What is the recommended anticoagulation therapy for patients with Atrial Fibrillation (AFib)?

Anticoagulation Therapy for Atrial Fibrillation

Direct oral anticoagulants (DOACs) are the preferred first-line therapy for stroke prevention in patients with nonvalvular atrial fibrillation, with apixaban 5 mg twice daily being the optimal choice for most patients due to its superior safety profile and efficacy. 1, 2

Risk Assessment for Anticoagulation

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

• CHA₂DS₂-VASc score ≥2 in men or ≥3 in women: Oral anticoagulation strongly recommended 1
• CHA₂DS₂-VASc score of 1 in men or 2 in women: Oral anticoagulation should be considered 1
• CHA₂DS₂-VASc score of 0: No antithrombotic therapy recommended 1

Risk factors to consider include:

• Prior stroke, TIA, or systemic embolism (high risk) 3
• Age ≥75 years (moderate risk) 3
• Hypertension (moderate risk) 3
• Diabetes mellitus (moderate risk) 3
• Heart failure or impaired left ventricular function (moderate risk) 3

First-Line Anticoagulation Options

DOACs (Preferred for Nonvalvular AF)

1. Apixaban (First Choice):

   • Standard dose: 5 mg twice daily 4
   • Reduced dose: 2.5 mg twice daily if patient has ≥2 of: age ≥80 years, weight ≤60 kg, or serum creatinine ≥1.5 mg/dL 4
   • Benefits: Lower rates of stroke, major bleeding, and mortality compared to warfarin 2

2. Dabigatran:

   • 150 mg twice daily (standard dose) 3
   • 110 mg twice daily (where available) for patients with high bleeding risk 3
   • Consider 150 mg twice daily specifically for patients at high risk of ischemic stroke 3, 5

3. Edoxaban:

   • 60 mg once daily (standard dose) 3
   • Consider for patients with prior bleeding risk 3

4. Rivaroxaban:

   • 20 mg once daily with food 2

Vitamin K Antagonist (Second Choice)

Warfarin:

• Target INR: 2.0-3.0 3
• Monitor INR weekly during initiation, monthly when stable 3, 1
• Consider if patient has valvular AF, mechanical heart valves, or severe renal impairment 1
• Aim for time in therapeutic range (TTR) ≥70% 3
• If TTR <65%, implement additional measures (more frequent INR tests, medication adherence review, education) or switch to a DOAC 3

Special Considerations

Valvular vs. Nonvalvular AF

• For patients with mechanical heart valves: Warfarin with target INR based on valve type (at least 2.5) 3
• For patients with rheumatic mitral stenosis: Warfarin (INR 2.0-3.0) 3

Renal Function

• For CrCl <15 mL/min or dialysis: Warfarin (INR 2.0-3.0) is recommended 1
• For moderate-to-severe CKD with CrCl >15 mL/min: Reduced doses of DOACs may be appropriate 1

Bleeding Risk

• For patients with prior unprovoked bleeding or at high bleeding risk: Consider apixaban, edoxaban, or dabigatran 110 mg 3
• For patients with prior gastrointestinal bleeding: Apixaban or dabigatran 110 mg may be preferable 3

Cardioversion

• For AF >48 hours or unknown duration undergoing elective cardioversion:
  • Therapeutic anticoagulation with warfarin (INR 2-3) or a DOAC for ≥3 weeks before cardioversion 3
  • Continue anticoagulation for at least 4 weeks after successful cardioversion 3
  • Long-term anticoagulation decisions should be based on CHA₂DS₂-VASc score, not rhythm status 1

Monitoring and Follow-up

• Warfarin: Monitor INR weekly during initiation, monthly when stable 3, 1
• DOACs: Regular assessment of renal function and medication adherence 1
• All patients: Reevaluate need for anticoagulation at regular intervals 3, 1

Common Pitfalls to Avoid

1. Underuse of anticoagulation in elderly patients - Advanced age increases stroke risk and is not a contraindication 1
2. Discontinuing anticoagulation after cardioversion - Stroke risk is determined by underlying risk factors, not rhythm status 1
3. Delaying anticoagulation unnecessarily in patients with acute AF and high stroke risk 1
4. Using aspirin alone for stroke prevention - Aspirin is substantially less effective than oral anticoagulants and is not recommended as primary therapy 6
5. Failure to adjust DOAC dosing based on patient characteristics (age, weight, renal function) 4