What is the recommended anticoagulant therapy for patients with atrial fibrillation (AF) and a high risk of stroke?

Anticoagulation Therapy for Atrial Fibrillation

For patients with atrial fibrillation, oral anticoagulation should be prescribed for those with one or more non-sex CHA₂DS₂-VASc stroke risk factors, with direct oral anticoagulants (DOACs) preferred over warfarin in eligible patients. 1, 2

Risk Assessment and Initial Decision-Making

• Use the CHA₂DS₂-VASc score for stroke risk stratification, which includes congestive heart failure, hypertension, age ≥75 years (doubled), diabetes mellitus, prior stroke/TIA (doubled), vascular disease, age 65-74, and sex category 1, 2
• No antithrombotic therapy is recommended for patients at low risk (CHA₂DS₂-VASc score = 0 in males, 1 in females) 1, 2
• Oral anticoagulation is recommended for patients with intermediate risk (CHA₂DS₂-VASc score = 1 in males) and high risk (CHA₂DS₂-VASc score ≥ 2) 1, 2
• Bleeding risk assessment should be performed for all patients with AF at every patient contact, focusing on potentially modifiable risk factors 1, 2

Choice of Anticoagulant

• DOACs (apixaban, dabigatran, rivaroxaban, edoxaban) are preferred over warfarin for non-valvular atrial fibrillation 2
• Dabigatran 150 mg twice daily is suggested over adjusted-dose vitamin K antagonist therapy 2, 3
• DOACs have demonstrated a lower risk of intracranial hemorrhage compared to warfarin 2
• For patients with mitral stenosis or mechanical heart valves, adjusted-dose warfarin is recommended with a target INR of 2.5 (range 2.0-3.0) 2, 4

Special Considerations

• DOACs require dose adjustment based on renal function:
  • For dabigatran, reduce dose to 75 mg twice daily when dronedarone or systemic ketoconazole is co-administered in patients with moderate renal impairment (CrCl 30-50 mL/min) 3
  • Avoid dabigatran in patients with severe renal impairment (CrCl 15-30 mL/min) when used with P-gp inhibitors 3
• Warfarin is preferred for patients on dialysis 2
• DOACs are not recommended for patients with triple-positive antiphospholipid syndrome (positive for lupus anticoagulant, anticardiolipin, and anti-beta 2-glycoprotein I antibodies) 3

Common Pitfalls to Avoid

• Using antiplatelet therapy alone when oral anticoagulation is indicated - antiplatelet therapy provides only modest protection (22% risk reduction) compared to oral anticoagulation (62% risk reduction) 2, 5
• Discontinuing anticoagulation after cardioversion or ablation in patients with ongoing stroke risk factors 2
• Overestimating bleeding risk leading to inappropriate withholding of anticoagulation 2
• Inadequate INR control (target 2.0-3.0) when using warfarin, which reduces both safety and effectiveness 2, 4

Monitoring and Follow-up

• For patients on warfarin, maintain INR between 2.0-3.0 for non-valvular AF 4
• For patients with mechanical heart valves, target INR depends on valve type and position:
  • For St. Jude Medical bileaflet valve in aortic position: target INR 2.5 (range 2.0-3.0) 4
  • For tilting disk valves and bileaflet valves in mitral position: target INR 3.0 (range 2.5-3.5) 4
• Regular assessment of bleeding risk using validated tools like HAS-BLED (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history, Labile INR, Elderly, Drugs/alcohol) 6, 7
• A HAS-BLED score ≥3 indicates high bleeding risk requiring careful monitoring, but does not contraindicate anticoagulation 7