Is a 29 mm Edwards Mitral Valve a Mechanical Valve?
No, a 29 mm Edwards mitral valve is a bioprosthetic (tissue) valve, not a mechanical valve. Edwards manufactures the Carpentier-Edwards Perimount series, which consists of stented bioprosthetic valves made from bovine pericardium mounted on a stent frame 1.
Valve Classification and Material Composition
Edwards Bioprosthetic Valves
- The Carpentier-Edwards Perimount is a stented bioprosthetic valve that uses bovine pericardium cut and sewn to stent posts, available in mitral sizes including 25 mm, 27 mm, and 29 mm 1.
- The normal effective orifice area (EOA) for a 29 mm Carpentier-Edwards Perimount mitral valve is 2.1 ± 0.5 cm² 1.
- Edwards also manufactures the SAPIEN transcatheter valves, which utilize bovine pericardium leaflets mounted on stainless steel or cobalt-chromium alloy frames 2.
Mechanical Valves in the Mitral Position
- Mechanical mitral valves are manufactured by different companies, primarily St. Jude Medical (Standard and Regent models) and MCRI On-X 1.
- For comparison, a 29 mm St. Jude Medical Standard mechanical mitral valve has an EOA of 1.8 ± 0.4 cm², while the MCRI On-X 29 mm has an EOA of 2.2 ± 0.9 cm² 1.
- Mechanical valves require lifelong anticoagulation with warfarin to prevent thrombosis 3, 4.
Clinical Implications of Valve Type
Bioprosthetic Valve Characteristics
- Bioprosthetic valves do not require long-term anticoagulation beyond the initial 3-6 months post-implantation, reducing bleeding risk compared to mechanical valves 5, 6.
- The primary disadvantage is structural valve deterioration requiring reoperation, with the reoperation hazard increasing progressively after 7 years for mitral tissue valves 5.
- All bioprosthetic tissues undergo glutaraldehyde fixation, which eliminates the need for immunosuppression 2.
Mechanical Valve Characteristics
- Mechanical valves have superior durability with lower reoperation rates (66% lower risk) compared to bioprosthetic valves 6.
- However, mechanical valves carry a 20-21% greater risk of major bleeding events and stroke/systemic embolism due to mandatory anticoagulation 6, 7.
- In patients under 65 years, mechanical mitral valve replacement demonstrates longer estimated survival (13.5 vs 11.3 years) compared to bioprosthetic valves 7.
Common Pitfall to Avoid
Do not confuse valve size with valve type. The 29 mm designation refers only to the labeled size of the prosthesis and cannot be used to determine whether a valve is mechanical or bioprosthetic 1. Both mechanical and bioprosthetic valves are available in 29 mm sizes for mitral position, but they are manufactured by different companies with distinct materials and hemodynamic profiles 1.