Prosthetic Heart Valves - A Comprehensive Overview

1. Introduction

2. Classification and Design

A. Mechanical Heart Valves (MHVs)

• Made from pyrolytic carbon - highly durable (>35-45 years freedom from SVD)
• Bileaflet valves have small "washing jets" (normal regurgitation from hinge points) that reduce thrombus formation
• 10-year freedom from valve-related death >90% for St. Jude and Carbomedics bileaflet valves
• All require lifelong anticoagulation with VKA

B. Biological (Bioprosthetic) Heart Valves (BHVs)

• Three biologic leaflets (porcine aortic valve or bovine pericardium) treated with glutaraldehyde to reduce antigenicity, mounted on a metal/polymer stented ring
• Open to a circular orifice in systole, resembling native aortic valve anatomy
• Most treated with anti-calcifying agents
• Examples: Medtronic Mosaic (porcine), Edwards Magna / Carpentier-Edwards Perimount (bovine pericardial)
• The Edwards Inspiris Resilia incorporates newer anti-calcification technology and an expandable sewing ring designed for future valve-in-valve implantation

• No rigid support frame; leaflets mounted directly
• Better hemodynamics (larger effective orifice area), potentially slower SVD
• Example: Medtronic Freestyle (porcine)
• Technically more demanding to implant

• Cadaveric human aortic or pulmonary valves
• Excellent hemodynamics and resistance to endocarditis
• Rarely used due to limited supply; most commonly used for pulmonary valve replacement
• No anticoagulation needed

• Patient's own pulmonary valve translocated to aortic position; pulmonary valve replaced with homograft
• Excellent durability and hemodynamics; grows with patient (ideal for children/young adults)
• Two valves at risk; technically demanding; risk of neoaortic dilation

• Balloon-expandable (e.g., Edwards SAPIEN 3, SAPIEN 3 Ultra)
• Self-expanding (e.g., Medtronic CoreValve Evolut R, Evolut PRO)
• Used for patients at intermediate-to-high surgical risk with aortic stenosis; increasingly used in lower-risk patients
• Sutureless valves (e.g., Sorin Perceval) reduce operative times for surgical implantation

3. Advantages and Disadvantages

4. Choosing a Prosthetic Valve

• No contraindication to long-term anticoagulation (low bleeding risk, good compliance)
• Increased risk of accelerated SVD (age <40, hyperparathyroidism)
• Existing indication for anticoagulation (existing mechanical prosthesis elsewhere, high thromboembolism risk, AF)
• Reasonable life expectancy beyond bioprosthesis durability
• High reoperation risk (porcelain aorta, prior radiation)

• Contraindication to anticoagulation (high bleeding risk, poor compliance)
• Reoperation for mechanical valve thrombosis despite adequate anticoagulation
• Low reoperation risk
• Young women contemplating pregnancy
• Patient preference/lifestyle (e.g., contact sports, occupations with injury risk)
• Life expectancy less than presumed bioprosthesis durability

• ACC/AHA: MHV preferred at age <50 years
• ESC: MHV preferred at age <60 years (aortic), <65 years (mitral)
• The trend toward bioprostheses in younger patients has accelerated due to improved new-generation durability and the availability of transcatheter valve-in-valve procedures for degenerated BHVs

5. Antithrombotic Therapy

Mechanical Heart Valves

• VKA (warfarin) is mandatory lifelong - prevents valve thrombosis and embolic events
• NOACs are contraindicated in patients with MHV (RE-ALIGN trial showed worse outcomes with dabigatran)
• INR monitoring: 2-3x/week when initiating, then at least monthly when stable
• Dedicated anticoagulation clinics improve outcomes vs. standard monitoring

• Mechanical AVR with no risk factors: INR 2.5
• Mechanical AVR with risk factors (AF, prior thromboembolism, LV dysfunction, hypercoagulable state) or older-generation valve: INR 3.0
• Mechanical MVR: INR 3.0
• Aspirin is no longer routinely added to VKA in the absence of other indications

• Minor procedures (dental): continue VKA with therapeutic INR
• Bileaflet mechanical AVR with no thrombosis risk factors: temporary interruption WITHOUT bridging is acceptable
• Bridging anticoagulation (LMWH or UFH) is reasonable for mechanical AVR with thromboembolic risk factors undergoing invasive procedures
• Bridging with UFH is recommended for mechanical MVR undergoing invasive procedures

Biological Heart Valves

• No routine anticoagulation required long-term
• Aspirin 75-100 mg/day is reasonable for all patients with a bioprosthetic aortic or mitral valve (Class IIa)
• Short-term anticoagulation (first 3 months after implantation) with VKA is reasonable in some guidelines for surgical bioprostheses

Transcatheter Heart Valves

• Managed per individual risk-benefit assessment; antiplatelet therapy commonly used

6. Complications

6a. Structural Valve Deterioration (SVD)

• MHVs: SVD is extremely rare with modern valves
• BHVs: Major mode of failure. Caused by leaflet calcification, fibrosis, tears, and perforations (lipid infiltration, inflammation, immune rejection, active mineralization)
• SVD begins within 5-7 years for earlier generations, varies by position and age at implant
• Mitral bioprostheses fail earlier than aortic ones (higher LV closing pressures)
• Process accelerated in: younger patients, disordered calcium metabolism, end-stage renal disease
• Treatment: valve-in-valve TAVR (increasingly preferred over redo surgery in high-risk patients)

6b. Prosthetic Valve Thrombosis (PVT)

• More common with MHVs (subtherapeutic anticoagulation is the main cause)
• Can also occur with transcatheter valves (subclinical leaflet thrombosis detected by CT)
• Diagnosis: echocardiography (TEE preferred), cinefluoroscopy
• Treatment: fibrinolytic therapy (for non-obstructive or high-risk surgery), emergency surgery (for obstructive thrombosis in hemodynamically compromised patients)

6c. Prosthetic Valve Endocarditis (PVE)

• Incidence: 1-6% of patients with valve prostheses
• Associated with poor prognosis
• Similar rates in MHV vs. BHV overall; some data suggest higher early (<1 year) infection with MHV, and higher rates of both early and late PVE with bioprosthetic AVR
• Organisms: Staphylococci (early PVE), Streptococci, Enterococci (late PVE)
• Diagnosis requires careful integration of echocardiography, blood cultures, clinical data (Duke Criteria)
• Management: prolonged IV antibiotics; surgery often needed for complicated cases

6d. Paravalvular Leak (PVL)

• Incomplete seating of the sewing ring leads to regurgitation outside the prosthesis
• Can cause hemolysis and heart failure
• More common after TAVR than surgical valve replacement
• Treatment: redo surgery, catheter-based closure, or medical palliation

6e. Patient-Prosthesis Mismatch (PPM)

• Occurs when the implanted valve is too small for the patient's body size (cardiac output requirements), resulting in abnormally high postoperative gradients
• Defined by indexed Effective Orifice Area (EOAI):
  • Aortic: PPM = EOAI <0.85 cm²/m²; Severe = <0.65 cm²/m²
  • Mitral: PPM = EOAI <1.2 cm²/m²; Severe = <0.5 cm²/m²
  • In obese patients (BMI ≥30): lower cutoffs (severe aortic PPM = <0.55 cm²/m²; severe mitral PPM = <0.75 cm²/m²)
• Prevalence: 20-70% after SAVR and >50% after MVR (moderate PPM); severe PPM 2-20%
• TAVR has lower PPM risk than SAVR, especially with self-expanding supra-annular designs
• Consequences: worse functional class, reduced LV hypertrophy regression, increased heart failure, pulmonary hypertension, and mortality
• Prevention: aortic root enlargement to allow larger prosthesis; use the projected EOAI before surgery
• Treatment options are limited; reintervention only if severe symptoms unresponsive to medical therapy

6f. Hemolysis

• Microangiopathic hemolytic anemia from turbulent blood flow across the prosthesis
• More common with perivalvular leaks; can also occur with normally functioning MHVs
• Markers: elevated LDH, low haptoglobin, schistocytes on blood smear

6g. Pannus Ingrowth

• Fibrous tissue overgrowth from the sewing ring into the orifice of MHVs
• Causes reduced leaflet opening and prosthetic valve obstruction
• Differentiated from thrombus by imaging (CT, TEE) and clinical context

7. Echocardiographic Assessment

• Bileaflet MHVs have normal small "washing jets" - two converging jets at hinge points
• TEE is superior to TTE for evaluating prosthetic valves, particularly mitral prostheses (acoustic shadowing)
• Cinefluoroscopy assesses leaflet motion in MHVs
• CT is increasingly used for subclinical leaflet thrombosis (especially in TAVR) and pre-procedural planning

8. Follow-Up Protocol

• Baseline TTE within 30 days of implantation (establishes reference values)
• Annual clinical evaluation
• Echo when there is a change in symptoms, new murmur, or concerning clinical finding
• For TAVR patients: CT at 1-3 months to screen for subclinical leaflet thrombosis
• Long-term monitoring for SVD, PVL, endocarditis, PPM

9. Special Considerations

Pregnancy

• MHVs pose anticoagulation management challenges during pregnancy
• Warfarin crosses the placenta (teratogenic in 1st trimester, fetal hemorrhage risk)
• LMWH can be used as an alternative but carries higher valve thrombosis risk
• BHV preferred in women of childbearing age; SVD may be accelerated by pregnancy

Infective Endocarditis Prophylaxis

• All prosthetic valve patients require IE prophylaxis (dental, invasive oropharyngeal procedures)

Recent Evidence (PubMed, 2024-2025)

• A 2025 meta-analysis (PMID: 40997282) in Neurology examined the timing of anticoagulation reinitiation after intracranial hemorrhage in patients with mechanical valves - a high-stakes clinical scenario where delaying VKA carries thromboembolism risk but early resumption increases rebleeding risk.
• A 2025 JACC comparative study (PMID: 40139884) compared bioprosthetic vs. mechanical AVR in patients aged 40-75 years, reflecting ongoing refinement of the age cutoffs in guidelines.

• Braunwald's Heart Disease, 2-Vol Set, A Textbook of Cardiovascular Medicine - Chapter 79: Prosthetic Heart Valves
• Fuster and Hurst's The Heart, 15th Edition - Chapter 29
• Textbook of Clinical Echocardiography - Chapter 13
• Washington Manual of Medical Therapeutics