Medtronic Evolution FX+ Aortic Valve Anticoagulation Requirements
The Medtronic Evolution FX+ is a bioprosthetic (tissue) valve, NOT a mechanical valve, and therefore does NOT require lifelong anticoagulation. 1
Immediate Post-Implantation Period (First 3-6 Months)
Anticoagulation with warfarin (INR target 2.5, range 2.0-3.0) is reasonable for at least 3 months and potentially up to 6 months after bioprosthetic aortic valve replacement in patients at low bleeding risk. 1
- The highest thromboembolic risk occurs within the first 90-180 days post-implantation, before complete endothelialization of the valve. 1
- A large Danish registry demonstrated significantly lower stroke rates with warfarin during this period (2.69 vs 7.00 per 100 person-years) without significantly increased bleeding risk. 1
- This recommendation applies to patients in sinus rhythm without additional risk factors. 1
Long-Term Management (After 3-6 Months)
After the initial 3-6 month period, aspirin 75-100 mg daily alone is recommended for long-term therapy. 1
- Patients with bioprosthetic aortic valves in sinus rhythm have an annual thromboembolic risk of approximately 0.7% per year on aspirin alone. 1
- This is substantially lower than the 8.6 per 100 patient-years risk seen with mechanical valves without anticoagulation. 1
Special Circumstances Requiring Continued Anticoagulation
Warfarin (INR 2.0-3.0) should be continued indefinitely if the patient has additional risk factors: 1
- Atrial fibrillation
- Previous thromboembolic events (stroke or TIA)
- Left ventricular dysfunction
- Hypercoagulable conditions
Critical Distinction: Mechanical vs Bioprosthetic Valves
The Medtronic Evolution FX+ must not be confused with mechanical valves (such as the Medtronic Hall mechanical valve), which DO require lifelong warfarin anticoagulation. 1
- Mechanical valves (bileaflet, tilting disk): Lifelong warfarin with INR 2.5 (range 2.0-3.0) for aortic position. 1
- Bioprosthetic valves (like Evolution FX+): Short-term warfarin (3-6 months), then aspirin only. 1
Common Pitfalls to Avoid
- Do not prescribe lifelong anticoagulation for bioprosthetic valves without specific additional indications. 1
- Do not use direct oral anticoagulants (DOACs) as they are not indicated for prosthetic valves of any type. 1
- Do not omit the initial 3-6 month anticoagulation period in appropriate candidates, as this is when thromboembolic risk is highest. 1