Venous Anastomosis Of Arteriovenous Graft Research Articles

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.

Stent grafts for treatment of cannulation zone stenosis and arteriovenous graft venous anastomosis.

Stent grafts (SGs) are widely used for treatment of failing vascular accesses, fistulas and grafts. The mechanical barrier of the covered stent prevents in-stent stenosis and can be used to effectively correct ruptured vein and aneurysms. Treatment of cannulation zone stenosis with SG can be justified when its use is obligatory, in order to prevent total access loss. Although there are worrying complications attendant on SG insertion and cannulation, including jeopardizing future access creation, most studies report no complications of SG in cannulation zone stenosis. SGs for treatment of arteriovenous graft venous anastomosis stenosis is controversial. Two large randomized trials conclusively demonstrate improved primary patency with SGs at the venous anastomosis of arteriovenous graft at up to two years when compared with percutaneous transluminal angioplasty, sustained for up to 2 years and reducing the number of interventions per patient year. However, the ultimate goal of SG treatment of venous anastomosis stenosis is preventing thrombosis and increasing graft longevity, which was unfortunately not fully achieved.

In vivo evaluation of the delivery and efficacy of a sirolimus-laden polymer gel for inhibition of hyperplasia in a porcine model of arteriovenous hemodialysis graft stenosis

Synthetic arteriovenous (AV) hemodialysis grafts are plagued by hyperplasia resulting in occlusion and graft failure yet there are no clinically available preventative treatments. Here the delivery and degradation of a sirolimus-laden polymer gel were monitored in vivo by magnetic resonance imaging (MRI) and its efficacy for inhibiting hyperplasia was evaluated in a porcine model of AV graft stenosis.Synthetic grafts were placed between the carotid artery and ipsilateral jugular vein of swine. A biodegradable polymer gel loaded with sirolimus (2.5mg/mL) was immediately applied perivascularly to the venous anastomosis, and reapplied by ultrasound-guided injections at one, two and three weeks. Control grafts received neither sirolimus nor polymer. The lumen cross-sectional area at the graft–vein anastomosis was assessed in vivo by non-invasive MRI. The explanted tissues also underwent histological analysis.A specifically developed MRI pulse sequence provided a high contrast-to-noise ratio (CNR) between the polymer and surrounding tissue that allowed confirmation of gel location after injection. Polymer signal decreased up to 80% at three to four weeks after injection, slightly faster than its degradation kinetics in vitro. The MR image of the polymer was confirmed by visual assessment at necropsy. On histological assessment, the mean hyperplasia surface area of the treated graft was 52% lower than that of the control grafts (0.43mm2 vs. 0.89mm2; p<0.003), while the minimum cross-sectional lumen area, as measured on MRI, was doubled (5.3mm2 vs 2.5mm2; p<0.05).In conclusion, customized MRI allowed non-invasive monitoring of the location and degradation of drug delivery polymer gels in vivo. Perivascular application of sirolimus-laden polymer yielded a significant decrease in hyperplasia development and an increase in lumen area at the venous anastomosis of AV grafts.

Percutaneous balloon cryoplasty: A new therapy for rapidly recurrent anastomotic venous stenoses of hemodialysis grafts?

Vascular access dysfunction is a major source of morbidity for end-stage renal disease patients on hemodialysis. The arteriovenous graft is a common access type for many of these patients. Frequent stenosis formation and thrombosis complicate this form of access. Patients may have a rapidly forming and recurrent venous stenosis at the graft-vein anastomosis that has been seen in both animal models and end-stage renal disease patients to be the result of neointimal hyperplasia. This venous lesion is particularly resistant and sometimes intractable to conventional angioplasty. As a result, new therapies have been developed to reduce the formation and/or recurrence of neointimal hyperplasia. These include special cutting balloons, drug-eluting stents, and endovascular brachytherapy. The authors present the cases of 5 patients with rapidly recurrent venous lesions at the graft-vein anastomosis that derived benefit from angioplasty with the cryoballoon. The time to stenosis or thrombosis in the arteriovenous grafts was increased from a mean of 3 weeks to more than 16 weeks with this technology. Cryotherapy with the cryoballoon (cryoplasty) may represent a useful therapy for patients with intractable stenoses at or near the venous anastomosis of arteriovenous grafts.

Leukocyte-polytetrafluoroethylene interaction enhances proliferation of vascular smooth muscle cells via tumor necrosis factor-α secretion

Intimal hyperplasia of vascular smooth muscle cells (VSMC) at the venous anastomosis of arteriovenous grafts represents the most common cause of vascular access failure in hemodialysis patients. Upstream release of growth factors from leukocytes activated by adhesion to the graft material may play a role in this lesion. We evaluated the effect of interaction of peripheral blood mononuclear cells (PBMC) with polytetrafluoroethylene (PTFE) on proliferation of VSMC. Vascular smooth muscle cell proliferation was significantly increased by conditioned media from human PBMC incubated with PTFE. Peripheral blood mononuclear cell adhesion to PTFE could not be antagonized by the beta 1 integrin ligand-containing peptide GRGDSP, but was attenuated by EDTA consistent with beta 2 integrin-mediated adhesion. Soluble scavenger receptor ligands at high concentrations had no effect on adhesion to PTFE excluding any contributory role of scavenger receptors in this interaction. Neutralizing antibodies to TNF-alpha significantly attenuated the mitogenic effect of PBMC/PTFE conditioned media and a marked increase in TNF-alpha secretion by PBMC on PTFE was detected by ELISA. These studies demonstrate that PBMC interaction with PTFE can promote proliferation of VSMC via increased production of TNF-alpha and perhaps other cytokines. Leukocyte interaction with PTFE causing enhanced secretion of TNF-alpha and consequent VSMC proliferation may account for the development of venous intimal hyperplasia in hemodialysis patients with arteriovenous grafts.