How do you use Oral Anticoagulants (OACs) in patients with Atrial Fibrillation (Afib)?

How to Use Oral Anticoagulants in Atrial Fibrillation

Risk Stratification and Initiation

Oral anticoagulation is recommended for all patients with atrial fibrillation who have a CHA₂DS₂-VASc score ≥2, and should be considered for those with a score of 1. 1

Step 1: Calculate CHA₂DS₂-VASc Score

• Congestive heart failure (1 point) 1
• Hypertension (1 point) 1
• Age ≥75 years (2 points) 1
• Diabetes mellitus (1 point) 1
• Stroke/TIA/thromboembolism history (2 points) 1
• Vascular disease (1 point) 1
• Age 65-74 years (1 point) 1
• Sex category (female) (1 point) 1

Step 2: Apply Treatment Algorithm

• Score 0: No anticoagulation needed 1
• Score 1: Consider oral anticoagulation (Class IIa recommendation) 1
• Score ≥2: Oral anticoagulation recommended (Class I recommendation) 1

Special populations requiring anticoagulation regardless of CHA₂DS₂-VASc score: 1

• Hypertrophic cardiomyopathy with AF 1
• Cardiac amyloidosis with AF 1
• Congenital heart disease with intracardiac repair, cyanosis, Fontan palliation, or systemic right ventricle 1

Choice of Anticoagulant

Direct oral anticoagulants (DOACs) are recommended in preference to vitamin K antagonists (VKAs) in eligible patients with non-valvular atrial fibrillation. 1

DOAC Selection (First-Line Options)

The following DOACs are approved and recommended: 1

• Dabigatran 150 mg twice daily (or 110 mg twice daily in specific populations) 1
• Rivaroxaban 20 mg once daily 1
• Apixaban 5 mg twice daily 1
• Edoxaban 60 mg once daily 2

When to Use VKA Instead of DOAC

VKAs (warfarin) are indicated for: 1, 3

• Mechanical heart valves (DOACs contraindicated) 1
• Moderate-to-severe rheumatic mitral stenosis 1
• Patients with excellent INR control (time in therapeutic range >70%) who are stable on VKA 1
• Patients aged ≥75 years with polypharmacy already stable on VKA (switching may increase bleeding risk) 1

Target INR for VKA: 2.0-3.0 3

Dose Reduction Criteria for DOACs

A reduced dose of DOAC is not recommended unless patients meet DOAC-specific criteria to prevent underdosing and avoidable thromboembolic events. 1

Specific Dose Reduction Criteria (Must Check Renal Function)

All DOACs require dose adjustment based on creatinine clearance: 1

• Dabigatran: Reduce to 110 mg twice daily if CrCl 30-50 mL/min or age ≥80 years 1
• Rivaroxaban: Reduce to 15 mg daily if CrCl 15-49 mL/min 1
• Apixaban: Reduce to 2.5 mg twice daily if ≥2 of: age ≥80 years, weight ≤60 kg, creatinine ≥1.5 mg/dL 1
• Edoxaban: Reduce to 30 mg daily if CrCl 15-50 mL/min or weight ≤60 kg 1

Bleeding Risk Assessment

Assessment and management of modifiable bleeding risk factors is recommended in all patients eligible for oral anticoagulation, but bleeding risk scores should NOT be used to decide whether to start or withhold anticoagulation. 1

HAS-BLED Score (For Identifying High-Risk Patients Needing Closer Monitoring)

• Hypertension (uncontrolled, >160 mmHg systolic) (1 point) 1
• Abnormal renal/liver function (1 point each) 1
• Stroke history (1 point) 1
• Bleeding history or predisposition (1 point) 1
• Labile INR (if on VKA) (1 point) 1
• Elderly (age >65 years) (1 point) 1
• Drugs/alcohol (antiplatelet agents, NSAIDs, alcohol) (1 point each) 1

HAS-BLED ≥3: Schedule more frequent review and follow-up, address modifiable risk factors 1, 4

Cardioversion Management

Therapeutic oral anticoagulation for at least 3 weeks is recommended before scheduled cardioversion, or perform transesophageal echocardiography to exclude thrombus for early cardioversion. 1

Pre-Cardioversion Protocol

• ≥3 weeks therapeutic anticoagulation (INR ≥2.0 for VKA or adherence to DOAC) before cardioversion 1
• OR perform TEE to exclude left atrial thrombus if urgent cardioversion needed 1
• DOACs are preferred over VKAs for cardioversion (Class I recommendation) 1

Post-Cardioversion Protocol

• Continue anticoagulation for at least 4 weeks after cardioversion in all patients 1
• Long-term anticoagulation based on CHA₂DS₂-VASc score, regardless of whether sinus rhythm is maintained 1

Special Clinical Scenarios

AF with Acute Coronary Syndrome or PCI/Stenting

Triple therapy duration should be minimized based on bleeding risk, followed by dual therapy, then OAC monotherapy. 1

Low Bleeding Risk (HAS-BLED 0-2)

• Elective PCI: Triple therapy (OAC + aspirin + clopidogrel) for 1 month → dual therapy (OAC + clopidogrel) until 12 months → OAC monotherapy 1
• ACS: Triple therapy for 6 months → dual therapy until 12 months → OAC monotherapy 1

High Bleeding Risk (HAS-BLED ≥3)

• Elective PCI: Triple therapy for 1 month → dual therapy for 6 months → OAC monotherapy 1
• ACS: Triple therapy for 1-3 months → dual therapy until 12 months → OAC monotherapy 1

Unusually High Bleeding Risk

• Consider OAC + clopidogrel only (no aspirin) for 6-9 months → OAC monotherapy 1

Aspirin dose when used: 75-100 mg daily with proton pump inhibitor 1

AF with Acute Ischemic Stroke

Long-term oral anticoagulation is recommended as secondary prevention, typically started within 2 weeks of acute ischemic stroke. 1

• Do NOT use heparinoids or VKA for very early anticoagulation (<48 hours) due to increased intracranial hemorrhage risk 1
• TIA: Restart anticoagulation after 1 day 1
• Small stroke: Restart after 3 days 1
• Moderate stroke: Restart after 6 days 1
• Large stroke: Wait 2-3 weeks before restarting 1

Surgical Procedures

Interventions at very low bleeding risk can be performed without interrupting anticoagulation. 1

• Low-risk procedures (dental extractions, minor skin procedures): Continue anticoagulation 1
• High-risk procedures: Interrupt anticoagulation with timing based on specific DOAC or VKA pharmacokinetics 1
• For catheter ablation or device implantation: Perform on uninterrupted VKA (therapeutic INR), dabigatran, or rivaroxaban 1

Left Atrial Appendage Occlusion

Surgical LAA closure is recommended as an adjunct to oral anticoagulation in patients undergoing cardiac surgery, but does NOT eliminate the need for long-term anticoagulation based on stroke risk. 1, 4

• Percutaneous LAA occlusion (Watchman device) suggested only for patients with absolute contraindications to OAC 1
• Continue OAC after LAA occlusion based on CHA₂DS₂-VASc score, not procedural success 4

Management of Bleeding on Anticoagulation

Interrupting anticoagulation and performing diagnostic interventions is recommended in patients with active bleeding until the cause is identified and resolved. 1

Bleeding Severity Algorithm

• Minor bleeding: Delay next dose or discontinue temporarily, supportive care 1
• Moderate-severe bleeding: Fluid replacement, blood transfusion, mechanical compression 1
• Life-threatening bleeding: Consider specific antidotes (idarucizumab for dabigatran, andexanet alfa for factor Xa inhibitors), prothrombin complex concentrate, or recombinant factor VIIa 1

Common Pitfalls to Avoid

• Never discontinue anticoagulation based solely on successful rhythm control (ablation, cardioversion) - decision must be based on CHA₂DS₂-VASc score 1, 4
• Never use bleeding risk scores to withhold anticoagulation - use them only to identify patients needing closer monitoring 1
• Never underdose DOACs without meeting specific dose reduction criteria 1
• Never add antiplatelet therapy to OAC for stroke prevention alone (only indicated for concurrent coronary disease) 1
• Never prolong dual antiplatelet therapy beyond 12 months in stable coronary disease patients requiring OAC 4