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Archives of cardiovascular diseases
Volume 109, n° 8-9
pages 465-475 (août 2016)
Doi : 10.1016/j.acvd.2016.01.015
Received : 21 July 2015 ;  accepted : 27 January 2016
Impact of percutaneous pulmonary valve implantation procedural steps on leaflets histology and mechanical behaviour: An in vitro study
Analyse de l’impact des manipulations pré-implantatoires sur la structure histologique et le comportement mécanique des feuillets valvulaires des prothèses pulmonaires percutanées : étude in vitro
 

Zakaria Jalal a, Louise Galmiche b, Christophe Beloin c, Younes Boudjemline a, d,
a Centre de référence malformations cardiaques congénitales complexes, M3C, hôpital Necker–Enfants-Malades, Assistance publique–Hôpitaux de Paris, paediatric cardiology, 149, rue de Sèvres, 75015 Paris cedex, France 
b Hôpital Necker–Enfants-Malades, laboratoire d’anatomopathologie, 75015 Paris, France 
c Unité de génétique des biofilms, département de microbiologie, institut Pasteur, 75015 Paris, France 
d Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France 

Corresponding author. Centre de référence malformations cardiaques congénitales complexes, M3C, hôpital Necker–Enfants-Malades, Assistance publique–Hôpitaux de Paris, paediatric cardiology, 149, rue de Sèvres, 75015 Paris cedex, France.
Summary
Background

Percutaneous pulmonary valve implantation (PPVI) using the bovine jugular vein Melody® valve (Medtronic Inc., Minneapolis, MN, USA) is safe and effective. However, post-procedural complications have been reported, the reasons for which are unclear.

Objective

To assess the impact of PPVI procedural steps on valvular histology and leaflet mechanical behaviour.

Methods

Three different valved stents (the Melody® valve and two homemade stents with bovine and porcine pericardium) were tested in vitro under four conditions: (1) control group; (2) crimping; (3) crimping plus inflation of low-pressure balloon; (4) condition III plus post-dilatation (high-pressure balloon). For each condition, valvular leaflets (and a venous wall sample for Melody® stents) were taken for histological analysis and mechanical uniaxial testing of the valve leaflets.

Results

Among the Melody® valves, the incidence of transverse fractures was significantly higher in traumatized samples compared with the control group (P <0.05), whereas the incidence and depth of transverse fractures were not statistically different between the four conditions for bovine and porcine pericardial leaflets. No significant modification of the mechanical behaviour of in vitro traumatized Melody® valvular leaflets was observed. Bovine and porcine pericardia became more elastic and less resilient after balloon expansion and post-dilatation (conditions III and IV), with a significant decrease in elastic modulus and stress at rupture.

Conclusion

Valved stent implantation procedural steps induced histological lesions on Melody® valve leaflets. Conversely, bovine and porcine pericardial valved stents were not histologically altered by in vitro manipulations, although their mechanical properties were significantly modified. These data could explain some of the long-term complications observed with these substitutes.

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Résumé
Contexte

Le remplacement valvulaire pulmonaire percutané utilisant le stent valvé Melody® est efficace et sécurisé, cependant, des endocardites infectieuses surviennent sur ces prothèses sans explication évidente.

Objectif

Évaluer l’impact des manipulations pré-implantatoires sur la structure histologique et le comportement mécanique des feuillets valvulaires.

Méthodes

Nous avons testé in vitro 3 types de stents valvés (prothèse Melody®, stents valvés en péricarde bovin et porcin fabriqués manuellement) dans 4 conditions différentes : (1) groupe témoin ne subissant aucune manipulation ; (2) sertissage sur un ballonnet ; (3) sertissage+inflation du ballonnet à basse pression ; (4) groupe III+surdilatation par ballonnet à haute pression. À l’issu de chaque manipulation, les feuillets valvulaires étaient prélevés sur les stents, puis analysés sur le plan histologique et mécaniques (test de traction uniaxiale).

Résultats

Pour les valves Melody®, on retrouvait plus de lésions histologiques sur les feuillets valvulaires dans les groupes II, III et IV par rapport au groupe témoin (p <0,05). L’incidence de ces lésions n’était pas différente entre les 4 conditions pour les stents valvés péricardiques. Les propriétés mécaniques des valves Melody® traumatisées n’étaient pas modifiées. Les péricardes bovin et porcin devenaient plus élastiques et moins résistants dans les conditions III et IV, avec une diminution du module d’élasticité et du stress à la rupture.

Conclusion

Les manipulations réalisées en salle de cathétérisme entraînent des lésions histologiques significatives sur les feuillets valvulaires des prothèses Melody®. Les stents valvés en péricarde bovin et porcin ne sont pas altérés histologiquement par ces manipulations mais voient leurs propriétés mécaniques se modifier significativement. Ces données pourraient expliquer certaines complications observées à long terme avec ces substituts.

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Keywords : Percutaneous valve, Pulmonary valve, Endocarditis

Mots clés : Valve percutanée, Valve pulmonaire, Endocardite

Abbreviations : BJV, IE, PPVI, RVOT


Background

Patients undergoing surgical right ventricular outflow tract (RVOT) reconstruction are subject to conduit degeneration later in life, requiring further interventions to alleviate the pulmonary stenosis and/or regurgitation that ensues. Since the first reported case in 2000, percutaneous pulmonary valve replacement (PPVI) using the Melody® valve (Medtronic Inc., Minneapolis, MN, USA) – a glutaraldehyde fixed bovine jugular vein (BJV) valve mounted on a balloon-expandable stent – is now recognized as an alternative to surgical pulmonary valve replacement in patients with failing RVOT [1, 2]. Recent reports showed that PPVI was feasible at a relatively low risk, and mid-term follow-up demonstrated a sustained improvement in haemodynamics up to 7 years after implantation [3, 4]. Despite these promising results, various mid-term and long-term complications have been described, including cases of infective endocarditis (IE) [5, 6, 7, 8, 9]. The reported annualized rate of IE ranges from 2.4% to 3.9% per patient-year [10, 11]. We and others have recently shown that IE occurs more frequently after PPVI than surgical pulmonary valve replacement [10, 12]. IE also involves other valved stents made with different valvular substrates – i.e. the Edwards SAPIEN® valve (Edwards Lifesciences, Irvine, CA, USA), made with bovine pericardium, and the CoreValve® valve (Medtronic Inc.), made with porcine pericardium [13, 14]. These results suggest that IE might be related to the implantation technique (i.e. percutaneous or surgical) used for valvular placement. One of the main differences between surgical and transcatheter valve replacement is that percutaneous valves undergo several manipulations before implantation (i.e. crimping) and during implantation (i.e. balloon expansion), whereas surgical prostheses are placed directly in the pulmonary pathway without valvular damage, theoretically. Traumatic injury to biological valve leaflets has been reported during valved stent preparation [15, 16]. In a recent work, we demonstrated that there was selective adhesion of Staphylococcus aureus and S.  sanguinis pathogenic strains on healthy Melody® valve tissue, which increased after implantation procedural steps [17].

In this in vitro study, we aimed to assess the effects of PPVI procedural steps on the histological and mechanical properties of Melody® valve leaflets, and to compare these results with other tissues used for valved stent fabrication (i.e. bovine and porcine pericardium).

Methods
Valvular substrates

Three types of valved stents were tested experimentally. The Melody® valve was obtained from Medtronic Inc. and stored in its commercial packaging. For the bovine pericardium valve, valvular leaflets were obtained from a bovine pericardial patch (10×15cm; Edwards Lifesciences), cut onto a 21-mm homemade three-leaflet valvular mould, and sutured into a vascular stent (CP8Z34; NuMED Canada Inc., Cornwall, ON, Canada); valved stents were then stored in 0.625% glutaraldehyde until use. For the porcine pericardium valve, valvular leaflets were obtained from a porcine pericardial patch (8×6cm; Vascutek Terumo Ltd., Swillington, Leeds, UK); porcine pericardial valved stents were then prepared similarly and stored in 0.625% glutaraldehyde until use.

In vitro manipulations

For each valved stent, we compared four experimental conditions, reproducing the sequential procedural steps leading to conventional PPVI (Figure 1). Before manipulation, valved stents were rinsed twice for 2minutes each in 500-mL saline baths to remove the glutaraldehyde.



Figure 1


Figure 1. 

Description of in vitro manipulations to the Melody® valved stent. A. Melody® valved stent after rinsing with saline solution. B and C. Crimping on sterile 5-mL and 2.5-mL syringes. D. Crimping on the Ensemble® delivery system. E. Covering of the valved stent by the sheath. F. Expansion of the valved stent in a 20-mm GORE-TEX® conduit. G. Post-dilatation using high-pressure balloon. H. Bovine jugular vein detached from the stent and opened on its longitudinal axis (note the three valvular leaflets). I. One valvular leaflet after sampling.

Zoom

Condition I: control group

Valved stents were not manipulated.

Condition II: compression group

Valved stents were crimped manually on 5-mL and 2.5-mL sterile syringes, and then onto the 22-mm balloon of the 22F Ensemble® delivery system (Medtronic Inc.) (Figure 1A). The sheath was advanced to cover the balloon-mounted valved stent over a 5-minute period; this duration was chosen arbitrarily, and aimed to reproduce the duration of crimping during conventional PPVI. The compressed prostheses were flushed regularly with a saline solution. The sheath was then drawn back, and the valved stent was manually enlarged and removed, avoiding damage to the valve.

Condition III: compression/expansion group

Valved stents were first prepared as in condition II. After the sheath was drawn back, the valved stents were deployed in a 20-mm GORE-TEX® (W.L. Gore & Associates Ltd., Dundee, UK) conduit by inflation of the inner and outer balloons of the delivery system. The balloons were then deflated and the delivery system was removed (Figure 1A and B).

Condition IV: compression/expansion/post-dilatation

Valved stents were first prepared as in condition III. After valve deployment, post-dilatation was performed, using a 22-mm high-pressure balloon (Atlas Gold; Bard Peripheral Vascular, Inc., Tempe, AZ, USA), inflated at 20 atm for 5seconds (Figure 1A–C).

The valved stents were analysed in each in vitro condition. For each Melody® valved stent in each condition, three additional samples of the BJV wall adjacent to the leaflets within the sinuses were taken, using an 8-mm diameter (i.e. 0.5 cm2) trepan, for histological tests. After sampling, valvular leaflets and BJV wall fragments were stored in 0.625% glutaraldehyde until histological processing (within 24hours) or in a saline solution before immediate mechanical testing (Figure 1D).

For each substrate, five leaflets from two valved stents underwent histological and mechanical evaluation in each of the four conditions.

Uniaxial tensile test

We determined the mechanical properties of the leaflets using uniaxial tensile tests with a universal testing machine (Adamel Lhomargy MTS 100; MTS Systems Corp., Eden Prairie, MN, USA) equipped with TestWorks 4 software (MTS Systems Corp.). The mechanical properties of native and prosthetic valvular leaflets have been published previously with validated methods [18, 19].

Five leaflets were tested for each substrate in each of the four conditions. Tissue thickness was measured with a caliper with a precision of 0.01mm. A 100-N load cell was used to apply a tensile force to the tissue samples, and the tissue was stretched at a constant rate of 0.5mm/min to obtain a stress-strain curve, on which stress at break, elongation at break, ultimate tensile strength (the maximum stress that a material can withstand while being stretched before breaking) and elastic modulus (the slope of the stress-strain curve in the elastic deformation region) were recorded.

Histological analysis

Macroscopic analysis preceded microscopic evaluation. After paraffin embedding, 5μm-thick samples were stained with haematoxylin and eosin (H&E), and digitalized pictures were obtained at×5 and×20 magnifications. Transverse tissue fracture, the basic lesion previously described for bovine pericardial valved stents, originated from one surface of the sample, deep inside the tissue [16]; it was considered as arbitrarily significant when its depth exceeded 25% of the sample's thickness. The depth of the biggest fracture was calculated as a percentage (fracture length/sample thickness). The number of fractures and the depth of the biggest fracture were determined at ×5 magnification. The pathologist was blinded to the type of in vitro manipulation that the sample underwent.

Statistical analysis

Results are expressed as mean (standard deviation) or median (range) for continuous variables, or as number (percentage) for categorical variables. The data from these experiments were analysed with non-parametric Mann-Whitney or Kruskal-Wallis tests; these tests were performed to compare variables between two groups (i.e. conditions I vs II; I vs III; I vs IV; II vs III; II vs IV; and III vs IV). The value of statistical significance was set at P 0.05.

Results
Uniaxial tensile tests

Bovine, porcine and Melody® valve leaflets had median thicknesses of 0.57mm (0.45–0.7mm), 0.23mm (0.18–0.25mm) and 0.1mm (0.08–0.1mm), respectively, and median widths of 8mm (5–12mm), 9mm (5–11mm) and 6mm (5–9mm), respectively. Uniaxial measurements showed typical non-linear J-shaped stress-strain curves. Table 1 shows the mechanical behaviour of each substrate obtained in the different in vitro conditions.

No statistical difference was observed for the Melody® valvular leaflets between the four different conditions, for each studied variable (stress and elongation at break, ultimate tensile strength and elastic modulus).

Concerning bovine pericardial valved stents, the stress at break was significantly lower in conditions III and IV compared with the control condition (I vs III, P =0.02; I vs IV, P =0.005). Elastic modulus was significantly lower in condition III compared with conditions I and II (I vs III, P =0.042; II vs III, P =0.001). No difference was observed between conditions III and IV for elastic modulus values.

Concerning porcine pericardial valved stents, stress at break and ultimate tensile strength were significantly lower in condition IV compared with the control condition I (P =0.032 and P =0.03, respectively). Elastic modulus was significantly lower in conditions III and IV compared with condition I (I vs III, P =0.04; I vs IV, P =0.031).

Histological analysis

No macroscopic lesion, such as perforation, tear or laceration of the leaflets (or venous wall for the Melody® valved stent) was observed, whatever the in vitro condition. Microscopic analysis revealed the presence of transverse fractures in all valvular leaflets (Melody® valve, bovine pericardium, porcine pericardium) but not in Melody® BJV wall samples (Figure 2 and Figure 3). Histological lesions had a heterogeneous distribution. Indeed, areas of healthy tissue surrounded areas of severely traumatized tissue within the same leaflet. Except for porcine pericardium, transverse fractures were rarely found in samples from the control groups (condition I). Histological lesions according to substrate and in vitro conditions are presented in Table 2.



Figure 2


Figure 2. 

Histological observation of Melody® valvular leaflets (haematoxylin and eosin staining; ×5 magnification). A. Microscopic aspect of a control valvular leaflet (condition I) with a conserved architecture. B. Microscopic aspect of an injured valvular leaflet (condition III: expansion); note the inhomogeneous architecture associated with a large transverse fracture (*).

Zoom



Figure 3


Figure 3. 

Histological observation of bovine (A and B) and porcine (C and D) pericardial leaflets (haematoxylin and eosin staining; ×5 magnification). A. Microscopic aspect of a control bovine pericardial valvular leaflet (condition I) with a preserved organization of collagen bundles. B. Microscopic aspect of a traumatized bovine pericardial valvular leaflet (condition IV: post-dilatation); note the complete architecture alteration associated with a large transverse fracture (*). C. Microscopic aspect of a control porcine pericardial valvular leaflet (condition I) with a slightly altered architecture. D. Microscopic aspect of an injured porcine pericardial valvular leaflet (condition III: expansion); note the presence of a large transverse fracture (*).

Zoom

Among the Melody® valvular leaflets, the incidence of transverse fractures was significantly higher in traumatized samples compared with the control group (I vs II, P =0.043; I vs III, P =0.043; I vs IV, P =0.042). No difference was observed between conditions II, III and IV. Transverse fractures were significantly deeper in the compression group (I vs II, P =0.042).

Among bovine and porcine pericardial leaflets, the incidence and depth of transverse fractures were not statistically different between the four in vitro conditions.

No histological lesion was observed in BJV wall samples, whatever the condition.

Discussion

The aims of this study were to assess the impact of implantation procedural steps on histological structure and mechanical behaviour of the Melody® transcatheter pulmonary valved stent leaflets, and to compare these results with other valvular substrates, such as bovine and porcine pericardia. Among the Melody® prostheses, we found that procedural steps resulted in significant histological lesions from the crimping and compression stage. Conversely, bovine and porcine pericardial valved stents were not histologically altered by in vitro manipulations, although their mechanical properties were significantly modified.

Histological lesions are induced from the early steps of valved stent implantation

Amahzoune et al. showed that histological lesions, such as transverse fractures and longitudinal cleavages, occurred during crimping and deployment, with more severe injuries induced by balloon-expandable valved stents [16]. These results suggested a cumulative effect of both crimping and balloon-expansion stages on the architecture of valvular leaflets. Other authors observed similar lesions with the bovine pericardial valved stent, using various assessment techniques [15, 17, 18, 19, 20]. Unlike Amahzoune et al., we did not find that bovine pericardial leaflets were significantly injured during in vitro manipulations [16]. This difference can be explained by the fact that fresh bovine pericardium obtained from a slaughterhouse was used in their study, while we performed our tests with commercially treated – and thus possibly more resistant – bovine pericardium. Furthermore, the stents were not the same in the two studies: the platinum and iridium CP8Z34 stent is more flexible and less sharp than the stainless steel stent used by Amahzoune et al. Finally, the fact that we analysed fewer samples than these authors can partially explain the absence of statistically significant results for this substrate.

We observed transverse fracture lesions in all traumatized substrates, except the Melody® jugular venous wall. In our analysis, we did not include the presence of longitudinal cleavages, which are possibly non-specific and may correspond to artefacts. We showed that the incidence and depth of transverse fractures were significantly higher in traumatized samples compared with in the control Melody® valvular leaflets group. No difference was observed between conditions II, III and IV. Moreover, it is noteworthy that the traumatized Melody® jugular venous wall was free of histological lesions. These results suggest that lesions appear from the early implantation procedural step (crimping/compression), without a cumulative impact of balloon expansion or post-dilatation. Crushing and shearing of valvular leaflets between the stent on one hand and the balloon on the other hand during crimping and balloon inflation may explain these lesions.

Schneider et al. [21] performed an ex-vivo assessment of nine percutaneously implanted valved Melody® conduits after surgical explantation, by means of histology and immunohistochemistry. The authors found that in the absence of infection, the valve cusps were clinically competent and histologically thin and intact. This is not consistent with our findings, but the authors did not focus on the presence of transverse fractures. In addition, although valvular fractures are induced in the early post-implantation period, in vivo neoendothelialization might be beneficial for these lesions by homogenizing the surface of the leaflets.

One could argue that the traumatic injury to leaflets observed in our experiment might theoretically lead to an accelerated deterioration of valvular prostheses. Indeed, fractures of collagen bundles may create new sites for calcium deposition, and thus decrease the lifespan of the valve [22]. However, after a mean implantation time of 3.2 years, Schneider et al. observed complete neoendothelialization for all specimens, without significant pseudo-intimal proliferation and without calcifications within the valves. To date, there are no published data reporting early calcification or degeneration of the Melody® valve in the pulmonary position. Although early failure of Melody® valves implanted within bioprosthetic tricuspid valves has been reported, the pathophysiology of these isolated cases remains unclear [21, 23]. Furthermore, the mid-term valvular function of the Melody® valve is encouraging, although long-term data are lacking [3, 4].

Mechanical behaviour of leaflets after traumatic injury

Soft biological tissues have specific mechanical properties. Mechanical behaviour is one of the key characteristics of cardiac valve function. These mechanical properties are mainly determined by valve tissular architecture, and by the balance between extracellular matrix components [24].

In our experiment, we found no significant modification of the mechanical behaviour of in vitro traumatized Melody® valvular leaflets. However, we can also conclude that BJV leaflets are a resilient substrate, affected slightly by traumatic injury. Munelly et al. analysed the mechanical behaviour of bovine pericardium after compression under forces similar to those exerted by valved stent crimping; they showed that bovine pericardium was significantly stiffened by this process, with an increase in elastic modulus [25]. We also found an increase in bovine pericardium elastic modulus in our compression group (condition II). Conversely, this substrate became more elastic and less resilient after balloon expansion and post-dilatation (conditions III and IV), with a significant decrease in elastic modulus and stress at rupture.

Similar results were observed with porcine pericardial stents, which became more elastic and less resilient after balloon expansion and post-dilatation. It is noteworthy that there was no difference between conditions III and IV, showing that there was no cumulative effect of post-dilatation.

Clinical implications

Our findings should be analysed in light of published data on the incidence of right-sided endocarditis in patients with congenital heart disease after surgery or PPVI. The role played by BJV in the pathophysiology of endocarditis is concerning. We clearly demonstrated for the first time that BJV leaflets were the most histologically altered by in vitro manipulations. In a recent work, we hypothesized that the transverse fractures observed on traumatized leaflets might constitute a possible target for bacterial germs to adhere to, and could possibly explain the high incidence of IE involving Melody® valves [17, 26, 27, 28]. However, scanning electron microscopy revealed that bacteria adhered over the entire sample surface in a heterogeneous way. Nevertheless, we suggested that histological traumatic lesions might increase surface roughness, by modifying the topographical characteristics of the sample, and thus enabling higher microbial adhesion [17].

We showed that the incidence of transverse fractures was significantly higher in traumatized samples compared with in the control Melody® valvular leaflets group. No difference was observed between conditions II, III and IV. These results suggest that lesions appear from the early implantation procedural step (crimping/compression), without cumulative impact of balloon expansion or post-dilatation. These results highlight the fact that traumatic leaflet lesions would not necessarily be avoided by the use of a valve mounted on a self-expanding stent, as crimping is also mandatory with such a device.

The usefulness of post-dilatation is debated in clinical practice for PPVI. In this experiment, we showed that regardless of the type of valvular substrate, post-dilatation was not deleterious, whether in terms of histological lesions or mechanical behaviour.

It is still unclear whatever the incidence of endocarditis is higher with BJV compared with pericardium valves in clinical practice. Results from the clinical study of the Edwards pulmonic valve are still awaited. However, two points should be taken into account when comparing data. First, the results from an initial USA cohort, reported only orally by Prof. Z.M. Hijazi at various meetings (Society for Cardiac Angiography and Interventions 2014, and Pediatric And Adult Interventional Cardiac Symposium 2014 and 2015), showed an incidence of endocarditis of 3.2% at 1 year (two cases of endocarditis in a cohort of 63 patients). Secondly, populations should be similar when comparing data. Indeed, from unpublished clinical data, included populations varied greatly between the two cohorts. With the Melody® valve, the patients included tended to have smaller conduits with stenotic and pulmonary regurgitation, while the Edwards pulmonic valve patients mostly had a large unobstructed RVOT; this could artificially decrease the incidence of endocarditis, as it has been reported that patients with pure pulmonary regurgitation and low RVOT gradient after Melody® valve implantation have less endocarditis. Larger comparative studies are therefore necessary before any conclusions can be drawn.

Study limitations

Our study suffers from limitations. The small sample size in each subgroup may have reduced the statistical significance of our results. Uniaxial tensile tests were only performed in the radial direction of the samples, while they are known to have an anisotropic behaviour. In our experiment, we induced in vitro acute lesions, and our model did not take into account the role of cardiac output, pressure gradients and shear stress forces.

Conclusion

Valved stent implantation procedural steps induce Melody® valve leaflet histological lesions right from the crimping stage. Conversely, bovine and porcine pericardial valves are not significantly altered by procedural manipulations on histological analysis. The mechanical properties of Melody® valve leaflets, the thinnest of all, are not altered by these manipulations, whereas bovine and porcine pericardial valves are significantly modified, which could have an impact on the long-term valvular function and durability of pericardial valves. On the other hand, despite reassuring data on mechanical properties with Melody® valves, the histological lesions observed on traumatized leaflets might constitute a possible target for bacterial germs, and may possibly explain the high incidence of IE involving Melody® valves. Further experimental studies are warranted to better understand this issue. Results from clinical studies with pericardial valves focusing on the issue of endocarditis are obviously needed to demonstrate any propensity of one tissue over another for IE.

Sources of funding

Z.J. was supported by a grant from the Fédération Française de Cardiologie. C.B. is supported by a grant from the Fondation pour la Recherche Médicale (Équipe FRM DEQ20140329508).

Disclosure of interest

Y.B. Proctor for the company Medtronic Inc.

The other authors declare that they have no competing interest.


Acknowledgments

The authors wish to thank Medtronic Inc. for providing the Melody® valves.

References

Bonhoeffer P., Boudjemline Y., Saliba Z., and al. Percutaneous replacement of pulmonary valve in a right-ventricle to pulmonary-artery prosthetic conduit with valve dysfunction Lancet 2000 ;  356 : 1403-1405 [cross-ref]
Hascoet S., Acar P., Boudjemline Y. Transcatheter pulmonary valvulation: current indications and available devices Arch Cardiovasc Dis 2014 ;  107 : 625-634 [cross-ref]
Cheatham J.P., Hellenbrand W.E., Zahn E.M., and al. Clinical and hemodynamic outcomes up to 7 years after transcatheter pulmonary valve replacement in the US melody valve investigational device exemption trial Circulation 2015 ;  131 : 1960-1970 [cross-ref]
McElhinney D.B., Hellenbrand W.E., Zahn E.M., and al. Short- and medium-term outcomes after transcatheter pulmonary valve placement in the expanded multicenter US melody valve trial Circulation 2010 ;  122 : 507-516 [cross-ref]
Atamanyuk I., Raja S.G., Kostolny M. Bartonella henselae endocarditis of percutaneously implanted pulmonary valve: a case report J Heart Valve Dis 2011 ;  20 : 94-97
Bhat D.P., Forbes T.J., Aggarwal S. A case of life-threatening Staphylococcus aureus endocarditis involving percutaneous transcatheter prosthetic pulmonary valve Congenit Heart Dis 2013 ;  8 : E161-E164
Fraisse A., Aldebert P., Malekzadeh-Milani S., and al. Melody (R) transcatheter pulmonary valve implantation: results from a French registry Arch Cardiovasc Dis 2014 ;  107 : 607-614 [inter-ref]
Patel M., Iserin L., Bonnet D., Boudjemline Y. Atypical malignant late infective endocarditis of Melody valve J Thorac Cardiovasc Surg 2012 ;  143 : e32-e35
Patel M., Malekzadeh-Milani S., Ladouceur M., Iserin L., Boudjemline Y. Percutaneous pulmonary valve endocarditis: incidence, prevention and management Arch Cardiovasc Dis 2014 ;  107 : 615-624 [inter-ref]
Malekzadeh-Milani S., Ladouceur M., Iserin L., Bonnet D., Boudjemline Y. Incidence and outcomes of right-sided endocarditis in patients with congenital heart disease after surgical or transcatheter pulmonary valve implantation J Thorac Cardiovasc Surg 2014 ;  148 : 2253-2259 [cross-ref]
McElhinney D.B., Benson L.N., Eicken A., Kreutzer J., Padera R.F., Zahn E.M. Infective endocarditis after transcatheter pulmonary valve replacement using the Melody valve: combined results of 3 prospective North American and European studies Circ Cardiovasc Interv 2013 ;  6 : 292-300 [cross-ref]
Van Dijck I., Budts W., Cools B., and al. Infective endocarditis of a transcatheter pulmonary valve in comparison with surgical implants Heart 2015 ;  101 : 788-793 [cross-ref]
Amat-Santos I.J., Messika-Zeitoun D., Eltchaninoff H., and al. Infective endocarditis after transcatheter aortic valve implantation: results from a large multicenter registry Circulation 2015 ;  131 : 1566-1574 [cross-ref]
Martinez-Selles M., Bouza E., Diez-Villanueva P., and al. Incidence and clinical impact of infective endocarditis after transcatheter aortic valve implantation EuroIntervention 2016 ;  11 : 1180-1187 [cross-ref]
Alavi S.H., Groves E.M., Kheradvar A. The effects of transcatheter valve crimping on pericardial leaflets Ann Thorac Surg 2014 ;  97 : 1260-1266 [cross-ref]
Amahzoune B., Bruneval P., Allam B., Lafont A., Fabiani J.N., Zegdi R. Traumatic leaflet injury during the use of percutaneous valves: a comparative study of balloon- and self-expandable valved stents Eur J Cardiothorac Surg 2013 ;  43 : 488-493 [cross-ref]
Jalal Z., Galmiche L., Lebeaux D., and al. Selective propensity of bovine jugular vein material to bacterial adhesions: an in vitro study Int J Cardiol 2015 ;  198 : 201-205 [cross-ref]
de Buhr W., Pfeifer S., Slotta-Huspenina J., Wintermantel E., Lutter G., Goetz W.A. Impairment of pericardial leaflet structure from balloon-expanded valved stents J Thorac Cardiovasc Surg 2012 ;  143 : 1417-1421 [cross-ref]
Kalejs M., Stradins P., Lacis R., Ozolanta I., Pavars J., Kasyanov V. St Jude Epic heart valve bioprostheses versus native human and porcine aortic valves – comparison of mechanical properties Interact Cardiovasc Thorac Surg 2009 ;  8 : 553-556 [cross-ref]
Stradins P., Lacis R., Ozolanta I., and al. Comparison of biomechanical and structural properties between human aortic and pulmonary valve Eur J Cardiothorac Surg 2004 ;  26 : 634-639 [cross-ref]
Schneider H., Vogt M., Boekenkamp R., and al. Melody transcatheter valve: histopathology and clinical implications of nine explanted devices Int J Cardiol 2015 ;  189 : 124-131 [cross-ref]
Liao K.K., Li X., John R., and al. Mechanical stress: an independent determinant of early bioprosthetic calcification in humans Ann Thorac Surg 2008 ;  86 : 491-495 [cross-ref]
Bentham J., Qureshi S., Eicken A., Gibbs J., Ballard G., Thomson J. Early percutaneous valve failure within bioprosthetic tricuspid tissue valve replacements Catheter Cardiovasc Interv 2013 ;  82 : 428-435 [cross-ref]
Zioupos P., Barbenel J.C. Mechanics of native bovine pericardium. I. The multiangular behaviour of strength and stiffness of the tissue Biomaterials 1994 ;  15 : 366-373 [cross-ref]
Munnelly A.E., Cochrane L., Leong J., Vyavahare N.R. Porcine vena cava as an alternative to bovine pericardium in bioprosthetic percutaneous heart valves Biomaterials 2012 ;  33 : 1-8 [cross-ref]
Boulangé-Petermann L., Rault J., Bellon-Fontaine M.N. Adhesion of streptococcus thermophilus to stainless steel with different surface topography and roughness Biofouling 1997 ;  11 : 201-216
Crawford R.J., Webb H.K., Truong V.K., Hasan J., Ivanova E.P. Surface topographical factors influencing bacterial attachment Adv Colloid Interface Sci 2012 ;  179–182 : 142-149 [cross-ref]
Hou S., Gu H., Smith C., Ren D. Microtopographic patterns affect Escherichia coli biofilm formation on poly(dimethylsiloxane) surfaces Langmuir 2011 ;  27 : 2686-2691 [cross-ref]



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