Anticoagulation for Prosthetic Valves with Atrial Fibrillation
For patients with prosthetic valves and atrial fibrillation, warfarin is the mandatory anticoagulant—mechanical valves require lifelong warfarin with INR targets based on valve type and position, while bioprosthetic valves require warfarin indefinitely due to the atrial fibrillation regardless of the initial post-operative period. 1, 2
Mechanical Prosthetic Valves with Atrial Fibrillation
Warfarin is the only acceptable anticoagulant for mechanical valves—DOACs are contraindicated. 1, 2
INR Targets for Mechanical Valves:
Bileaflet valve (e.g., St. Jude Medical) in aortic position: Target INR 2.5 (range 2.0-3.0) 1, 3
Tilting disk valves or bileaflet valves in mitral position: Target INR 3.0 (range 2.5-3.5) 1, 3
Older generation valves (caged ball/caged disk): Target INR 3.0 (range 2.5-3.5) plus aspirin 75-100 mg daily 1, 3
Mechanical valves with additional risk factors (including atrial fibrillation, left ventricular dysfunction, hypercoagulable state, or prior thromboembolism): Consider higher INR target of 3.0 (range 2.5-3.5) 1, 2
Critical Contraindications:
Direct thrombin inhibitors (dabigatran) are absolutely contraindicated in mechanical valves (Class III: Harm), based on the RE-ALIGN trial showing increased thromboembolic and bleeding complications leading to early termination. 1, 2, 4
Factor Xa inhibitors (rivaroxaban, apixaban, edoxaban) have not been assessed and are not recommended (Class III: Harm) for mechanical valves. 1, 2
Bioprosthetic Valves with Atrial Fibrillation
The presence of atrial fibrillation mandates indefinite warfarin therapy regardless of valve position or time since surgery. 5, 6, 3
INR Target:
- Warfarin with target INR 2.5 (range 2.0-3.0) for all bioprosthetic valves when atrial fibrillation is present 1, 5, 6
Rationale:
Atrial fibrillation is the most common reason patients continue warfarin beyond the initial 3-6 month post-operative period. 5 The American College of Cardiology provides a Grade 1C recommendation for indefinite warfarin in patients with bioprosthetic valves and atrial fibrillation. 5
DOAC Consideration for Bioprosthetic Valves:
DOACs are NOT routinely recommended for bioprosthetic valves, even with atrial fibrillation, due to harm demonstrated in the GALILEO trial and lack of robust supporting evidence. 5 While DOACs are approved for non-valvular atrial fibrillation, the 2019 AHA/ACC/HRS guidelines exclude patients with moderate-to-severe mitral stenosis or mechanical valves from DOAC use. 1 The evidence base for DOACs in bioprosthetic valves with atrial fibrillation remains insufficient, making warfarin the safer choice. 5
Monitoring Requirements
- INR should be checked at least weekly during warfarin initiation 1
- INR should be checked at least monthly when stable and therapeutic 1, 6
- Regular reassessment of stroke and bleeding risks is essential 1
Aspirin Addition
Consider adding low-dose aspirin (75-100 mg daily) to warfarin in mechanical valve patients at low bleeding risk, particularly those with older generation valves or additional thromboembolic risk factors. 1, 2, 3 For bioprosthetic valves with atrial fibrillation on warfarin, aspirin addition may be considered but increases bleeding risk. 1, 5
Common Pitfalls to Avoid
Never use dabigatran in any patient with a mechanical valve—this is a Class III: Harm recommendation with strong evidence from the RE-ALIGN trial. 1, 4
Do not assume DOACs are equivalent to warfarin for bioprosthetic valves—the evidence does not support this substitution despite their approval for non-valvular atrial fibrillation. 5
Do not target lower INR ranges in mechanical valves with atrial fibrillation—the presence of AF is an additional risk factor warranting standard or higher intensity anticoagulation. 1, 2
Avoid interrupting anticoagulation without bridging in mechanical valve patients—these patients require unfractionated or low-molecular-weight heparin bridging for procedures. 1