Stent Mesh Research Articles

Three-dimensional numerical simulation of a failed coronary stent implant at different degrees of residual stenosis. Part II: Apparent viscosity and wall permeability

ABSTRACTThe influence of the degree of residual stenosis (DOR) on the hemodynamics inside coronary arteries is investigated through three-dimensional (3D) numerical simulations. The vascular wall permeability is investigated and the effect of the non-Newtonian viscosity discussed. The results agree in predicting an abrupt increase in wall permeability above 45% DOR, indicating that the implant could lead to a massive restenosis. This behavior is considered to be due to the shift of the regions involved by low and oscillatory wall shear stress (WSS), from the zone adjacent to the struts toward the center of the stent meshes.

Endovascular Treatment of Symptomatic Renal Artery Aneurysm with Hostile Anatomy

A 33 year old patient with no relevant medical history was admitted after the incidental finding of a right renal artery aneurysm on ultrasound performed for persistent flank pain. Computed tomography angiography confirmed a distal 21 mm saccular aneurysm, involving the artery's trifurcation and proximal inferior segmental artery (A). To preserve renal perfusion, a self expandable open-cell nitinol stent (Xpert, Abbott Vascular, Abbott Park, IL, USA) was deployed from the renal to the anterior segmental artery, after which microcatheter coil embolisation (AZUR, Terumo, Shibuya, Tokyo, Japan) of the sac was performed through the stent mesh. Completion angiography revealed total aneurysm exclusion (B) with full preservation of renal perfusion.

Severe aortic coarctation incidentally discovered in a young university student

Coarctation of the aorta is a narrowing of the descending aorta, resulting in left ventricular overload, arterial hypertension and cardiovascular and neurological complications. It is frequently diagnosed in infancy and childhood; first-time presentation in adults is rare. The classic symptom is arterial hypertension; most patients are asymptomatic unless hypertension is present. We report the case of a 19-year-old woman who presented with a headache, tiredness and arterial hypertension. Clinical examination revealed that blood pressure was significantly lower in the lower extremities than in the upper extremities and radiofemoral delay (delayed femoral pulses). Severe aortic coarctation was confirmed by computerized tomography aortography; echocardiography was inconclusive. The lesion was successfully treated with balloon dilatation and mesh stent placement.

Use of Sheet Material for Rapid Prototyping of Cardiovascular Stents

Manufacturing of cardiovascular stents most commonly involve the use of tubular precursors and laser microcutting of the stent mesh, followed by chemical and electrochemical surface treatments. For mass manufacturing purposes, this production route is well-established, while for small batch or prototype production it proves to be cumbersome. Especially concerning newly developed alloys based, the production of microtubes is time consuming and highly costly. On the other hand, production of these new alloys in sheet metal form is a simpler approach, since the process uses non-dedicated tools and is easier as opposed to extrusion and tube drawing. Accordingly, in this work, the use of sheet material as precursor for rapid prototyping of cardiovascular stents is proposed. In particular, a ns-pulsed fiber laser is used for cutting permanent AISI 316L. Laser microcutting conditions are investigated in terms of generated spatter and kerf geometry. Chemical etching is employed to clean the dross generated around the cut kerf. A novel stent geometry allowing for transforming the sheet material to a tubular form is employed to produce prototype stents.

Advances in ureteral stent development.

Ureteral stents are commonly used in urology, but there is no perfect ureteral stent. This review documents developing ureteral technologies and strategies over the past 2 years. This area has some progressive advances in the foreseeable future. Publications from 2014 and 2015 from a PubMed search with the words 'ureter' and 'stent' in the title were reviewed. Topics that affected patient symptoms from stents include selecting the proper length of stent, patient education regarding stent symptoms, and how the stent is removed. Stent extraction strings have been studied and not increased the incidence of infection or pain. There have been several publications examining antirefluxing ureteral stents that reduced vesicoureteral reflux during micturition and infection of transplanted kidneys. Other novel methods of removing a stent include new biodegradable ureteral stents and metal beads attached to the stent used in tandem with a magnetic catheter. Several new metal and mesh stents were described for use in patients with malignant ureteral obstruction. Last, new stent coatings with antimicrobial peptides have also been described. The search continues for the perfect stent and there has been promising progress over the past 2 years.

Rapid Virtual Stenting for Intracranial Aneurysms.

The rupture of Intracranial Aneurysms is the most severe form of stroke with high rates of mortality and disability. One of its primary treatments is to use stent or Flow Diverter to divert the blood flow away from the IA in a minimal invasive manner. To optimize such treatments, it is desirable to provide an automatic tool for virtual stenting before its actual implantation. In this paper, we propose a novel method, called ball-sweeping, for rapid virtual stenting. Our method sweeps a maximum inscribed sphere through the aneurysmal region of the vessel and directly generates a stent surface touching the vessel wall without needing to iteratively grow a deformable stent surface. Our resulting stent mesh has guaranteed smoothness and variable pore density to achieve an enhanced occlusion performance. Comparing to existing methods, our technique is computationally much more efficient.

Stent for Crohn's disease strictures: Which one and when?

Stent for Crohn's disease strictures: Which one and when?

Fast Virtual Stenting with Active Contour Models in Intracranical Aneurysm.

Intracranial stents are becoming increasingly a useful option in the treatment of intracranial aneurysms (IAs). Image simulation of the releasing stent configuration together with computational fluid dynamics (CFD) simulation prior to intervention will help surgeons optimize intervention scheme. This paper proposed a fast virtual stenting of IAs based on active contour model (ACM) which was able to virtually release stents within any patient-specific shaped vessel and aneurysm models built on real medical image data. In this method, an initial stent mesh was generated along the centerline of the parent artery without the need for registration between the stent contour and the vessel. Additionally, the diameter of the initial stent volumetric mesh was set to the maximum inscribed sphere diameter of the parent artery to improve the stenting accuracy and save computational cost. At last, a novel criterion for terminating virtual stent expanding that was based on the collision detection of the axis aligned bounding boxes was applied, making the stent expansion free of edge effect. The experiment results of the virtual stenting and the corresponding CFD simulations exhibited the efficacy and accuracy of the ACM based method, which are valuable to intervention scheme selection and therapy plan confirmation.

Living history of medicine: vascular scaffolding, from dream to reality.

Following the launch of balloon angioplasty in 1977, its deficiencies-abrupt occlusion requiring emergency bypass surgery in one in twenty attempts and recurrence in one in three cases-became soon apparent. The attempts to eliminate the element of chance from this otherwise highly attractive technique resulted in the concept of intra-vascular scaffolding. Following the inception of self-expanding mesh stents made from stainless steel and extensive bench testing and animal experiments, the first clinical data were obtained in Switzerland almost 30 years ago in 1986 with promising, albeit not undisputed results. Technical improvements including potent platelet inhibitors have made the technique a cornerstone of catheter-treatment of vascular disease. This paper gives an account of the sometimes difficult beginnings of coronary and non-coronary stenting at the University of Lausanne in Switzerland.

Neointima development in externally stented saphenous vein grafts.

IntroductionThe main limitation of coronary artery bypass grafting (CABG) is rapid neointimal hyperplasia leading to graft failure.AimTo assess plaque formation in saphenous vein grafts (SVG) covered by an external Dacron stent in comparison with the classical technique.Material and methodsIn the study group vein grafts covered by external stent mesh made of Dacron were implanted. An intravascular ultrasonography (IVUS) study was performed in 35 aorto-coronary SVG covered by an external Dacron stent and in 64 normal SVG during the first year after CABG. In each SVG 25 mm of good quality IVUS image, volumes of lumen, plaque (neointima), outer border of the vein graft (external SVG) and adventitia were calculated in three time periods: 0–130 days, 130–260 days and 260–390 days.ResultsBetween the first and second time period, lumen volume (mm3) was reduced from 10.33 ±4.4, to 6.80 ±2.23 in the second period and 5.69 ±1.26 in the third one. This effect was much less marked in normal grafts. The corresponding lumen volume (mm3) was: 10.90 ±3.9, 9.15 ±2.94 and 8.92 ±2.93 in consecutive time periods. Plaque volume (mm3) did not change in control grafts during the course of the study, but it increased very significantly in stented grafts from 0.86 ±1.24 in the first period to 2.70 ±1.58 in the second and 3.29 ±2.66 in the third one.ConclusionsThe experimental technique of implanting SVG covered with an external elastic Dacron stent seems to be inferior to traditional ones. This is probably due to the more complicated process of vein implantation and higher micro-injury occurrence during the surgery.

Endoscopic multiple metal stenting for the treatment of enteral leaks near the biliary orifice: A novel effective rescue procedure

Between April 2013 and October 2015, 6 patients developed periampullary duodenal or jejunal/biliary leaks after major abdominal surgery. In all patients, percutaneous drainage of the collection or re-operation with primary surgical repair was attempted at first but failed. A fully covered enteral metal stent was placed in all patients to seal the leak. Subsequently, we cannulated the common bile duct and, in some cases, and the main pancreatic duct inserting hydrophilic guidewires through the stent after dilating the stent mesh with a dilatation balloon or breaking the meshes with Argon Plasma Beam. Finally, we inserted a fully covered biliary metal stent to drain the bile into the lumen of the enteral stent. In cases of normal proximal upper gastrointestinal anatomy, a pancreatic plastic stent was also inserted. Oral food intake was initiated when the abdominal drain outflow stopped completely. Stent removal was scheduled four to eight weeks later after a CT scan to confirm the complete healing of the fistula and the absence of any perilesional residual fluid collection. The leak resolved in five patients. One patient died two days after the procedure due to severe, pre-existing, sepsis. The stents were removed endoscopically in four weeks in four patients. In one patient we experienced stent migration causing small bowel obstruction. In this case, the stents were removed surgically. Four patients are still alive today. They are still under follow-up and doing well. Bilio-enteral fully covered metal stenting with or without pancreatic stenting was feasible, safe and effective in treating postoperative enteral leaks near the biliopancreatic orifice in our small series. This minimally invasive procedure can be implemented in selected patients as a rescue procedure to repair these challenging leaks.

Novel approach to recanalizing an occluded cystic duct after cholecystoduodenostomy by lumen-apposing metal mesh stent for malignant obstructive jaundice

Novel approach to recanalizing an occluded cystic duct after cholecystoduodenostomy by lumen-apposing metal mesh stent for malignant obstructive jaundice

A Novel Intelligent Vascular Stent: Preparation and Characterization of Hydrophobic Steel Mesh Stent with Liquid Surface Tension Response.

An intelligent vascular stent was fabricated from a hydrophobic mesh tube, which cans in-situ release thrombolytic drugs only by an injection of nitroglycerin solution. The mesh with 80# pore size has the highest hydrophobic property and the most sensitive response performance after 3.00 wt% (Heptadecafluoro-1,1,2,2,-tetradecyl)trimethoxysilane (HFTES) treatment. This may be due to the larger hydrophobic effective area and more active fluorine groups of 80# mesh surface treated by 3.00 wt% HFTES. It was proved that the "thrombolytic medicine" could be easily and efficiently into the interior of the stent after triggered only by an injection of nitroglycerin liquid. The in-situ thrombolytic effect and the spent time were satisfactory. The thrombosis had been completely dissolved. This technology provides a potential therapy for vascular restenosis and has great potential applications in the therapy for in-stent restenosis.

Artificial Ureter: UVENTA Metallic Mesh Stent Serving as a Novel Palliative Replacement Device in Malignant Ureterovaginal Fistula

Abstract Introduction and Objective: A novel, double-layered, coated self-expandable mesh ureteral stent (UVENTA™ Taewoong Medical, Korea) is reported to be a safe and effective palliative treatmen...

Early Application of Permanent Metallic Mesh Stent in Substitution for Temporary Polymeric Ureteral Stent Reduces Unnecessary Ureteral Procedures in Patients With Malignant Ureteral Obstruction

To identify risk factors for metal stent failure in patients who received polymeric double J (PDJ) ureteral stents for malignant ureteral obstructions (MUOs) and review our clinical experiences using a ureteral metallic stent. Patients who underwent metallic stent placement to replace a double J ureteral stent for nonurological MUO between January 2011 and February 2014 were included. The collected data included gender, age, laterality, cause of obstruction, PDJ ureteral stenting duration, immediate success of the metal stent, and additional procedures to relieve obstruction after metal stenting (eg, additional metal stenting or percutaneous nephrostomy (PCN) indwelling catheter placement). Cox regression tests were used for the statistical analyses. In this analysis 40 ureteral units were included. There was no initial technical failure. However, 9 (22.5%) units required additional procedures due to de novo ureteral obstruction, including additional indwelling metal stents (7.5%), additional PDJ stenting (10%), or indwelling percutaneous nephrostomy (5%). Univariate and multivariate analyses revealed that the duration of previous PDJ ureteral stenting was an independent prognostic factor for predicting ureteral metal stent failure (hazard ratio = 1.063, 95% confidence interval = 1.004-1.125; P = .037). Long-term indwelling of a PDJ ureteral stent increases the risk of additional management for de novo ureteral stricture after ureteral metal stent replacement for nonurological MUO. Our data suggest that careful patient selection and counseling for those at high risk are needed when metal stent replacement is considered for patients with long-term PDJ ureteral stents for MUO.

Influence of Iliac Vein Stent Implantation on the Contralateral Iliac Vein.

Stent implantation is frequently used to treat iliac vein occlusion. However, the recommended extension of the stent mesh into the inferior vena cava (IVC) may affect blood flow through the contralateral iliac vein. We analyzed the influence of iliac vein stent extension on contralateral iliac vein patency and neointima formation in a dog surgery model. Bare stents were implanted into the left iliac veins of 12 beagles with the proximal end covering the opening of the contralateral iliac vein. Blood flow was measured by color Doppler 4, 8, and 12 weeks postoperation. At each measurement point, a subgroup was killed, and the stents and veins were removed for pathological examination. Stents were successfully implanted, and there was no immediate stent occlusion or iliac vein thrombus by color Doppler examinations. Contralateral blood flow was maintained with no obvious abnormalities for 12 weeks. Neointima formed and advanced toward the center of the stent, but small coverage of the contralateral iliac vein opening did not change significantly with time postoperation (9.33% ± 1.54% at 4 weeks, 10.65% ± 1.01% at 8 weeks, and 10.92% ± 1.30% at 12 weeks; P > .05). Scanning electron microscopy showed neointima covering the surface of stent wires at the opening of the contralateral iliac vein, which did increase with time: 63.58% ± 12.39% at 4 weeks, 97.13% ± 2.71% at 8 weeks (P < .001 vs 4 weeks), and 99.63% ± 0.60% after 12 weeks (P > .05 vs 8 weeks; P < .001 vs 4 weeks). The neointimal coverage rate of the meshes increased obviously with time. However, no neointima was found forming a mesh between stent wires. Although there was intimal hyperplasia on the rim of the bare stent in the IVC, expansion was limited and did not block the opening of the contralateral iliac vein. The stent had no obvious influence on blood backflow in the contralateral iliac vein.

In situ coronary stent paving by Pluronic F127-alginate gel blends: Formulation and erosion tests.

In this work the development of an experimental protocol to perform the in situ gel-paving of coronary stent is presented. Biocompatible aqueous blends of Pluronic F127 and sodium alginates are used as potential drug dosage system for pharmacological in situ treatment of coronary in-stent restenosis. Pluronic F127/alginate aqueous blend has the unique characteristic to be liquid at room condition and to form gel at physiological temperature. The proposed protocol is based on the blend injection on stent wall previously implanted in a flexible silicon pipe mimicking the coronary artery. Injected blend is warmed up until human body temperature achieving a soft gel, then it is reticulated by copper bivalent ions to obtain an hard gel. To test the gel paving resistance to erosion phenomena when it is exposed to fluid flux (i.e. blood flux) a dedicated device, (the Simulated Artery Device, SAD), was built to simulate the human circulatory apparatus. The SAD is an hydraulic circuit in which a buffer solution (at pH 7.4) was fluxed by a peristaltic pump through the pipe hosting the covered stent. Erosion tests were performed monitoring, by gravimetric and spectrophotometric methods, the residual mass anchored to stent mesh after given times. The obtained results showed that the in situ gel-paving developed protocol was efficacious and reliable. The gel-paving was completely eroded in a time of the same order of magnitude of the physiological period required to restore the coronary lesion (subsequent to the atheroma removal) and of a pharmacological therapy to inhibit the in-stent-restenosis pathology. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1013-1022, 2016.

Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents.

Extrinsic malignant compression of the ureter is not uncommon, often refractory to decompression with conventional polymeric ureteral stents, and frequently associated with limited survival. Alternative options for decompression include tandem ureteral stents, metallic stents and metal-mesh stents, though the preferred method remains controversial. We reviewed and updated our outcomes with tandem ureteral stents for malignant ureteral obstruction, and carried out a PubMed search using the terms "malignant ureteral obstruction," "tandem ureteral stents," "ipsilateral ureteral stents," "metal ureteral stent," "resonance stent," "silhouette stent" and "metal mesh stent." A comprehensive review of the literature and summary of outcomes is provided. The majority of studies encountered were retrospective with small sample sizes. The evidence is most robust for metal stents, whereas only limited data exists for tandem or metal-mesh stents. Metal and metal-mesh stents are considerably more expensive than tandem stenting, but the potential for less frequent stent exchanges makes them possibly cost-effective over time. Urinary tract infections have been associated with all stent types. A wide range of failure rates has been published for all types of stents, limiting direct comparison. Metal and metal-mesh stents show a high incidence of stent colic, migration and encrustation, whereas tandem stents appear to produce symptoms equivalent to single stents. Comparison is difficult given the limited evidence and heterogeneity of patients with malignant ureteral obstruction. It is clear that prospective, randomized studies are necessary to effectively scrutinize conventional, tandem, metallic ureteral and metal-mesh stents for their use in malignant ureteral obstruction.

Retrieval of migrated coils with stent retrievers: an animal study.

Coil migration is a potentially serious complication of endovascular aneurysm treatment. The aim of the study was to systematically investigate the effectiveness of coil retrieval with a stent retriever in an animal model. A total of 148 coils of various types and sizes were placed into arteries of varying diameters in a porcine in vivo model. Coil retrieval was performed by placing a Trevo ProVue stent retriever over the coil and trying to trap a part of the platinum coil within the stent mesh by advancing the microcatheter over the stent or simply by retrieving the stent without trying to trap the coil by advancing the microcatheter. Coil retrieval was successful in 101 of 102 cases (99%), in which trapping of the coil within the stent retriever by advancing the microcathter was applied. When we only pulled back the stent without trapping the coil, retrieval was successful in only 5 of 46 cases (11%). Coil type, coil structure (2D versus 3D), actual coil shape in the affected vessel, investigator experience, aspiration, coil localization, and vessel diameter had no significant influence on retrieval outcome. There was no case of vessel perforation. Retrieval of migrated platinum coils with a stent retriever is an effective treatment option for migrated coils when the correct technique is applied.

Use and evaluation of a semi-permeable mesh implant in vertebral augmentation for the treatment of painful osteoporotic vertebral compression fractures

ObjectiveTo assess the efficacy of a semi-permeable mesh implant in the treatment of painful thoracic and lumbar osteoporotic vertebral compression fractures.MethodsPatients with painful thoracic and lumbar osteoporotic vertebral compression fractures...