Residency · Residency · Cardiology

Prosthetic Valve Management

Prosthetic Valve Types

Mechanical Valves

Bileaflet tilting disc valves, including the St. Jude Medical and On-X designs, feature two semicircular occluders and represent the most commonly implanted mechanical valve type, offering low profile and excellent hemodynamics. Single tilting disc valves such as the Medtronic-Hall and Bjork-Shiley are largely historical, featuring a single disc with eccentric pivot and higher thrombogenicity than bileaflet designs. Caged-ball valves, exemplified by the Starr-Edwards design, are obsolete but still occasionally encountered in elderly patients, characterized by high profile and obstructive hemodynamics. The primary advantage of mechanical valves is virtually unlimited durability without structural degeneration. Their disadvantages include the requirement for lifelong anticoagulation with warfarin, a thromboembolic risk of 1 to 2% per year despite anticoagulation, mechanical hemolysis, and audible clicks that may affect patient quality of life. The On-X valve is unique in having evidence supporting a lower INR target of 1.5 to 2.0 in the aortic position after 3 months, per the PROACT trial, when combined with aspirin.

Bioprosthetic Valves

Stented pericardial valves, including the Edwards Perimount and Magna Ease constructed from bovine pericardium mounted on a stent frame, represent the most commonly used surgical bioprostheses. Stented porcine valves such as the Medtronic Hancock and Mosaic use intact porcine aortic valves mounted on stents. Stentless valves including the Medtronic Freestyle and Toronto SPV offer better hemodynamics through larger effective orifice but require more complex implantation. The advantages of bioprosthetic valves include the avoidance of long-term anticoagulation, with aspirin alone after an initial 3 to 6-month period, and lower thromboembolic risk. Their primary disadvantage is structural valve degeneration over time, with 10-year freedom from degeneration of approximately 85 to 90% in the aortic position and 70 to 80% in the mitral position. Degeneration occurs faster in younger patients under 50, those with renal failure, hyperparathyroidism, and during pregnancy.

Transcatheter Heart Valves

Balloon-expandable valves, including the Edwards SAPIEN 3 and Ultra constructed from bovine pericardium in a cobalt-chromium frame, are used primarily in the aortic position. Self-expanding valves, including the Medtronic Evolut R and PRO+ constructed from porcine pericardium in a nitinol frame, are also used primarily for aortic applications. Transcatheter mitral valve replacement remains largely investigational, though valve-in-valve, valve-in-ring, and valve-in-MAC procedures are currently available. Durability data at 5 years are comparable to surgical bioprostheses, with 10-year data still emerging. Subclinical leaflet thrombosis, detected as hypoattenuating leaflet thickening on 4D CT, occurs in 10 to 15% of cases.

Valve Selection: Shared Decision-Making

Factors Favoring Mechanical Valve

Mechanical valves are favored in patients under 50 years of age who face the longest exposure to structural valve degeneration risk, patients already requiring lifelong anticoagulation for conditions such as atrial fibrillation, prior venous thromboembolism, or hypercoagulable states, those with reliable anticoagulation compliance and access to monitoring, patients desiring to avoid reintervention, and those with renal failure on dialysis in whom bioprosthetic degeneration is accelerated.

Factors Favoring Bioprosthetic Valve

Bioprosthetic valves are favored in patients over 65 years of age in whom structural valve degeneration risk is lower within expected lifespan and the valve-in-valve TAVR option exists for future degeneration, those with contraindications or inability to take warfarin, patients desiring freedom from anticoagulation monitoring, women desiring future pregnancy given the teratogenic effects of warfarin, those with active lifestyles carrying high bleeding risk, and patients with limited life expectancy from comorbidities.

Current Guideline Recommendations (2020 ACC/AHA)

The 2020 guidelines indicate that mechanical valves are reasonable in patients under 50 for AVR or MVR who can maintain therapeutic anticoagulation, while bioprosthetic valves are reasonable in patients over 65 for AVR or at any age when anticoagulation cannot be taken. For patients aged 50 to 65, shared decision-making is appropriate with either valve type acceptable, requiring thorough discussion of the trade-offs between anticoagulation and potential reintervention.

Antithrombotic Management

Mechanical Valves

Warfarin is mandatory and lifelong for all mechanical valves. Direct oral anticoagulants are absolutely contraindicated, as demonstrated by the RE-ALIGN trial in which dabigatran caused excess thromboembolic and bleeding events in mechanical valve recipients, leading to early trial termination. This contraindication applies to all DOACs. INR targets are position-dependent: for aortic bileaflet or On-X valves in low-risk patients the target is 2.0 to 3.0, with the On-X valve uniquely permitting a target of 1.5 to 2.0 after 3 months per PROACT trial data. Aortic bileaflet valves with additional risk factors including atrial fibrillation, prior thromboembolism, left ventricular dysfunction, or hypercoagulable states require an INR target of 2.5 to 3.5. All mitral mechanical valves regardless of type require an INR target of 2.5 to 3.5 because the mitral position carries inherently higher thrombotic risk, and double mechanical valves similarly require 2.5 to 3.5. Aspirin at 75 to 100 mg daily is added to warfarin for all mechanical valves, as this combination reduces thromboembolic events and mortality at the cost of a slight increase in bleeding. INR monitoring should occur at least monthly when stable, with more frequent assessment during medication changes, illness, or dietary changes.

Bioprosthetic Valves

For surgical bioprostheses, aspirin at 75 to 100 mg daily is prescribed lifelong. Warfarin with an INR target of 2.0 to 3.0 for the first 3 to 6 months post-surgery is a Class IIa recommendation, after which aspirin alone is continued. For TAVR, the POPular-TAVI trial established aspirin monotherapy as the standard. If atrial fibrillation is present, a DOAC alone without additional antiplatelet therapy is recommended per ENVISAGE-TAVI AF data. If atrial fibrillation develops in any patient with a bioprosthetic valve, either a DOAC or warfarin is appropriate.

Bridging Anticoagulation

For high-risk patients for thromboembolism, including those with mechanical mitral valves, recent thromboembolism, or older-generation mechanical aortic valves with atrial fibrillation, bridging with therapeutic-dose LMWH or unfractionated heparin is indicated when the INR falls below 2.0, with warfarin resumed post-procedure. For lower-risk patients with bileaflet aortic mechanical valves without additional risk factors, bridging may be omitted for minor procedures, with low-risk bridging for major procedures. Warfarin is stopped 3 to 5 days before procedures targeting an INR below 1.5, restarted the evening of the procedure day if hemostasis is adequate, and bridging continues until the INR becomes therapeutic.

Management of Supratherapeutic INR

For INR of 3.0 to 5.0 in asymptomatic patients, holding 1 to 2 warfarin doses and resuming at a lower dose is sufficient without vitamin K. For INR of 5.0 to 9.0 without bleeding, warfarin is held with consideration of low-dose vitamin K at 1 to 2.5 mg orally if bleeding risk is high, but excessive vitamin K must be avoided in mechanical valve patients due to the risk of valve thrombosis. For INR above 9.0 or major bleeding, IV vitamin K at 5 to 10 mg is administered, with 4-factor prothrombin complex concentrate for life-threatening bleeding, and warfarin is restarted carefully once stable.

<image> A detailed comparison table illustration of mechanical versus bioprosthetic valve characteristics. Two columns with icons. Left column "Mechanical Valve" with an image of a bileaflet mechanical valve (two semicircular carbon leaflets in open position): Durability: unlimited (star rating 5/5); Anticoagulation: lifelong warfarin required (red warning icon); INR target aortic: 2.0-3.0, mitral: 2.5-3.5; TE risk: 1-2%/year on warfarin; Bleeding risk: 1-2%/year on warfarin; Hemolysis: mild chronic (small red cell fragments icon); Best for: age <50, reliable anticoagulation, already on warfarin. Right column "Bioprosthetic Valve" with an image of a stented pericardial valve (three leaflets within a fabric-covered stent): Durability: 10-20 years (degrades faster if younger, star rating 3/5); Anticoagulation: aspirin only long-term (green checkmark); SVD rate: 15-30% at 15 years; TE risk: lower than mechanical; Reoperation risk: 15-25% at 15 years; Valve-in-valve: option for future degeneration; Best for: age >65, anticoagulation contraindication, pregnancy desire. Bottom comparison bar showing age spectrum: <50 favors mechanical, 50-65 shared decision, >65 favors bioprosthetic. </image>

Prosthetic Valve Dysfunction

Structural Valve Degeneration (SVD) -- Bioprosthetic

Structural valve degeneration occurs through leaflet calcification, fibrosis, tearing, and commissural stiffening, manifesting as progressive stenosis with rising gradients over time or regurgitation from leaflet tear or perforation. Risk factors for accelerated degeneration include young age, renal failure or dialysis, hyperparathyroidism, mitral position, small valve size, and patient-prosthesis mismatch. Monitoring begins with baseline echocardiography within 30 days of implantation, followed by annual assessment after 5 years or sooner if symptoms or suspicion of dysfunction develop. Management options include surgical re-replacement or valve-in-valve TAVR for aortic bioprostheses, with growing experience for mitral valve-in-valve and valve-in-ring procedures.

Prosthetic Valve Thrombosis

Prosthetic valve thrombosis carries higher risk with mechanical valves, especially in the mitral position, and with subtherapeutic anticoagulation, though it is also reported with bioprosthetic and TAVR valves. Obstructive thrombosis presents with elevated gradients, reduced leaflet motion, and symptoms of valve obstruction including dyspnea, syncope, and new heart failure, with fluoroscopy demonstrating restricted disc or leaflet motion. Non-obstructive thrombosis may be subclinical, detected on CT or echocardiography, and may be incidental or cause embolic events. Management of obstructive mechanical valve thrombosis depends on location: for left-sided thrombosis, surgery is preferred when available and the patient is stable, with fibrinolysis using alteplase as an alternative when surgery is unavailable, surgical risk is high, or for right-sided thrombosis, where fibrinolysis is preferred over surgery. Intravenous unfractionated heparin serves as bridging therapy for non-obstructive thrombosis with intensified anticoagulation. Subclinical leaflet thrombosis in TAVR valves typically resolves with warfarin for 3 months, though the long-term significance for valve durability remains uncertain.

Pannus Formation

Pannus represents fibrous tissue ingrowth over the prosthetic sewing ring that gradually obstructs the orifice. Distinguishing pannus from thrombus has major therapeutic implications: pannus develops chronically with gradual gradient increases over months to years, appears dense or calcified on CT, and does not resolve with anticoagulation. Thrombus develops acutely or subacutely, often appears as low-density material on CT, and may resolve with anticoagulation. CT with valve motion analysis provides the best imaging for differentiation. Management involves surgical excision for significant pannus obstruction and a trial of anticoagulation when the etiology is uncertain.

Paravalvular Leak (PVL)

Paravalvular leak results from regurgitation through gaps between the sewing ring and native annulus, caused by suture dehiscence, endocarditis, annular calcification, or technical factors. Mild PVL is common, particularly after TAVR, and is usually hemodynamically insignificant. Significant PVL produces heart failure symptoms and hemolytic anemia from high shear stress through the narrow regurgitant orifice. Management includes reoperation for severe PVL with heart failure or significant hemolysis, and percutaneous PVL closure using Amplatzer plugs or coils at experienced centers for suitable anatomy.

Patient-Prosthesis Mismatch (PPM)

Patient-prosthesis mismatch occurs when the effective orifice area of the prosthesis is too small relative to the patient's body size. Indexed effective orifice area thresholds define moderate PPM at below 0.85 cm^2/m^2 and severe PPM at below 0.65 cm^2/m^2 in the aortic position. Consequences include higher residual gradients, reduced exercise capacity, failure of left ventricular hypertrophy regression, and potentially worse long-term survival, especially with severe PPM. Prevention requires preoperative valve sizing to predict indexed effective orifice area, with aortic root enlargement procedures such as Nicks, Manouguian, or Konno performed as needed to accommodate a larger prosthesis.

Prosthetic Valve Endocarditis

Early vs. Late PVE

Early PVE occurring within 60 days involves nosocomial organisms including S. aureus, coagulase-negative staphylococci, gram-negatives, and fungi, carries the highest mortality at 40 to 50%, and often requires surgery. Late PVE beyond 60 days involves community-acquired organisms including viridans streptococci, enterococcus, and S. aureus, with similar microbiology to native valve endocarditis. Intermediate PVE occurring between 60 and 365 days has mixed etiology.

Diagnosis and Management

TEE is essential given TTE sensitivity of only 50% for PVE, and FDG-PET/CT serves as a major criterion in the 2023 Duke update. Antibiotic courses are longer, at a minimum of 6 weeks, with rifampin added to all staphylococcal PVE regimens for its anti-biofilm activity. The threshold for surgery is lower than in native valve endocarditis, with indications including valve dehiscence, abscess, persistent bacteremia, heart failure, and recurrent emboli. Early PVE, particularly when staphylococcal, carries high surgical mortality but even higher medical mortality.

<image> A diagnostic imaging comparison for prosthetic valve dysfunction. Four panels showing different imaging modalities applied to a mechanical aortic valve. Panel 1: Transthoracic echo showing elevated mean gradient (35 mmHg) across a bileaflet mechanical valve with CW Doppler tracing displayed, showing increased peak velocity. Panel 2: TEE showing a small echogenic mass on the ventricular side of the mechanical disc (vegetation vs. thrombus vs. pannus). Panel 3: Cardiac CT 4D reconstruction showing restricted opening of one leaflet of the bileaflet valve (one disc open, one partially stuck), with a low-attenuation mass (thrombus, shown in dark) versus high-attenuation mass (pannus, shown in bright) annotated. Panel 4: Fluoroscopy showing the normal opening angle of a bileaflet valve (approximately 85 degrees) versus abnormal restricted opening (45 degrees) with reference lines drawn. Each panel labeled with the modality name and key finding. Include a small reference box showing normal hemodynamic parameters for the specific valve type and size. </image>

Special Situations

Pregnancy with Mechanical Valves

Warfarin is teratogenic during the first trimester, causing nasal hypoplasia, chondrodysplasia punctata, and CNS abnormalities, with risk being dose-dependent and lower when the warfarin dose is 5 mg or below. Three anticoagulation strategies exist: warfarin throughout pregnancy carries the lowest maternal thromboembolic risk at approximately 4% and is the maternal-preferred approach when the dose is 5 mg or below, with a switch to heparin at 36 weeks for delivery. LMWH during the first trimester followed by warfarin until 36 weeks reduces fetal risk but increases maternal thromboembolic risk to 9 to 12%, requiring anti-Xa monitoring with a target of 0.8 to 1.2 U/mL measured 4 to 6 hours post-dose. UFH during the first trimester followed by warfarin until 36 weeks carries the highest maternal thromboembolic risk at approximately 25% and is generally not preferred. Shared decision-making is essential given the trade-offs between maternal and fetal risk, and management requires a multidisciplinary team of cardiologists, obstetricians, and hematologists.

Noncardiac Surgery in Patients with Prosthetic Valves

Mechanical valve patients require management of anticoagulation with decisions regarding bridging versus omission of bridging based on valve position and risk factors. Bioprosthetic valve patients not on anticoagulation face minimal added risk from the prosthetic valve itself. Endocarditis prophylaxis is required for all prosthetic valves before dental procedures involving gingival manipulation.

Key Clinical Pearls

• DOACs are absolutely CONTRAINDICATED in mechanical heart valves -- the RE-ALIGN trial (dabigatran) was stopped early due to excess valve thrombosis and stroke; this applies to all DOACs
• The On-X valve is the only mechanical valve with evidence supporting lower INR targets (1.5-2.0) in the aortic position after 3 months -- do not extrapolate to other mechanical valves or the mitral position
• Valve-in-valve TAVR for degenerated surgical bioprostheses is an increasingly available option, but small surgical valves (labeled size <= 21 mm) are at high risk for patient-prosthesis mismatch after valve-in-valve -- consider bioprosthetic valve fracture (intentional balloon fracture of the surgical valve stent to allow larger TAVR expansion)
• Distinguishing pannus from thrombus on a mechanical valve has major therapeutic implications: trial of heparin/intensified anticoagulation favors thrombus resolution; persistent obstruction despite anticoagulation suggests pannus requiring surgery
• Low-grade hemolysis is expected with all mechanical valves; clinically significant hemolysis (declining Hb, elevated LDH, low haptoglobin) should prompt investigation for paravalvular leak or valve dysfunction

References

• Otto CM, et al. 2020 ACC/AHA Guideline for the Management of Patients with Valvular Heart Disease. Circulation. 2021;143:e72-e227.
• Eikelboom JW, et al. Dabigatran versus Warfarin in Patients with Mechanical Heart Valves (RE-ALIGN). NEJM. 2013;369:1206-1214.
• Puskas J, et al. Reduced Anticoagulation After Mechanical Aortic Valve Replacement: Interim Results from the PROACT Randomized Trial. J Thorac Cardiovasc Surg. 2014;147:1202-1211.
• Baumgartner H, et al. 2017 ESC/EACTS Guidelines for the Management of Valvular Heart Disease. Eur Heart J. 2017;38:2739-2791.
• Nishimura RA, et al. 2017 AHA/ACC Focused Update on Prosthetic Valve Issues. JACC. 2017;70:e1-e50.

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