A novel tissue treatment to reduce mineralization of bovine pericardial heart valves

Does valve size impact hemodynamic, left ventricular mass regression, and prosthetic valve deterioration with a sutureless aortic valve?

OBJECTIVE

To assess the mid-term clinical outcomes, hemodynamics, left ventricular (LV) mass regression, and structural valve deterioration (SVD) in patients implanted with the Perceval aortic sutureless valve across valve sizes.

METHODS

Data were obtained from a multicenter European trial and a US Investigational Device Exemption trial. Echocardiography data were analyzed by an echocardiography core lab. A mixed-effects regression model was used to assess relationships between hemodynamic outcomes, time from the procedure, and valve sizes. The Valve Academic Research Consortium (VARC)-3 definition for bioprosthetic valve failure was applied.

RESULTS

A Perceval sutureless valve was implanted in 970 patients. The median patient age was 77.8 years, 57.2% were female, the median Society of Thoracic Surgeons predicated risk of mortality was 3.3% (range, 2.1%-6.2%), and 33.4% had a concomitant procedure. The median clinical follow-up was 45.7 months (range, 28.2-76.1 months). Small and medium valves were implanted more commonly in women than in men (16.9% vs 1.9% for small and 55.1% vs 19.5% for medium; P < .001). The mean aortic valve gradients decreased significantly postimplantation and remained stable across all valve sizes throughout the follow-up period. All patients were free from severe patient-prosthesis mismatch (with an effective orifice area/m2 of >0.8). Significant LV mass regression was documented regardless valve sizes, plateaued at -9.1% at 5 years. Freedom from SVD and reintervention were 95.2% and 96.3%, respectively, at 5 years and were independent of implanted valve size (P = .22). The VARC-3 stage 3 bioprosthetic valve failure rate was low, 2.8% at 5 years.

CONCLUSIONS

The Perceval valve demonstrated low and stable mean gradients, significant LV mass regression, and low SVD and reintervention rates across all valve sizes.

Sutureless Valves, a "Wireless" Option for Patients With Aortic Valve Disease: JACC State-of-the-Art Review

Transcatheter technologies triggered the recent revision of the guidelines that progressively widened the indications for the treatment of aortic stenosis. On the surgical realm, a technology avoiding the need for sutures to anchor the prosthesis to the aortic annulus has been developed with the aim to reduce the duration of cardiopulmonary bypass and simplify the process of valve implantation. In addition to a transcatheter aortic valve replacement (TAVR)-like stent that exerts a radial force, these so-called "rapid deployment valves" or "sutureless valves" for aortic valve replacement also have cuffs to improve sealing and reduce the risk of paravalvular leak. Despite promising, the actual advantage of sutureless valves over traditional surgical procedures (surgical aortic valve replacement) or TAVR is still debated. This review summarizes the current comparative evidence reporting outcomes of "sutureless valves" for aortic valve replacement to TAVR and surgical aortic valve replacement in the treatment of aortic valve stenosis.

Early outcomes of aortic valve replacement with Perceval PLUS sutureless valve: results of the prospective multicentric MANTRA study

BACKGROUND

The aim of this study is to report the preliminary real-word clinical and hemodynamic performance from the MANTRA study in patients undergoing aortic valve replacement with Perceval PLUS sutureless valve.

METHODS

MANTRA is an ongoing "umbrella" prospective, multi-center, international post-market study to collect real-life safety and performance data on Corcym devices (Corcym S.r.l, Saluggia, Italy). Clinical and echocardiographic outcomes were collected preoperatively, at discharge and at each follow up. KCCQ-12 and EQ-5D-5L quality of life questionnaires were collected preoperatively and at 30-days.

RESULTS

A total of 328 patients underwent aortic valve replacement with Perceval PLUS in 29 International institutions. Patients were enrolled from July 2021 to October 2023 and enrollment is still ongoing. Mean age was 71.9 ± 6.4 years, mean EuroSCORE II was 2.9 ± 3.9. Minimally invasive approach was performed in 44.2% (145/328) of patients; concomitant procedures were done in 40.8% (134/328) of cases. Thirty-day mortality was 1.8% (6/328) and no re-interventions were reported. Pacemaker implant was required in 4.0% (13/328) of the patients. The assessment of the functional status demonstrated marked and stable improvement in NYHA class in most patients at 30-day follow-up, with significant increase of KCCQ-12 summary score (from 58.8 ± 23.0 to 71.8 ± 22.1, p < 0.0001) and EQ-5D-5L VAS score (from 64.5 ± 20.4 to 72.6 ± 17.5, p < 0.0001). Mean pressure gradient decreased from 46.2 ± 17.3 mmHg to 10.1 ± 4.7 mmHg at 30-day follow-up. Low or no incidence of moderate-to-severe paravalvular or central leak was reported.

CONCLUSIONS

Preliminary results demonstrate good clinical outcomes and significant improvement of Quality of Life at 30-days, excellent early hemodynamic performance within patient implanted with Perceval PLUS.

TRIAL REGISTRATION

The MANTRA study has been registered in ClinicalTrials.gov (NCT05002543, Initial release 26 July 2021).

Functional Oxidized Hyaluronic Acid Cross-Linked Decellularized Heart Valves for Improved Immunomodulation, Anti-Calcification, and Recellularization

Tissue engineering heart valves (TEHVs) are expected to address the limitations of mechanical and bioprosthetic valves used in clinical practice. Decellularized heart valve (DHV) is an important scaffold of TEHVs due to its natural three-dimensional structure and bioactive extracellular matrix, but its mechanical properties and hemocompatibility are impaired. In this study, DHV is cross-linked with three different molecular weights of oxidized hyaluronic acid (OHA) by a Schiff base reaction and presented enhanced stability and hemocompatibility, which could be mediated by the molecular weight of OHA. Notably, DHV cross-linked with middle- and high-molecular-weight OHA could drive the macrophage polarization toward the M2 phenotype in vitro. Moreover, DHV cross-linked with middle-molecular-weight OHA scaffolds are further modified with RGD-PHSRN peptide (RPF-OHA/DHV) to block the residual aldehyde groups of the unreacted OHA. The results show that RPF-OHA/DHV not only exhibits anti-calcification properties, but also facilitates endothelial cell adhesion and proliferation in vitro. Furthermore, RPF-OHA/DHV shows excellent performance under an in vivo hemodynamic environment with favorable recellularization and immune regulation without calcification. The optimistic results demonstrate that OHA with different molecular weights has different cross-linking effects on DHV and that RPF-OHA/DHV scaffold with enhanced immune regulation, anti-calcification, and recellularization properties for clinical transformation.

Crosslinking strategies of decellularized extracellular matrix in tissue regeneration

By removing the immunogenic cellular components through various decellularization methods, decellularized extracellular matrix (dECM) is considered a promising material in the field of tissue engineering and regenerative medicine with highly preserved physicochemical properties and superior biocompatibility. However, decellularization treatment can lead to some loss of structural integrity, mechanical strength, degradation stability, and biological performance of dECM biomaterials. Therefore, physical and chemical crosslinking methods are preferred to restore or even improve the biomechanical properties, stability, and bioactivity, and to achieve a delicate balance between degradation of the implanted biomaterial and regeneration of the host tissue. This review provides an overview of dECM biomaterials, and describes and compares the mechanisms and characteristics of commonly used crosslinking methods for dECM, with a focus on the potential applications of versatile dECM-based biomaterials derived from skin, cardiac tissues (pericardium, heart valves, myocardial tissue), blood vessels, liver, and kidney, modified with different chemical crosslinking reagents, in tissue and organ regeneration.

A Controlled Trial Comparing One-Year Hemodynamics of Two Bovine Pericardial Valves

BACKGROUND

 This randomized controlled trial was designed to compare 1-year hemodynamic performances and clinical outcomes after aortic valve replacement (AVR) using a recently introduced (the AVALUS group) and worldwide used (the CEPME group) bovine pericardial bioprostheses.

METHODS

 Patients were screened to enroll 70 patients in each group based on a noninferiority design. The primary endpoint of the trial was the mean pressure gradient across the aortic valve (AVMPG) at 1 year after surgery. One-year echocardiographic data were obtained from 92.1% (129 of 140 patients) of the study patients.

RESULTS

 There were no differences in baseline characteristics, including sex and body surface area (1.64 ± 0.18 vs. 1.65 ± 0.15 m2) between the groups. The AVMPG on 1-year echocardiography was 14.0 ± 4.3 and 13.9 ± 5.1 mmHg in the AVALUS and CEPME groups, respectively (the p-value for noninferiority was 0.0004). In the subgroup analyses for the respective size of the prostheses, AVMPG of the 19-mm prostheses was significantly lower in the AVALUS group than in the CEPME group (14.0 ± 4.3 vs. 20.0 ± 4.7 mmHg, p = 0.012), whereas those of the other sizes were not significantly different between the two groups. There were no significant differences in the effective orifice area (1.49 ± 0.40 vs. 1.53 ± 0.38 cm2, p = 0.500) or effective orifice area index (0.91 ± 0.22 vs 0.93 ± 0.23 cm2/m2, p = 0.570) in all the patients, or in the subgroup analysis for the 19-mm prosthesis. There were no differences in the 1-year clinical outcomes between the two groups.

CONCLUSION

 The 1-year hemodynamic and clinical outcomes of the AVALUS group were noninferior to those of the CEPME group (NCT03796442).

Genetically engineered sheep: A new paradigm for future preclinical testing of biological heart valves

BACKGROUND

Heart valve implantation in juvenile sheep to demonstrate biocompatibility and physiologic performance is the accepted model for regulatory approval of new biological heart valves (BHVs). However, this standard model does not detect the immunologic incompatibility between the major xenogeneic antigen, galactose-α-1,3-galactose (Gal), which is present in all current commercial BHVs, and patients who universally produce anti-Gal antibody. This clinical discordance leads to induced anti-Gal antibody in BHV recipients, promoting tissue calcification and premature structural valve degeneration, especially in young patients. The objective of the present study was to develop genetically engineered sheep that, like humans, produce anti-Gal antibody and mirror current clinical immune discordance.

METHODS

Guide RNA for CRISPR Cas9 nuclease was transfected into sheep fetal fibroblasts, creating a biallelic frame shift mutation in exon 4 of the ovine α-galactosyltransferase gene (GGTA1). Somatic cell nuclear transfer was performed, and cloned embryos were transferred to synchronized recipients. Cloned offspring were analyzed for expression of Gal antigen and spontaneous production of anti-Gal antibody.

RESULTS

Two of 4 surviving sheep survived long-term. One of the 2 was devoid of the Gal antigen (GalKO) and expressed cytotoxic anti-Gal antibody by age 2 to 3 months, which increased to clinically relevant levels by 6 months.

CONCLUSIONS

GalKO sheep represent a new, clinically relevant advanced standard for preclinical testing of BHVs (surgical or transcatheter) by accounting for the first time for human immune responses to residual Gal antigen that persists after current BHV tissue processing. This will identify the consequences of immune disparity preclinically and avoid unexpected past clinical sequelae.

Monomeric glutaraldehyde fixation and amino acid detoxification of decellularized bovine pericardium for production of biocompatible tissue with tissue-guided regenerative potential

The effect of monomeric glutaraldehyde fixation and amino acid detoxification on biocompatibility and tissue-guided regenerative potential of decellularized bovine pericardium was evaluated. The degree of cross-linking, porosity, enzymatic degradation, alpha-galactosyl content, the efficacy of detoxification, and cytotoxicity towards human epithelial cells were assessed. Tissue was subcutaneously implanted for eight weeks in male juvenile Sprague-Dawley rats, and mechanical properties, host cell infiltration, and calcification were evaluated. Three groups were compared i) decellularized tissue, ii) decellularized, monomeric glutaraldehyde fixed and amino acid detoxified tissue, and iii) commercial glutaraldehyde fixed non-decellularized tissue (Glycar®) (n = 6 rats per group). The fixation process gave a high degree of cross-linking (>85%), and was resistant to enzymatic degradation, with no significant effect on porosity. The detoxification process was effective, and the tissue was not toxic to mammalian cells in vitro. Tissue from both decellularized groups had significantly higher (p < 0.05) porosity and host cell infiltration in vivo. The process mitigated calcification. A non-significant decrease in the alpha-galactosyl content was observed, which increased when including the alpha-galactosidase enzyme. Mechanical properties were maintained. The fixation and detoxification process adequately removes free aldehyde groups and reduces toxicity, preventing enzymatic degradation and allowing for host cell infiltration while mitigating calcification and retaining the mechanical properties of the tissue. This process can be considered for processing decellularized bovine pericardium with tissue-guided regeneration potential for use in cardiovascular bioprostheses; however, methods of further reducing antigenicity, such as the use of enzymes, should be investigated.

Free-aldehyde neutralized and oligohyaluronan loaded bovine pericardium with improved anti-calcification and endothelialization for bioprosthetic heart valves

The number of patients with valvular heart disease is increasing yearly, and valve replacement is the most effective treatment, during which bioprosthetic heart valves (BHVs) are the most widely used. Commercial BHVs are mainly prepared with glutaraldehyde (Glut) cross-linked bovine pericardial or porcine aortic valves, but the residual free aldehyde groups in these tissues can cause calcification and cytotoxicity. Moreover, insufficient glycosaminoglycans (GAGs) in tissues can further reduce biocompatibility and durability. However, the anti-calcification performance and biocompatibility might be improved by blocking the free aldehyde groups and increasing the GAGs content in Glut-crosslinked tissues. In our study, adipic dihydrazide (ADH) was used to neutralize the residual free aldehyde groups in tissues and provide sites to blind with oligohyaluronan (OHA) to increase the content of GAGs in tissues. The modified bovine pericardium was evaluated for its content of residual aldehyde groups, the amount of OHA loaded, physical/chemical characteristics, biomechanical properties, biocompatibility, and in vivo anticalcification assay and endothelialization effects in juvenile Sprague-Dawley rats. The results showed that ADH could completely neutralize the free aldehyde groups in the Glut-crosslinked bovine pericardium, the amount of OHA loaded increased and the cytotoxicity was reduced. Moreover, the in vivo results also showed that the level of calcification and inflammatory response in the modified pericardial tissue was significantly reduced in a rat subcutaneous implantation model, and the results from the rat abdominal aorta vascular patch repair model further demonstrated the improved capability of the modified pericardial tissues for endothelialization. Furthermore, more α-SMA+ smooth muscle cells and fewer CD68+ macrophages infiltrated in the neointima of the modified pericardial patch. In summary, blocking free-aldehydes and loading OHA improved the anti-calcification, anti-inflammation and endothelialization properties of Glut-crosslinked BHVs and in particularly, this modified strategy may be a promising candidate for the next-generation of BHVs.

Ten years' experience with the sutureless aortic valve replacement: incidence and predictors for survival and valve durability at follow-up

OBJECTIVES

Aortic valve replacement with a sutureless prosthesis [sutureless aortic valve replacement (Su-AVR)] is an option for patients with severe aortic valve stenosis. However, data regarding long-term outcomes and prosthesis durability are still lacking.

METHODS

All consecutive patients who successfully underwent Su-AVR with the Perceval valve in our centre between 2010 and 2020 were included in the analysis and followed prospectively with echocardiography. Risk factor analysis was performed to assess variables associated with worse survival and bioprosthetic valve failure.

RESULTS

Study population consisted of 547 patients: the mean age was 76.4 (5.2) years, 51% were female and the mean logistic EuroSCORE was 13% (11). The median survival was 7.76 years [95% confidence interval (CI) = 6.9-8.6]. Risk factor analysis identified age [hazard ratio (HR) 1.06, 95% CI 1.03-1.11; P < 0.001), EuroSCORE II (HR 1.08, 1.02-1.13; P < 0.001), baseline dialysis (HR 2.14, 95% CI 1.4-4.4; P = 0.038) and postoperative acute kidney injury ≥2 (HR 8.97, 95% CI 4.58-17.6; P < 0.001) as factors significantly correlated with worse survival. The reported HRs for age are per 1 year and for EuroSCORE II is 1 percentage point. Structural valve deterioration (SVD) was observed in 23 patients, of whom 19 underwent reintervention (median freedom from SVD 10.3 years). In multivariable Cox analysis, age (HR 0.89, 95% CI 0.82-0.95; P < 0.001) was found to be a significant predictor of SVD. Overall, 1.8% was referred for prosthetic valve endocarditis (confirmed or suspected) during follow-up. One patient showed moderate non-SVD and none developed prosthetic valve thrombosis.

CONCLUSIONS

The sutureless valve represents a reliable bioprosthesis for aortic valve replacement in patients with a 10-year life expectancy. Younger age at the time of implant is the only factor associated with the risk of long-term SVD.

Current development of bovine jugular vein conduit for right ventricular outflow tract reconstruction

Right ventricular outflow tract (RVOT) reconstruction is a common surgical method to treat congenital cardiac lesions, and bovine jugular vein conduit (BJVC) has become a prevalent candidate of prosthetic material for this procedure since 1999. Although many clinical studies have shown encouraging results on BJVCs, complications such as stenosis, aneurysmal dilatation, valve insufficiency, and infective endocarditis revealed in other clinical outcomes still remain problematic. This review describes the underlying mechanisms causing respective complications, and summarizes the current technological development that may address those causative factors. Novel crosslinking agents, decellularization techniques, conduit coatings, and physical reinforcement materials have improved the performances of BJVCs. The authors expect that the breakthroughs in the clinical application of BJVC may come from new genetic research findings and advanced characterization apparatuses and bioreactors, and are optimistic that the BJVC will in the future provide sophisticated therapies for next-generation RVOT reconstruction.

Mechanisms and Drug Therapies of Bioprosthetic Heart Valve Calcification

Valve replacement is the main therapy for valvular heart disease, in which a diseased valve is replaced by mechanical heart valve (MHV) or bioprosthetic heart valve (BHV). Since the 2000s, BHV surpassed MHV as the leading option of prosthetic valve substitute because of its excellent hemocompatible and hemodynamic properties. However, BHV is apt to structural valve degeneration (SVD), resulting in limited durability. Calcification is the most frequent presentation and the core pathophysiological process of SVD. Understanding the basic mechanisms of BHV calcification is an essential prerequisite to address the limited-durability issues. In this narrative review, we provide a comprehensive summary about the mechanisms of BHV calcification on 1) composition and site of calcifications; 2) material-associated mechanisms; 3) host-associated mechanisms, including immune response and foreign body reaction, oxidative stress, metabolic disorder, and thrombosis. Strategies that target these mechanisms may be explored for novel drug therapy to prevent or delay BHV calcification.

Improved Cytocompatibility and Reduced Calcification of Glutaraldehyde-Crosslinked Bovine Pericardium by Modification With Glutathione

Bioprosthetic heart valves (BHVs) used in clinics are fabricated via glutaraldehyde (GLUT) crosslinking, which results in cytotoxicity and causes eventual valve calcification after implantation into the human body; therefore, the average lifetime and application of BHVs are limited. To address these issues, the most commonly used method is modification with amino acids, such as glycine (GLY), which is proven to effectively reduce toxicity and calcification. In this study, we used the l-glutathione (GSH) in a new modification treatment based on GLUT-crosslinked bovine pericardium (BP) as the GLUT + GSH group, BPs crosslinked with GLUT as GLUT-BP (control group), and GLY modification based on GLUT-BP as the GLUT + GLY group. We evaluated the characteristics of BPs in different treatment groups in terms of biomechanical properties, cell compatibility, aldehyde group content detection, and the calcification content. Aldehyde group detection tests showed that the GSH can completely neutralize the residual aldehyde group of GLUT-BP. Compared with that of GLUT-BP, the endothelial cell proliferation rate of the GLUT + GSH group increased, while its hemolysis rate and the inflammatory response after implantation into the SD rat were reduced. The results show that GSH can effectively improve the cytocompatibility of the GLUT-BP tissue. In addition, the results of the uniaxial tensile test, thermal shrinkage temperature, histological and SEM evaluation, and enzyme digestion experiments proved that GSH did not affect the ECM stability and biomechanics of the GLUT-BP. The calcification level of GLUT-BP modified using GSH technology decreased by 80%, indicating that GSH can improve the anti-calcification performance of GLUT-BP. Compared with GLUT-GLY, GLUT + GSH yielded a higher cell proliferation rate and lower inflammatory response and calcification level. GSH can be used as a new type of anti-calcification agent in GLUT crosslinking biomaterials and is expected to expand the application domain for BHVs in the future.

Tissue response, macrophage phenotype, and intrinsic calcification induced by cardiovascular biomaterials: Can clinical regenerative potential be predicted in a rat subcutaneous implant model?

The host immune response to an implanted biomaterial, particularly the phenotype of infiltrating macrophages, is a key determinant of biocompatibility and downstream remodeling outcome. The present study used a subcutaneous rat model to compare the tissue response, including macrophage phenotype, remodeling potential, and calcification propensity of a biologic scaffold composed of glutaraldehyde-fixed bovine pericardium (GF-BP), the standard of care for heart valve replacement, with those of an electrospun polycarbonate-based supramolecular polymer scaffold (ePC-UPy), urinary bladder extracellular matrix (UBM-ECM), and a polypropylene mesh (PP). The ePC-UPy and UBM-ECM materials induced infiltration of mononuclear cells throughout the thickness of the scaffold within 2 days and neovascularization at 14 days. GF-BP and PP elicited a balance of pro-inflammatory (M1-like) and anti-inflammatory (M2-like) macrophages, while UBM-ECM and ePC-UPy supported a dominant M2-like macrophage phenotype at all timepoints. Relative to GF-BP, ePC-UPy was markedly less susceptible to calcification for the 180 day duration of the study. UBM-ECM induced an archetypical constructive remodeling response dominated by M2-like macrophages and the PP caused a typical foreign body reaction dominated by M1-like macrophages. The results of this study highlight the divergent macrophage and host remodeling response to biomaterials with distinct physical and chemical properties and suggest that the rat subcutaneous implantation model can be used to predict in vivo biocompatibility and regenerative potential for clinical application of cardiovascular biomaterials.

A Well-Designed Two-Fold Crosslinked Biological Valve Leaflets with Heparin-Loaded Hydrogel Coating for Enhancing Anticoagulation, Endothelialization, and Anticalcification

Commercial biological valve leaflets (BVLs) crosslinked with Glutaraldehyde (GA) are at risk of accelerating damage and even failure, owing to high cell toxicity of GA, acute thrombosis, and calcification in...

Swim bladder as an alternative biomaterial for bioprosthetic valves

Valvular structural deterioration and calcification are the main indications for secondary intervention after bioprosthetic valve replacement, promoting an urgent requirement for more durable cardiovascular biomaterials for clinical applications. The swim bladder of carp we introduced in this study has several advantages as a raw biomaterial when compared to the bovine pericardium. First, the results of in vitro assays demonstrated that the cross-linked carp swim bladder exhibited superior biocompatibility compared to the bovine pericardium, and the anti-calcification property was verified by subcutaneous implantation experiments in rats. Furthermore, the cross-linked swim bladder tissue was sutured on a cobalt-chromium alloy stent to fabricate a pulmonary bioprosthetic valve, and then the feasibility and durability of the bioprosthetic valve were proved by a fatigue test in vitro. Finally, a sheep pulmonary bioprosthetic valve replacement in situ experiment further confirmed the superior calcification resistance, immune-compatibility, endothelialization, and hemodynamic properties of the swim bladder, suggesting that it might be used as an alternative biomaterial for bioprosthetic valves.

Comparison on the properties of bovine pericardium and porcine pericardium used as leaflet materials of transcatheter heart valve

BACKGROUND

In order to obtain the smaller delivery diameter, porcine pericardium had been used as a substitute material of bovine pericardium for the leaflet materials of transcatheter heart valve (THV). However, the differences between them had not been fully studied. Therefore, this study compared the microstructure, biochemical and mechanical properties of two materials and hydrodynamics of THV made by the two materials in detail.

METHODS

In this study, firstly, the microstructure of pericardium was analyzed by staining and scanning electron microscope; secondly, the biochemical properties of pericardium after different processes were compared by heat shrinkage temperature test, free amino and carboxyl concentration test, enzyme degradation test, subcutaneous implantation calcification analysis in rats; finally, the mechanical properties were evaluated by uniaxial tensile test before and after the pericardium being crimped, and then, the hydrodynamics of THV was studied according to the ISO5840 standard.

RESULTS

Compared with bovine pericardium, after the same process, porcine pericardium showed a looser and tinier fiber bundle, a similar free carboxyl concentration, a lower resistance to enzyme degradation, a significantly lower calcification, bearing capacity and damage after being crimped, a better hydrodynamic and adaption with lower cardiac output and deformation of implantation position. Meanwhile the dehydration process of pericardium almost had preserved all the biochemical advantages of two materials.

CONCLUSION

In this study, porcine and bovine pericardium showed some significant differences in biochemical, mechanical properties and hydrodynamics. According to the results, it was presumed that the thinner porcine pericardium might be more suitable for THV of right heart system. Meanwhile, more attention should be taken for the calcification of THV made by the bovine pericardium.

Morphologic investigation on Perceval S, a sutureless pericardial valve prosthesis: collagen integrity after collapsing-ballooning and structural valve deterioration at distance

Perceval S is a self-expandable, stent-mounted bioprosthetic valve (BPV), with glutaraldehyde treated bovine pericardium, processed with homocysteic acid as an anti-calcification treatment. The stent is crimpable but the valve insertion is done surgically via a shorter procedure which does not require sutures. OBJECTIVES: MATERIAL AND METHODS: RESULTS: CONCLUSIONS: Collapsing and ballooning do not alter cusp collagen periodicity. Structural valve deterioration with stenosis, due to dystrophic calcification and fibrous tissue overgrowth, seldom occurred in the mid-term. Glutaraldehyde fixed pericardium has the potential to undergo structural valve deterioration with time, similar to well-known BPV failure. This supports the recommendation to pursue improvement of tissue valve treatment with enhanced durability.

Generation of glycans depleted decellularized porcine pericardium, using digestive enzymatic supplements and enzymatic mixtures for food industry

BACKGROUND

Xenogeneic pericardium has been used largely for various applications in cardiovascular surgery. Nevertheless, xenogeneic pericardial patches fail mainly due to their antigenic components. The xenoantigens identified as playing a major role in recipient immune response are the Galα1-3Gal (α-Gal) epitope, the non-human sialic acid N-glycolylneuraminic acid (Neu5Gc), and the porcine SDa antigen, associated with both proteins and lipids. The reduction in glycans from porcine pericardium might hinder or reduce the immunogenicity of xenogeneic scaffolds.

METHODS

Decellularized porcine pericardia were further treated at different time points and dilutions with digestive enzymatic supplements and enzymatic mixtures applied for food industry, for the removal of potentially immunogenic carbohydrates. Carbohydrates removal was investigated using up to 8 different lectin stains for the identification of N- and O-glycosylations, as well as glycolipids. Histoarchitectural changes in the ECM were assessed using Elastica van Gieson stain, whereas changes in mechanical properties were investigated via uniaxial tensile test and burst pressure test.

RESULTS

Tissues after enzymatic treatments showed a dramatic decrease in lectin stainings in comparison to tissues which were only decellularized. Histological assessment revealed cell-nuclei removal after decellularization. Some of the enzymatic treatments induced elastic lamellae disruption. Tissue strength decreased after enzymatic treatment; however, treated tissues showed values of burst pressure higher than physiological transvalvular pressures.

CONCLUSIONS

The application of these enzymatic treatments for tissue deglycosylation is totally novel, low cost, and appears to be very efficient for glycan removal. The immunogenic potential of treated tissues will be further investigated in subsequent studies, in vitro and in vivo.

A novel detergent-based decellularization combined with carbodiimide crosslinking for improving anti-calcification of bioprosthetic heart valve

Currently, valve replacement surgery is the only therapy for the end-stage valvular diseases because of the inability of regeneration for diseased heart valves. Bioprosthetic heart valves (BHVs), which are mainly derived from glutaraldehyde (GA) crosslinked porcine aortic heart valves or bovine pericardium, have been widely used in the last decades. However, it is inevitable that calcification and deterioration may occur within 10-15 years, which are still the main challenges for the BHVs in clinic. In this study, N-Lauroylsarcosine sodium salt (SLS) combined with N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were utilized to decellularize and crosslink the heart valves instead of GA treatment. The obtained BHVs exhibited excellent extracellular matrix stability and mechanical properties, which were similar with GA treatment. Moreover, the obtained BHVs exhibited betterin vitrobiocompatibilities than GA treatment. After subcutaneous implantation for 30 d, the obtained BHVs showed mitigated immune response and reduced calcification compare with GA treatment. Therefore, all the above results indicated that the treatment of SLS-based decellularization combined with EDC/NHS crosslink should be a promising method to fabricate BHVs which can be used in clinic in future.

Magna ease bioprosthetic aortic valve: mid-term haemodynamic outcomes in 1126 patients

OBJECTIVES

The Magna Ease aortic valve (Edwards Lifesciences, Irvine, CA) is a third-generation bioprosthetic valve developed as a modification of the well-studied Perimount and Magna valve designs. This study's objective is to evaluate a large, single-centre experience with Magna Ease aortic valve replacement (AVR) focusing on clinical outcomes and haemodynamic performance.

METHODS

All patients undergoing AVR between 8/2010 and 10/2018 at our institution implanted with the Magna Ease valve were included except those undergoing ventricular assist device or congenital aortic surgery. Primary outcomes were overall survival and freedom from reoperation. Mean transprosthetic gradient (mTPG) and structural valve deterioration (SVD) served as secondary outcomes.

RESULTS

Totally 1126 consecutive implantations of Magna Ease valves were included. Concomitant procedures were performed in 56.5% (n = 636). No severe patient-prosthesis mismatch (PPM) was present at implantation. Overall survival at 30 days, 1 year, 5 years and 9 years was 97.2%, 95.0%, 86.1% and 78.2%, respectively, with improved survival for isolated AVR. Total of 2.4% (n = 27) of patients required reoperation with 0.3% (n = 4) for SVD. Echocardiographic follow-up data revealed low mTPG throughout the study period. SVD occurred in 28.7% of patients at a mean of 3.9 years post implantation.

CONCLUSIONS

Magna Ease AVR maintained low mean transprosthetic gradients throughout mid-term evaluation and was associated with excellent overall survival and freedom from reoperation at nine years post implantation.

Abdominal cavity unidirectional shunt for refractory pericardial effusion 7 months after cardiac valve replacement: A case report

Refractory pericardial effusion after repeated pericardial drainage and drug therapy for nearly half a year after cardiac valve replacement is rare. We present the case of a 36-year-old female patient who underwent an abdominal cavity unidirectional shunt for refractory massive pericardial effusion through a subxiphoid mini-incision, 7 months after cardiac valve replacement. The head end of a prefabricated bovine pericardial short tube with double leaflets on the tail was sutured to the small incised hole of the diaphragm, whereas the body and the tail of the short tube were dissociated in the left anterior hepatic space. Three months later, the pericardial effusion completely disappeared, no peritoneal effusion occurred, and all symptoms vanished.

A glimpse of hope: cardiac surgery in low- and middle-income countries (LMICs)

Currently, more than five times more people live in low- and middle-income countries (LMICs) than in high-income countries (HICs). As such, the downward trend in cardiac surgical needs in HICs reflects only the situation of one sixth of the world population while the vast majority living in LMICs has still no or limited access to life saving heart operations. In these countries, rheumatic heart disease (RHD) still accounts for a significant proportion of cardiac surgical needs. In low- and lower-middle income countries it remains the single most common cardiovascular disease in young adult and adolescent patients in need of heart surgery outweighing other indications such as congenital cardiac defects almost 4-fold. Compared to HICs with their predominance of calcific aortic stenosis in the elderly mitral valve surgery is required in >90% of the largely young patients with RHD in low-income countries (LICs) and still in 70% of the often middle aged patients in middle-income countries (MICs). Although recent government initiatives in LICs led to the establishment of local, independent cardiac surgical services gradually replacing fly-in missions, these centers still only cover less than 2% of the needs of their populations. In MICs, cardiac surgical needs continually grow with the emergence of degenerative diseases. As such, in spite of the concomitant growth of cardiac surgical capacity, significantly less than half the estimated patients in need have access. Capacities in LICs range from 0.5 to 7 cardiac operations/million population; 100-481/million in MICs and >1,200/million in HICs such as the USA and Germany. While a new level of awareness of the scope and magnitude of the problem has begun to emerge in LICs and the establishment of local cardiac surgical capacity has given rise to a glimpse of hope, the challenges of expanding these fledgling services to a significant proportion of the population still seem insurmountable. Challenges in MICs are on the other hand the widening gap between private cardiac medicine for the affluent few and overwhelmed public services for the many and the rural urban divide with the underappreciation of the ongoing dominance of RHD in the rural and indigent population on the other. Overshadowing all LMICs is the low level of valve-repair skills associated with insufficient cardiac surgical capacity and the unavailability of suitable replacement valves which address the young age of the patients and the difficulties of anticoagulation in a socioeconomic environment distinctly different from the elderly patients of HICs.

Sterilization and Cross-Linking Combined with Ultraviolet Irradiation and Low-Energy Electron Irradiation Procedure: New Perspectives for Bovine Pericardial Implants in Cardiac Surgery

BACKGROUND

 Bovine pericardium is the major natural source of patches and aortic valve substitutes in cardiac repair procedures. However, long-term tissue durability and biocompatibility issues lead to degeneration (e.g., calcification) that requires reoperation. Tissue preparation strategies, including glutaraldehyde fixation, are reasons for the deterioration of pericardial tissues. We describe a pretreatment procedure involving sterilization and cross-linking combined with ultraviolet (UV) irradiation and low-energy electron irradiation (SULEEI). This innovative, glutaraldehyde-free protocol improves the mechanical aspects and biocompatibility of porcine pericardium patches.

METHODS

 We adopted the SULEEI protocol, which combines decellularization, sterilization, and cross-linking, along with UV irradiation and low-energy electron irradiation, to pretreat bovine pericardium. Biomechanics, such as ultimate tensile strength and elasticity, were investigated by comparing SULEEI-treated tissue with glutaraldehyde-fixed analogues, clinical patch materials, and an aortic valve substitute. Histomorphological and cellular aspects were investigated by histology, DNA content analysis, and degradability.

RESULTS

 Mechanical parameters, including ultimate tensile strength, elasticity (Young's modulus), and suture retention strength, were similar for SULEEI-treated and clinically applied bovine pericardium. The SULEEI-treated tissues showed well-preserved histoarchitecture that resembled all pericardial tissues investigated. Fiber density did not differ significantly. DNA content after the SULEEI procedure was reduced to less than 10% of the original tissue material, and more than 50% of the SULEEI-treated pericardium was digested by collagenase.

CONCLUSION

 The SULEEI procedure represents a new treatment protocol for the preparation of patches and aortic valve prostheses from bovine pericardial tissue. The avoidance of glutaraldehyde fixation may lessen the tissue degeneration processes in cardiac repair patches and valve prostheses.

Decellularization as a method to reduce calcification in bovine pericardium bioprosthetic valves

OBJECTIVES

Decellularization is an alternative method for processing biological tissues with decreased antigenicity and resistance to calcification. The aim of this study was to characterize the properties of decellularized (dCell) bovine pericardium fixed with 0.1% glutaraldehyde (GA) and to evaluate outcomes of bioprosthetic valves constructed with this tissue when implanted in the mitral position of juvenile sheep.

METHODS

Bioprosthetic mitral valves were constructed with fresh bovine pericardium fixed in 0.5% GA (control group) or dCell bovine pericardium fixed in 0.1% GA (study group). Before implantation, samples were submitted to histological (haematoxylin-eosin, Movat and 4',6-diamidino-2-phenylindole), biochemical (residual deoxyribonucleic acid and α-gal epitopes) and biomechanical characterization. Valves were implanted (n = 8 in each group) as a mitral valve replacement for 180 days in sheep and explants were re-evaluated histologically and for calcification with radiological studies and calcium content determination.

RESULTS

Unimplanted dCell pericardia exhibited a well-preserved extracellular matrix with absence of cells, a 77% reduction in deoxyribonucleic acid levels and with no detectable α-gal epitopes. When compared to controls, they had lower ultimate tensile strength (7.3 ± 5.4 vs 10.2 ± 3.0 mPa, P = 0.04) and greater percentage elongation in the longitudinal direction (29 ± 6.5% vs 23.8 ± 5.1%, P = 0.02). After 180 days in mitral position, dCell valves showed pliable leaflets without macroscopic signs of calcification. Histologically, dCell leaflets had intact collagen fibres, better tissue remodelling and a significant 89% reduction in calcium content.

CONCLUSIONS

This study demonstrates that bioprosthetic valves constructed with dCell bovine pericardium fixed in low GA concentration were resistant to calcification and may thereby improve long-term durability of the tissue.