Structural valve deterioration

Article written and reviewed by Dr Luca Moretti

Structural valve deterioration is the intrinsic and permanent deterioration of a valvular bioprosthesis. Calcification, fibrosis, thickening, tearing or detachment of a leaflet can alter opening and coaptation to the point of causing stenosis, regurgitation or a mixed lesion. This definition does not encompass every form of prosthetic valve malfunction: thrombosis, endocarditis, paravalvular leak, mismatch and malposition have different mechanisms and, in some cases, potential reversibility.

The distinction is clinically decisive because an increase in gradient caused by thrombus may regress with anticoagulation, whereas a calcified, rigid leaflet is not repaired by medication. Labeling any high gradient as “degeneration” may therefore lead to unnecessary reinterventions, just as attributing a structural tear to thrombosis risks delaying appropriate treatment. Classification therefore requires convergence between serial echocardiography and anatomical imaging.

The lifespan of a bioprosthesis does not correspond to an expiration date but reflects a continuous process influenced by biological age, valve position, model, hemodynamics, renal function and mineral metabolism. Population averages are useful in the initial choice, but they cannot predict when the valve in an individual patient will fail; for this very reason, the baseline examination and serial surveillance become increasingly important over time.

International definitions separate morphological damage, hemodynamic deterioration and clinical bioprosthetic valve failure. This terminology avoids comparing studies that used “durability” for different events and allows intervention before an anatomical lesion causes irreversible heart failure, without turning every subclinical change into an indication for a procedure.

Biology, morphological patterns and risk factors

Bovine or porcine tissue is fixed and treated to reduce immunogenicity and degradation, but it remains biologically and mechanically vulnerable. Cyclic stress, turbulence, collagen damage and lipid accumulation promote mineralization. Inflammatory cells and mediators participate in an active process that shares some features with atherosclerosis, without antiatherosclerotic therapy having been shown to halt an already degenerating bioprosthesis.

Deterioration may present with a predominantly stenotic phenotype, mainly due to thickening, fibrosis and calcification that reduce leaflet excursion and orifice area, or with a regurgitant phenotype related to leaflet tearing, perforation, retraction or flail and sometimes capable of presenting abruptly. The two components are not mutually exclusive, however: stiffened tissue may lose coaptation and a tear may also alter gradients, which is why morphological description must always accompany hemodynamic quantification.

Younger age at implantation is the main predictor of accelerated deterioration, probably because of the combination of more active calcific metabolism and longer exposure. Renal failure, dialysis, hyperparathyroidism and calcium-phosphate abnormalities further increase mineralization, whereas diabetes, metabolic syndrome and smoking have been associated with deterioration in observational studies without allowing deterministic prediction in an individual patient.

Valve position modifies the load. A mitral bioprosthesis is exposed to high closing pressures and tends to deteriorate earlier than a comparable aortic prosthesis; pulmonary prostheses in patients with congenital heart disease have different geometries and populations. Small size, residual gradient and prosthesis-patient mismatch increase stress and may accelerate deterioration or make it clinically apparent with relatively modest changes.

Design, anticalcification treatment, mounting and implantation technique differ among models. A nominal size does not correspond to the same internal diameter; for TAVI, intra-annular or supra-annular position and frame underexpansion modify mechanical stresses. Results from one device generation cannot be transferred uncritically to all bioprostheses or extrapolated beyond the duration actually observed.

Subclinical or clinical thrombosis may interact with degeneration through processes of organization and fibrosis, but this association does not justify universal preventive anticoagulation. Endocarditis may also destroy leaflets and leave permanent structural damage, while remaining separately classified because of its different pathogenesis and specific anti-infective treatment. Over a lifetime, therefore, the same prosthesis may accumulate different mechanisms that must be recognized individually.

There is no validated drug capable of preventing prosthetic valve calcification. Control of blood pressure, renal function and cardiovascular risk factors protects the ventricles and overall prognosis, but it does not replace surveillance. The initial choice of prosthesis, avoidance of an excessive gradient and lifetime planning are the main measures that reduce the clinical impact of future deterioration.

Definitions of bioprosthetic valve deterioration and failure

Morphological structural valve deterioration may be documented by calcification, thickening, tearing or alteration of the supporting structure even before severe dysfunction develops. Hemodynamic deterioration, by contrast, is defined through a change from baseline rather than on the basis of a single absolute value, whereas bioprosthetic valve failure represents the most advanced clinical stage and, depending on the definition adopted, includes severe dysfunction, reintervention or valve-related death.

For aortic bioprostheses, contemporary frameworks classify deterioration as moderate when the mean gradient increases by at least 10 mmHg to a value of at least 20 mmHg, with a concordant reduction in effective orifice area or DVI, or when at least moderate intraprosthetic regurgitation develops or worsens. Severe deterioration requires larger changes and higher final values, or severe intraprosthetic regurgitation.

Thresholds cannot be transferred mechanically from one valve position to another. In the mitral position, for example, the gradient is strongly influenced by heart rate and flow, whereas an acute tear may produce severe regurgitation without any pressure increase. VARC-3 and the EAPCI documents were developed mainly for aortic prostheses and research; in clinical practice, assessment must therefore integrate morphology, hemodynamic consequences, possible measurement errors and specific imaging recommendations.

The requirement for a concordant change from baseline reduces the risk of false-positive diagnoses. A higher gradient during anemia or tachycardia, if not accompanied by a reduction in area or DVI, does not demonstrate degeneration; conversely, new severe regurgitation may represent failure even with a low gradient. Heart rate, blood pressure, hemoglobin and stroke volume should therefore accompany every serial comparison.

The concept of bioprosthetic valve failure is closer to the impact on the patient, but it also depends on the likelihood and decision to reintervene. In older populations, for example, competing mortality reduces the number of subsequent procedures and may make a device appear more durable than its true biological lifespan. Durability analyses should therefore use methods that account for competing risks and report hemodynamic deterioration and clinical events separately.

Mechanical prostheses can rarely fracture or fail mechanically, but in the principal consensus documents the term SVD is reserved for bioprostheses. Pannus, thrombosis and paravalvular regurgitation belong to separate categories, a terminological precision that is necessary to avoid confusing the material durability of a mechanical prosthesis with freedom from any valve-related complication.

In the clinical report it is therefore useful to state which definition has been applied, identify the baseline examination used for comparison and describe the stenotic and regurgitant components separately. The expression “moderate SVD” alone, without measurements, morphology and temporal trend, does not allow its accuracy to be verified: standardized terminology should increase the information available, not replace it with an acronym.

Echocardiographic diagnosis and multimodality imaging

The baseline post-implant echocardiogram documents velocity, gradients, area, DVI, regurgitation, chamber dimensions and ventricular function and becomes the reference for subsequent examinations, which should use a comparable technique. A progressive increase in acceleration time associated with a rounded contour supports the hypothesis of stenosis, whereas the appearance of an eccentric intraprosthetic jet suggests a leaflet abnormality; in parallel, ventricular response and pulmonary pressure allow the consequences to be quantified.

When transthoracic echocardiography is limited, transesophageal echocardiography allows visualization of thickening, calcification, flail, perforation and the mechanism of regurgitation, with three-dimensional imaging being particularly useful in the mitral position and in distinguishing an intraprosthetic from a paravalvular origin. Because artifacts and shadowing may still affect the examination, severity should never depend on a single view or solely on color Doppler jet size.

Cardiac CT adds anatomical information on calcium distribution, leaflet motion, frame expansion and relationships with surrounding structures. Hypoattenuated thickening associated with reduced motion suggests prosthetic valve thrombosis, whereas dense calcification, retraction or tearing more strongly support degeneration; when the distinction remains uncertain, a therapeutic trial of anticoagulation may be considered only if clinically safe.

CT is essential in valve-in-valve planning because it defines the true internal diameter, coronary height and distance, sinuses, sinotubular junction and orientation of the old prosthesis and, in mitral procedures, allows simulation of the neo-LVOT. It does not replace echocardiography for serial quantification, but it transforms the diagnosis of failure into a true procedural map.

Cardiac magnetic resonance can quantify volumes and regurgitant fraction when echocardiography provides discordant data, although artifacts impose limitations. In apparently asymptomatic patients, a selected exercise test may instead objectify symptoms and the hemodynamic response, while biomarkers such as natriuretic peptides contribute to the assessment of heart failure without being specific for prosthetic degeneration.

The differential diagnosis includes high-flow states, mismatch, measurement errors, thrombosis, endocarditis and non-structural dysfunction. Degeneration tends to progress and alters the tissue, mismatch is instead present from the first examination with normal leaflets, and thrombosis may appear rapidly and regress with treatment; fever, masses, dehiscence or abscesses, finally, require a specific endocarditis pathway.

When findings are discordant, the images should be reviewed in a Valve Centre because a wrong diagnosis may alter not only immediate therapy but the entire sequence of future interventions. Before considering a bioprosthesis irreversibly failed, it is therefore reasonable to exclude all potentially correctable causes with complementary modalities and adequate clinical data.

Surveillance, progression and timing of reintervention

Bioprostheses require regular clinical follow-up and serial imaging according to type, valve position, time since implantation and guidelines. An earlier examination is indicated for dyspnea, reduced exercise capacity, a new murmur, heart failure or embolism. As the years since implantation increase and morphological changes appear, the interval is shortened because progression may accelerate.

Surveillance should not wait for severe dysfunction to develop. Moderate SVD should be confirmed, distinguished from thrombosis and followed for its rate of progression, documenting symptoms, ventricular function, pulmonary pressure and the status of the other valves. Because patients may unknowingly reduce their activity and describe themselves as asymptomatic, exercise testing or a structured functional assessment can avoid a false impression of stability.

The indication for reintervention is based mainly on symptomatic severe dysfunction, ventricular consequences or the risk of further deterioration, with criteria adapted to the valve position. Acute regurgitation caused by tearing requires prompt evaluation, whereas slowly progressive stenosis allows more gradual planning; intervening before shock preserves therapeutic options, but treating a mild change without consequences exposes the patient to risk without demonstrated benefit.

Durability is discussed at the time of the initial prosthesis choice. In a young adult, a bioprosthesis is more likely to deteriorate during the patient’s lifetime, but the balance relative to a mechanical prosthesis also depends on bleeding risk, preferences, pregnancy and the possibility of reintervention. Likewise, the prospect of a future valve-in-valve cannot automatically be considered favorable if the first ring is small or if coronary anatomy makes a subsequent procedure problematic.

Comparisons between TAVI and surgery must be interpreted in light of follow-up duration, device generation, study population and the definition of deterioration used. In low-risk trials, medium-term results are reassuring, but they do not amount to proof of durability for decades in very young patients; moreover, a lower observed incidence of SVD may reflect not only better hemodynamics but also competing mortality or differences in classification.

The patient should retain the name and size of the prosthesis together with baseline examinations because this information allows expected reference curves to be used and a possible second device to be planned accurately. In contrast, fragmented follow-up without comparable images risks recognizing failure only when symptoms develop, narrowing the options to an urgent procedure.

Redo surgery, valve-in-valve and lifetime strategy

Redo surgery removes the degenerated bioprosthesis and offers the possibility of enlarging the annulus, replacing the root, correcting coronary disease or other valves and treating infected tissue. It is more invasive and technically complex than the first operation, but it can provide the best hemodynamics in patients with a small annulus and long life expectancy. Risk is estimated by an experienced Heart Team, not by age alone.

Valve-in-valve consists of implanting a new transcatheter bioprosthesis inside a failed surgical or transcatheter prosthesis. In many high-risk patients it reduces procedural trauma and accelerates recovery, but the old ring inevitably limits the space available and, in small prostheses, may leave a substantial residual gradient. Some models allow controlled fracture of the bioprosthetic ring, a technique that may improve expansion but is not universally applicable and carries specific risks.

Coronary obstruction, although uncommon, is one of the most feared complications of valve-in-valve. Risk depends on coronary height, sinus dimensions, the leaflets of the old prosthesis and the sinotubular junction; CT and virtual simulation therefore allow experienced centers to plan coronary protection strategies or intentional leaflet laceration. Even when immediate occlusion appears unlikely, the possibility of future coronary access must be considered.

In mitral valve-in-valve, the dominant problem may be left ventricular outflow tract obstruction because the new device can displace the anterior leaflet toward the septum. Prediction of the neo-LVOT, the aortomitral angle and septal anatomy guides patient selection and preventive strategies; paravalvular leaks, incomplete rings and unstable prostheses instead require a different approach from that used for a circular stented bioprosthesis.

The final choice integrates operative risk, anatomy, mechanism of failure, valve position, life expectancy and the feasibility of subsequent procedures. A frail patient with a large aortic bioprosthesis may derive clear benefit from valve-in-valve, whereas a young adult with a small annulus and unfavorable coronary anatomy may obtain a more durable solution from redo surgery with enlargement. There is therefore no superiority independent of the anatomical and clinical context.

After reintervention, a new baseline examination should be obtained, antithrombotic therapy defined and follow-up scheduled. Immediately documenting any residual gradient prevents it from being interpreted years later as new degeneration, while surveillance must continue because a second bioprosthesis also remains exposed to thrombosis, infection and deterioration.

Well-organized management transforms degeneration from an apparently sudden event into a predictable phase of valve life. Correct terminology identifies the process, serial comparison measures its rate, CT anticipates anatomical constraints and shared decision-making allows the timing and route of reintervention to be selected. From this perspective, durability indicates not only how long a leaflet lasts, but also how many safe options remain available when that leaflet no longer functions.

Interpreting durability requires methodological care. Freedom from reintervention overestimates biological durability when many patients die before the prosthesis fails or are not treated because of risk. Conversely, a sensitive surveillance program identifies subclinical deterioration that would not have produced an event. Comparative studies should therefore report competing mortality, completeness of echocardiographic follow-up, baseline examination, number of patients still at risk and the definition applied to each endpoint.

Differences among valve positions prevent simple extrapolation of aortic data. In the mitral position, closing pressures, heart rate and atrioventricular compliance modify gradients and stress; in the pulmonary position, many patients are young and have congenital heart disease, conduits or surgically altered anatomy. The timing and type of reintervention should follow the physiology of the valve position while maintaining the general separation among degeneration, thrombosis, infection and non-structural defects.

An acute regurgitant lesion requires particular attention because a leaflet tear can generate a severe eccentric jet that transthoracic echocardiography underestimates because of shadowing or rapid pressure equalization. The ventricle may also remain normal in size, without the typical signs of chronic regurgitation. The appearance of new dyspnea, a dense Doppler signal and evidence of flail therefore require prompt transesophageal echocardiography and procedural evaluation, even when the mean gradient appears reassuring.

At the opposite extreme, degenerative stenosis may progress slowly and be accompanied by a progressive reduction in cardiac output. When the ventricle loses contractile strength, the gradient may stop increasing even though the orifice continues to narrow; apparent stabilization of the value therefore does not necessarily correspond to biological stability. Area, DVI, stroke volume and morphology allow the true trajectory to be reconstructed and prevent waiting for a high gradient in a patient who is no longer able to generate it.

When planning a second bioprosthesis, the possibility of a third procedure should also be considered from the outset. A sequence of surgery, valve-in-valve and a further TAVI can overlap multiple frames, progressively reduce the effective area and make coronary access difficult. In some young patients, surgical removal of the first prosthesis while operative risk is still acceptable preserves more future options; in others, a transcatheter procedure offers the best balance. The strategy should therefore be individualized on the basis of anatomical simulation, not a predefined sequence.

Communication with the patient should clearly distinguish the concept of change from that of failure. Saying that a bioprosthesis shows moderate deterioration does not mean it is about to rupture, but it does indicate the need for closer follow-up and for beginning to prepare alternatives. Explaining symptoms to report, likelihood of progression and margins of uncertainty reduces both unjustified alarm and delays, because the patient understands why an intervention is not yet indicated but also why they should not wait for the next scheduled visit if dyspnea, syncope or a rapid decline in functional capacity develops.

In the final report it is useful to separate certain findings from probable interpretations. Visible calcification, for example, is an anatomical finding, whereas attributing the entire gradient to it is a conclusion that requires consistency with Doppler data. Stating the level of certainty facilitates the choice among CT, a trial of anticoagulation and reintervention and prevents a simple hypothesis from being carried forward in subsequent follow-up as an established diagnosis.