Contemporary outcomes for arterial reconstruction with non-saphenous vein cryo-preserved conduits.

OBJECTIVE: Cryopreserved (CP) products are utilized during challenging cases when autogenous or prosthetic conduit use is not feasible. Despite decades of experience with cadaveric greater saphenous vein (GSV), there is limited available data regarding the outcomes and patency of other CP products, specifically arterial and deep venous grafts. This study was designed to evaluate outcomes of non-GSV CP conduits in patients undergoing urgent, emergent, and elective arterial reconstruction at our institution. We hypothesized that non-GSV CP allografts have adequate patency and outcomes and are therefore a feasible alternative to GSV in settings where autologous graft is unavailable or prosthetic grafts are contraindicated. METHODS: This study was approved by the Institutional Review Board at our institution. We retrospectively reviewed charts of patients undergoing arterial reconstructions using CP conduits from 2010 to 2022. Data collected included demographics, comorbidities, smoking status, indications for surgery, indication for CP conduit use, anatomic reconstruction, urgency of procedure, and blood loss. Time-to-event outcomes included primary and secondary graft patency rates, follow-up amputations, and mortality; other complications included follow-up infection/reinfection and 30-day complications, including return to the operating room and perioperative mortality. Time-to-event analyses were evaluated using product-limit survival estimates. RESULTS: Of 96 identified patients receiving CP conduits, 56 patients received non-GSV conduits for 66 arterial reconstructions. The most common type of non-GSV CP product used was femoral artery (31 patients), followed by aorto-iliac artery (22 patients), and femoral vein (19 patients), with some patients receiving more than one reconstruction or CP product. Patients were mostly male (75%), with a mean age of 63.1 years and a mean body mass index of 26.7 kg/m2. Indications for CP conduit use included infection in 53 patients, hostile environment in 36 patients, contaminated field in 30 patients, tissue coverage concerns in 30 patients, inadequate conduit in nine patients, and patient preference in one patient. Notably, multiple patients had more than one indication. Most surgeries (95%) were performed in urgent or emergent settings. Supra-inguinal reconstructions were most common (53%), followed by extra-anatomic bypasses (47%). Thirty-day mortality occurred in 10 patients (19%). Fifteen patients (27%) required return to the operating room for indications related to the vascular reconstructions, with 10 (18%) cases being unplanned and five (9%) cases planned/staged. Overall survival at 6, 12, and 24 months was 80%, 68%, and 59%, respectively. Primary patency at 6, 12, and 24 months was 86%, 70%, and 62%, respectively. Amputation freedom at 6 months, 12 months, and 24 months was 98%, 95%, and 86%, respectively for non-traumatic indications. CONCLUSIONS: Non-GSV CP products may be used in complex arterial reconstructions when autogenous or prosthetic options are not feasible or available.

Impact of storage time prior to cryopreservation on mechanical properties of aortic homografts.

Optimal time spans in homograft procurement are still debatable among tissue banks and needs to be further investigated. Cell viability decreases at longer preparation intervals, but the effect on collagen and elastic fibers has not been investigated to the same extent. These fibers are of importance to the homograft elasticity and strength. The objective of this study was to analyze the mechanical properties of homograft tissue at different time spans in the procurement process. Ten aortic homografts were collected at the Tissue Bank in Lund. Twelve samples were obtained from each homograft, cryopreserved in groups of three after 2-4 days, 7-9 days, 28-30 days, and 60-62 days in antibiotic decontamination. Mechanical testing was performed with uniaxial tensile tests, calculating elastic modulus, yield stress and energy at yield stress. Two randomly selected samples were assessed with light microscopy. Procurement generated a total of 120 samples, with 30 samples in each time group. Elastic modulus and yield stress was significantly higher in samples cryopreserved after 2-4 days (2.7 MPa (2.5-5.0) and 0.78 MPa (0.68-1.0)) compared to 7-9 days (2.2 MPa (2.0-2.6) and 0.53 MPa (0.46-0.69)), p = 0.008 and 0.011 respectively. Light microscopy did not show any difference in collagen and elastin at different time spans. There was a significant decrease in elastic modulus and yield stress after 7 days of decontamination at 4 °C compared to 2-4 days. This could indicate some deterioration of elastin and collagen at longer decontamination intervals. Clinical significance of these findings remains to be clarified.

How to counteract the lack of donor tissue in cardiac surgery? Initial experiences with a newly established homograft procurement program.

Homograft heart valves may have significant advantages and are preferred for the repair of congenital valve malformations, especially in young women of childbearing age, athletes and in patients with active endocarditis. A growing problem, however, is the mismatch between tissue donation and the increasing demand. The aim of this paper is to describe the initiation process of a homograft procurement program to attenuate the shortage of organs. A comprehensive description of the infrastructure and procedural steps required to initiate a cardiac and vascular tissue donation program combined with a prospective follow-up of all homografts explanted at our institution. Between January 2020 and May 2022, 28 hearts and 12 pulmonary bifurcations were harvested at our institution and delivered to the European homograft bank. Twenty-seven valves (19 pulmonary valves, 8 aortic valves) were processed and allocated for implantation. The reasons for discarding a graft were either contamination (n = 14), or morphology (n = 13) or leaflet damage (n = 2). Five homografts (3 PV, 2 AV) have been cryopreserved and stored while awaiting allocation. One pulmonary homograft with a leaflet cut was retrieved by bicuspidization technique and awaits allocation, as a highly requested small diameter graft. The implementation of a tissue donation program in cooperation with a homograft bank can be achieved with reasonable additional efforts at a transplant center with an in-house cardiac surgery department. Challenging situations with a potential risk of tissue injury during procurement include re-operation, harvesting by a non-specialist surgeon and prior central cannulation for mechanical circulatory support.

20-year follow-up and comparison of homografts with bovine jugular vein conduits in children less than 2 years of age.

OBJECTIVES:  Repair of congenital heart defects involving right ventricular outflow tract (RVOT) may require pulmonary valve replacement at time of primary repair or reoperation. This study compares the outcomes of cryopreserved homografts with bovine jugular vein conduits (BJVC) in children < 2 years of age with RVOT reconstruction. METHODS:  Retrospective, single-center review of 70 conduits implanted in 63 patients undergoing right ventricle-to-pulmonary artery reconstruction with valved conduit from 2002 to 2022. RESULTS: A total of 70 conduits were implanted in 63 patients, with mean age of 4.5 ± 6.9 months (range 1 day ‒ 23.5 months). The following conduits were used; homografts 38 (54.2 %), BJVC 32 (45.8 %). During mean follow-up of 6.2 ± 5.6 years, there were 12 deaths, 24 conduit reoperations, and 25 catheter reinterventions. Overall survival, reoperation-free, and catheter reintervention-free survival at 15 years was 82.7 %, 31.2 %, and 25.7 %, respectively. Multivariate analysis revealed that low patient weight, age < 30 days at repair, ventilation time, and ICU length of stay were associated with increased risk of death. CONCLUSION: The performance of homografts and BJVC is comparable in patients ent between the two groups (Tab. 3, Fig. 3, Ref. 16).

Comparison of the function and structural integrity of cryopreserved pulmonary homografts versus decellularized pulmonary homografts after 180 days implantation in the juvenile ovine model.

Homograft availability and durability remain big challenges. Increasing the post-mortem ischaemic harvesting time beyond 24 h increases the potential donor pool. Cryopreservation, routinely used to preserve homografts, damages the extracellular matrix (ECM), contributing to valve degeneration. Decellularization might preserve the ECM, promoting host-cell infiltration and contributing towards better clinical outcomes. This study compared the performance of cryopreserved versus decellularized pulmonary homografts in the right ventricle outflow tract (RVOT) of a juvenile ovine model. Homografts (n = 10) were harvested from juvenile sheep, subjected to 48 h post-mortem cold ischaemia, cryopreserved or decellularized and implanted in the RVOT of juvenile sheep for 180 days. Valve performance was monitored echocardiographically. Explanted leaflet and wall tissue evaluated histologically, on electron microscopical appearance, mechanical properties and calcium content. In both groups the annulus diameter increased. Cryopreserved homografts developed significant (¾) pulmonary regurgitation, with trivial regurgitation (») in the decellularized group. Macroscopically, explanted cryopreserved valve leaflets retracted and thickened while decellularized leaflets remained thin and pliable with good coaptation. Cryopreserved leaflets and walls demonstrated loss of interstitial cells with collapsed collagen, and decellularized scaffolds extensive, uniform ingrowth of host-cells with an intact collagen network. Calcific deposits were shown only in leaflets and walls of cryopreserved explants. Young fibroblasts, with vacuoles and rough endoplasmic reticulum in the cytoplasm, repopulated the leaflets and walls of decellularized scaffolds. Young's modulus of wall tissue in both groups increased significantly. Cryopreserved valves deteriorate over time due to loss of cellularity and calcification, while decellularized scaffolds demonstrated host-cell repopulation, structural maintenance, tissue remodelling and growth potential.

Appraising 5 years in activity of the largest public Canadian vascular graft bank.

BACKGROUND: In Canada, tissue distribution is managed by provincial entities. In 2014, Hema-Quebec established a cryopreserved vascular tissue bank accessible to all Canadian hospitals. The objectives of this report were to review the first 5 years of activity of Hema-Quebec's vascular bank and to briefly assess the competitiveness of its products. METHODS: Deceased donors, ages 15 to 60, were screened for common blood-borne diseases. Grafts were treated in a triple-antibiotic solution at 35°C before preservation at -100°C. Hema-Quebec's vascular graft records were analyzed from 2014 to 2019 inclusively. RESULTS: The average donor age was 35 years old and 78% of donors were men. Overall, 63% of harvested grafts cleared the quality management system. Positive microbial cultures and morphologic defects were the major reasons for graft discard. As such, a total of 60 grafts were delivered between 2016 and 2019 to 8 hospital centers. Moreover, the bank achieved a mean activity increase of 55% per year and Hema-Quebec's homografts were 48% less costly compared with similar homographs from for-profit organizations. CONCLUSIONS: Our findings demonstrate that Hema-Quebec has established a viable cryopreserved vascular tissue bank with steady increase in activity and an acceptable graft discard rates and pricing. Based on our findings, we recommend that efforts should be directed to expand the tissue bank graft distribution outside the province of Quebec.

Stability analysis of the antibiotic cocktail used by Treviso Tissue Bank Foundation for tissues decontamination.

Although careful donor selection reduces tissue contamination, close microbiological control of harvested allografts remains a key task of tissue banks. To guarantee the safety of human tissues for allograft transplantation, a decontamination regimen must be adopted which, as recommended by European guidelines, is active against the majority of microorganisms isolated in tissues. Antibiotic decontamination methods differ from one tissue bank to another in terms of antimicrobial agents, temperature and length of exposure. After identifying the most effective antibiotics against the bacterial strains most commonly isolated in allografts, Treviso Tissue Bank Foundation demonstrated the efficacy of an antibiotic cocktail for tissue decontamination containing Gentamicin, Vancomycin and Meropenem. The aim of this study was to analyse the degradation kinetics of the three antibiotics according to preparation method and use. The results show that only Meropenem is unstable at + 4 °C, while Gentamicin and Vancomycin are valid for over 10 days. We thus established to add Meropenem before the start of the tissue decontamination phase.

Cadaver donation: structural integrity of pulmonary homografts harvested 48 h post mortem in the juvenile ovine model.

Cryopreserved pulmonary homograft (CPH) implantation remains the gold standard for reconstruction of the right ventricular outflow tract (RVOT). Harvesting homografts < 24-h post mortem is the international norm, thereby largely excluding cadaveric donors. This study examines the structural integrity and stability of ovine pulmonary homografts harvested after a 48-h post mortem period, cryopreserved and then implanted for up to 180 days. Fifteen ovine pulmonary homografts were harvested 48-h post mortem and cryopreserved. Five CPH served as a control group (group 1; n = 5). CPH were implanted in the RVOT of juvenile sheep and explanted after 14 days (group 2; n = 5) and 180 days (group 3; n = 5). Leaflet integrity was evaluated by strength analysis, using tensile strength (TS), Young's modulus (YM) and thermal denaturation temperature (Td), and morphology, including haematoxylin and eosin (H&E), Picrosirius red staining, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and von Kossa stains. Echocardiography confirmed normal function in all implants. In explants, no reduction in TS, YM or Td could be demonstrated and H&E showed mostly acellular leaflet tissue with no difference on Picrosirius red. TEM demonstrated consistent collagen disruption after cryopreservation in all three groups, with no morphological deterioration during the study period. von Kossa stains showed mild calcification in group 3. No deterioration of structural integrity could be demonstrated using strength or morphological evaluations between the controls and implant groups over the study period. Extending the post mortem harvesting time of homografts beyond 24 h did not appear to negatively affect the long-term performance of such transplanted valves in this study.

[Use of antibiotics in bones : Prophylaxis and current treatment standards]. / Anwendung von Antibiotika im Knochen : Prophylaxe und aktuelle Therapiestandards.

BACKGROUND: Treatment of bone infection is difficult due the systemic administration of antibiotics, which means that only low concentrations reach the inflamed bone tissue. Loss of bone stock is common in osteomyelitis and device associated infection. Local antibiotics are administered in several ways for prophylactic purposes and also for treatment of bone infection. We intend to show the options and limitations of clinical use of antibiotic-loaded bone grafts. SUITABILITY: Bone grafts are a suitable carrier system for antibiotics. Bone grafts may be loaded with a variety of antimicrobial agents so that individual therapies may be carried out. Critical systemic side effects are unlikely even though extreme high drug concentrations are obtained locally, if the thresholds for loading with antibiotics are respected. Thus, antibiotic-loaded bone grafts are appropriate for prophylaxis and therapy as well. If processing is done in the operating theatre compliance to the legal rules must be respected. RULES: Due to a lack of standardised procedures for loading, application and performance of the application of antibiotic-loaded bone grafts medical societies are being asked to initiate consensus meetings in order to issue recommendations or guidelines with respect to antibiotic-loaded bone grafts to establish reliable rules for surgeons using these devices.

[Biological downsizing : Acetabular defect reconstruction in revision total hip arthroplasty]. / Biologisches Downsizing : Azetabuläre Knochendefekte in der Hüftrevisionsendoprothetik.

BACKGROUND: Periacetabular bony defects remain a great challenge in revision total hip arthroplasty. After assessment and classification of the defect and selection of a suitable implant the primary stable fixation and sufficient biological reconstitution of a sustainable bone stock are essential for long term success in acetabular revision surgery. Biological defect reconstruction aims for the down-sizing of periacetabular defects for later revision surgeries. TECHNIQUE: In the field of biological augmentation several methods are currently available. Autologous transplants feature a profound osseointegrative capacity. However, limitations such as volume restrictions and secondary complications at the donor site have to be considered. Structural allografts show little weight bearing potential in the long term and high failure rates. In clinical practice, the usage of spongious chips implanted via impaction bone grafting technique in combination with antiprotrusio cages for the management of contained defects have shown promising long time results. Nevertheless, when dealing with craniolateral acetabular and dorsal column defects, the additional implantation of macroporous metal implants or augments should be considered since biological augmentation has shown little clinical success in these particular cases. PROSPECT: This article provides an overview of the current clinically available biological augmentation methods of peri-acetabular defects. Due to the limitations of autologous and allogeneic bone transplants in terms of size and availability, the emerging field of innovative implantable tissue engineering constructs gains interest and will also be discussed in this article.

Is Transcatheter Aortic Valve Implantation of Living Tissue-Engineered Valves Feasible? An In Vitro Evaluation Utilizing a Decellularized and Reseeded Biohybrid Valve.

Transcatheter aortic valve implantation (TAVI) is a fast-growing, exciting field of invasive therapy. During the last years many innovations significantly improved this technique. However, the prostheses are still associated with drawbacks. The aim of this study was to create cell-seeded biohybrid aortic valves (BAVs) as an ideal implant by combination of assets of biological and artificial materials. Furthermore, the influence of TAVI procedure on tissue-engineered BAV was investigated. BAV (n=6) were designed with decellularized homograft cusps and polyurethane walls. They were seeded with fibroblasts and endothelial cells isolated from saphenous veins. Consecutively, BAV were conditioned under low pulsatile flow (500 mL/min) for 5 days in a specialized bioreactor. After conditioning, TAVI-simulation was performed. The procedure was concluded with re-perfusion of the BAV for 2 days at an increased pulsatile flow (1100 mL/min). Functionality was assessed by video-documentation. Samples were taken after each processing step and evaluated by scanning electron microscopy (SEM), immunohistochemical staining (IHC), and Live/Dead-assays. The designed BAV were fully functioning and displayed physiologic behavior. After cell seeding, static cultivation and first conditioning, confluent cell layers were observed in SEM. Additionally, IHC indicated the presence of endothelial cells and fibroblasts. A significant construction of extracellular matrix was detected after the conditioning phase. However, a large number of lethal cells were observed after crimping by Live/Dead staining. Analysis revealed that the cells while still being present directly after crimping were removed in subsequent perfusion. Extensive regions of damaged cell-layers were detected by SEM-analysis substantiating these findings. Furthermore, increased ICAM expression was detected after re-perfusion as manifestation of inflammatory reaction. The approach to generate biohybrid valves is promising. However, damages inflicted during the crimping process seem not to be immediately detectable. Due to severe impacts on seeded cells, the strategy of living TE valves for TAVI should be reconsidered.

Analysis of the effectiveness of Sodium Hypochlorite decontamination of cadaveric human tissues at retrieval.

Bacterial contamination of tissues retrieved from cadaveric donors is a common feature worldwide, and every tissue bank, albeit using different methods, conducts decontamination to guarantee safe tissues suitable for clinical use. The effectiveness of the methods used to eradicate pathogens differs. In order to reduce the tissue bioburden at retrieval, we have introduced a new method involving rinsing tissues in a sodium hypochlorite solution. To test its effectiveness we analyzed two comparable groups of tissues: Group A: 1881 tissues, all rinsed with isotonic saline solution after retrieval, and Group B: 1968 tissues immersed in an isotonic saline solution containing sodium hypochlorite (final concentration 0.1 %) for different lengths of time and subsequently rinsed with isotonic saline. The rinsing solution of each tissue was then sampled for microbiological cultures in both groups. The resultant overall contamination rate was 40.5 % for Group A and 6.7 % for Group B, with an 82.8 % difference in the reduction of contamination between the two groups. This was especially the case for commensal skin bacteria in musculoskeletal tissue, which accounted for over half the overall contamination. Our data highlighted that decontamination with sodium hypochlorite was helpful in reducing the bacterial bioburden in tissues retrieved from cadaveric donors.

[Patellar tendon injuries after total knee arthroplasty : Classification and management]. / Rupturen der Patellarsehne nach Kniegelenkersatz : Klassifikation und Management.

BACKGROUND: Ruptures of the patellar tendon after total knee arthroplasty represent a rare but severe complication, which in general requires surgical therapy. OBJECTIVES: To implement a classification and correspondent therapy algorithm in consideration of the current literature for the treatment of patellar tendon ruptures after TKA. MATERIAL AND METHODS: A review of the recent literature and the author's experience are summarized in a classification and correspondent therapy algorithm for the treatment of patellar tendon ruptures after TKA. RESULTS: Ruptures of the patella tendon can be classified as avulsions (Type I), acute (Type II) and chronic ruptures (Type III). Avulsions are often of iatrogenic nature and can be sufficiently treated by transosseous refixation prior to implantation of the revision TKA. Acute ruptures of the patellar tendon can originate from trauma or intraoperative injury. The rupture can be restored by primary suture in combination with a wire cerclage in the case of good tendon quality and the absence of patient comorbidities (Type IIA). In the case of poor tendon quality or existing comorbidities (Type IIB) additional augmentation of the ruptured tendon, utilizing the autologous semitendinosus/gracilis tendon, is recommended. Chronic ruptures revealing a good patellar bone stock (Type IIIA) can be treated by a combination of a semitendinosus augmentation and a turndown quadriceps tendon flap. In the case of a poor patellar bone stock (Type IIIB) transpatellar fixation of the semitendinosus tendon is virtually impossible, so that an allograft augmentation or the use of a soft tissue muscle flap (i. e. the gastrocnemius flap) has to be considered. A failed complex reconstruction with or without infection (Type IIIC) is an invidious surgical task and needs to be addressed by the utilization of a muscle flap, an allograft or a patellectomy with or without arthrodesis.

Does prolonged post-mortem cold ischemic harvesting time influence cryopreserved pulmonary homograft tissue integrity?

This study investigated cryopreserved pulmonary homograft (CPA) structural integrity after prolonged cold ischemic harvesting times in a juvenile sheep model. Three groups with different post-mortem cold ischemic harvesting times were studied, i.e. Group 1 (24 h, n = 10); group 2 (48 h, n = 10); group 3 (72 h, n = 10). In each group, 5 CPAs were studied in vitro after cryopreservation and thawing. The other 5 CPAs were implanted in juvenile sheep for a minimum of 180 days. Serology samples were obtained and echocardiography was performed before euthanasia. Hematoxylin and eosin (H&E), scanning electron microscopy (SEM), von Kossa, Picrosirius red, α-actin, immunohistochemistry [von Willebrand factor (vWF), CD4, CD31 and CD34] and calcium content analyses were performed on explanted CPAs. The in vitro and in vivo studies failed to demonstrate any change in tensile strength, Young's Modulus and thermal denaturation (Td) results between the groups. SEM demonstrated a reduction in endothelial cells (50 % at 24 h, 60.9 % at 48 h and 40.9 % at 72 h), but H&E could not demonstrate autolysis in any CPA in vitro. All cultures were negative. In the explanted groups, IgE, IgM and IgG results were inconclusive. Echocardiography demonstrated normal valve function in all groups. H&E and Picrosirius red staining confirmed tissue integrity. vWF, CD31 and CD34 staining confirmed a monolayer of endothelial cells in all explanted valves. Calcium content of explanted CPA leaflets was similar. This experimental study supports the concept of prolonging the cold ischemic harvesting time of cryopreserved homografts to reduce homograft shortage.

Choice of valve substitutes.

Infective endocarditis often necessitates surgical intervention, and the choice of valve substitute remains a topic of controversy and highly debatable due to the wide range of available options and recent technical advancements. This manuscript reviews the different valve substitutes in the context of infective endocarditis, including mechanical and bioprosthetic valves, homografts, xenografts, and tissue-engineered valves. The patient's age, sex, demographic location, intellectual quotient, comorbidities, available options, and the experience of the surgeon should all be taken into consideration while choosing the best valve substitute for that individual. While valve repair and reconstruction are preferred whenever feasible, valve replacement may be the only option in certain cases. The choice between mechanical and bioprosthetic valves should be guided by standard criteria such as age, sex, expected lifespan, associated comorbidities, and anticipated adherence to anticoagulation therapy and accessibility of medical facilities for follow-up. For patients with severe chronic illness or a history of intracranial bleeding or associated hematological disorders, the use of mechanical prostheses may be avoided. Homografts and bioprosthetic valves provide an alternative to mechanical valves, thereby decreasing the necessity for lifelong anticoagulation after surgery and diminishing the likelihood of bleeding complications. The manuscript also discusses specific valve substitutes for different heart valves (aortic, mitral, pulmonary, tricuspid positions) and highlights emerging techniques such as the aortic valve neocuspidization (Ozaki procedure) and tissue-engineered valves. Ultimately, the ideal valve substitute in IE should be evidence based on a comprehensive elucidation of clinical condition of the patient and available options.

Bovine jugular vein conduit replacement after homograft degeneration in patients with tetralogy of Fallot: The results of re-redo cases.

Background: This study aims to present our experience and results in terms of reconstruction with bovine jugular vein conduit in re-redo patients who developed severe homograft degeneration with pulmonary homograft valve replacement. Methods: Between May 2018 and May 2021, a total of 10 re-redo patients (4 males, 6 females; mean age: 16.5±3.0 years; range, 12 to 21 years) who underwent bovine jugular vein conduit replacement due to homograft degeneration were retrospectively analyzed. The clinical, pre-, intra-, and postoperative data of the patients were recorded. Results: The mean age of the second operation (homograft replacement) was 8.5±3.8 (range, 4 to 14) years in the patients who underwent homograft replacement. No postoperative mortality was observed. When the pre- and postoperative findings were compared, the right ventricular outflow tract gradient, the degree of pulmonary and tricuspid regurgitation, and right ventricular dilatation were regressed (p<0.05). A significant improvement in the New York Heart Association functional class was observed in all patients after surgery. Conclusion: After tetralogy of Fallot corrective surgery, repetitive surgical interventions are inevitable due to pulmonary valve deterioration. Therefore, a bovine jugular vein conduit may be a good alternative for conduit preference after pulmonary homograft failure in re-redo cases.

The biomechanical and biological effect of supercooling on cortical bone allograft.

BACKGROUND: The need for a storage method capable of preserving the intrinsic properties of bones without using toxic substances has always been raised. Supercooling is a relatively recently introduced preservation method that meets this need. Supercooling refers to the phenomenon of liquid in which the temperature drops below its freezing point without solidifying or crystallizing. OBJECTIVES: The purpose of this study was to identify the preservation efficiency and applicability of the supercooling technique as a cortical bone allograft storage modality. METHODS: The biomechanical effects of various storage methods, including deep freezing, cryopreservation, lyophilization, glycerol preservation, and supercooling, were evaluated with the three-point banding test, axial compression test, and electron microscopy. Additionally, cortical bone allografts were applied to the radial bone defect in New Zealand White rabbits to determine the biological effects. The degree of bone union was assessed with postoperative clinical signs, radiography, micro-computed tomography, and biomechanical analysis. RESULTS: The biomechanical properties of cortical bone grafts preserved using glycerol and supercooling method were found to be comparable to those of normal bone while also significantly stronger than deep-frozen, cryopreserved, and lyophilized bone grafts. Preclinical research performed in rabbit radial defect models revealed that supercooled and glycerol-preserved bone allografts exhibited significantly better bone union than other groups. CONCLUSIONS: Considering the biomechanical and biological superiority, the supercooling technique could be one of the optimal preservation methods for cortical bone allografts. This study will form the basis for a novel application of supercooling as a bone material preservation technique.

Aortic Valve Replacement in Adult Patients with Decellularized Homografts: A Single-Center Experience.

BACKGROUND: decellularized aortic homografts (DAH) represent a promising alternative for aortic valve replacement in young adults due to their low immunogenicity and thrombogenicity. Herein, we report our midterm, single-center experience in adult patients with non-frozen DAH from corlife. METHODS: safety, durability, and hemodynamic performance were evaluated according to current guidelines in all consecutive patients who had received a DAH at our center since 03/2016. RESULTS: seventy-three (mean age 47 ± 11 years, 68.4% (n = 50) male) patients were enrolled. The mean diameter of the implanted DAH was 24 ± 2 mm. Mean follow-up was 36 ± 27 months, with a maximum follow-up of 85 months and cumulative follow-up of 215 years. No cases of stenosis were observed, in four (5.5%) cases moderate aortic regurgitation occurred, but no reintervention was required. No cases of early mortality, non-structural dysfunction, reoperation, valve endocarditis, or thrombosis were observed. Freedom from bleeding and thromboembolic events was 100%; freedom from re-intervention was 100%; survival was 98.6% (n = 72). CONCLUSIONS: early and mid-term results showed low mortality and 100% freedom from reoperation, thromboembolic events, and bleeding at our center. However, in order for this novel approach to be established as a valid alternative to aortic valve replacement in young patients, long-term data are required.

20-Year follow-up and comparison of valved conduits used for right ventricular outflow tract reconstruction: single-centre, propensity score match analysis.

OBJECTIVES: Surgical repair of complex congenital heart defects with hypoplasia or atresia of the right ventricular outflow tract (RVOT) may require pulmonary valve implantation or replacement during the primary repair or reoperation. The purpose of this study is to evaluate the outcomes of cryopreserved homografts, bovine jugular vein conduits and decellularized Matrix P Plus N conduits in patients undergoing RVOT reconstruction at a single centre. METHODS: Retrospective, single-centre review of 173 patients with 199 conduits undergoing right ventricle-to-pulmonary artery reconstruction with valved conduit from 2002 to 2022. RESULTS: A total of 199 conduits were implanted in 173 patients (62.8% male), with a mean age of 8.97 ± 8.5 years. The following 3 types of conduits were used: homografts 129 (64.8%), bovine jugular vein conduits 45 (22.7%) and Matrix P Plus N 25 (12.5%). During the mean follow-up duration of 8.6 ± 5.8 years, there were 20 deaths, 35 conduit reoperations and 44 catheter reinterventions. Overall survival, reoperation-free and catheter reintervention-free survival at 20 years were 83%, 67.8% and 65.6%, respectively. Multivariable Cox analysis identified younger patient age, smaller conduit size, low patient weight and primary diagnosis of common arterial trunk as risk factors for reoperation and catheter reintervention. CONCLUSIONS: Long-term outcomes of reconstruction of the RVOT using homografts, bovine jugular vein and Matrix P Plus N conduits were acceptable. The reoperation rate for conduit dysfunction did not differ significantly among groups. Over time, the need for conduit replacement was higher in smaller conduits and in patients with common arterial trunk diagnosis.

Impact of Three Different Processing Techniques on the Strength and Structure of Juvenile Ovine Pulmonary Homografts.

Homografts are routinely stored by cryopreservation; however, donor cells and remnants contribute to immunogenicity. Although decellularization strategies can address immunogenicity, additional fixation might be required to maintain strength. This study investigated the effect of cryopreservation, decellularization, and decellularization with additional glutaraldhyde fixation on the strength and structure of ovine pulmonary homografts harvested 48 h post-mortem. Cells and cellular remnants were present for the cryopreserved group, while the decellularized groups were acellular. The decellularized group had large interfibrillar spaces in the extracellular matrix with uniform collagen distribution, while the additional fixation led to the collagen network becoming dense and compacted. The collagen of the cryopreserved group was collapsed and appeared disrupted and fractured. There were no significant differences in strength and elasticity between the groups. Compared to cryopreservation, decellularization without fixation can be considered an alternative processing technique to maintain a well-organized collagen matrix and tissue strength of homografts.