Histological examination of explanted tissue-engineered bovine pericardium following heart valve repair

The Use of the CardioCel 3D 60° Patch for Aortic Arch Reconstruction in Infancy-A Word of Caution

BACKGROUND

There are limited data on outcomes after implantation of the CardioCel 3D 60° patch in great vessel repair. After anecdotally witnessing an increase in negative outcomes, we reviewed our experience using this patch in our neonate and infant patients undergoing aortic arch repair.

METHODS

Aortic arch repair with implantation of the CardioCel 3D 60° patch was performed in 24 patients between July 2018 and July 2021. Dominant cardiac morphologies were hypoplastic left heart syndrome (66%), atrioventricular canal defects (13%), and other (21%). Median age at implantation was 44 days (interquartile range [IQR], 6-112 days). Recurrent obstruction was defined as the need for reoperation or catheter intervention or recurrent peak pressure gradient of descending aorta ≥25 mm Hg on echocardiography.

RESULTS

Five deaths occurred after a median of 217 days (IQR, 69-239 days). Twelve patients (50%) had recurrent obstruction. Three patients (13%) required redo aortic arch operation after a median of 148 days (IQR, 128-193 day), with extensive fibrous coating of the patch interior causing obstruction. Eleven patients (46%) required at least 1 balloon angioplasty on their aorta after a median of 102 days (IQR, 83-130 days) after repair, and 3 needed >1 catheter intervention. The estimated probability of having recurrent obstruction was 85% at 6 months and 71% at the 1-year follow (P = .06).

CONCLUSIONS

Recurrent aortic obstruction occurred in half of our patients shortly after repair. The use of the CardioCel 3D 60° patch for aortic arch reconstruction in neonates and infants should be reevaluated.

Ectopic Calcification in Congenital Heart Surgery: A Material-Centric Review

The modern congenital heart surgeon has an array of materials available for cardiovascular repair. With advancements in the surgical outcomes for pediatric cardiac defects, choice of material has become increasingly dependent on late-term complications associated with each material. Calcification is a leading long-term complication and is increasing in prevalence with materials lasting longer in patients. Material calcification can impair functionality, lead to subsequent complications, and require additional interventions. A comprehensive literature review was conducted to investigate ectopic calcification of commonly used materials for congenital heart defect repair. Mechanisms of ectopic calcification among commonly used materials were investigated. Ectopic calcification is initiated by material-specific immunological reactions. Recent efforts have focused on developing new materials that are not prone to calcification. ePTFE was widely used in cardiovascular applications but still has reported instances of calcification in various situations, such as long-term use. Tissue engineering techniques have shown reduced calcification in reports. Calcification can occur in all conventional materials we reviewed and, in some cases, has led to life-threatening complications. Favorable outcomes have been reported with tissue-engineered materials, with the expectation of continued positive results in future reports. With an array of synthetic and biological materials now displaying acceptable surgical and short-term outcomes, there is a pressing need to review the long-term viability of these materials, especially considering improved patient survival to adulthood. Furthermore, developing new materials to mitigate calcification remains a promising avenue of research in this field.

Midterm results after aortic valve neocuspidization

Objectives

Aortic valve neocuspidization with autologous pericardium is gaining increasing attention as a surgical treatment option for aortic valve disease. However, little is known about midterm durability and valve-related events.

Methods

Patients undergoing aortic valve neocuspidization between 2016 and 2021 were included. Transthoracic echocardiography was performed before the operation, at discharge, and annually thereafter. Data were analyzed for incidences of structural valve deterioration, bioprosthetic valve failure, survival, freedom from reoperation, and hemodynamic performance.

Results

A total of 162 patients underwent aortic valve neocuspidization (mean age, 52.6 ± 16.6 years; range, 13-78 years); 114 (70.4%) were male. A total of 132 patients presented with a bicuspid aortic valve (81.5%) and 126 patients presented with aortic valve stenosis (77.8%). Concomitant procedures were performed in 63 patients (38.9%). Mean follow-up was 3.5 ± 1.2 years. At discharge, peak and mean pressure gradients were 15.6 ± 7.2 mm Hg and 8.4 ± 3.7 mm Hg, respectively, with a mean effective orifice area of 2.4 ± 0.8 cm2. After 5 years, peak and mean pressure gradients were 14.5 ± 4.6 mm Hg and 7.5 ± 2.2 mm Hg, respectively, with a mean effective orifice area of 2.3 ± 0.8 cm2. At 5 years, cumulative incidences of moderate and severe structural valve deterioration and bioprosthetic valve failure were 9.82% ± 3.87%, 6.96% ± 3.71%, and 12.1% ± 4.12%, respectively. Survival was 97.3% ± 1.4%, and freedom from reoperation was 91.3% ± 2.4%.

Conclusions

Aortic valve neocuspidization accomplishes low pressure gradients early after initial surgery and during follow-up. Survival in this young patient population is excellent. The main reason for reoperation is endocarditis, and rates for structural valve degeneration are low.

Nonlocal damage evaluation of a sigmoid-based damage model for fibrous biological soft tissues

The comprehension and modeling of the mechanical behavior of soft biological tissues are essential due to their clinical applications. This knowledge is essential for predicting tissue responses accurately and enhancing our ability to compute the behavior of biological structures and bio-prosthetic devices under specific loading conditions. The current research is centered on modeling the initiation and progression of soft tissues damage, which typically exhibit intricate anisotropic and nonlinear elastic characteristics. For this purpose, the following study presents a comparative analysis of the computational performance of two distinct damage modeling techniques. The first technique employs a well-established damage model, based on a piece-wise exponential damage function as proposed by Calvo et al. (Int J Numer Methods Eng 69:2036-2057, 2007. https://doi.org/10.1002/nme.1825 ). The second approach adopts a sigmoid function, as proposed by López-Campos et al. (Comput Methods Biomech Biomed Eng 23(6):213-223. https://doi.org/10.1080/10255842.2019.1710742 ). The aim of this study is to verify the validity of the López-Campos sigmoid-based damage model to be used in finite element simulation, the implementation of which is unknown. For this proposal, both models were implemented within a commercial Finite Element software package, and their responses to local and non-local damage algorithms were assessed in depth through two standard benchmark tests: a plate with a hole and a ball burst. The results of this study indicate that, for a wide range of cases, such as in-plane stresses, out-plane stresses, stress concentration and contact, all over large displacement conditions, the López-Campos damage model shows a good response to non-local algorithms achieving mesh independence and convergence in all these cases. The results obtained are in line with those obtained for the Calvo's damage model, showing, in addition, larger deformations under in-plane stress and stress concentration conditions and a lower number of iterations under out-plane stress and contact conditions. Consequently, the López-Campos' damage model emerges as a valuable and useful tool in the field of mechanical damage research in biological systems.

Beyond Synthetics: Promising Outcomes With the Invengenx® Bovine Pericardial Patch for Ventricular Septal Defect Repair in a Young Pediatric Population

Ventricular septal defects (VSDs) are a prevalent congenital heart anomaly demanding safe and lasting interventions. This paper explores the application of Invengenx® bovine pericardial patch (Tisgenx, Irvine, California), a promising biomaterial, in VSD repair. We present two case studies: a seven-month-old infant and a three-year-old child undergoing VSD closure using autologous and bovine pericardial patches, respectively. Both patients tolerated the procedures well, experiencing no intra-operative complications and demonstrating excellent postoperative recovery. Echocardiography postoperatively showed no complications and improved clinical outcomes. Notably, the pericardial patches exhibited excellent integration and suture retention, highlighting their durability and compatibility with the growing heart. These cases establish the feasibility and effectiveness of the Invengenx® pericardial patch for VSD repair. The favorable outcomes in terms of safety and efficacy support the potential of this biomaterial as a valuable alternative in pediatric cardiac surgery, particularly for complex VSDs or patients with contraindications to synthetic patches. Further research is crucial to unlock the full potential of bovine pericardium as a durable and advantageous option for VSD repair in a broader range of pediatric patients.

CardioCel® for repair of congenital heart defects: nationwide results of over 1000 implants

OBJECTIVES

To assess the mid-term performance of CardioCel for the repair of congenital heart defects.

METHODS

Data were retrospectively collected from databases and hospital records in 3 congenital cardiac surgery centres in Australia. Kaplan-Meier curves and log-rank tests were used to test for associations between patient age, gender, patch type and site of implantation. Multivariable Cox regression was used to test whether any specific implantation site was associated with reintervention risk, after adjusting for age group, gender and patch type.

RESULTS

A total of 1184 CardioCel patches were implanted in 752 patients under the age of 18 years. Median age at implant was 12 months [interquartile range (IQR) 3.6-84]. Median follow-up was 2.1 years (IQR 0.6-4.6). Probability of freedom from CardioCel-related reintervention was 93% [95% confidence interval (CI) 91-95] at 1 year, 91% (95% CI 88-93) at 3 years and 88% (95% CI 85-91) at 5 years, respectively. On multivariable regression analysis, aortic valve repair had a higher incidence of reintervention [hazard ratio (HR) = 7.15, P = 0.008] compared to other sites. The probability of reintervention was higher in neonates (HR = 6.71, P = 0.0007), especially when used for augmentation of the pulmonary arteries (HR = 14.38, P = 0.029), as compared to other age groups.

CONCLUSIONS

CardioCel can be used for the repair of a variety of congenital heart defects. In our study, in patients receiving a CardioCel implant, reinterventions were higher when CardioCel was used to augment the pulmonary arteries in neonates and for aortic valve repair as compared to other sites.

Hemocompatibility tuning of an innovative glutaraldehyde-free preparation strategy using riboflavin/UV crosslinking and electron irradiation of bovine pericardium for cardiac substitutes

Hemocompatibility tuning was adopted to explore and refine an innovative, GA-free preparation strategy combining decellularization, riboflavin/UV crosslinking, and low-energy electron irradiation (SULEEI) procedure. A SULEEI-protocol was established to avoid GA-dependent deterioration that results in insufficient long-term aortic valve bioprosthesis durability. Final SULEEI-pericardium, intermediate steps and GA-fixed reference pericardium were exposed in vitro to fresh human whole blood to elucidate effects of preparation parameters on coagulation and inflammation activation and tissue histology. The riboflavin/UV crosslinking step showed to be less efficient in inactivating extracellular matrix (ECM) protein activity than the GA fixation, leading to tissue-factor mediated blood clotting. Intensifying the riboflavin/UV crosslinking with elevated riboflavin concentration and dextran caused an enhanced activation of the complement system. Yet activation processes induced by the previous protocol steps were quenched with the final electron beam treatment step. An optimized SULEEI protocol was developed using an intense and extended, trypsin-containing decellularization step to inactivate tissue factor and a dextran-free, low riboflavin, high UV crosslinking step. The innovative and improved GA-free SULEEI-preparation protocol results in low coagulant and low inflammatory bovine pericardium for surgical application.

Performance of CardioCel in Cardiac Surgery: A Systematic Review

A systematic review was performed for evaluation of the performance of CardioCel^® in cardiac surgery. The review included all studies published from January 2013 to December 2020. We conclude that CardioCel is a strong, flexible tissue substitute with good handling characteristics and a low incidence of thrombosis, aneurysm formation, infection, or structural degeneration. It can be used for a variety of intracardiac and extracardiac repairs of congenital heart defects in all age groups with good durability at mid-term follow-up. However, the use of CardioCel in certain positions requires caution. Information on the long-term performance of CardioCel is lacking.

Early and late results of mitral valve repair with anterior leaflet patch augmentation

OBJECTIVES

The aim of this study was to determine the long-term results of mitral valve (MV) repair with anterior leaflet patch augmentation.

METHODS

Between 2012 and 2015, 45 patients underwent MV repair using the anterior leaflet patch augmentation technique at our institution. The mean age of the patients was 65.9 ± 13.0 years (16 males). We reviewed the MV pathology and the surgical techniques used and assessed the early and late results.

RESULTS

In terms of MV pathology, 43 patients (95.6%) had pure mitral regurgitation (MR) and 2 patients (4.4%) had mixed mitral stenosis and MR. Rheumatic changes were seen in 18 patients (40.0%). Postoperative echocardiography showed that 95.6% of patients had none to mild MR. During a median follow-up period of 5.5 years (range 0.1–8.3 years), there were 8 late deaths. Nine patients (20%) required reoperation. The mean interval between the initial operation and redo operation was 3.7 ± 3.1 years (range: 0.4–7.8 years). The causes of reoperation included patch dehiscence (n = 4), progression of mitral stenosis (n = 2), band dehiscence (n = 1), patch enlargement (n = 1) and unknown (n = 1). Eight patients underwent MV replacement and 1 underwent repeat MV repair. The freedom from reoperation at 3 and 5 years was 85.7 ± 6.7% and 81.2 ± 7.7%, respectively.

CONCLUSIONS

Anterior leaflet patch augmentation can provide excellent early results in the majority of the patients even in the presence of rheumatic pathology; however, we observed late reoperation in 20% of patients. Thus, this technique should be used with caution and careful follow-up with serial echocardiography is essential.

Bioengineering Human Tissues and the Future of Vascular Replacement

Cardiovascular defects, injuries, and degenerative diseases often require surgical intervention and the use of implantable replacement material and conduits. Traditional vascular grafts made of synthetic polymers, animal and cadaveric tissues, or autologous vasculature have been utilized for almost a century with well-characterized outcomes, leaving areas of unmet need for the patients in terms of durability and long-term patency, susceptibility to infection, immunogenicity associated with the risk of rejection, and inflammation and mechanical failure. Research to address these limitations is exploring avenues as diverse as gene therapy, cell therapy, cell reprogramming, and bioengineering of human tissue and replacement organs. Tissue-engineered vascular conduits, either with viable autologous cells or decellularized, are the forefront of technology in cardiovascular reconstruction and offer many benefits over traditional graft materials, particularly in the potential for the implanted material to be adopted and remodeled into host tissue and thus offer safer, more durable performance. This review discusses the key advances and future directions in the field of surgical vascular repair, replacement, and reconstruction, with a focus on the challenges and expected benefits of bioengineering human tissues and blood vessels.

An overview of post transplantation events of decellularized scaffolds

Regenerative medicine and tissue engineering are reasonable techniques for repairing failed tissues and could be a suitable alternative to organ transplantation. One of the most widely used methods for preparing bioscaffolds is the decellularization procedure. Although cell debris and DNA are removed from the decellularized tissues, important compositions of the extracellular matrix including proteins, proteoglycans, and glycoproteins are nearly preserved. Moreover, the obtained scaffolds have a 3-dimensional (3D) structure, appropriate naïve mechanical properties, and good biocompatibility. After transplantation, different types of host cells migrate to the decellularized tissues. Histological and immunohistochemical assessment of the different bioscaffolds after implantation reveals the migration of parenchymal cells, angiogenesis, as well as the invasion of inflammatory and giant foreign cells. In this review, the events after transplantation including angiogenesis, scaffold degradation, and the presence of immune and tissue-specific progenitor cells in the decellularized scaffolds in various hosts, are discussed.

Industrial Processing Induces Pericardial Patch Degeneration

Background

Autologous pericardium is considered gold standard for various reconstructive surgical procedures in children. However, processed bovine, equine, and porcine pericardial tissue are also widely used. We investigated structural differences and analyzed alterations caused by industrial processing. Additionally human and equine pericardium explants, used during aortic valve reconstruction were analyzed.

Methods

Pericardial tissues (native, processed and explanted) were gathered and stained with HE and EvG to visualize collagen as well as elastic fibers. Fiber structures were visualized by light and polarization microscopy. Antibody staining against CD 3, CD 20, and CD 68 was performed to identify inflammation.

Results

Native pericardium of different species showed small differences in thickness, with bovine pericardium being the thickest [bovine: 390 μm (± 40.6 μm); porcine: 223 μm (± 30.1 μm); equine: 260 μm (± 28.4 μm)]. Juvenile pericardium was 277 μm (± 26.7 μm). Single collagen bundle diameter displayed variations (~3–20 μm). Parallel collagen fibers were densely packed with small inter-fibrillary space. After industrial tissue processing, loosening of collagen network with inter-fibrillary gapping was observed. Pericardium appeared thicker (mean values ranging from 257–670 μm). Processed tissue showed less birefringence under polarized light. All analyzed tissues showed a small number of elastic fibers. Fibrosis, calcification and inflammatory processes of autologous and equine pericardium were observed in patient explants.

Conclusion

None of the analyzed tissues resembled the exact structure of the autologous pericardial explant. Degeneration of pericardium starts during industrial processing, suggesting a potential harm on graft longevity in children. A careful surgical approach prior to the implantation of xenografts is therefore needed.

An study on the influence of collagen fiber directions in TAVs performance using FEM

Transcatheter Aortic Valve Implantation (TAVI) or Replacement (TAVR) is a promising treatment for aortic valve stenosis, consisting of a procedure to replace a damaged native aortic valve by a bioprosthetic one. This replacement valve control the flow of blood using leaflets that are similar to the ones of a native aortic valve. Commonly manufactured using bovine or porcine pericardium, it is a tissue histologically composed of collagen fibers embedded into a nearly-isotropic matrix, where their distribution makes the pericardium behave as an anisotropic hyperelastic material. Because of such complicated behavior, bioprosthetic pericardium valves are, as expected, sensitive to the distribution and orientation of these fibers in such device. Therefore, the objective of this work is a thorough systematic study on the influence of these fibers' distribution. First, a Finite Element model of a bioprosthetic valve is generated; then, a material routine to accurately describe the behavior of pericardium is implemented in a commercial software package; in addition, a dedicated algorithm to specify the direction of fibers is developed. Finally, a systematic study on the influence that fiber orientations have on the overall behavior of the TAV is performed. As a result of this study, two extreme behaviors are highlighted depending on the preferential orientation of collagen fibers; namely, one with fibers in circumferential direction and the opposite with fibers in an axial orientation. Then, it is concluded that the behavior of fibers in circumferential direction is very sensitive to small variations of the orientation angle, whereas such orientation is not as determining when the aim is to achieve a behavior near to the one corresponding with axial orientation.

Mammalian Pericardium-Based Bioprosthetic Materials in Xenotransplantation and Tissue Engineering

Bioprosthetic materials based on mammalian pericardium tissue are the gold standard in reconstructive surgery. Their application range covers repair of rectovaginal septum defects, abdominoplastics, urethroplasty, duraplastics, maxillofacial, ophthalmic, thoracic and cardiovascular reconstruction, etc. However, a number of factors contribute to the success of their integration into the host tissue including structural organization, mechanical strength, biocompatibility, immunogenicity, surface chemistry, and biodegradability. In order to improve the material's properties, various strategies are developed, such as decellularization, crosslinking, and detoxification. In this review, the existing issues and long-term achievements in the development of bioprosthetic materials based on the mammalian pericardium tissue, aimed at a wide-spectrum application in reconstructive surgery are analyzed. The basic technical approaches to preparation of biocompatible forms providing continuous functioning, optimization of biomechanical and functional properties, and clinical applicability are described.