Vascular allografts for clinical application in Europe: assessment of 30 years of experience with vascular tissue banking in Brussels

Vascular tissue banking has been carried out in Brussels for over 30 years in compliance with EU and Swiss tissue banking regulations. A total of 2.765 vascular tissue donations were performed in Belgian, French, Netherlands and Suisse transplant centres: 547(20%), 1.013(37%) and 1.205(43%) during the first, second and third periods, respectively. 85% and 18% increase in donations during the second and third decades compared to previous one, were remarkable. Of the 7.066 evaluated vascular tissues, 2.407(227, 921 and 1.259) were discarded (34.1%), whereas 4.659(523, 1.861 and 2.275) accepted (65.9%) during the respective period. Of the 92 donated veins, 44(47.8%) were discarded and 48(52.2%) accepted. Allografts available for clinical application were stored in vapours of liquid nitrogen. A total of 4.636 allografts were delivered and transplanted for cases of infection (58%), critical limb ischaemia (16%) and congenital cardiac surgery (15%). Thirty veins were implanted. The progressive increases in donations of 20%, 37% and 43% and in transplantations of 20.8%, 34.6% and 45% during the first, second and third periods, respectively, were remarkable. Complications were reported after transplantation and these included acute rejection of two femoral arteries one month after transplantation. We conclude that the donation and transplantation of cryopreserved vascular allografts was stable with a progressive increase over time. Allografts were used predominantly for the treatment of infection, limb salvage for critical ischaemia and for neonates and infants with congenital cardiac malformation. Immune related rejection was observed. This should be a subject of future investigation.

Ten-year experience with cryopreserved vascular allografts in the Croatian Cardiovascular Tissue Bank

The Croatian Cardiovascular Tissue Bank (CTB) was established in June 2011. Activities managed by CTB are processing of heart valves and blood vessels, as well as quality control, storage, medical release and distribution of allografts. The aim of this report is to present CTB's vascular tissue activities and retrospectively evaluate the outcomes of their use in the University Hospital Centre Zagreb. Between June 2011 and July 2021, 90 vascular allografts (VAs) from 55 donors after brain death were referred to CTB. Only 54% of VAs met the tissue quality requirements while 46% of tissues were discarded. The most frequent reasons for discard were unacceptable morphology and initial microbiological contamination. Altogether 42 VAs were released for transplantation and 37 of them were used in 27 surgical procedures. The most common indication for surgery was prosthetic graft or stent infection. According to the anatomic position of vascular reconstruction, patients were divided in the aortic and peripheral reconstruction group. A total of 23 patients were treated. In the aortic reconstruction group 58% of patients did not experience any graft-related complications. In the group of patients who underwent peripheral reconstruction significant incidence of reinfection was observed highlighting it as a major graft-related complication. Despite the small patient groups and limited duration of follow-up, presented clinical outcomes provide valuable information on the efficacy of vascular allografts. Additional clinical results collected on a larger patient groups and comparison to other reconstructive treatment options are necessary.

Management and Outcome of Prosthetic Vascular Graft Infections: A Single Center Experience

Background:

Prosthetic vascular graft infection (PVGI) remains a severe and challenging complication in vascular surgery with high morbidity and mortality rates. Incidence has been reported between 1% and 6%. The aim of this study was to report our experience in terms of general and surgical management as well as outcome, over 15 years.

Methods:

A retrospective consecutive study was conducted of all patients treated in our department for PVGI between January 2000 and December 2015. We analyzed all data relative to primary operation, duration interval between initial surgery and infections signs, infection site, type of microorganism involved, and surgical treatment modality, as well as evaluation of short- and long-term results.

Results:

Sixty-two patients were admitted for PVGI. Primary revascularization procedures consisted of a peripheral bypass in 42 (68%) patients and an aortic bypass in the remaining 20 (32%) patients. Median interval between primary procedure and reintervention was 3 months (interquartile range 17 [IQR 17]) in the peripheral group and 48 months (IQR 70.5) in the aortic group. Complete excision of the prosthetic graft was carried out in 85% of the cases. Thirty-day mortality was 0% and 9.5% in the aortic and peripheral group, respectively. The overall survival rate was 62.3% at 2-years, 46.4% in the aortic group, and 69.7% in the peripheral group.

Conclusions:

Prosthetic vascular graft infection needs a multidisciplinary management with appropriate antibiotherapy, radical removal of the infected graft, and in situ reconstruction. This strategy gives satisfactory results in terms of mortality, morbidity, patency rates, and infection control.

Late Fate of Cryopreserved Arterial Allografts

OBJECTIVE

Initial enthusiasm for use of cryopreserved arterial allografts was subsequently tempered by suboptimal long-term outcome. Thrombosis, anastomotic pseudo-aneurysm, allograft disruption, aneurysmal degeneration, recurrent intestinal fistulization, and persistent infection are commonly reported in series with long-term follow-up. The authors reviewed their experience over the past 15 years with the use of cryopreserved arterial allografts as a vascular substitute for vascular prosthetic infection or for primary arterial infection, to investigate allograft-related complications.

MATERIAL AND METHODS

A retrospective analysis of prospectively collected data was conducted for 103 cryopreserved arterial allografts inserted in 96 patients between July 2000 and July 2015. There were 78 patients with infected vascular prosthesis (IVP), nine patients with an aorto-enteric fistula (AEF), and nine patients with primary arterial infection (PAI).

RESULTS

The in-hospital mortality was eight out of 78 (9%) IVP patients, three out of nine AEF patients, and zero out of nine PAI patients. Median follow-up was 49 months. Allograft-related re-interventions were necessary in 29% of the patients with IVP and four of the patients with AEF, but none of the patients with PAI. Five-year survival for the IVP, AEF, and PAI patients was 53%, 44%, and 90%, respectively.

CONCLUSION

This series highlights some shortcomings of cryopreserved arterial allografts in the long term, including suboptimal outcome-results and shortage of material. The authors discuss the allograft-related complications and suggest some tricks to minimize their risk.

Tolerance to incompatible ABO blood group antigens is not observed following homograft implantation

Failure to develop antibodies to nonself A and B blood group antigens is well described after infant ABO-incompatible heart transplantation and suggests that exposure to incompatible ABO antigens early in life may lead to tolerance rather than immunogenicity. If this finding is also true following ABO-incompatible cryopreserved homograft implantation, then such patients who require transplantation may be able to accept certain ABO-incompatible organs. In this study, we measured anti-A and -B antibody titers (isohemagglutinins) and allosensitization to human leukocyte antigens (HLA) in 21 patients after homograft placement (12 of whom were <1 year of age at initial homograft exposure) in childhood. We also examined homograft explant specimens for endothelial preservation and expression of HLA and A and B blood group antigens. We observed no differences in isohemagglutinins between patients who received ABO-incompatible versus ABO-compatible homografts. Allosensitization to HLA was present in 88% of patients (9 of 9 ABO-incompatible recipients and 5 of 7 ABO-compatible recipients). In 7 homograft explant specimens (median implant duration 10.1 years), the vasa vasorum endothelium was intact with ABO blood group antigen expression on 3 of 5 non-O homografts. These data suggest that tolerance to incompatible A and B blood group antigens does not occur following placement of ABO-incompatible homografts in childhood.

Effects of cryopreservation and thawing on the structure of vascular segment

The objective of this study was to analyze the importance of the quality of the vascular segment to be cryopreserved and the influence of storage in a gas phase, a liquid phase, or after accidental immersion in liquid nitrogen. In addition, we investigated the effects of rapid versus slow thawing on the occurrence of fractures and changes in the structure of the vessel wall. The tissue sources were whole thoracic and abdominal aortas from 15 pigs. Each aorta was cut into equal segments and randomly assigned to each study group. One segment of fresh unfrozen aorta of the same size was used as a control. The samples were cryopreserved using a programmed apparatus. After 2 weeks the arterial segments were thawed rapidly or slowly. A great variation in the results was obtained depending on the quality of the control. Although endothelial cells were better preserved in the liquid phase, the internal elastic lamina and elastic lamelli showed better preservation and fewer microfractures in the gas phase. The internal elastic lamina showed a greater number of microfractures when an accidental immersion in liquid nitrogen had taken place. Furthermore, better preservation of the structure of the vascular segment was observed with a slow thawing method. In general, the conditions of storage and the method of thawing seem to damage the structure of vascular segments. It is necessary to use a severe protocol of donor and vascular segment selection to optimize the post-thaw quality of the cryopreserved samples.

Banking of the human heart valves and the arteries at the European homograft bank (EHB) – Overview of a 14-year activity in this International Association in Brussels*

Processing of the human heart valves and arteries has been carried out at the European Homograft Bank (EHB) in Brussels since 1989 and 1991, respectively. Heart valve donors of 0-65 years were classified in (1) Beating heart donors (BHD), of which recipients of heart transplantation (RHT) and multiorgan donors (MOD) after brain death, and (2) non-beating heart donors (NBHD) with warm ischaemic time (WIT) of less then 6 h. Past history of the donors has been checked for malignant and chronic diseases, as well as biology for transmissible and infectious diseases. Perfect collaboration has been established with the transplant coordinators and transplant teams of the implanting centres. Dissection, decontamination, cryopreservation and storing in fluid nitrogen has been carried out in accordance with the Belgian and European Standards of cardiovascular allografts. During this period, a total of 2.828 hearts, 28 predissected valves and 616 batches of arteries arrived in the EHB. 3.537 valves and 1.137 different arteries were accepted for implantation. The main reasons for tissue rejection were morphology, contamination and cuts during the tissue retrieval or dissection. A huge network of different hospitals in Belgium and elsewhere in Europe and Switzerland were included in this process. Pulmonary allografts were not sent for implantation in the left ventricular outflow tract after 1998, since the early and mid-term results after 76 implantations were disappointing. The number of implanted aortic and pulmonary allografts remains stable from year to year, however the number of the allografts used for Ross operation is still increasing. Since the results of the follow up were disappointing, we still only require the implantation and immediate postoperative results, whereas the follow-up information only for specific study purposes.

Technical details with the use of cryopreserved arterial allografts for aortic infection: influence on early and midterm mortality

PURPOSE

In situ repair with cryopreserved vascular allografts improves the results in the surgical treatment of aortic infection. This study evaluated the technical pitfalls with the use of allografts that influence early and midterm mortality.

METHODS

Between 1990 and 1999, 49 patients, 21 (43%) with a mycotic aneurysm and 28 (57%) with a prosthetic graft infection of the thoracic and abdominal aorta including pelvic and groin vessels, underwent in situ repair with cryopreserved arterial allografts. Seventeen patients (35%) had aortobronchial, aortoesophageal, or aortoenteric fistulas.

RESULTS

Allograft-related technical problems occurred in eight patients (16%) in this series, and they included: intraoperative rupture caused by allograft friability; allograftenteric fistula from ligated allograft side branches rupturing 8, 18, and 48 months after implantation; anastomotic failure caused by inappropriate mechanical stress; anastomotic stricture after partial replacement of infected prosthetic grafts; allograft failure caused by inappropriate wound drainage; and recurrence of infection after inappropriate duration of antifungal treatment. Seven of the eight technical problems (87%) occurred in the first 10 patients (80%) in this series. There was one technical failure in the remaining 39 patients (2.6%; P =.0002) because of various technical adaptations, such as critical selection of allografts, use of allograft strips supporting large anastomoses, sealing with antibiotic-impregnated fibrin glue, and change in technique of allograft side-branch ligature. The 30-day mortality rate was 6% for the whole series; however, it was 2.6% for last 39 patients, with no recurrence of infection or allograft-related late death.

CONCLUSIONS

In situ repair with cryopreserved arterial allografts achieves excellent early and late results in the treatment of aortic infection. However, distinct allograft-related technical problems had to be overcome to improve the outcome of patients with major vascular infections.

Use of cryopreserved arterial homografts for management of infected prosthetic grafts: a multicentric study

The objective of this study was to evaluate the effectiveness of cryopreserved arterial homografts for management of prosthetic graft infection. Between October 1992 and July 1998, 90 patients (84 men) with a mean age of 64 years from six different hospitals were treated for prosthesis infection by in situ replacement using a cryopreserved arterial homograft (CAH). In 43 patients (47%), the primary procedure had been performed at a nonparticipating center. Prosthetic graft infection occurred early (i.e., within 1 month after the primary procedure) in 15 cases and late in 75 cases. In the late group, the mean interval between the primary procedure and CAH replacement was 34 months (range, 3 to 330 months). In 41 patients, infection was located in the aortic region, including 17 presenting with enteroprosthetic fistula (EPF). In 49 patients, infection was confined to the femoral, popliteal, or subclavian region. Bacteriologic cultures were positive for one or more germs in 75 patients and negative in 15. The surgical procedure consisted of complete or partial removal of the infected prosthetic graft, debridement, and in situ reconstruction using one or more CAH. Our results showed that management of prosthetic graft infection, a grave complication, using a CAH is a promising technique, especially for patients in stable condition prior to reconstruction.

The mechanical properties of fresh and cryopreserved arterial homografts

OBJECTIVES

To assess the effect of cryopreservation on the elasticity and compliance of arterial allografts.

MATERIALS AND METHODS

Iliofemoral segments of arteries and veins harvested from multiorgan donors were divided into two groups: fresh-control, tested for 24 hours after harvesting, and cryopreserved in liquid nitrogen after pretreatment with 20% dimethylsulphoxide and stored for an average time of 22 days. Vessel wall elastic properties were evaluated from the stress-strain relationship in a specially designed test cell fixed to the Instron Universal Testing Machine.

RESULTS

The elastic modulus of the artery control group (1.54+/-0.33 MPa, n=20) was not significantly different from the cryopreserved group (1.69+/-0.61 MPa, n=15). Similarly, values for unfrozen veins (3.11+/-0.65 MPa, n=47) were not significantly different from those of frozen samples (2.71+/-0.85 MPa, n=38). Control compliance (6. 86+/-1.79x10(-5)%/Pa, for arteries; 3.84+/-0.81x10(-5)%/Pa, for veins) was similar to that of the cryopreserved group (6.66+/-1. 80x10(-5)%/Pa, for arteries; 4.16+/-1.21x10(-5)%/Pa, for veins).

CONCLUSIONS

Cryopreservation maintains the important elastic properties of arterial and venous allografts during average storage time of 22 days.

Management of infected aortic grafts: development of less invasive surgery using cryopreserved homografts

BACKGROUND

Aortic graft infection is associated with significant mortality and morbidity. Total graft replacement with homografts provides an effective treatment. Partial graft replacement at the site of infection may simplify the surgical procedure.

METHODS

Between January 1991 and December 1996, homografts were used in 18 patients (mean age, 61+/-12 years; range 41-85) with thoracic (4/18; 22%) or abdominal (14/18; 78%) aortic graft infection. Sepsis was present in 14 patients (78%); 6 (33%) had various aortic fistulae. Total graft replacement using homografts was performed in 14 (78%), and partial graft replacement at the site of infection in 4 patients (22%).

RESULTS

Hospital mortality was 11%. During the follow-up period of 22+/-15 months (range, 12-65) there was 1 infection and 1 homograft-related late death after complete homograft replacement, and 1 percutaneous vascular stent placement after partial graft replacement. No other instances of reinfection, suture line rupture or anastomotic aneurysms were observed.

CONCLUSION

Total graft replacement with homografts provides an effective treatment for infected aortic grafts. Partial graft replacement at the site of infection is feasible and safe.

Explanted cryopreserved allografts: a morphological and immunohistochemical comparison between arterial allografts and allograft heart valves from infants and adults

OBJECTIVE

Life expectancy of cryopreserved allografts implanted in infants is different from those implanted in adults. A morphological study of explanted allograft heart valves was performed to determine the mechanism of deterioration and to compare cryopreserved arterial and heart valve allografts from adult patients with those explanted from infants.

METHOD

Between 1987 and 1996, 209 cryopreserved allografts were implanted: 125 valved conduits or monocusps to reconstruct the right ventricular outflow tract in congenital heart disease, 50 allograft heart valves to treat native aortic and prosthetic aortic valve endocarditis and 34 cryopreserved arterial allografts to replace mycotic aortic aneurysms or infected aortic prosthetic grafts. Two months to 8 years after implantation, 23 heart valve allografts, 11 right-sided and 12 left-sided, and four arterial allografts had to be explanted for reasons such as degeneration, recurrent infection, aneurysm formation or rupture. Besides conventional staining, immunohistochemical detection of cell populations was performed as follows: CD45RO, CD3 and CD43 for T lymphocytes, CD20 for B lymphocytes, CD68 for macrophages, protein S100 for Langerhans-cells, vimentin for fibroblasts, alpha-actin for smooth muscle cells and factor VIII for endothelial cells.

RESULTS

Explanted cryopreserved allografts were all fibrotic, acellular, non-vital and without endothelial cells. The fibrous tissue was preserved. T lymphocytes, indicating rejection, were found in all right-sided allografts from the paediatric population, but only in 9% of left-sided valves explanted from adults and in one of the four of arterial allografts. Macrophages and Langerhans-cells were found only in right-sided allografts from paediatric patients.

CONCLUSION

Right-sided cryopreserved allografts from a paediatric population showed ongoing cellular rejection. By contrast, there was only a weak T-cell mediated rejection to adult heart valve and arterial allografts. Therefore, similar long-term results can be expected in adult arterial and heart valve allografts, whereas longevity of right-sided heart valve allograft in the paediatric age group seems endangered by cellular rejection.

Cryopreserved arterial allografts in the treatment of major vascular infection: a comparison with conventional surgical techniques

OBJECTIVE

Recent findings with cryopreserved heart valve allografts in the treatment of infectious endocarditis suggest that the use of cryopreserved arterial allografts may improve the outcome in patients with vascular infections.

METHODS

Seventy-two patients with mycotic aneurysms (n = 29) or infected vascular prostheses (n = 43) of the thoracic (n = 26) or abdominal aorta (n = 46) were treated with in situ repair and extra-anatomic reconstruction using prosthetic material (n = 38) or implantation of a cryopreserved arterial allograft (n = 34). Disease-related survival and survival free of reoperation were assessed. Morbidity, cumulative lengths of intensive care, hospitalization, antibiotic treatment, and costs were calculated per year of follow-up.

RESULTS

The use of cryopreserved arterial allografts was superior to conventional surgery in terms of disease-related survival (P =.008), disease-related survival free of reoperation (P =.0001), duration of intensive care per year of follow-up (median 1 vs 11 days; range 1 to 42 vs 2 to 120 days; P =.001), hospitalization (14 vs 30 days; range 7 to 150 vs 15 to 240 days; P =.002), duration of postoperative antibiotic therapy (21 vs 40 days; range 21 to 90 vs 60 to 365 days; P =.002), incidence of complications (24% vs 63%; P =.005), and elimination of infection (91% vs 53%; P =.001). In addition, costs were 40% lower in the group treated by allografts (P =.005).

CONCLUSIONS

The use of cryopreserved arterial allografts is a more effective treatment for mycotic aneurysms and infected vascular prostheses than conventional surgical techniques.