Collapse of a cephalic arch stent: An atypical complication of hemodialysis vascular access

Access dysfunction is a significant contributor to morbidity in hemodialysis patients. The cephalic arch is a common location of vascular stenosis, with a considerable risk of relapse. While covered stents demonstrated a higher patency rate when compared to percutaneous transluminal angioplasty, their placement has some issues. Stent collapse and guttering are well-documented in arteries but not in arteriovenous fistulas. This report describes an unusual case of a cephalic arch stent collapsing 1 month after its positioning, as evidenced by access dysfunction.

Stenosis to stented: decrease in flow disturbances following stent implantation of a diseased arteriovenous fistula

The arteriovenous fistula (AVF) is commonly faced with stenosis at the juxta-anastomotic (JXA) region of the vein. Implantation of a flexible nitinol stent across the stenosed JXA has led to the retention of functioning AVFs leading to the resulting AVF geometry being distinctly altered, thereby affecting the haemodynamic environment within it. In this study, large eddy simulations of the flow field within a patient-specific AVF geometry before and after stent implantation were conducted to detail the change in flow features. Although the diseased AVF had much lower flow rates, adverse flow features, such as recirculation zones and swirling flow at the anastomosis, and jet flow at the stenosis site were present. Larger velocity fluctuations (leading to higher turbulent kinetic energy) stemming from these flow features were apparent in the diseased AVF compared to the stented AVF. The unsteadiness at the stenosis created large regions of wall shear stress (WSS) fluctuations downstream of the stenosis site that were not as apparent in the stented AVF geometry. The larger pressure drop across the diseased vein, compared to the stented vein, was primarily caused by the constriction at the stenosis, potentially causing the lower flow rate. Furthermore, the WSS fluctuations in the diseased AVF could lead to further disease progression downstream of the stenosis. The change in bulk flow unsteadiness, pressure drop, and WSS behaviour confirms that the haemodynamic environment of the diseased AVF has substantially improved following the flexible stent implantation.

Stent migration as complication of endovascular treatment of vascular access stenosis: A systemic review

Outflow vein stenosis is one of the commonest complications of both native and prosthetic vascular access. Together with angioplasty, first-line treatment is stenting. Although it has been described as a uncommon complication, the risk of stent migration should be always considered. We aimed to conduct a systematic review of literature concerning stents migration in vascular access, the possible outcomes and treatments. This study was performed applying Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Searches were conducted in PubMed/Medline, Scopus, and Google scholar databases. Studies selection, data abstraction was done by two different reviewers. We identified 17 studies, comprising 18 cases (M:F 1:1, mean age 56 ± 18 (range 33-88)). All the patients underwent stenting for vascular access outflow stenosis. The commonest type of device reported was self expandible bare-metal stent. Intraoperative evidence of stent migration occurred in six cases at the final quality control, or for intraprocedure dyspnea onset. In two patients it was a incidental diagnosis. In the remaining cases, chest pain or dyspnea were the common delayed presentation symptoms. Even if stent migration is an uncommon event, it is burdened with low mortality and morbidity. Literature provide only few and frequently inadequate data. Stent removal is the treatment of choice when severe symptoms or cardiopulmonary complication are present. Endovascular procedures demonstrated to be an effective and safe alternative, while open surgical treatment is preferred whenever endovascular therapy failed or in selected cases.

Truncated YY1 interacts with BASP1 through a 339KLK341 motif in YY1 and suppresses vascular smooth muscle cell growth and intimal hyperplasia after vascular injury

AIMS

In-stent restenosis and late stent thrombosis are complications associated with the use of metallic and drug-coated stents. Strategies that inhibit vascular smooth muscle cell (SMC) proliferation without affecting endothelial cell (EC) growth would be helpful in reducing complications arising from percutaneous interventions. Our group previously showed that the forced expression of the injury-inducible zinc finger (ZNF) transcription factor, yin yang-1 (YY1) comprising 414 residues inhibits neointima formation in carotid arteries of rabbits and rats. YY1 inhibits SMC proliferation without affecting EC growth. Identifying a shorter version of YY1 retaining cell-selective inhibition would make it more amenable for potential use as a gene therapeutic agent.

METHODS AND RESULTS

We dissected YY1 into a range of shorter fragments (YY1A-D, YY1Δ) and found that the first two ZNFs in YY1 (construct YY1B, spanning 52 residues) repressed SMC proliferation. Receptor Binding Domain analysis predicts a three residue (339KLK341) interaction domain. Mutation of 339KLK341 to 339AAA341 in YY1B (called YY1Bm) abrogated YY1B's ability to inhibit SMC but not EC proliferation and migration. Incubation of recombinant GST-YY1B and GST-YY1Bm with SMC lysates followed by precipitation with glutathione-agarose beads and mass spectrometric analysis identified a novel interaction between YY1B and BASP1. Overexpression of BASP1, like YY1, inhibited SMC but not EC proliferation and migration. BASP1 siRNA partially rescued SMC from growth inhibition by YY1B. In the rat carotid balloon injury model, adenoviral overexpression of YY1B, like full-length YY1, reduced neointima formation, whereas YY1Bm had no such effect. CD31 immunostaining suggested YY1B could increase re-endothelialization in a 339KLK341-dependent manner.

CONCLUSIONS

These studies identify a truncated form of YY1 (YY1B) that can interact with BASP1 and inhibits SMC proliferation, migration and intimal hyperplasia after balloon injury of rat carotid arteries as effectively as full length YY1. We demonstrate the therapeutic potential of YY1B in vascular proliferative disease.

Outcomes of the Gore Excluder abdominal aortic aneurysm leg endoprosthesis for treatment of central vein stenosis or occlusion in patients with chronic hemodialysis

OBJECTIVE

Central venous occlusive disease is a critical complication in long-term hemodialysis patients with arteriovenous (AV) dialysis circuits. The purpose of this retrospective, single-arm cohort study was to evaluate the effectiveness of an abdominal aortic aneurysm (AAA) contralateral leg endoprosthesis to treat symptomatic central venous occlusive diseases in patients with chronic hemodialysis.

METHODS

A prospective cohort study included 60 patients on hemodialysis presenting with central venous stenosis or occlusion, who were treated with a Gore Excluder AAA contralateral leg stent graft between December 2013 and July 2018. Follow-up angiography was obtained at 3, 6, and 12 months. The outcomes and duration of primary circuit and target site patency were measured from the time of the stent graft implantation to the first reintervention for AV circuit dysfunction and target site restenosis. Secondary patency was calculated from stent graft implantation to the point when AV access was no longer attainable.

RESULTS

Circuit primary patency rate was 54.9% at 1 year of Gore Excluder AAA contralateral leg or iliac extender stent grafts, implanted in 60 hemodialysis patients with central vein occlusive disease. Cumulative target site primary patency rate was 88.3% at 1 year. Secondary patency rate was 95% during follow-up. Patients with concomitant lesions had a significantly higher risk of circuit primary patency dysfunction.

CONCLUSIONS

Treatment of central vein obstructions in hemodialysis patients with stent grafts has been appealing owing to the tapered shape with a larger diameter and the availability of various lengths.