban 60 mg once daily (reduced to 30 mg once daily if CrCl 15-50 mL/min or weight ≤60 kg) 1

Vitamin K Antagonists (Warfarin)

• Target INR 2.0-3.0 with time in therapeutic range (TTR) ideally ≥70% 1, 3
• Preferred in specific situations:
  • Mechanical heart valves (target INR depends on valve type and position) 1, 3
  • Mitral stenosis 1, 3
  • Severe renal impairment (CrCl <15 mL/min) 1

Special Considerations

Bleeding Risk

• For patients with prior unprovoked bleeding, warfarin-associated bleeding, or high bleeding risk:
  • Apixaban, edoxaban, or dabigatran 110 mg (where available) are preferred as they demonstrate less major bleeding compared to warfarin 1
  • For patients with prior gastrointestinal bleeding, apixaban or dabigatran 110 mg may be preferable 1, 2

Renal Function

• DOACs require dose adjustment based on renal function 1
• Dabigatran is contraindicated in severe renal impairment (CrCl ≤30 mL/min) 1
• Warfarin is preferred for patients on dialysis or with end-stage renal disease 1

Cardioversion

• For patients undergoing elective cardioversion with AF >48 hours or unknown duration:
  • Therapeutic anticoagulation with warfarin (INR 2-3) or a DOAC for at least 3 weeks before cardioversion 1
  • Continue anticoagulation for at least 4 weeks after successful cardioversion 1
• For AF ≤48 hours, start anticoagulation at presentation and proceed with cardioversion 1

Comparative Effectiveness and Safety of DOACs

• Apixaban has been associated with the most favorable effectiveness, safety, and persistence profile among DOACs 2
• Apixaban and dabigatran are associated with lower bleeding risk compared to rivaroxaban 4, 2
• All DOACs demonstrate lower risk of intracranial bleeding compared to warfarin 5
• Treatment persistence is highest with apixaban (82%) compared to dabigatran and warfarin (64%) 2

Common Pitfalls and Caveats

• Do not use aspirin alone for stroke prevention in high-risk patients as it is significantly less effective than anticoagulation 6
• Do not discontinue anticoagulation after successful cardioversion or ablation in patients with stroke risk factors 1
• For patients with suboptimal TTR on warfarin (<65%), consider switching to a DOAC or implementing additional measures to improve INR control 1
• Dabigatran should not be used with mechanical heart valves 1
• Consider using the SAMe-TT₂R₂ score to identify patients likely to do well on warfarin versus those who might benefit more from a DOAC 1