What are the guidelines for anticoagulant therapy in patients with non-valvular atrial fibrillation (AFib)?

Anticoagulation Guidelines for Non-Valvular Atrial Fibrillation

For patients with non-valvular atrial fibrillation, use the CHA₂DS₂-VASc score to determine anticoagulation need: oral anticoagulation is recommended for scores ≥2, reasonable to omit for score 0, and individualized for score 1. 1

Risk Stratification Algorithm

Step 1: Calculate CHA₂DS₂-VASc Score 1

The score includes:

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

Step 2: Apply Treatment Based on Score 1

CHA₂DS₂-VASc Score ≥2 (Class I Recommendation)

Oral anticoagulation is mandatory. 1 Options include:

• Direct oral anticoagulants (DOACs): Apixaban, dabigatran, or rivaroxaban (Level of Evidence: B) 1
• Warfarin: Target INR 2.0-3.0 (Level of Evidence: A) 1, 2

DOACs are preferred over warfarin as first-line therapy due to superior safety profiles and at least equivalent efficacy. 3

CHA₂DS₂-VASc Score = 0 (Class IIa Recommendation)

Omit antithrombotic therapy. 1 This applies to patients <65 years with lone AF and no other risk factors.

CHA₂DS₂-VASc Score = 1 (Class IIb Recommendation)

Either no therapy, oral anticoagulation, or aspirin may be considered. 1 The 2019 ESC Working Group opinion suggests that OAC should be considered for most patients with a score of 1, as the thromboembolic event rate approaches 1% per year, which justifies anticoagulation. 1

Anticoagulant Selection and Dosing

DOAC Options (Preferred) 1, 3

For normal renal function:

• Apixaban: 5 mg twice daily 1
• Dabigatran: 150 mg twice daily 1
• Rivaroxaban: 20 mg once daily with evening meal 1

Warfarin Dosing 1, 2

Target INR 2.0-3.0 (target 2.5). 1, 2 Monitor INR weekly during initiation, then monthly when stable. 1

When to Choose Warfarin Over DOACs 1

• End-stage chronic kidney disease (CrCl <15 mL/min) or hemodialysis (Class IIa) 1
• Inability to maintain therapeutic INR with warfarin: Switch to DOAC (dabigatran, rivaroxaban, or apixaban) 1

Special Populations and Critical Caveats

Chronic Kidney Disease 1

Moderate-to-severe CKD with CHA₂DS₂-VASc ≥2:

• Reduced-dose DOACs may be considered, but safety/efficacy not fully established (Class IIb) 1

End-stage CKD or dialysis:

• Warfarin is reasonable (INR 2.0-3.0) 1
• Dabigatran and rivaroxaban are NOT recommended due to lack of clinical trial evidence (Class III: No Benefit) 1

Renal function monitoring is mandatory: Evaluate before initiating DOACs and reassess at least annually. 3

Mechanical Heart Valves (Class III: Harm) 1

Dabigatran must NOT be used in patients with mechanical heart valves. 1 Warfarin is required with target INR based on valve type and position (2.0-3.0 for aortic, 2.5-3.5 for mitral). 1, 2

Prior Stroke or TIA 1

Oral anticoagulation is mandatory regardless of CHA₂DS₂-VASc score. 1 These patients have already demonstrated thromboembolic risk.

Pattern of Atrial Fibrillation Does Not Matter

Anticoagulation decisions are identical whether AF is paroxysmal, persistent, or permanent. 1 The stroke risk is equivalent across all patterns, and treatment should be based solely on the CHA₂DS₂-VASc score. 1

Atrial flutter requires identical anticoagulation management as atrial fibrillation. 1, 3

Ongoing Management Requirements

Monitoring and Reassessment 1, 3

• Periodic reevaluation of stroke and bleeding risks is required (Class I) 1
• Renal function monitoring at least annually for DOAC patients 3
• INR monitoring weekly during warfarin initiation, then monthly when stable 1

Bridging for Procedures 1

Without mechanical valves:

• Balance stroke and bleeding risks when deciding on bridging with LMWH or UFH 1
• Many procedures (pacemaker implantation, catheter ablation) can be performed without interrupting warfarin 1

With mechanical valves:

• Bridging with UFH or LMWH is recommended when warfarin must be interrupted 1

Common Pitfalls to Avoid

Do not use aspirin as monotherapy for stroke prevention in AF with elevated CHA₂DS₂-VASc scores. 1 While older guidelines mentioned aspirin as an option for score of 1, current evidence shows oral anticoagulation is far superior. 1

Do not withhold anticoagulation based on bleeding risk alone. 1 The decision should balance absolute risks of stroke versus bleeding, but high CHA₂DS₂-VASc scores generally favor anticoagulation. 1

Do not prescribe dabigatran or rivaroxaban for dialysis patients. 1 Use warfarin instead.

Do not forget that female sex alone (score of 1) does not mandate anticoagulation - women require additional risk factors beyond sex to reach the treatment threshold. 1