What are the types of valves used for mitral valve replacement?

Types of Mitral Valve Prostheses for Replacement

Mitral valve replacement involves choosing between mechanical valves and bioprosthetic valves, with the decision based primarily on patient age, comorbidities, and preferences regarding anticoagulation and potential reoperation.

Mechanical Valves

• Three main types of mechanical valves are available for mitral valve replacement: ball-and-cage valves, single-tilting disc valves, and bileaflet prostheses 1
• Ball-and-cage valves have been effective but can cause some degree of left ventricular outflow tract obstruction by projecting into it, a problem not present with bileaflet or disc valves 1
• Mechanical valves require lifelong anticoagulation with vitamin K antagonists (VKA) maintained at an INR of 2.5 to 3.5 indefinitely 1
• Mechanical valves are associated with higher risk of bleeding (21% greater risk) and stroke/systemic embolism (20% greater risk) compared to bioprosthetic valves 2
• Mechanical valves demonstrate superior long-term durability with 66% lower risk of mitral reoperation compared to bioprosthetic valves 2

Bioprosthetic Valves

• Two main types of bioprosthetic valves are available: porcine heterografts and bovine pericardial heterografts 1
• Second-generation porcine heterografts and bovine pericardial valves show a slower rate of structural valve deterioration compared to earlier versions 1
• Bioprosthetic valves have a higher failure rate in the mitral position compared to the aortic position (50% vs 29% needing reoperation by 15 years) 1
• Bioprosthetic valves typically do not require long-term anticoagulation unless other risk factors are present (atrial fibrillation, LV dysfunction, hypercoagulable condition, or previous thromboembolism) 1
• Newer-generation bioprosthetic valves have improved durability and can potentially undergo valve-in-valve transcatheter procedures when valve failure occurs 1

Age-Based Recommendations

• The American College of Cardiology/American Heart Association (ACC/AHA) recommends mechanical valves for mitral valve replacement in patients under 65 years of age with long-standing atrial fibrillation 1
• A bioprosthesis is recommended for mitral valve replacement in patients 65 years of age or older 1
• The European Society of Cardiology (ESC) recommends mechanical valves for patients <65 years for mitral position, while ACC/AHA uses a lower age cutoff of 50 years 1
• Recent evidence shows mechanical valves confer significantly better long-term survival and freedom from reintervention for patients <65 years, while no benefit is observed at age 65-75 years compared to bioprosthetic valves 3

Special Considerations

• A bioprosthesis is indicated for mitral valve replacement in patients who cannot or will not take warfarin, or who have clear contraindications to warfarin therapy 1
• Mechanical valves should be considered for patients who already have a mechanical valve in another position (aortic or tricuspid) 1
• For patients with end-stage renal failure, especially those undergoing chronic dialysis, mechanical prostheses are recommended due to accelerated calcification of bioprosthetic valves 1
• In cases of prosthetic valve endocarditis, homografts or stentless xenografts may be preferred for extensive annular destruction 4

Decision-Making Process

• The choice of valve prosthesis should be a shared decision-making process accounting for patient values and preferences 1
• Discussion should include the trade-off between potential need for reintervention with bioprosthetic valves versus risks associated with long-term anticoagulation with mechanical valves 1
• Some patients prefer to avoid repeat surgery and accept the risks of lifelong anticoagulant therapy, while others are unwilling to consider long-term VKA therapy due to lifestyle considerations 1
• The potential for valve-in-valve transcatheter procedures for failed bioprosthetic valves should be considered, though long-term follow-up data is still limited 1

Outcomes and Mortality

• Mechanical mitral valves are associated with 16% lower risk of long-term mortality compared to bioprosthetic valves in matched/adjusted studies 2
• In patients under 70 years, mechanical valves demonstrate better long-term survival compared to bioprosthetic valves 5
• The 10-year survival rate for patients <65 years is superior with mechanical valves versus bioprosthetic valves (78.2% vs 69.8%) 3
• For patients between 65-75 years, there are no significant differences between mechanical and bioprosthetic valves in 10-year survival (64.6% vs 60.8%) 3

Common Pitfalls and Caveats

• Choosing a bioprosthetic valve for younger patients (<65 years) significantly increases reoperation risk and decreases long-term survival 3
• Mechanical valves require careful monitoring of anticoagulation to balance the risks of thromboembolism and bleeding 1
• The durability of bioprosthetic valves is significantly worse in the mitral position compared to the aortic position 1
• Not all bioprosthetic valves, particularly smaller-sized valves, will be suitable for future valve-in-valve procedures 1
• Early routine surveillance echocardiography is important for certain types of prostheses (e.g., Mitroflow) known to be associated with early structural deterioration 1