Modes of Failure in Explanted Mitroflow Pericardial Valves

Case Series of Early Structural Valve Deterioration of Trifecta Bioprosthesis - New Zealand Experience

PURPOSE

Structural valve deterioration (SVD) remains a limitation on the use of bioprosthetic valves, with patient and valve-related factors contributing to early SVD. The Trifecta valve has been reported to have excellent hemodynamics but studies have highlighted early failure. We present a review and case series at a New Zealand tertiary hospital defining early SVD as failure within 3 years of implant.

METHODS

A retrospective review from January 2015 to July 2019 included 525 patients undergoing surgical aortic valve replacement with 263 patients receiving an Abbott Trifecta or Trifecta Glide Technology (GT) valve. Our review found an acceptable safety profile for the valve with excellent hemodynamics, with a low mortality, stroke, and permanent pacemaker rate.

RESULTS

Three patients out of 263 were identified from the study period as having early SVD requiring reintervention within 3 years of valve implantation leading to a 1.14% failure rate. One of the valves that had early SVD was a new generation Trifecta GT. An additional four patients were identified to have valves implanted prior to the study period and had valve failure at greater than 3 years post implantation. Five cases had cusp tears as their mechanism of failure, raising concerns about durability.

CONCLUSION

The Trifecta valve has an acceptable safety profile and offers good hemodynamics due to the externally mounted leaflets. However, our experience of early SVD and failure is concerning for valve durability. Further comparison to other bioprosthetic valves and longer term follow-up are required to characterize the mechanism of failures.

Surgical Valve Choices for Pulmonary Valve Replacement

The range of valve choices available to the cardiac surgeon for placement in the pulmonary position continues to expand. This article will provide a brief compendium of the most clinically relevant among these choices and review the contemporary literature regarding their relative durability as well as risk factors for structural valve deterioration and reintervention. The unique advantages and disadvantages of each of these valve choices will be discussed as they pertain to unique patient-specific factors, including patient size and the anatomy of the right ventricular outflow tract, that inform the choice of one prosthesis over another. Finally, general principles regarding the approach to valve choice, and future directions will be discussed.

Review of bioprosthetic structural valve deterioration: Patient or valve?

BACKGROUND

With guidelines progressively recommending bioprosthetic aortic valves in younger patients, a greater emphasis is placed on structural valve deterioration (SVD) as an important clinical endpoint for both transcatheter and surgically implanted valves. However, SVD of bioprosthetic valves is a complex entity with varying definitions in the literature and a multifaceted pathogenesis.

AIM

This review first aims to establish the most updated definitions of SVD as per the literature. We then explore the patient- and valve-related factors that play the greatest roles in facilitating early SVD.

METHODS

A PubMed literature review was conducted to identify the relevant research in this field within the past two decades.

CONCLUSION

Increasing rates of obesity and metabolic syndrome pose a significant risk to the longevity of bioprosthetic valves. Additionally, externally mounted valves have proven to sacrifice durability for superior haemodynamics. Bioprosthetic SVD continues to be a multifactorial issue that will require various patient- and valve-related factors to be addressed.

Design consideration of a novel polymeric transcatheter heart valve through computational modeling

Transcatheter heart valve replacement is becoming a more routine procedure, and this is further supported by positive outcomes from studies involving low-risk patients. Nevertheless, the lack of long-term transcatheter heart valve (TAV) durability is still one of the primary concerns. As a result, more research has been focused on improving durability through various methods such as valve design, computational modeling, and material selection. Recent advancements in polymeric valve fabrication showed that linear low-density polyethylene (LLDPE) could be used as leaflet material for transcatheter heart valves. In this paper, a parametric study of computational simulations showed stress distribution on the leaflets of LLDPE-TAV under diastolic load, and the results were used to improve the stent design. The in silico experiment also tested the effect of shock absorbers in terms of valve durability. The results demonstrated that altering specific stent angles can significantly lower peak stress on the leaflets (13.8 vs. 6.07 MPa). Implementing two layers of shock absorbers further reduces the stress value to 4.28 MPa. The pinwheeling index was assessed, which seems to correlate with peak stress. Overall, the parametric study and the computational method can be used to analyze and improve valve durability.

Preliminary Results with a Novel expanded Polytetrafluoroethylene-based Pulmonary Valved Conduit

BACKGROUND

A novel polymeric pulmonary valved conduit, resistant to calcification and structural valve deterioration, may provide a more durable therapy option for the pediatric population by preventing loss of right ventricular function and increasing freedom from valve-related reintervention and mortality.

METHODS

This was a prospective, multicenter, single-arm study evaluating safety and performance of an investigational novel ePTFE-based valve. Patients met study inclusion/exclusion criteria, had a signed informed consent, had pre- and post-operative evaluation via transthoracic echocardiography and six-month cardiac magnetic resonance imaging (cMRI).

RESULTS

Seventeen patients were enrolled from 3 sites. Median age was 12 years (range, 6-17) with 52.9% male. BSA ranged from 0.82 to 1.57 m². There has been no mortality and 100% freedom from device related reinterventions. Baseline compared to six-month cMRI (in 11 of 16 patients with available data) suggests favorable right ventricular remodeling (RVEDV 123±37 to 94±25 mL/m²) with no significant change in ejection fraction. Through current follow-up, no patient has an RVOT gradient > 20 mmHg, (mean 11.2 ± 4.3 mmHg). No evidence of worsening valvular insufficiency was observed throughout postoperative serial TTE evaluations. No pulmonary regurgitation above baseline (≤ mild) was observed. No patient developed endocarditis. No thrombus or calcification was identified.

CONCLUSIONS

This preliminary evaluation of a novel ePTFE-based valved conduit suggests promising valve function with no thromboembolic or infectious complications, no valve related reinterventions, no valve-related adverse events or unexpected findings, improved right ventricular volumes, and encouraging hemodynamic performance through current follow-up.

The pathology of early failure in Mitroflow pericardial valve bioprosthesis (12A/LX)

BACKGROUND

Limited mid-term durability of 12A/LX Mitroflow bioprosthesis has been reported. Aim of the study was to ascertain the pathologic substrates and possible mechanisms of structural valve deterioration in explants from animals and humans.

METHODS

Nine aortic 12A/LX Mitroflow bioprostheses preserved in hypotonic solution and three aortic 12A/LX bioprostheses, preserved in isotonic solution, were explanted from juvenile sheep, mean time from implant 95.66 ± 36.04 days and 132.33 ± 28.88 days from implant respectively. One stented unimplanted 12A/LX Mitroflow preserved in isotonic colution before glutaraldeyde fixation served as control. Ten aortic 12A/LX Mitroflow bioprostheses were explanted from humans because of severe dysfunction: five children, (3 females and 2 males, mean age 14.19 ± 4.77 years, range 11-21), 26 ± 8.24 months from implant and 5 adults (4 females and 1 male, mean age 57.4 ± 19.85 years, range 31-72), 64.4 ± 26.94 months from implant. X-ray, histology, and transmission electron microscopy were carried out as well as spectroscopy for calcium (Ca++) and phosphorus (P) content in human explants.

RESULTS

Explants, from both animals and humans, showed cusp folding and stiffness, with coarse calcific deposits at gross examination and X-ray. Severe collagen denaturation, plasma insudation and massive calcification, involving both collagen and cell debris, were observed microscopically. Mean Ca++ content of 183.27 ± 62.48 and P content of 94.35 ±33.76 mg/g dry weight was found in children and Ca++ content of 205.49 ± 2.23 and P content of 99.75 ± 0.11 mg/g dry weight in adults. Obstructive fibrous tissue overgrowth was detected in 6 human cases.

CONCLUSIONS

Collagen denaturation was observed in pericardial Mitroflow 12A/LX bioprosthesis with premature structural valve deterioration. Optimal collagen fixation and preservation as well as phospholipids reduction by removing cell debris, as employed in the novel CROWN PRT Mitroflow bioprosthesis, are expected to solve the flaw and achieve long-term durability.

The Real Need for Regenerative Medicine in the Future of Congenital Heart Disease Treatment

Bioabsorbable materials made from polymeric compounds have been used in many fields of regenerative medicine to promote tissue regeneration. These materials replace autologous tissue and, due to their growth potential, make excellent substitutes for cardiovascular applications in the treatment of congenital heart disease. However, there remains a sizable gap between their theoretical advantages and actual clinical application within pediatric cardiovascular surgery. This review will focus on four areas of regenerative medicine in which bioabsorbable materials have the potential to alleviate the burden where current treatment options have been unable to within the field of pediatric cardiovascular surgery. These four areas include tissue-engineered pulmonary valves, tissue-engineered patches, regenerative medicine options for treatment of pulmonary vein stenosis and tissue-engineered vascular grafts. We will discuss the research and development of biocompatible materials reported to date, the evaluation of materials in vitro, and the results of studies that have progressed to clinical trials.

Noncalcific Mechanisms of Bioprosthetic Structural Valve Degeneration

Bioprosthetic heart valves (BHVs) largely circumvent the need for long‐term anticoagulation compared with mechanical valves but are increasingly susceptible to deterioration and reduced durability with reoperation rates of ≈10% and 30% at 10 and 15 years, respectively. Structural valve degeneration is a common, unpreventable, and untreatable consequence of BHV implantation and is frequently characterized by leaflet calcification. However, 25% of BHV reoperations attributed to structural valve degeneration occur with minimal leaflet mineralization. This review discusses the noncalcific mechanisms of BHV structural valve degeneration, highlighting the putative roles and pathophysiological relationships between protein infiltration, glycation, oxidative and mechanical stress, and inflammation and the structural consequences for surgical and transcatheter BHVs.

Intentional Fracture of Bioprosthetic Valve Frames in Patients Undergoing Valve-in-Valve Transcatheter Pulmonary Valve Replacement

BACKGROUND

Percutaneous transcatheter pulmonary valve replacement (TPVR) has good clinical and hemodynamic outcomes in treating dysfunctional bioprosthetic valves (BPV) in the pulmonary position. Valve-in-valve therapy can further decrease the inner diameter (ID), potentially resulting in patient-prosthesis mismatch in patients with smaller BPVs.

METHODS AND RESULTS

To evaluate feasibility and outcomes of intentional BPV fracture to enlarge the pulmonary valve orifice with TPVR, 37 patients from 13 centers who underwent TPVR with intended BPV fracture were evaluated. A control cohort (n=70) who underwent valve-in-valve TPVR without attempted fracture was evaluated. BPV was successfully fractured in 28 patients and stretched in 5 while fracture was unsuccessful in 4. A Melody valve was implanted in 25 patients with fractured/stretched frame and a Sapien (XT 3) valve in 8. Among patients whose BPV was fractured/stretched, the final ID was a median of 2 mm larger (0-6.5 mm) than the valve's true ID. The narrowest diameter after TPVR in controls was a median of 2 mm smaller ( P<0.001) than true ID. Right ventricular outflow tract gradient decreased from median 40 to 8 mm Hg in the fracture group. Cases with fracture/stretching were matched 1:1 (weight, true ID) to controls. Post-TPVR peak gradient was lower but not significant (8.3±5.2 versus 11.8±9.2 mm Hg; P=0.070). There were no fracture-related adverse events.

CONCLUSIONS

Preliminary experience shows intentional fracture of BPV frame can be useful for achieving larger ID and better hemodynamics after valve-in-valve TPVR.

Early First-Generation Trifecta Valve Failure: A Case Series and a Review of the Literature

BACKGROUND

The Trifecta valve (Abbott, St Paul, MN) has excellent hemodynamic performance with acceptable rates of freedom from structural valve degeneration. However, some recent studies have reported early Trifecta valve failure. Here, we report a case series of seven Trifecta valve failures with a review of the literature.

METHODS

Of 107 implantations of Trifecta bioprostheses between 2012 and 2014, we encountered seven Trifecta valve failures (6.5%). Failure of a 19-mm Trifecta valve occurred in 1 patient, failure of a 21-mm Trifecta valve occurred in 5 patients, and failure of a 23-mm Trifecta valve occurred in 1 patient. The mean duration of valve durability was 51 ± 16 months. The mean effective orifice area index on the first echocardiogram after Trifecta valve implantation was 0.96 ± 0.26. The mode of presentation was prosthetic valve stenosis in 3 patients and severe aortic regurgitation in 4 patients.

RESULTS

Six patients underwent redo surgical aortic valve replacement. The common pathologic findings were circumferential pannus formation with noncoronary cusp tear and leaflet calcification. The rates of preoperative end-renal stage disease and postoperative prosthesis-patient mismatch were higher in patients with Trifecta valve failure. The incidence of early Trifecta valve failure was 3.1% at 48 months and 13.1% at 72 months.

CONCLUSIONS

In our experience, early Trifecta valve failure was caused by cusp tears or leaflet calcification. Patients with end-renal stage disease and prosthesis-patient mismatch should be closely followed. Some patients with cusp tears may require urgent surgery.

Early structural degeneration of Mitroflow aortic valve: another issue in addition to the mismatch?

We reported two cases of early structural valve degeneration (SVD) with Mitroflow prosthesis in aortic position in patients above the age of 65 years. Microscopic aspects have been analysed to investigate the intrinsic mechanism of SVD. New techniques to improve the structure and the preservation of this prosthesis are needed in order to reduce potential dangerous early complications.

Surgical retrieval of a degenerated Sapien 3 valve after 29 months

A 70-year-old man developed heart failure due to severe mixed disease of a degenerated transcatheter aortic valve prosthesis. The patient underwent retrieval of the transcatheter aortic valve and implantation of a 25-mm bioprosthesis through a redo sternotomy.

Transcatheter aortic valve implantation: where are we now?

Transcatheter aortic valve implantation (TAVI) was first used in clinical practice in 2002. Since 2002, there has been a rapid increase in TAVI activity in patients with symptomatic severe aortic stenosis. This has been supported by systematic randomized data comparing TAVI against the gold standard treatment for the last 50 years’ surgical aortic valve replacement. TAVI is now currently a recommended therapeutic intervention in the treatment of severe aortic stenosis patients who are deemed either high risk or inoperable. The indications for TAVI continue to expand. Within this review we will focus on the current guidelines for TAVI, the evidence for it, the complications of TAVI, postprocedure care, the technology available to clinicians now and finally the future perspectives for TAVI.

Pulmonic Valve Disease: Review of Pathology and Current Treatment Options

PURPOSE OF REVIEW

Our review is intended to provide readers with an overview of disease processes involving the pulmonic valve, highlighting recent outcome studies and guideline-based recommendations; with focus on the two most common interventions for treating pulmonic valve disease, balloon pulmonary valvuloplasty and pulmonic valve replacement.

RECENT FINDINGS

The main long-term sequelae of balloon pulmonary valvuloplasty, the gold standard treatment for pulmonic stenosis, remain pulmonic regurgitation and valvular restenosis. The balloon:annulus ratio is a major contributor to both, with high ratios resulting in greater degrees of regurgitation, and small ratios increasing risk for restenosis. Recent studies suggest that a ratio of approximately 1.2 may provide the most optimal results. Pulmonic valve replacement is currently the procedure of choice for patients with severe pulmonic regurgitation and hemodynamic sequelae or symptoms, yet it remains uncertain how it impacts long-term survival. Transcatheter pulmonic valve replacement is a rapidly evolving field and recent outcome studies suggest short and mid-term results at least equivalent to surgery. The Melody valve® was FDA approved for failing pulmonary surgical conduits in 2010 and for failing bioprosthetic surgical pulmonic valves in 2017 and has been extensively studied, whereas the Sapien XT valve®, offering larger diameters, was approved for failing pulmonary conduits in 2016 and has been less extensively studied. Patients with pulmonic valve disease deserve lifelong surveillance for complications. Transcatheter pulmonic valve replacement is a novel and attractive therapeutic option, but is currently only FDA approved for patients with failing pulmonary conduits or dysfunctional surgical bioprosthetic valves. New advances will undoubtedly increase the utilization of this rapidly expanding technology.

Calcification and Oxidative Modifications Are Associated With Progressive Bioprosthetic Heart Valve Dysfunction

Background

Bioprosthetic heart valves (BHVs), fabricated from glutaraldehyde‐pretreated bovine pericardium or porcine aortic valves, are widely used for the surgical or interventional treatment of heart valve disease. Reoperation becomes increasingly necessary over time because of BHV dysfunction.

Methods and Results

Forty‐seven explanted BHV aortic valve replacements were retrieved at reoperation for clinically severe BHV dysfunction over the period 2010–2016. Clinical explant analyses of BHV leaflets for calcium (atomic absorption spectroscopy) and oxidized amino acids, per mass spectroscopy, were primary end points. Comorbidities for earlier BHV explant included diabetes mellitus and coronary artery bypass grafting. Mean calcium levels in BHV leaflets were significantly increased compared with unimplanted BHV (P<0.001); however, time to reoperation did not differ comparing calcified and noncalcified BHV. BHV dityrosine, an oxidized amino acid cross‐link, was significantly increased in the explants (227.55±33.27 μmol/mol [dityrosine/tyrosine]) but was undetectable in unimplanted leaflets (P<0.001). BHV regional analyses revealed that dityrosine, ranging from 57.5 to 227.8 μmol/mol (dityrosine/tyrosine), was detectable only in the midleaflet samples, indicating the site‐specific nature of dityrosine formation. 3‐Chlorotyrosine, an oxidized amino acid formed by myeloperoxidase‐catalyzed chlorinating oxidants, correlated with BHV calcium content in leaflet explant analyses from coronary artery bypass graft patients (r=0.62, P=0.01) but was not significantly correlated with calcification in non–coronary artery bypass graft explanted BHV.

Conclusions

Both increased BHV leaflet calcium levels and elevated oxidized amino acids were associated with bioprosthesis dysfunction necessitating reoperation; however, BHV calcium levels were not a determinant of implant duration, indicating a potentially important role for oxidized amino acid formation in BHV dysfunction.

Acute Structural Failure of the Trifecta Aortic Valve Bioprosthesis

Advancements in bioprosthetic valve technology have greatly enhanced the haemodynamic performance and long-term durability of tissue valves. These features, along with the key advantage of avoiding lifelong anticoagulation, have made bioprosthetic valves increasingly attractive for clinicians and patients alike. The St Jude Trifecta valve is a novel, bovine pericardial bioprosthesis with promising early data for performance and safety. However, no prosthetic valve is perfect and prosthesis failure can occur with even the most reliable and well-designed devices. We report a case of early and acute structural deterioration (stent-post leaflet rupture) of the Trifecta valve, explanted after 33 months, in a 76-year-old male.

Mechanism of valve failure and efficacy of reintervention through catheterization in patients with bioprosthetic valves in the pulmonary position

BACKGROUND

Surgical and transcatheter bioprosthetic valves (BPVs) in the pulmonary position in patients with congenital heart disease may ultimately fail and undergo transcatheter reintervention. Angiographic assessment of the mechanism of BPV failure has not been previously described.

AIMS

The aim of this study was to determine the mode of BPV failure (stenosis/regurgitation) requiring transcatheter reintervention and to describe the angiographic characteristics of the failed BPVs and report the types and efficacy of reinterventions.

MATERIALS AND METHODS

This is a retrospective single-center review of consecutive patients who previously underwent pulmonary BPV placement (surgical or transcatheter) and subsequently underwent percutaneous reintervention from 2005 to 2014.

RESULTS

Fifty-five patients with surgical (41) and transcutaneous pulmonary valve (TPV) (14) implantation of BPVs underwent 66 catheter reinterventions. The surgically implanted valves underwent fifty reinterventions for indications including 16 for stenosis, seven for regurgitation, and 27 for both, predominantly associated with leaflet immobility, calcification, and thickening. Among TPVs, pulmonary stenosis (PS) was the exclusive failure mode, mainly due to loss of stent integrity (10) and endocarditis (4). Following reintervention, there was a reduction of right ventricular outflow tract gradient from 43 ± 16 mmHg to 16 ± 10 mmHg (P < 0.001) and RVp/AO ratio from 0.8 ± 0.2 to 0.5 ± 0.2 (P < 0.001). Reintervention with TPV placement was performed in 45 (82%) patients (34 surgical, 11 transcatheter) with no significant postintervention regurgitation or paravalvular leak.

CONCLUSION

Failing surgically implanted BPVs demonstrate leaflet calcification, thickness, and immobility leading to PS and/or regurgitation while the mechanism of TPV failure in the short- to mid-term is stenosis, mainly from loss of stent integrity. This can be effectively treated with a catheter-based approach, predominantly with the valve-in-valve technique.

Dysregulation of ossification-related miRNAs in circulating osteogenic progenitor cells obtained from patients with aortic stenosis

CAVD (calcific aortic valve disease) is the defining feature of AS (aortic stenosis). The present study aimed to determine whether expression of ossification-related miRNAs is related to differentiation intro COPCs (circulating osteogenic progenitor cells) in patients with CAVD. The present study included 46 patients with AS and 46 controls. Twenty-nine patients underwent surgical AVR (aortic valve replacement) and 17 underwent TAVI (transcatheter aortic valve implantation). The number of COPCs was higher in the AS group than in the controls (P<0.01). Levels of miR-30c were higher in the AS group than in the controls (P<0.01), whereas levels of miR-106a, miR-148a, miR-204, miR-211, miR-31 and miR-424 were lower in the AS group than in the controls (P<0.01). The number of COPCs and levels of osteocalcin protein in COPCs were positively correlated with levels of miR-30a and negatively correlated with levels of the remaining miRNAs (all P<0.05). The degree of aortic valve calcification was weakly positively correlated with the number of COPCs and miR-30c levels. The number of COPCs and miR-30c levels were decreased after surgery, whereas levels of the remaining miRNAs were increased (all P<0.05). Changes in these levels were greater after AVR than after TAVI (all P<0.05). In vitro study using cultured peripheral blood mononuclear cells transfected with each ossification-related miRNA showed that these miRNAs controlled levels of osteocalcin protein. In conclusion, dysregulation of ossification-related miRNAs may be related to the differentiation into COPCs and may play a significant role in the pathogenesis of CAVD.

Durability after aortic valve replacement with the Mitroflow versus the Perimount pericardial bioprosthesis: a single-centre experience in 2393 patients

OBJECTIVES

This study compares the durability and risk of reoperation in patients undergoing aortic valve replacement (AVR) with either a Mitroflow or a Carpentier-Edwards (CE) pericardial bioprosthesis. Since AVR with bioprosthetic valves has increased progressively in recent years as compared to mechanical valves, especially in patients aged 60-70 years, there has been renewed interest in the long-term durability of current pericardial bioprostheses.

METHODS

We compared 440 AVR with Mitroflow valves with 1953 AVR with CE pericardial valves implanted from 1999 to 2014 with regard to reoperation, reoperation for structural valve deterioration (SVD) and all-cause mortality.

RESULTS

Ten-year freedom from explant of any cause was higher for CE Perimount (98 ± 0.7%) than for Mitroflow (95 ± 1.4%, P < 0.01). Reasons for explant for CE Perimount were SVD (n = 2), endocarditis (n = 8) and paraprosthetic leak (n = 10). The reasons for explant for Mitroflow were SVD (n = 11), endocarditis (n = 3) SVD and pericarditis (n = 1) and paraprosthetic leak (n = 2). Ten-year freedom from explant due to SVD was higher for CE Perimount (100%) than for Mitroflow (96%) (P < 0.01). In small aortic annuli (bioprosthesis size 19-21 mm), freedom from SVD at 10 years for CE Perimount and Mitroflow was 100 versus 96%, respectively. By multivariate analysis, it was found that bioprosthesis size was not a risk factor for SVD. The choice of valve type could not be demonstrated to influence long-term survival.

CONCLUSIONS

The Mitroflow pericardial bioprosthesis provides less than optimal mid- and long-term durability compared with the CE Perimount pericardial valve, especially for small aortic diameter implants (19 and 21 mm). This study hereby confirms the existence of a real risk of valvular deterioration of the Mitroflow valve that might compromise the prognosis of the patients.

Structural analysis of a stented pericardial heart valve with leaflets mounted externally

Our aim was to understand the structural and functional behaviour of a pericardial heart valve with biological leaflets attached externally to a stent. To our knowledge, there is little if any literature concerning these kinds of bioprosthetic heart valves, while there is more concerning bioprosthetic heart valves with leaflets mounted internally. We studied the problem using a finite element approach considering leaflets and stent interaction, the influence of leaflet anisotropy and stent stiffness, by comparing quasi-static and dynamic loadings. Although we considered the problem to be symmetric and fluid-structure interaction was not implemented, we believe that our results could be a solid basis for valve optimization. We found regions of high stress concentration at the commissure near the stent tip and at the base of the leaflet cusp. The structural behaviour in the first region was complex, while the stress in the second region acted radially because of high bending. Although leaflet tissue anisotropy and stent stiffness exerted a significant influence on the structural and functional behaviours, they had a contrasting effect on leaflet stress state, coaptation and valve opening. Therefore, a good optimization should take into account both structural and functional requirements when tuning tissue properties and stent stiffness.

Bioprosthetic Heart Valves: Impact of Implantation on Biomaterials

Prosthetic heart valves are commonly used in the treatment of valvular heart disease. Mechanical valves are more durable than the bioprosthetic valves; however, the need for long-term anticoagulant therapy renders them unsuitable for some patient groups. In this paper we discuss the different types and models of bioprosthesis, and in particular, pericardial bioprosthesis. We also discuss the preimplantation preparation processes, as well as their postimplantation changes and modes of failure.

The year in review: the surgical treatment of valvular disease-2011

This review highlights important advances in techniques, guidelines, outcomes and innovations in valve surgery during 2011.