Do we start anticoagulation for a patient with atrial fibrillation?

Anticoagulation for Atrial Fibrillation

Yes, anticoagulation should be initiated for patients with atrial fibrillation unless they have lone AF (AF without risk factors) or specific contraindications to anticoagulation. 1

Risk Assessment for Anticoagulation

The decision to start anticoagulation should be based on stroke risk assessment using the CHA₂DS₂-VASc score:

• For patients with nonvalvular AF with prior stroke, TIA, or CHA₂DS₂-VASc score ≥2, oral anticoagulation is recommended 1
• For patients with mechanical heart valves, warfarin is required with target INR based on valve type and location 1

High-Risk Features Requiring Anticoagulation:

• Age ≥75 years (especially women)
• Heart failure
• LV ejection fraction ≤0.35
• History of hypertension
• Diabetes mellitus
• Coronary artery disease
• Prior thromboembolism
• Rheumatic heart disease (particularly mitral stenosis)
• Prosthetic heart valves
• Persistent atrial thrombus on TEE 1

Anticoagulation Options

For Nonvalvular AF:

• Direct oral anticoagulants (DOACs) are preferred for eligible patients:

  • Dabigatran
  • Rivaroxaban
  • Apixaban (dose: 5mg twice daily; or 2.5mg twice daily if ≥2 of: age ≥80 years, weight ≤60kg, or creatinine ≥1.5mg/dL) 2

• Warfarin (target INR 2.0-3.0) if DOACs are contraindicated or patient has mechanical valve 1

For Valvular AF (with mechanical valves):

• Warfarin is required with target INR 2.5-3.5 1

Monitoring and Follow-up

For patients on warfarin:

• INR should be checked at least weekly during initiation
• Monthly when stable
• Target INR 2.0-3.0 for most patients (higher for mechanical valves) 1

For patients on DOACs:

• Regular assessment of renal function
• No routine coagulation monitoring required 2

Special Considerations

Cardioversion:

• Anticoagulation is required regardless of method used (electrical or pharmacological)
• For AF lasting >48h or unknown duration: anticoagulate for at least 3-4 weeks before and after cardioversion
• For acute AF with hemodynamic instability: immediate cardioversion with concurrent heparin, followed by oral anticoagulation 1

Temporary Interruption:

• For elective surgery with moderate/high bleeding risk: discontinue DOACs 48h prior
• For low bleeding risk procedures: discontinue 24h prior
• Bridging with heparin is generally not required for DOACs but is necessary for patients with mechanical valves 2

Common Pitfalls to Avoid

1. Undertreatment: Not anticoagulating patients with AF who have risk factors for stroke
2. Overreliance on aspirin: Aspirin is substantially less effective than anticoagulation for stroke prevention in AF
3. Discontinuing anticoagulation after ablation: Continuation of anticoagulation after AF ablation should be based on CHA₂DS₂-VASc score, not perceived procedural success 1
4. Premature discontinuation: Stopping anticoagulation without appropriate indication increases thrombotic risk 2
5. Inadequate INR control: For patients on warfarin, poor time in therapeutic range increases both stroke and bleeding risks

Conclusion

For most patients with AF, the benefits of stroke prevention with anticoagulation outweigh the bleeding risks. The most recent evidence supports using DOACs over warfarin for nonvalvular AF due to similar efficacy with lower bleeding risk, particularly intracranial hemorrhage 3. Regular reassessment of stroke and bleeding risks is essential for optimal management.