Graft Vessels Research Articles

Specific Graft Treatment Solution Enhances Vascular Endothelial Function.

Saline is still the most widely used storage and rinsing solution for vessel grafts during cardiac surgery despite knowing evidence of its negative influence on the human endothelial cell function. Aim of this study was to assess the effect of DuraGraft©, an intraoperative graft treatment solution, on human saphenous vein segments and further elaborate the vasoprotective effect on rat aortic segments in comparison to saline. Human Saphenous vein (HSV) graft segments from patients undergoing aortocoronary bypass surgery (n = 15), were randomized to DuraGraft© (n = 15) or saline (n = 15) solution before intraoperative storage. Each segment was divided into two subsegmental parts for evaluation. These segments as well as rat aortic segments stored in DuraGraft© underwent assessment of vascular function in a multichamber isometric myograph system in comparison to Krebs-Henseleit solution (KHS), a physiologic organ buffer solution. Potassium-Chloride (KCL)-induced contraction depicted a tendency towards increase when treated with DuraGraft© compared to saline preservation of HSV segments (23.02 14.77 vs 14.44 9.13 mN, p = 0.0571). Vein segments preserved with DuraGraft© showed a significant improvement of endothelium-dependent vasorelaxation in response to cumulative concentrations of bradykinin compared to saline treated segments (p 0.05). Rat aortic segments stored in saline showed significantly impaired vasoconstriction (3.59 4.20, p 0.0001) and vasorelaxation when compared to KHS and DuraGraft© (p 0.0001). DuraGraft© demonstrated a favorable effect on graft relaxation and contraction indicating preservation of vascular endothelial function. NCT04614077.

Association Between Pretransplant Dialysis Modality and Kidney Transplant Outcomes

The benefits and disadvantages of different pretransplant dialysis modalities and their posttransplant outcomes remain unclear in contemporary kidney transplant care. To summarize the available evidence of the association of different pretransplant dialysis modalities, including hemodialysis and peritoneal dialysis (PD), with posttransplant outcomes. MEDLINE, Embase, PubMed, Cochrane Library, Scopus, CINAHL, and gray literature were searched from inception to March 18, 2022 (updated to April 1, 2022), for relevant studies and with no language restrictions. Randomized clinical trials and nonrandomized observational (case-control and cohort) studies that investigated the association between pretransplant dialysis modality and posttransplant outcomes regardless of age or donor sources (living or deceased) were abstracted independently by 2 reviewers. Following Preferred Reporting Items for Systematic Reviews and Meta-analyses and Meta-analysis of Observational Studies in Epidemiology reporting guidelines, 2 reviewers independently extracted relevant information using a standardized approach. Random-effects meta-analysis was used to estimate pooled adjusted hazard ratio (HR) or odds ratio and 95% CI. Primary outcomes included all-cause mortality, overall graft failure, death-censored graft failure, and delayed graft function. Secondary outcomes included acute rejection, graft vessel thrombosis, oliguria, de novo heart failure, and new-onset diabetes after transplant. The study analyzed 26 nonrandomized studies (1 case-control and 25 cohort), including 269 715 patients (mean recipient age range, 14.5-67.0 years; reported proportions of female individuals, 29.4%-66.9%) whose outcomes associated with pretransplant hemodialysis vs pretransplant PD were compared. No significant difference, with very low certainty of evidence, was observed between pretransplant PD and all-cause mortality (13 studies; n = 221 815; HR, 0.92 [95% CI, 0.84-1.01]; P = .08) as well as death-censored graft failure (5 studies; n = 96 439; HR, 0.98 [95% CI, 0.85-1.14]; P = .81). However, pretransplant PD was associated with a lower risk for overall graft failure (10 studies; n = 209 287; HR, 0.96 [95% CI, 0.92-0.99]; P = .02; very low certainty of evidence) and delayed graft function (6 studies; n = 47 118; odds ratio, 0.73 [95% CI, 0.70-0.76]; P < .001; low certainty of evidence). Secondary outcomes were inconclusive due to few studies with available data. Results of the study suggest that pretransplant PD is a preferred dialysis modality option during the transition to kidney transplant. Future studies are warranted to address shared decision-making between health care professionals, patients, and caregivers as well as patient preferences.

AORTOCORONARY SAPHENOUS VEIN GRAFT ANEURYSM: A SILENT COMPLICATION

AORTOCORONARY SAPHENOUS VEIN GRAFT ANEURYSM: A SILENT COMPLICATION

Surgical treatment strategies for patients with type A aortic dissection involving arch anomalies.

ObjectiveThe aim of the study was to investigate surgical modalities and outcomes in patients with type A aortic dissection involving arch anomalies.MethodPatients with type A aortic dissection who underwent surgical treatment at our center between January 2017 and 31 December 2020 were selected for this retrospective analysis. Data including computed tomography (CT), surgical records, and cardiopulmonary bypass records were analyzed. Perioperatively survived patients were followed up, and long-term mortality and aortic re-interventions were recorded.ResultA total of 81 patients with arch anomalies were included, 35 with “bovine” anomalies, 23 with an aberrant right subclavian artery, 22 with an isolated left vertebral artery, and one with a right-sided arch + aberrant left subclavian artery. The strategies of arch management and cannulation differed according to the anatomic variation of the aortic arch. In total, seven patients (9%) died after surgery. Patients with “bovine” anomalies had a higher perioperative mortality rate (14%) and incidence of neurological complications (16%). Overall, four patients died during the follow-up period, with a 6-year survival rate of 94.6% (70/74). A total of four patients underwent aortic re-intervention during the follow-up period; before the re-intervention, three received the en bloc technique (13.6% 3/22) and one received hybrid therapy (11.1% 1/9).ConclusionWith complete preservation and reconstruction of the supra-arch vessels, patients with type A aortic dissection combining arch anomalies can achieve a favorable perioperative prognostic outcome. Patients who received the en bloc technique are more likely to require aortic re-intervention than patients who underwent total arch replacement with a four-branched graft vessel. Cannulation strategies should be tailored according to the variation of anatomy, but routine cannulation with the right axillary artery can still be performed in most patients with arch anomalies, even for patients with an aberrant right subclavian artery.

425.5: Achieving Localized Immunosuppression Through Ex Vivo Engineering of Organ Blood Vessels

Introduction: Classic immunosuppressants lead to systemic immune shutdown, though necessary to mediate transplant rejection, it may lead to various complications. To reduce off-target immunosuppression while retaining increased organ survival, we propose direct modification of the endothelium of vascular transplants ex vivo to achieve localized immunomodulation. The glycocalyx (eGcx), made up of membrane-bound glycoproteins, is of particular interest due to its ability to control cell to cell communication and the activation of immune response through cell recognition. During organ transplantation, inflammation and oxidative damage occurs and can lead to the shedding and damage of the eGcx layer; this has been linked to organ failure and rejection. We developed an enzymatic approach to modify the surface of the endothelium with immunosuppressive polymers to induce immunomodulatory effects locally. We tested the efficacy of this approach in murine transplants.Method: We developed a method using tissue transglutaminase (tTGase) as the surface immobilizing enzyme and polyglycerol polymers containing sialic acid or sulfate moieties that is compatible with UW organ preservation solution at 4°C. In vitro mechanistic studies were performed using EaHy.926 cells to replicate the endothelium and PBMCs and CAR-T cells were used to test immune cytotoxicity. In vivo efficacy of graft rejection was assessed through aortic vessel or renal grafts from BALB/c donor mice into C57BL/6 recipient mice. Polymer treated and untreated grafts were assessed by serology and histology at various timepoints (day 2, 15 and 42 for vessel grafts and day 30 for renal grafts). Results: In vitro, polymer modified endothelial cells were able to evade CAR-T cell induced cytoxicity and reduced oxidative stress. Moreover, polymer treatment reduced TNF release in M1 macrophages. In vivo, modified grafts showed reduced medial thickening and leukocyte infiltration in vessel transplants; further confirmed in the reduction of pro-inflammatory cytokines in serum. In 42 day studies, donor-specific antibody was reduced in polymer-treated grafts compared to untreated. Finally, histological analysis of polymer-treated renal grafts revealed less infiltration and mesangial expansion relating to a healthier graft after 30 days.Conclusion: Here, the use of a polymer-mediated organ engineering approach leads to vascular protection that prevents immune-mediated rejection of organ transplants. Ex-vivo delivery of these immune cloaking polymers that engineer the blood vessel lumen allow for localized immune protection, making this an enticing and viable strategy for the reduction in the use of broad-active immunosuppressants post-transplantation. The protocol remains simple and easy to deliver, thereby enhancing its potential clinical applicability. To further validate this novel approach, studies in larger animal models that more closely replicate human transplant conditions are being planned. Canadian Institutes of Health Research. Natural Sciences and Engineering Council of Canada. Heart and Stroke Foundation of Canada. Canadian Glycomics Network, GlycoNet.

312.7: Liver Transplantation in a Complex Recipient Anatomy.

A 22-year-old man with situs inversus totalis and end-stage liver disease secondary to congenital biliary atresia and previous Kasai portoenterostomy at two months who was referred to our center with portal hypertensive bleeding, recurrent cholangitis, and hepatocellular carcinoma. He completed the liver transplant protocol. Preoperative liver angiotomography revealed, besides the mirror image orientation of the viscera and dextrocardia, inferior vena cava (IVC) and portal vein (PV) with good patency, splenorenal shunt, collateral circulation, and common hepatic artery arising from the superior mesenteric artery. A suitable 59-year-old cadaveric male donor with no anatomic variation was accepted. He underwent to liver transplant, his BMI was 16.7kg/m2, MELD and Child-Pugh scores were 24 and 7 points. The donor’s liver weighed 1725g.A bilateral subcostal incision was made; after extensive lysis of adhesions, the hepatectomy was performed with preservation of the recipient’ s IVC. The donor’s liver was placed on the left side rotated 90° clockwis; this allowed perfect alignment of the recipient and dolor hila. The donor infrahepatic vena cava was anastomosed end-to-side to recipient IVC previous closing of the suprahepatic vena cava. The artery and PV were anastomosed end-to-end without vessel grafts. A choledocojejunostomy was performed using the previous Roux-en-Y. The patient had satisfactory evolution and was discharged on the 8th postoperative day with normal liver function.

Robotic Kidney Transplantation Under Regional Hypothermia.

The technique of robotic kidney transplantation (RKT) under regional hypothermia is being described. It may be performed in all patients requiring kidney transplantation with some relative contraindications. Unlike open transplantation, RKT is a transperitoneal procedure. Patient lies supine with low lithotomy and 15° to 20° reverse Trendelenburg position. Port placement is like standard radical prostatectomy with a multiport device placed at the umbilicus. The graft after harvest needs special care on the bench to ligate all vascular communications and placed in a gauze jacket for easy handling. After transplant bed preparation, the graft is introduced in peritoneal cavity through the umbilical opening and placed over the bladder flap bed with ice slush for hypothermia. End-to-side vascular anastomoses of renal vein and artery are done with the graft lying in pelvic hollow and renal vessels facing laterally to external iliac vessels. After vascular anastomoses, the graft is rotated laterally to iliac fossa to be fixed with preformed peritoneal flap. A stented ureterovesicostomy to the recipient is done using extravesical technique. The external opening for introducing the graft and the robotic port openings is closed after leaving a drain. Postoperative (PO) care and PO immunosuppression are like the open counterpart, except the treatment of drain, which is removed on second PO day. Obese recipients and multiple graft vessels may be handled comfortably during RKT with described techniques. It is important to follow certain checkpoints to avoid bleeding. With graft and patient survival of 95.2% and 94.5%, respectively, RKT outcomes are noninferior to open technique in the published data. The RKT has less incidence of PO pain, wound infection, and symptomatic lymphoceles.

Abstract P1017: Tissue Engineered Human Acellular Blood Vessels For Coronary Artery Bypass Grafting

Objective: Conduit for coronary artery bypass grafting (CABG) can be limited due to poor quality or prior removal of saphenous veins. A human acellular vessel (HAV) bioengineered from vascular cells and then decellularized for implantation may provide a readily available, off-the-shelf conduit for CABG. Here we evaluate the use of small diameter HAV for CABG in a non-human primate model. Methods: Adult male baboons (n=7; 26.8 - 37.0 kg) were imaged by left heart catheterization and computed tomography angiography. CABG was performed using a 3.5 mm diameter HAV to the left anterior descending (LAD) or right coronary artery (RCA) via sternotomy with cardiopulmonary bypass. The proximal coronary artery was ligated to prevent competitive flow and graft transit time flowmetry (TTFM) was assessed after implant. Angiography at 2 weeks, 1, 3, and 6 months evaluated graft patency and heart function. HAVs explanted at 6 months were assessed by immunohistochemistry for host cellular response and remodeling. Results and Conclusion: Baboons underwent CABG using a 3.5 mm HAV from the ascending aorta to the LAD (n=2) or RCA (n=5). The diminutive LAD led to early graft loss due to size mismatch and poor runoff. HAV bypass to the dominant RCA (TTFM: 22 ± 7.7 mL/min) resulted in sustained graft patency for up to 6 months post-implantation. HAV explant histology revealed infiltration of multiple host cell populations with formation of a neoadventitial layer and evidence of luminal endothelization. HAV conduits retained structural integrity with no evidence of mechanical failure throughout the study. These results demonstrate that tissue-engineered HAVs may provide an off-the-shelf conduit for CABG.

Construction and Evaluation of Small-Diameter Bioartificial Arteries Based on a Combined-Mold Technology.

Arterial stenosis or blockage is the leading cause of cardiovascular disease, and the common solution is to substitute the arteries by autologous veins or bypass the blood vessels physically. With the development of science and technology, arteries with diameter larger than 6 mm can be substituted by unbiodegradable polymers, such as polytetrafluoroethylene, clinically. Nevertheless, the construction of a small-diameter (less than 6 mm) artery with living cells has always been a thorny problem. In this study, a suit of combined mold was designed and forged for constructing small-diameter arterial vessels. Based on this combined mold, bioactive arterial vessels containing adipose-derived stem cells (ASCs) and different growth factors (GFs) were assembled together to mimic the inner and middle layers of the natural arteries. Before assembling, ASCs and GFs were loaded into a gelatin/alginate hydrogel. To enhance the mechanical property of the bilayer arterial vessels, polylactic–glycolic acid (PLGA) was applied on the surface of the bilayer vessels to form the outer third layer. The biocompatibility, morphology and mechanical property of the constructed triple-layer arterial vessels were characterized. The morphological results manifested that cells grow well in the gelatin/alginate hydrogels, and ASCs were differentiated into endothelial cells (ECs) and smooth muscle cells (SMCs), respectively. In addition, under the action of shear stress produced by the flow of the culture medium, cells in the hydrogels with high density were connected to each other, similar to the natural vascular endothelial tissues (i.e., endothelia). Especially, the mechanical property of the triple-layer arterial vessels can well meet the anti-stress requirements as human blood vessels. In a word, a small-diameter arterial vessel was successfully constructed through the combined mold and has a promising application prospect as a clinical small-diameter vessel graft.

Does the Inverted Kidney Transplantation Technique Promote the Feasibility and Safety of Right Living Donor Nephrectomy?

The aim of this study is to compare the outcomes of right- and left-sided live donor nephrectomies using the inverted kidney transplantation technique for right live donor nephrectomy on transplantation. A retrospective review was done for the cases of live donor nephrectomy, either as open donor nephrectomy or laparoscopic donor nephrectomy between 2004 and 2019. Inverted kidney transplantation was used with right-sided grafts. The variables of the right- and left-sided live donor nephrectomies were compared. There were 202 live donor nephrectomies including 71 (35.1%) open donor nephrectomies and 131 (64.9%) laparoscopic donor nephrectomies with 4 cases of conversion to open donor nephrectomy. There were 119 (58.9%) right-sided and 83 (41.1%) left-sided live donor nephrectomies with insignificantly different mean operative time (123 and 127 minutes; P=.09), mean warm ischemia time (82.3 and 84.5 seconds; P=.32), and mean blood loss (73 and 78 mL; P=.18), respectively. Inverted kidney transplantation was performed for 86% of grafts from right live donor nephrectomies. Discharge from hospital was on an average of 4.3 days postoperatively. There were only 3 complications (1 in right live donor nephrectomy and 2 in left live donor nephrectomies) with grade 2 according to Clavien-Dindo Classification. Incidence of delayed graft function (P=.09), transplant vein thrombosis (1 case in each group), 1-year graft survival rate (93.2% vs. 94.8%; P=.12), and 1-year serum creatinine levels (1.4 ± 0.3 vs. 1.3 ± 0.2; P=.09) revealed statistically insignificant differences. Regardless of the surgical technique, the right live donor nephrectomy seems to be technically as safe as the left live donor nephrectomy for both the donors and the recipients. Using inverted kidney transplantation provided convenient extensions of graft's vessels to full length with no significant increased incidence of vascular thrombosis.

Establishment and Evaluation of a Porcine Vein Graft Disease Model.

Venous graft disease (VGD) is the leading cause of coronary artery bypass graft (CABG) failure. Large animal models of CABG-VGD are needed for the investigation of disease mechanisms and the development of therapeutic strategies. To perform the surgery, we enter the cardiac chamber through the third intercostal space and carefully dissect the internal mammary vein and immerse it in normal saline. The right main coronary artery is then treated for ischemia. The target vessel is incised, a shunt plug is placed, and the distal end of the graft vein is anastomosed. The ascending aorta is partially blocked, and the proximal end of the graft vein is anastomosed after perforation. The graft vein is checked for patency, and the proximal right coronary artery is ligated. CABG surgery is performed in minipigs to harvest the left internal mammary vein for its use as a vascular graft. Serum biochemical tests are used to evaluate the physiological status of the animals after surgery. Ultrasound examination shows that the proximal, middle, and distal end of the graft vessel are unobstructed. In the surgical model, turbulent blood flow in the graft is observed upon histological examination after the CABG surgery, and venous graft stenosis associated with intimal hyperplasia is observed in the graft. The study here provides detailed surgical procedures for the establishment of a repeatable CABG-induced VGD model.

O-037 Revascularization of human ovarian grafts occurs equally efficient from both sides of the cortex tissue: implications for clinical practice

Abstract Study question Does revascularization of xenotransplanted human ovarian grafts occur equally efficient from both the cortical and medullary side of the cortex tissue? Summary answer Murine vessels were established equally efficient from both sides of human ovarian grafts, demonstrating that the fibrous cortical side does not hinder the neovascularization process. What is known already There is a lack of consensus regarding the surgical approach for transplanting frozen-thawed ovarian tissue and various techniques are being used clinically worldwide. Some centers attach ovarian tissue with stitches or Interceed® on top of the decorticated remaining ovary to mimic normal ovarian architecture. Other centers transplant ovarian tissue in subcortical pockets made by longitudinal or transverse incisions in the remaining intact ovary to facilitate vascularization from both sides of the graft. While other centers transplant to sub-peritoneal pelvic sites only. It is unknown which techniques and transplantation sites provide the most efficient revascularization of the ovarian grafts. Study design, size, duration Three pieces of cryopreserved ovarian cortex (approximately 5x5x1 mm in size) were donated and thawed from 12 women and two of the pieces were transplanted to subcutaneous pockets on the dorsal side of ovariectomized immunodeficient female mice. The third piece was processed as an ungrafted control. Ovarian grafts were retrieved after 8 days to analyze the spatial distribution of graft-revascularization using immunohistochemical detection of murine CD31, and after 8 weeks to evaluate follicle density (follicles/mm3). Participants/materials, setting, methods Ovarian cortex was donated from 12 women aged 27-31 years having their tissue frozen for fertility preservation. The CD31 positive vessel area and density were quantified using a custom designed application (APP) from Visiopharm®. Three regions of interest (ROIs) were defined in each tissue section; the cortical side, the center, and the medullary side. Vessels were sub-divided into three categories according to size: micro-vessels (&amp;lt;300 µm2), small vessels (300-1000 µm2), and large vessels (1000-3000 µm2). Main results and the role of chance After 8 days xenotransplantation, a statistical significant lower density of vessels was found in the center of the human ovarian grafts compared to the cortical and medullary sides (cortical side: 323 ± 14 vessels/mm2; center: 240 ± 12 vessels/mm2; medullary side: 301 ± 18 vessels/mm2; p &amp;lt; 0.001). The mean percentage of CD31 positive vessel area in the human ovarian grafts was similar in the three ROIs, but lowest in the center of the grafts (cortical side: 3.9% ± 0.2 (SEM); center: 3.5% ± 0.2; medullary side: 4.0% ± 0.3; p = 0.17). Micro-vessels comprised 89-91% of all vessels in the three ROIs, demonstrating that the vast majority of vessels were newly formed. Heatmaps were generated for each section based on the CD31 positive area to visualize the localization of vessels in the ovarian grafts and the maps showed highly variable vascularization patterns in the grafts from different patients. Overall, vascularization appeared to occur equally efficient in all peripherical areas of the ovarian grafts. The follicle density in ungrafted cortex tissue was 51.8 ± 17.3 follicles/mm3 and 14.7 ± 3.7 follicles/mm3 after 8 weeks xenografting, resulting in an average follicle survival rate of 28%. Limitations, reasons for caution The current study was not designed to directly compare clinically used transplantation techniques, which should be studied in larger animal models, like sheep, in which the structure of ovarian tissue is similar to human. Wider implications of the findings Revascularization was established equally efficient from both sides of xenotransplanted human ovarian cortex, suggesting that transplantation techniques ensuring revascularization from both sides of the ovarian graft, such as sub-cortical or peritoneal pockets, may facilitate a more efficient revascularization of the graft than techniques allowing revascularization from only the medullary side. Trial registration number not applicable

Treatments and outcomes of intra-operative portal vein thrombosis in living-donor liver transplantation due to biliary atresia

Pediatric living-donor liver transplantation (LDLT) has become one of the most effective therapies for pediatric end-stage liver diseases. We aim to investigate the risk factors for intra-operative portal vein thrombosis (PVT) and the short- and long-term outcomes in children post LDLT. This was a retrospective analysis from 584 cases of biliary atresia (BA) patients who had undergone LDLT from January 2014 to December 2019 at our hospital. Patients were divided into PVT and non-PVT groups according to the occurrence of PVT during LDLT. The median age of recipients at transplantation was 7.22 (quartiles, 6.03, 9.50) months, the incidence of intra-operative PVT was 5.31% (31/584). The independent risk factors for intra-operative PVT were the diameter of the recipient's PV not greater than 4mm and a higher ratio of graft-to-recipient PV diameter. The cumulative survival rates of grafts and recipients were 93.5% and 93.5% in the PVT group, and 94.9% and 95.3% in the non-PVT group, respectively, without significant difference. The recovery of graft function was similar in recipients with or without interposed graft vessel (IGV). However, the incidence of PV stenosis was higher in recipients with IGV after LDLT. Intra-operative PVT is a common complication in pediatric LDLT, but an excellent prognosis can be achieved by appropriate and individualized surgical treatment. We noted that intra-operative PVT did not affect the survival rates of grafts and recipients, but there was a higher incidence of PV complications after LDLT. Ⅲ.

Angiographic Characteristics of Cerebral Perfusion and Hemodynamics of the Bridging Artery After Surgical Treatment of Unilateral Moyamoya Disease.

PurposeTo investigate the characteristics of cerebral perfusion and hemodynamics of bypass grafting in the treatment of moyamoya disease (MMD) using the iFlow color-coded flow map in comparison with magnetic resonance imaging–perfusion-weighted imaging (MRI–PWI) and computational fluid dynamic (CFD) analysis.Materials and MethodsPatients with MMD treated with bypass grafting who had undergone MRI PWI and digital subtraction angiography for iFlow color-coded map was retrospectively enrolled and CFD was performed for calculating the hemodynamic stresses around the bypass grafting.ResultsForty-five patients with unilateral MMD treated with bypass surgery were enrolled. The bypass surgery was successful in all patients, with no severe neurological complications during the periprocedural period. Followed up for 4–12 months (median 5.5), the neurological function was good in all patients. The cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP) were significantly (p < 0.05) improved in the middle cerebral artery distribution area on the surgical side before and after vascular bypass, and the difference of TTP (s) measured from the proximal bifurcation of common carotid artery to the confluence of sinus was also significant (p < 0.05). A significant (p < 0.05) positive correlation existed in the perfusion parameters between the iFlow blood perfusion and the MRI–PWI perfusion, with r-value for TTP of 0.765 (p < 0.01). The iFlow color-coded blood flow map showed warm color changes on the diseased side, similar to those on the contralateral side. In CFD analysis, the hemodynamic stresses were all improved, in and around the bypass grafting and distal vessels, which were beneficial to blood flow entering distal arterial branches.ConclusionThe iFlow color-coded flow map can be used to analyze cerebral perfusion after bypass grafting for MMD, similar to MRI–PWI, and CFD can be used to analyze the hemodynamics after bypass grafting, revealing improved hemodynamics to promote blood flow entering distal arteries.

An in vitro analysis of the effect of geometry-induced flows on endothelial cell behavior in 3D printed small-diameter blood vessels

Clinical recovery from vascular diseases has increasingly become reliant upon the successful fabrication of artificial blood vessels (BVs) or vascular prostheses due to the shortage of autologous vessels and the high incidence of vessel graft diseases. Even though many attempts at the clinical implementation of large artificial BVs have been reported to be successful, the development of small-diameter BVs remains one of the significant challenges due to the limitation of micro-manufacturing capacity in complexity and reproducibility, as well as the development of thrombosis. The present study aims to develop 3D printed small-diameter artificial BVs that recapitulate the longitudinal geometric elements in the native BVs using biocompatible polylactic acid (PLA). As their intrinsic physical properties are crystallinity dependent, we used two PLA filaments with different crystallinity to investigate the suitability of their physical properties in the micro-manufacturing of BVs. To explore the mechanism of venous thrombosis, our study provided a preliminarily comparative analysis of the effect of geometry-induced flows on the behavior of human endothelial cells (ECs). Our results showed that the adhered healthy ECs in the 3D printed BV exhibited regulated patterns, such as elongated and aligned parallel to the flow direction, as well as geometry-induced EC response mechanisms that are associated with hemodynamic shear stresses. Furthermore, the computational fluid dynamics simulation results provided insightful information to predict velocity profile and wall shear stress distribution in the geometries of BVs in accordance with their spatiotemporally-dependent cell behaviors. Our study demonstrated that 3D printed small-diameter BVs could serve as suitable candidates for fundamental BV studies and hold great potential for clinical applications.

Evaluation of Early and Late Effects of Surgical Treatment of Early Hepatic Artery Thrombosis After Liver Transplantation

Hepatic artery thrombosis (HAT) is the most severe vascular complication after liver transplantation and one of the major causes of early graft loss and mortality after transplantation. The number of retransplantations and recipient deaths can be decreased with an urgent thrombectomy of the hepatic artery. The aim of the study was to analyze the early and long-term outcomes of the surgical revascularization of early hepatic artery thrombosis after liver transplantation. Four hundred eleven orthotopic liver transplantations in 380 patients were performed at our center between 2005 and 2020. A Doppler evaluation of the graft vessels patency was performed daily for the first 5 days after transplantation in all recipients. After angio-computed tomography confirmation, most of the cases of HAT qualified for surgical revascularization. Early HAT was diagnosed in 20 cases (4.9%), occurring most frequently between the first and third day after transplantation. Sixteen patients underwent revascularization surgery. Among them, in the early post-transplantation period, 4 died and 2 more had retransplantation. Of the remaining 10 recipients, 2 had no biliary complications, 1 had bile leakage, and 7 had common bile duct stenosis, all treated endoscopically. Among 4 nonoperated patients, 1 died and the other 2 had retransplantation in the early post-transplantation period; the last of these 4 recipients had bile duct stenosis. The urgent surgical revascularization in liver recipients with early HAT allows the avoidance of early retransplantation. However, these patients require intensified surveillance owing to the high risk of biliary complications that may affect shortened graft and patient survival.

Computational Fluid Dynamic Evaluation of Deep Inferior Epigastric Artery Perforator (DIEP) Flap End-to-Side Anastomosis.

BackgroundEnd-to-side (ETS) microvascular anastomoses are utilized within deep inferior epigastric artery perforator (DIEP) flap breast reconstruction procedures. Optimization of these anastomoses via a computational fluid dynamic (CFD) model can minimize ischemia and contribute to flap success.Methods A CFD model of a deep inferior epigastric artery to internal mammary artery anastomosis was constructed with OpenFOAM software (OpenCFD Ltd., Bracknell, UK). Blood was modelled as an incompressible Newtonian fluid. Viscosity and density were assumed to be constant throughout the simulation. Mean arterial pressure was held constant at 100 mmHg. Individual virtual meshes were created for 30-, 45-, 60-, 75-, and 90-degree anastomotic angle simulations. Fluid flow was visualized with line integral convolution (LIC) and pure fluid velocity (PFV) techniques. Vessel wall shear stress (WSS) was also visualized.Results The LIC revealed blood recirculation was associated with large anastomotic angles with minimal to no recirculation seen in the 45- and 30-degree simulations. Any recirculation visualized was confined to the toe of the bifurcation. This recirculation was associated with stagnation in the toe of the graft vessel as well, as visualized by the PFV model. A linear relationship was identified between anastomotic angle and percentage of stagnant fluid, with stagnation increasing as the anastomotic angle increased. Wall shear stress increased with the anastomotic angle and was concentrated in the heel and toe of the model.Conclusions The CFD modelling shows that increased acuity of anastomotic angles in ETS DIEP flaps is essential to minimize stagnation, recirculation, and WSS. Successful implementation of this recommendation may directly decrease the risk of flap failure from ischemia.

Cerebral Bypass Using the Descending Branch of the Lateral Circumflex Femoral Artery: A Case Series.

When performing extracranial to intracranial (EC-IC) and intracranial to intracranial (IC-IC) bypass, the choice of donor vessel and interposition graft depends on several factors: vessel size and accessibility, desired blood flow augmentation, revascularization site anatomy, and pathology. The descending branch of the lateral circumflex femoral artery (DLCFA) is an attractive conduit for cerebrovascular bypass. To present our institutional experience using DLCFA grafts for cerebral revascularization. Retrospective review of perioperative data and outcomes for patients undergoing cerebrovascular bypass surgery using a DLCFA graft from 2016 to 2019. Twenty consecutive patients underwent EC-IC bypass using a DLCFA interposition graft. Bypass indications included 13 (65%) intracranial aneurysms, 4 (20%) medically refractory atherosclerotic large artery occlusions (internal carotid artery or middle cerebral artery), 2 (10%) internal carotid artery dissections, and 1 (5%) patient with moyamoya disease. Most commonly, a donor superior temporal artery was bypassed to a recipient middle cerebral artery (14 of 20; 70%). Two cases demonstrated graft spasm. Graft occlusion occurred in one patient and was asymptomatic. Perioperative bypass surgery-related ischemia occurred in 3 patients: 1 patient with insufficient bypass flow, 1 patient with graft stenosis because of an adventitial band, and 1 patient with focal status epilepticus in the bypassed territory resulting in cortical ischemia. One donor site hematoma occurred. The median (range) modified Rankin scale (mRS) score on follow-up was 1.5 (1-4) at 7.8 (1-27) months, with most patients achieving good functional outcomes (mRS ≤2). The DLCFA is a versatile graft for cerebral revascularization surgery, demonstrating good outcomes with minimal graft harvest site morbidity and an acceptable graft patency rate.

The Importance of Protecting the Structure and Viability of Adipose Tissue for Fat Grafting.

Fat grafting is widely used for soft-tissue augmentation; however, the related clinical outcome remains variable and technique-dependent. The mechanisms underlying fat graft survival are not fully understood, particularly regarding the contributions of different cell types, such as functional adipocytes. This study evaluated the importance of adipose tissue structure and viability in fat grafting and, to some extent, revealed the effect of adipocytes in fat grafting. Human lipoaspirate was harvested using suction-assisted liposuction and processed using three separate methods: cotton-pad filtration, soft centrifugation (400 g for 1 minute), and Coleman centrifugation (1200 g for 3 minutes). Then all samples were subjected to second cotton-pad concentration. Adipose tissue structure and viability, the numbers of adipose-derived stem cells, and their proliferation and multilineage differentiation abilities were compared in vitro. The volume retention rate and fat graft quality were evaluated in vivo. Cell structure destruction and viability decline were more evident in the Coleman centrifugation group compared to the cotton-pad filtration group and the soft centrifugation group. However, no intergroup differences were observed in the numbers, proliferation, or multilineage differentiation abilities of adipose-derived stem cells. After transplantation, the volume retention rates were similar in the three groups. However, greater structural and functional damage was associated with poorer graft quality, including decreased levels of graft viability, vessel density, and vascular endothelial growth factor secretion and increased levels of vacuoles, necrotic areas, fibrosis, and inflammation. Protecting adipose tissue structure and viability is crucial for improving fat grafting outcomes. The protection of the structure and viability of adipose tissue should be ensured throughout the whole process of fat grafting to reduce complications and improve graft quality.

Impact of pre-transplant dialysis modality on kidney transplant outcomes: a systematic review and meta-analysis.

For end-stage renal disease (ESRD), patients receiving kidney transplantation, peritoneal dialysis (PD) and hemodialysis (HD) are both appropriate modes of pre-transplant dialysis. The aim of this review is to assess the impact of pre-transplant PD compared to HD on kidney transplant outcomes in ESRD patients. A comprehensive search in digital databases, like PubMed, SCOPUS and EMBASE and a manual search were conducted to identify cohort studies comparing the kidney transplant outcomes of both pre-transplant dialysis modalities. The data were subjected to both qualitative and quantitative analysis. A meta-analysis was carried out to calculate the effect estimate for patient survival, graft survival and delayed graft function, death-censored graft survival, acute rejection-free graft survival, graft vessel thrombosis, urological complications, surgical complications, any infections, and onset of diabetes after transplantation. The qualities of the included studies were judged by the New-castle Ottawa scale. The overall patient survival is shown to be better with patients who underwent pre-transplant PD compared to HD with OR 1.34 95% CI [1.11, 1.61], p = 0.002. Delayed graft function was found to be highly associated with HD compared to PD with OR 0.60 [0.52, 0.70], p<0.0001 with moderate heterogeneity (i2 = 48%). However, no difference was observed in terms of graft survival, complications, infections, and new onset of diabetes mellitus compared to patients undergoing pre-transplant HD. Within the limitations of the review, it can be concluded that ESRD patients undergoing pre-transplant PD were found to have better patient survival and lower incidence of delayed graft function.