Anticoagulation for Valvular Atrial Fibrillation
For patients with valvular atrial fibrillation—defined as AF with moderate-to-severe rheumatic mitral stenosis or mechanical prosthetic heart valves—warfarin is the only recommended anticoagulant, with a target INR of 2.0-3.0 for mitral stenosis and 2.5-3.5 for mechanical valves depending on valve type and position. 1, 2
Defining Valvular AF
The critical first step is correctly identifying what constitutes "valvular" AF, as this determines whether direct oral anticoagulants (DOACs) can be used:
- "Valvular AF" refers exclusively to patients with moderate-to-severe rheumatic mitral stenosis or mechanical prosthetic heart valves. 1, 3
- All other valve conditions—including mitral regurgitation, aortic stenosis, aortic insufficiency, and bioprosthetic valves—are classified as "non-valvular AF" and can be treated with DOACs. 3
- DOACs are absolutely contraindicated in patients with mitral stenosis or mechanical valves due to lack of safety and efficacy data. 1
Anticoagulation Algorithm for Valvular AF
For Rheumatic Mitral Stenosis with AF:
- Warfarin with target INR 2.0-3.0 is mandatory. 4, 1, 2
- Never substitute aspirin alone or aspirin-clopidogrel combination, as warfarin is vastly superior for stroke prevention in this high-risk population. 1
- DOACs (dabigatran, rivaroxaban, apixaban, edoxaban) must never be used, even if stenosis is mild. 1
For Mechanical Prosthetic Valves with AF:
- Warfarin is the only acceptable anticoagulant. 4, 2
- Target INR depends on valve type and position: 4, 2
- St. Jude Medical bileaflet valve in aortic position: INR 2.5 (range 2.0-3.0)
- Tilting disk or bileaflet valves in mitral position: INR 3.0 (range 2.5-3.5)
- Caged ball or caged disk valves: INR 3.0 (range 2.5-3.5) plus aspirin 75-100 mg daily
- The higher target INR for mitral position valves reflects the greater thrombogenic risk compared to aortic position. 2
For Bioprosthetic Valves with AF:
- Warfarin with target INR 2.5 (range 2.0-3.0) is recommended for the first 3 months after valve insertion. 2
- After 3 months, patients can be transitioned to DOACs using the same risk stratification as non-valvular AF, as bioprosthetic valves do not carry the same thrombogenic risk as mechanical valves. 5, 3
Monitoring Requirements
- INR must be checked at least weekly during warfarin initiation. 4, 1, 2
- Once stable in therapeutic range, check INR monthly. 4, 1, 2
- The risk of thromboembolism is identical whether AF is paroxysmal, persistent, or permanent—all patterns require the same anticoagulation intensity. 4, 1
Critical Pitfalls to Avoid
- Never use DOACs in patients with any degree of mitral stenosis or mechanical valves—this is an absolute contraindication that applies even to mild stenosis. 1
- Do not underdose warfarin due to bleeding concerns in high-risk patients, as inadequate anticoagulation dramatically increases stroke risk. 4, 1
- Avoid confusing "valvular AF" with "AF in the presence of any valve disease"—only mitral stenosis and mechanical valves require warfarin; other valve diseases can use DOACs. 3
- Do not substitute aspirin alone for warfarin in patients with valvular AF, as anticoagulation reduces stroke risk by 39% compared to antiplatelet therapy. 6, 1
- INR targets above 4.0 provide no additional benefit and significantly increase bleeding risk. 2
Special Considerations
- For patients requiring cardioversion, maintain therapeutic anticoagulation for ≥3 weeks before and ≥4 weeks after the procedure. 6
- Elderly patients (≥75 years) with valvular AF have higher bleeding risk but also higher stroke risk, making anticoagulation particularly beneficial despite age. 4, 6
- Patients with prior stroke or TIA are at highest risk and derive the greatest benefit from anticoagulation. 4, 6
- For procedures with bleeding risk, warfarin can be interrupted for up to 1 week without bridging heparin in patients without mechanical valves or high thromboembolism risk. 4