Synthetic Arteriovenous Grafts Research Articles

Realtime monitoring of thrombus formation in vivo using a self-reporting vascular access graft

BackgroundChronic kidney disease (CKD) affects 10% of the global population costing over a hundred billion dollars per annum and leading to increased risk of cardiovascular disease. Many patients with CKD require regular haemodialyses. Synthetic arteriovenous grafts (AVG) are increasingly used to provide rapid vascular connection for dialysis. Initially, they have excellent patency rates but are critically limited by neointimal hyperplasia at the venous anastomosis, which drives subsequent thrombosis, graft failure and death.MethodsHere, we describe a system in which electrical impedance spectroscopy sensors are incorporated circumferentially into the wall of a synthetic arteriovenous graft. This is combined with an implantable radiotelemetry system for data transmission outside the patient. The system was tested using monolayers of endothelial and smooth muscle cells as well as swine blood and clots with explanted human carotid artery plaques. Sensor testing was then performed in vitro and the device was implanted in vivo in female swine.ResultsThe device can wirelessly report the accumulation of biological material, both cells and blood. Differences are also detected when comparing controls with pathological atheroma. In swine differences between blockage formation in a graft were remotely obtained and wireless reported.ConclusionsCombining electrical impedance spectroscopy and an implantable radiotelemetry system enables graft surveillance. This has the potential to be used for early detection of venous stenosis and blood clot formation in real-time in vivo. In principle, the concept could apply to other cardiovascular diseases and vascular implantable devices.

Management of Immature Arteriovenous Fistulas.

In patients requiring long-term hemodialysis for chronic kidney disease, an arteriovenous fistula is the preferred mode of hemodialysis access over synthetic arteriovenous graft or hemodialysis catheters. The National Kidney Foundation recommended in their Kidney Dialysis Outcomes Quality Initiative (KDOQI) Clinical Practice Guidelines that the creation of an autogenous arteriovenous fistula should initially be sought whenever possible. In 2003, a program named the Fistula First Breakthrough Initiative was initiated in the U.S. to increase the use of arteriovenous fistula for hemodialysis and to ultimately surpass the goal of 50% fistula use in incident and 40% fistula use in prevalent hemodialysis patients per recommendation by KDOQI Guidelines. While this goal was achieved, the encouraged creation of arteriovenous fistulas saw a rise in fistulas that failed to mature. Researchers have focused on developing strategies to optimize fistula maturation. Studies have revealed that the presence of stenoses and accessory draining veins may contribute to unsuccessful fistula maturation. Endovascular treatment, including balloon angioplasty and accessory vein embolization, aim to correct anatomical factors that negatively affect the maturation process. This article reviews the techniques and outcomes of endovascular treatment in the management of immature fistulas.

Management of Thrombosed Dialysis Access Circuits.

Thrombotic occlusion of autologous arteriovenous fistulas or synthetic arteriovenous grafts is a serious adverse event in hemodialysis patients and declotting should be performed before next hemodialysis session, in order to avoid a central venous catheter. Various techniques exist to declot a thrombosed vascular access, including open surgical thrombectomy, catheter-directed thrombolysis and use of different types of percutaneous thrombo-aspiration catheters and mechanical thrombectomy devices. These devices can be categorized as devices with direct wall contact and hydrodynamic devices without direct wall contact. Technical and early clinical outcome results of percutaneous hemodialysis declotting are high and ranging between 70 and 100%; late clinical patency results are much lower related to restenosis or re-thrombosis; these patency results are higher for autologous arteriovenous fistulas compared to synthetic arteriovenous grafts and mainly depend on the combined efficacy of successful thrombectomy and durable treatment of the underlying stenoses, associated with the acute thrombosis.

Surgical creation of lower extremity fistula and grafts.

Lower limb vascular access (LLVA) should be considered for patients in whom upper extremity access has been exhausted. The decisional process around vascular access (VA) site selection should incorporate a patient centered approach that aligns with End Stage Kidney Disease life-plan as recently described in proffered in 2019 Vascular Access Guidelines. The current surgical approaches to LLVA can be divided into two main groups: (A) autologous arteriovenous fistulas (AVFs); (B) synthetic arteriovenous grafts (AVGs). The autologous AVFs include both the femoral vein (FV) and great saphenous vein (GSV) transpositions, while prosthetic AVGs in the thigh position are appropriate for certain patient subtypes. Good durability has been described for autogenous FV transposition as well as AVGs with both demonstrating acceptable primary and secondary patency rates. Major complications such as steal syndrome, limb edema, and bleeding and minor complications such as wound-related infection, hematoma and delayed wound healing have been noted. LLVA is commonly reserved for the patient in whom the only alternative VA may be a tunneled catheter with its attendant morbidity. In this clinical circumstance, successful LLVA has the opportunity to be a life-saving surgical therapy when successfully performed. We describe a thoughtful approach that focuses on patient selection to optimize success and mitigate complications associated with LLVA.

Comparison of Primary Patency Rate between Drug- Coated Balloon and Plain Balloon Angioplasty in Hemodialysis Access

Objective: Hemodialysis adequacy in end-stage renal disease patients plays a crucial role in their quality of life. Repeated stenosis at the anastomotic site of arteriovenous fistula and synthetic arteriovenous graft are a major cause of access failure resulting in hospitalization, catheter usage, and contributing substantially to increased health care costs. Although standard plain balloon angioplasty (PBA) is successful, the patency rate over time is often poor. Drug-coated balloons (DCB) delivering an anti-restenosis agent, Paclitaxel, may improve patency. In this study, we aimed to investigate whether there is an increase in primary patency rate in drug-coated balloon angioplasty compared to conventional plain balloon angioplasty.Materials and Methods: We performed a retrospective analysis of 55 patients with stenotic arteriovenous fistulas (AVF), and arteriovenous grafts (AVG) treated with DCB or PBA. Thirty-five patients were treated with drug-coated balloons, while twenty patients were treated with the standard plain balloon angioplasty. Follow up assessment was scheduled at three months, six months, and nine months. Our primary outcome was the primary patency rate, defined as the interval from the time of intervention until hemodialysis inadequacy.Results: There were 55 patients including twenty-one males and thirty-four females participated in the study. The average age of the 55 patients was 65.43 ± 12.89 years. Thirty (54.5%) patients were diabetes mellitus and 40 (72.7%) patients had hypertension. Seven patients (12.7%) had dyslipidemia. Eight patients (14.5%) had ischemic heart disease. And four patients (7.3%) had hyperparathyroidism. No significant differences in patency rate were found between gender, age group and patients’ underlying diseases. The proportion of primary patency rate comparing between the DCB and PBA treatment was 96.3% versus 73.9% at 6 months (P=0.017) and 92.6% versus 40% at 9 months (P<0.001). After multivariable analysis was performed (adjusted for sex, age, and underlying diseases), we found that stenosis was more likely to occur in patients who had undergone plain balloon angioplasty rather than drug-coated balloon angioplasty (HR 15.75; 95% CI 2.5%-99.1%, P=0.003).Conclusion: Drug-coated balloon angioplasty, when compared with plain balloon angioplasty, achieves a more desirable primary patency rate at 6 months and 9 months after the procedure.

The secondary patency after patch venoplasty versus balloon venoplasty in management of neointimal hyperplasia of the venous anastomosis of thrombosed arteriovenous grafts for hemodialysis

Background The pathogenesis of neointimal hyperplasia associated with hemodialysis arteriovenous (AV) grafts is complex and likely involves surgical manipulation of the tissues, material biocompatibility, and mechanical factors. Both surgical and radiological interventions for stenosed and thrombosed AV graft have been described aiming at the optimal restoration of morphology and function. Aim To compare the secondary patency after patch venoplasty and balloon venoplasty in management of neointimal hyperplasia of the venous anastomosis of AV graft for dialysis. Patients and methods This is a double-armed randomized prospective study that was carried out at Ain Shams University hospitals for 2 years. A total of 20 patients with thrombosed synthetic AV graft were enrolled in this study. The first group (10 patients) was treated with patch venoplasty, and the second group (10 patients) with balloon venoplasty adjunctive after surgical thrombectomy. Results Graft patency at 6-month and 12-month follow-up was 90 and 70% for the balloon angioplasty group versus 60 and 40% for the surgical patch venoplasty group (P=0.3 and 0.37, respectively). Conclusion In the present study, the outcome of balloon venoplasty was better than and patch venoplasty for thrombosed AV grafts. In addition to better graft patency, balloon venoplasty offers the advantage of shorter operative time and lower morbidity. Further studies with a large sample size and multicentric cooperation are required to confirm the present findings.

Comparison of vascular access patency and patient survival between native arteriovenous fistula and synthetic arteriovenous graft according to age group.

Arteriovenous fistula (AVF) is historically known to be the ideal option for vascular access (VA) for hemodialysis compared with arteriovenous graft (AVG). However, this approach has been recently questioned in the aging population because of their poor vessel quality and multiple comorbidities. Data from a total of 2200 patients from the VA category of The Catholic Medical Center nephrology registry from March 2009 to February 2017 were analyzed. We compared VA patency and patient survival between two groups, AVF and AVG, according to age. Compared with the AVG group, survival benefit in the AVF group continued even in patients ≥80 years. In the whole population, all the primary patency (PP), primary-assisted patency (PAP), and secondary patency (SP) measures were superior in the AVF group. With regard to subgroups, PP was comparable between the two groups in patients ≥65 years, whereas PAP and SP were superior in the AVF group even in septuagenarian patients who are from 70 to 79 years old. In patients ≥80 years, all the patency measures were comparable between the two groups. When the separate comparison of lower-arm AVF (or upper-arm AVF) and AVG, lower-arm AVF failed to demonstrate its superiority in any kind of patency in septuagenarian patients compared with AVG, whereas upper-arm AVF demonstrated its superiority in PAP and SP in septuagenarian patients. However, even upper-arm AVF failed to demonstrate its superiority in any kind of patency in patients ≥80 years. Arteriovenous fistula if using upper-arm vessel showed the superior VA patency up to septuagenarian patients, whereas, in HD patients ≥80 years, AVF and AVG were comparable in VA patency.

Short Term Success of Treatments to Salvage Thrombosed or Failing Synthetic Arteriovenous Grafts in End Stage Renal Disease: A Systematic Review and Network Meta-Analysis of Randomised Controlled Trials

There is currently uncertainty regarding the ideal treatment to salvage thrombosed or failing synthetic arteriovenous grafts (AVGs) in patients with end stage renal disease. Therefore, a systematic review up to December 2018 and network meta-analysis of randomised control trials (RCTs) that compared three month failure risk of available treatments was carried out.

A novel hybrid silk-fibroin/polyurethane three-layered vascular graft: towards in situ tissue-engineered vascular accesses for haemodialysis

Clinically available alternatives of vascular access for long-term haemodialysis—currently limited to native arteriovenous fistulae and synthetic grafts—suffer from several drawbacks and are associated to high failure rates. Bioprosthetic grafts and tissue-engineered blood vessels are costly alternatives without clearly demonstrated increased performance. In situ tissue engineering could be the ideal approach to provide a vascular access that profits from the advantages of vascular grafts in the short-term (e.g. early cannulation) and of fistulae in the long-term (e.g. high success rates driven by biointegration). Hence, in this study a three-layered silk fibroin/polyurethane vascular graft was developed by electrospinning to be applied as long-term haemodialysis vascular access pursuing a ‘hybrid’ in situ engineering approach (i.e. based on a semi-degradable scaffold). This Silkothane® graft was characterized concerning morphology, mechanics, physical properties, blood contact and vascular cell adhesion/viability. The full three-layered graft structure, influenced by the polyurethane presence, ensured mechanical properties that are a determinant factor for the success of a vascular access (e.g. vein-graft compliance matching). The Silkothane® graft demonstrated early cannulation potential in line with self-sealing commercial synthetic arteriovenous grafts, and a degradability driven by enzymatic activity. Moreover, the fibroin-only layers and extracellular matrix-like morphology, presented by the graft, revealed to be crucial in providing a non-haemolytic character, long clotting time, and favourable adhesion of human umbilical vein endothelial cells with increasing viability after 3 and 7 d. Accordingly, the proposed approach may represent a step forward towards an in situ engineered hybrid vascular access with potentialities for vein-graft anastomosis stability, early cannulation, and biointegration.

Autologous fat transplants to deliver glitazone and adiponectin for vasculoprotection

The insulin sensitizing glitazone drugs, rosiglitazone (ROS) and pioglitazone (PGZ) both have anti-proliferative and anti-inflammatory effects and induce adipose tissue (fat) to produce the vaso-protective protein adiponectin. Stenosis due to intimal hyperplasia development often occurs after placement of arteriovenous synthetic grafts used for hemodialysis. This work was performed to characterize the in vitro and in vivo effects of ROS or PGZ incorporation in fat and to determine if fat/PGZ depots could decrease vascular hyperplasia development in a porcine model of hemodialysis arteriovenous graft stenosis.Powdered ROS or PGZ (6–6000μM) was mixed with fat explants and cultured. Drug release from fat was quantified by HPLC/MS/MS, and adiponectin and monocyte chemotactic protein-1 (MCP-1) levels in culture media were measured by ELISA. The effect of conditioned media from the culture of fat with ROS or PGZ on i) platelet-derived growth factor-BB (PDGF-BB)-stimulated proliferation of human venous smooth muscle cells (SMC) was measured by a DNA-binding assay, and ii) lipopolysaccharide (LPS)-induced human monocyte release of tumor necrosis factor-alpha (TNFα) was assessed by ELISA. In a porcine model, pharmacokinetics of PGZ from fat depots transplanted perivascular to jugular vein were assessed by HPLC/MS/MS, and retention of the fat depot was monitored by MRI. A porcine model of synthetic graft placed between carotid artery and ipsilateral jugular vein was used to assess effects of PGZ/fat depots on vascular hyperplasia development.Both ROS and PGZ significantly induced the release of adiponectin and inhibited release of MCP-1 from the fat. TNF production from monocytes stimulated with LPS was inhibited 50–70% in the presence of media conditioned by fat alone or fat and either drug. The proliferation of SMC was inhibited in the presence of media conditioned by fat/ROS cultures. Fat explants placed perivascular to the external jugular vein were retained, as confirmed by MRI at one week after placement. PGZ was detected in the fat depot, in the external jugular vein wall and in adjacent tissue at clinically relevant levels, whereas levels in plasma were below detection. External jugular vein exposed to fat incorporated with PGZ had increased adiponectin expression compared to vein exposed to fat alone. However, the development of hyperplasia within the arteriovenous synthetic grafts was unchanged by treatment with fat/PGZ depots compared to no treatment.

Lower Extremity Permanent Dialysis Vascular Access.

Hemodialysis remains the most commonly used RRT option around the world. Technological advances, superior access to care, and better quality of care have led to overall improvement in survival of patients on long-term hemodialysis. Maintaining a functioning upper extremity vascular access for a prolonged duration continues to remain a challenge for dialysis providers. Frequently encountered difficulties in clinical practice include (1) a high incidence of central venous catheter-related central vein stenosis and (2) limited options for creating a functioning upper extremity permanent arteriovenous access. Lack of surgical skills, fear of complications, and limited involvement of the treating nephrologists in the decision-making process are some of the reasons why lower extremity permanent dialysis access remains an infrequently used option. Similar to upper extremity vascular access options, lower extremity arteriovenous fistula remains a preferred access over arteriovenous synthetic graft. The use of femoral tunneled catheter as a long-term access should be avoided as far as possible, especially with the availability of newer graft-catheter hybrid devices. Our review provides a summary of clinical evidence published in surgical, radiology, and nephrology literature highlighting the pros and cons of different types of lower extremity permanent dialysis access.

Aspirex Thrombectomy in Occluded Dialysis Access: A Retrospective Study.

This study is the first to present the outcomes of the Straub Aspirex device for the salvage of occluded renal dialysis access fistulae. This is a retrospective study, using data from the Renal Unit and Radiology Department database. It included all the patients between 2010 and 2014 who underwent percutaneous mechanical thrombectomy (PMT) treated by JD. Aspirex is an over-the-wire, 6-10 French catheter within which is a rapidly rotating helix which draws thrombus into a window near the tip which it then macerates and removes. Access survival was assessed using the Kaplan-Meier method, and multi-variant analysis was performed using the Cox proportional hazards model. Significance was considered if p<0.05. A total of 27 procedures were performed for 19 patients. 13 had autologous arterio-venous fistulae, and 14 had synthetic (PTFE) arterio-venous grafts. 15 were males, 4 females. 100% of the patients successfully had a channel of thrombus removed. This resulted in an 81.5% initial clinical success, with primary patency rates of 53.6, 44.3 and 33% by days 30, 90 and 480, respectively, without significant difference of any analysed covariates. No major complication (pulmonary embolus, paradoxical cerebral infarction, limb ischaemia or significant haemorrhage) occurred. Aspirex has rates of patency and complication similar to other PMT devices. No covariant studied affected outcome.

Assessment of Novel Anti-thrombotic Fusion Proteins for Inhibition of Stenosis in a Porcine Model of Arteriovenous Graft.

BackgroundHemodialysis arteriovenous synthetic grafts (AVG) provide high volumetric blood flow rates shortly after surgical placement. However, stenosis often develops at the vein-graft anastomosis contributing to thrombosis and early graft failure. Two novel fusion proteins, ANV-6L15 and TAP-ANV, inhibit the tissue factor/factor VIIa coagulation complex and the factor Xa/factor Va complex, respectively. Each inhibitor domain is fused to an annexin V domain that targets the inhibitor activity to sites of vascular injury to locally inhibit thrombosis. This study’s objective was to determine if these antithrombotic proteins are safe and effective in inhibiting AVG stenosis.MethodsA bolus of either TAP-ANV or ANV-6L15 fusion protein was administered intravenously immediately prior to surgical placement of a synthetic graft between the external jugular vein and common carotid artery in a porcine model. At surgery, the vein and artery were irrigated with the anti-thrombotic fusion protein. Control animals received intravenous heparin. At 4 weeks, MRI was performed to evaluate graft patency, the pigs were then euthanized and grafts and attached vessels were explanted for histomorphometric assessment of neointimal hyperplasia at the vein-graft anastomosis. Blood was collected at surgery, immediately after surgery and at euthanasia for serum metabolic panels and coagulation chemistries.ResultsNo acute thrombosis occurred in the control group or in either experimental group. No abnormal serum chemistries, activated clotting times or PT, PTT values were observed after treatment in experimental or control animals. However, at the vein-graft anastomosis, there was no difference between the control and experimental groups in cross-sectional lumen areas, as measured on MRI, and no difference in hyperplasia areas as determined by histomorphometry. These results suggest that local irrigation of TAP-ANV or ANV-6L15 intra-operatively was as effective in inhibiting acute graft thrombosis as intravenous administration of heparin, but failed to inhibit hyperplasia development and stenosis in AVG.

Influence of drugs on arteriovenous vascular access dysfunction.

Vascular access dysfunction, due to venous stenosis at the vein-artery anastomosis in arteriovenous fistulas and vein-graft anastomosis in synthetic arteriovenous grafts, is a major cause of morbidity and mortality in dialysis patients. The two overarching approaches to prevent and treat vascular access dysfunction are from systemic or local (including endovascular and perivascular) routes. However, there are currently very few effective therapies to treat vascular access dysfunction. This article will review major studies evaluating systemic, endovascular, and perivascular therapies for vascular access dysfunction. Ongoing research to evaluate novel innovations to prevent and/or manage vascular access dysfunction appears promising.

Drug-eluting versus plain balloon angioplasty for the treatment of failing dialysis access: Final results and cost-effectiveness analysis from a prospective randomized controlled trial (NCT01174472)

ObjectiveTo report the final results and cost-effectiveness analysis of a prospective randomized controlled trial investigating drug-eluting balloon (DEB) versus plain balloon angioplasty (BA) for the treatment of failing dialysis access (NCT01174472). Methods40 patients were randomized to angioplasty with either DEB (n=20) or BA (n=20) for treatment of significant venous stenosis causing a failing dialysis access. Both arteriovenous fistulas (AVF) and synthetic arteriovenous grafts (AVG) were included. Angiographic follow up was scheduled every two months. Primary endpoints were technical success and target lesion primary patency at 1 year. Cumulative and survival analysis was performed. Incremental net benefit (INB) and incremental cost effectiveness ratio (ICER) were calculated and the cost-effectiveness acceptability curve (CEAC) was drawn. ResultsBaseline variables were equally distributed between the two groups. At 1 year, cumulative target lesion primary patency was significantly higher after DEB application (35% vs. 5% after BA, p<0.001). Overall, median primary patency was 0.64 years in case of DEB vs. 0.36 years in case of BA (p=0.0007; unadjusted HR=0.27 [95%CI: 0.13–0.58]; Cox adjusted HR=0.23 [95%CI: 0.10–0.50]). ICER was 2198 Euros (€) per primary patency year of dialysis access gained. INB was 1068€ (95%CI: 31–2105€) for a willingness-to-pay (WTP) threshold of 5000€ (corresponding acceptability probability >97%). ConclusionDEB angioplasty may be a cost-effective option that significantly improves patency after angioplasty of venous stenoses of failing vascular dialysis access. Further large-scale randomized trials are warranted.

Vascular Access for Hemodialysis: When and how?

Abstract As chronic kidney disease (CKD) progresses to the terminal stage, proper actions must be taken to prepare the patient for the initiation of the renal replacement therapy (RRT). If hemodialysis is an option for RRT, decisions should be made about the right vascular access for each individual patient. The available options for vascular access include the use of native arteriovenous fistulas (AVF), synthetic arteriovenous grafts (AVG) and double lumen dialysis catheters. With the help of ultrasound mapping, chances for choosing a right access are today very high. For hemodialysis patients the selection of the proper vascular access is of vital issue in regard of preventing complications and unnecessary procedures. Planning, creation and monitoring of the vascular access in dialysis patients should involve not only the nephrologist, but also the vascular surgeon and the interventional radiologist. Thus, multidisciplinary approach should be taken, in order to choose the way that has the most advantages and the least damage for the patient. That is the proper mode for hemodialysis patients to have longer and better quality of life.

Aberrant Soluble Epoxide Hydrolase and Oxylipin Levels in a Porcine Arteriovenous Graft Stenosis Model

Synthetic arteriovenous grafts (AVGs) used for hemodialysis frequently fail due to the development of neointimal hyperplasia (NH) at the vein-graft anastomosis. Inflammation and smooth-muscle cell (SMC) and myofibroblast proliferation and migration likely play an important role in the pathogenesis of NH. Epoxyeicosatrienoic acids (EETs), the products of the catabolism of arachidonic acid by cytochrome P450 enzymes, possess anti-inflammatory, antiproliferative, antimigratory and vasodilatory properties that should reduce NH. The degradation of vasculoprotective EETs is catalyzed by the enzyme, soluble epoxide hydrolase (sEH). sEH upregulation may thus contribute to NH development by the enhanced removal of vasculoprotective EETs. In this study, sEH, cytochrome P450 and EETs were examined after AVG placement in a porcine model to explore their potential roles in AVG stenosis. Increased sEH protein expression, decreased P450 epoxygenase activity and dysregulation of 5 oxylipin mediators were observed in the graft-venous anastomotic tissues when compared to control veins. Pharmacological inhibitors of sEH decreased the growth factor-induced migration of SMCs and fibroblasts, although they had no significant effect on the proliferation of these cells. These results provide insights on epoxide biology in vascular disorders and a rationale for the development of novel pharmacotherapeutic strategies to prevent AVG failure due to NH and stenosis.

Access of Dysfunctional Arteriovenous Fistulas via Outflow Vein Side Branches

The patterns of stenosis in dysfunctional arteriovenous (AV) fistulas (AVFs) are not as predictable as in synthetic AV grafts. Accessing of AV fistula venous side branches has the potential to provide bidirectional access to the fistula and may reduce the need for multiple fistula puncture sites via the use of the technique described here. Institutional review board approval was not required for the present report.

Comparison of the Neointima Inhibition Between Paclitaxel- and Sirolimus-Eluting Expanded Polytetrafluoroethylene Hemodialysis Grafts in a Porcine Model

Neointimal hyperplasia causes vascular access dysfunction in hemodialysis patients with synthetic arteriovenous (AV) grafts. Several studies have reported that paclitaxel- or sirolimus-eluting AV grafts inhibit neointimal hyperplasia and display lower rates of stenosis compared with control grafts. However, there have been few comparative studies of the efficacy of paclitaxel- and sirolimus-eluting grafts. We compared the neointimal hyperplasia of paclitaxel- and sirolimus-eluting grafts. AV grafts were implanted laterally between the common carotid artery and the external jugular vein in 12 female Landrace pigs. The animals were sacrificed six weeks after surgery. The neointimal hyperplasia at the anastomosis sites of the grafts was quantified using the ratio of the intragraft hyperplasia to the graft area (H/G ratio) at the graft–vessel interface. The area of intimal hyperplasia at the venous (paclitaxel 1.06 [0.72-1.56] vs sirolimus 2.40 [1.72-3.0] mm 2 , P = 0.04) and arterial anastomosis sites (paclitaxel 0.93 [0.57-1.48] vs sirolimus 2.40 [1.72-3.0] mm 2 , P = 0.04) was significantly different between the two groups. However, the H/G ratios for the venous anastomosis site (paclitaxel 0.25 (0.17-0.38) vs sirolimus 0.38 (0.2-0.66), P = 0.4) and the arterial anastomosis site (paclitaxel 0.19 (0.08-0.39) vs sirolimus 0.41 (0.34-0.50), P = 0.1) did not differ significantly between the groups. In conclusion, there was no significant difference in the inhibition of neointimal hyperplasia by sirolimus- and paclitaxel-eluting AV grafts.

Biological vascular grafts for hemodialysis access

Evaluation of: Tillman BW, Yazdani SK, Neff LP et al. Bioengineered vascular access maintains structural integrity in response to arteriovenous flow and repeated needle puncture. J. Vasc. Surg. 56(3), 783–793 (2012).Alternatives to autogenous arteriovenous hemodialysis (HD) access, such as synthetic arteriovenous bypass grafts and central venous catheters, are associated with a higher rate of complications. The evaluated article assessed the repeated cannulation challenges of HD in tissue-engineered blood vessels implanted in a bovine in vivo model (n = 15). Two groups were studied. A short-term group in which the graft was explanted and histologically examined (n = 7) and a second group in which the graft was left in for 6 months or until outflow venous stenosis occurred (n = 8). Two grafts from each group occluded 1-month postoperatively. Of the 11 remaining, cannulation was well tolerated with adequate hemostasis. Histological analysis demonstrated host cell repopulation of the outer surface in the short-term group (n = 5) and stable wall geometry in the long-term group. The authors concluded that their study proves the concept of using a scaffold-based approach to tissue-engineered blood vessels for HD access.