Anticoagulation for Valvular Atrial Fibrillation
For patients with valvular atrial fibrillation—defined as AF with moderate-to-severe mitral stenosis or a mechanical prosthetic heart valve—warfarin is the only recommended anticoagulant, and direct oral anticoagulants (DOACs) are absolutely contraindicated. 1, 2
Defining Valvular AF: The Critical First Step
The term "valvular AF" has a precise definition that determines your entire treatment approach:
Valvular AF includes ONLY: 1, 2
- Moderate-to-severe rheumatic mitral stenosis (of any degree requiring potential surgical intervention)
- Mechanical prosthetic heart valves
Valvular AF does NOT include: 1, 3
- Mild mitral stenosis
- Mitral regurgitation
- Aortic stenosis or regurgitation
- Bioprosthetic valves
- Mitral valve repair or annuloplasty rings
- Tricuspid regurgitation
This distinction is critical because DOACs were studied in patients with these "non-valvular" lesions and showed efficacy, but they have never been proven safe in true valvular AF. 1
Warfarin Dosing and Target INR
For mitral stenosis with AF: 2, 4, 5
- Target INR: 2.0-3.0
- This applies to any degree of mitral stenosis, even if mild 4
For mechanical prosthetic valves with AF: 5, 6
- St. Jude Medical bileaflet valve in aortic position: Target INR 2.0-3.0
- Tilting disk or bileaflet valves in mitral position: Target INR 2.5-3.5
- Caged ball or caged disk valves: Target INR 2.5-3.5 plus aspirin 75-100 mg daily
INR Monitoring Requirements
The monitoring schedule is non-negotiable for patient safety: 1, 2
- During warfarin initiation: Check INR at least weekly
- Once stable in therapeutic range: Check INR at least monthly
- If time in therapeutic range (TTR) falls below 65-70%: Increase monitoring frequency, review medication adherence, address factors affecting INR control, and provide education/counseling 1
Why DOACs Are Absolutely Contraindicated
DOACs (dabigatran, rivaroxaban, apixaban, edoxaban) must never be used in valvular AF because: 2, 4
- All major DOAC trials explicitly excluded patients with moderate-to-severe mitral stenosis and mechanical valves
- The RE-ALIGN trial of dabigatran in mechanical valves was terminated early due to increased thrombotic and bleeding events
- There is zero safety or efficacy data supporting DOAC use in this population
This is an absolute contraindication—not a relative one. Even if a patient has difficulty maintaining therapeutic INR on warfarin, switching to a DOAC is not an option. 2, 4
Special Cardioversion Considerations
For patients with valvular AF requiring cardioversion: 1, 2, 6
- Maintain therapeutic anticoagulation (INR 2.0-3.0) for ≥3 weeks before elective cardioversion
- Continue anticoagulation for ≥4 weeks after successful cardioversion
- Long-term anticoagulation continues indefinitely based on the underlying valvular pathology—not on whether cardioversion was successful 2
Common Pitfalls to Avoid
Never use DOACs in any patient with mitral stenosis (even mild) or mechanical valves—this is the single most dangerous error in valvular AF management. 2, 4
Do not substitute aspirin alone or aspirin-clopidogrel for warfarin in high-risk valvular AF patients, as anticoagulation is vastly superior for stroke prevention. 4, 6
Do not stop anticoagulation based on AF pattern—the thromboembolic risk is identical whether AF is paroxysmal, persistent, or permanent. 2, 4
Do not underdose warfarin due to bleeding concerns in elderly patients—while bleeding risk increases with age, stroke risk increases even more, making anticoagulation particularly beneficial in patients ≥75 years. 2
Managing Suboptimal INR Control
If TTR is consistently <65-70%, implement these measures rather than abandoning warfarin: 1
- Increase INR testing frequency
- Conduct structured medication adherence review
- Identify and address dietary vitamin K intake, drug interactions, and alcohol use
- Provide intensive patient education and counseling
- Consider using the SAMe-TT₂R₂ score to identify patients needing more intensive management 1