Stent Application Research Articles

Long-term surveillance of zinc implant in murine artery: Surprisingly steady biocorrosion rate.

Previous studies have shown zinc to be a promising candidate material for bioresorbable endovascular stenting applications. An outstanding question, however, is whether a zinc implant would ultimately passivate through the production of stable corrosion products or via a cell mediated tissue encapsulation process that prevented the diffusion of critical reactants and products at the metal surface. We found that zinc wires implanted in the murine artery exhibit steady corrosion for up to at least 20months post-implantation. The results confirm earlier predictions that zinc stents could safely degrade within a time frame of approximately 1-2years.

PC022 Thoracic Endovascular Repair for Acute Complicated Type B Aortic Dissections

This study assessed in-hospital mortality and midterm results of emergency thoracic endovascular aortic repair (TEVAR) stent grafting for patients with life-threatening complications of acute type B aortic dissections (acTBD). Between March 2001 and Sept 2016, 53 patients (38 men; mean age, 55 ± 13) with an acTBD were treated with TEVAR for malperfusion (55%), aortic rupture (15%), or persistent untreatable pain (30%) as a sign of pending rupture. Four patients (8%) had undergone previous aortic surgery. Technical success (coverage of the primary tear site) was achieved in 48 patients (91%). Overall hospital mortality rate was 9% (n = 5). Causes of death were rupture during the procedure or on the first postinterventional day in two patients and redissection (ascending aorta n = 2, descending aorta n = 1) with consequent aortic rupture after TEVAR in the remaining three. Permanent neurologic dysfunction occurred in 3 patients (stroke n = 1, paraplegia n = 2). Nineteen patients (36%) developed early endoleaks (type Ia, n = 5; type Ib, n = 11; type II, n = 2; type Ib plus II, n = 1) and were observed throughout the postinterventional period. These seven patients (37%) needed secondary endovascular intervention (n = 3) or conventional surgery (n = 4) due to aortic progression (mean interval after procedure 92 ± 56 months). Secondary endoleaks were observed in nine patients with consequent reintervention in three patients. The actuarial survival was 88%, 76%, and 58% at 1, 5, and 10 years, respectively. Freedom from treatment failure at 1, 5, and 10 years (including reintervention, aortic rupture, device-related complications, aortic-related death, or sudden, unexplained late death) was 76 %, 74%, and 74%, respectively. TEVAR in the treatment of acute complicated type B aortic dissection proves to be an excellent treatment modality in this high risk patient cohort. Refinements, especially in stent design and application, may further reduce the rate of endoleaks and improve the prognosis of patients in this life-threatening situation.

Primary clinical application of Y-shaped jogged stent in patients with malignant hilar biliary obstruction

Objective To evaluate the feasibility, safety, and efficacy of Y-shaped jogged stent in patients with malignant hilar biliary obstruction. Methods During the period of January 2010 to June 2015, We retrospectively reviewed 98 cases of malignant hilar biliary obstruction who were received implantation of biliary tract stent. 17 consecutive patients who were treated with Y-shaped jogged stent were identified (group A) during January 2012 to June 2015. Group A was carefully matched according to patients' age, sex, type of tumor, stage, type of biliary obstruction, level of bilirubin at diagnosis, presence of metastasis and treatment, and 17 patients who were underwent unilateral stent placement alone with PTCD were chosen as control group (group B). Patients' baseline characteristics, stenting strategy, complications, stent patency time and survival rates were analyzed, and continuous variables of the two groups were compared using Student's t-test. Categorical variables were analyzed using the Fisher exact test. Results Y-shaped jogged stent implantation group and control groups were closely matched in terms of patients' age, sex, type of tumor, stage, type of biliary obstruction, level of bilirubin at diagnosis, presence of metastasis and treatment (P>0.05). The bilirubin decreased rate in the two groups was 88.2% and 53.0% respectively (P<0.05). The median time of stent patency after stent implantation was (7.3±1.0) months and (5.7±0.9) months respectively (χ2=4.04,P=0.044), and the median survival time was (9.1±1.5) months and (7.2±1.1) months (χ2=4.60,P=0.032), with significant difference according to Kaplan-Meier analysis. There were no severe complications such as massive hemorrhage, perforation, biliary fistula and severe pancreatitis, which were associated with stent implantation. Conclusions The application of Y-shaped jogged stent is safe, feasible and effective in patients with malignant hilar biliary obstruction. It can relieve the clinical symptoms of biliary obstruction effectively with prolongation of stent patency time and survival rate significantly. Key words: Jaundice, obstructive; Neoplasms; Radiology, interventional; Y-shaped jogged stent

A promising biodegradable magnesium alloy suitable for clinical vascular stent application

We report a Mg alloy Mg-2.2Nd-0.1Zn-0.4Zr (wt.%, denoted as JDBM-2) showing great potential in clinical vascular stent application by integrating the advantages of traditional medical stainless steel and polymer. This alloy exhibits high yield strength and elongation of 276 ± 6 MPa and 34.3 ± 3.4% respectively. The JDBM-2 with a stable degradation surface results in a highly homogeneous degradation mechanism and long-term structural and mechanical durability. In vitro cytotoxicity test of the Mg extract via human vascular endothelial cells (HUVECs) indicates that the corrosion products are well tolerated by the tested cells and potentially negligible toxic effect on arterial vessel walls. This alloy also exhibits compromised foreign body response (FBR) determined by human peripheral blood derived macrophage adhesion, foreign body giant cell (FBGC) formation and inflammatory cytokine and chemokine secretion. Finally, vascular stents manufactured from the JDBM-2 were implanted into rabbits for long-term evaluation. The results confirm excellent tissue compatibility and up to 6-month structural and mechanical integrity of the stent in vivo. Thus, the JDBM-2 stent with up to 6-month structural and mechanical integrity and excellent tissue compatibility represents a major breakthrough in this field and a promising alternative to traditional medical stainless steel and polymer for the clinical application.

Research on Endothelial Cytocompatibility of Magnesium Alloy

In-stent restenosis is a main problem in the application of stents. It has been proved that rapid endothelialization of stents after implantation is the key point for solving the problem of restenosis. Recent years researchers focus on developing biodegradable magnesium alloy stents. The cytocompatibility is essential for the design of magnesium alloy stents. In this article, recent research about the endothelial cytocompatibility of magnesium alloy was reviewed, including methods, results, shortcomings and advice.

Systemic application of sirolimus prevents neointima formation not via a direct anti-proliferative effect but via its anti-inflammatory properties

BackgroundSystemic treatment with sirolimus, as used for immunosuppression in transplant patients, results in markedly low rates of in-stent restenosis. Since the underlying mechanisms remain obscure, we aimed to determine the molecular and cellular effects of systemic sirolimus treatment on vascular remodeling processes. Methods and resultsSystemic sirolimus treatment significantly reduced smooth muscle cell (SMC) proliferation 14days after wire-induced injury and neointima formation 28days after injury in C57BL/6 mice, while simultaneously impairing re-endothelialization. Interestingly, in vitro, sirolimus had no direct effect on the proliferation of SMC or endothelial cells (EC) at serum concentrations observed after systemic application. In contrast, sirolimus reduced the adhesion of leukocytes (CD45+) and bone marrow-derived progenitor cells (CD34+) to activated EC by down-regulating the adhesion molecules ICAM-1 and VCAM-1. In addition, sirolimus treatment also significantly reduced the upregulation of ICAM-1 and VCAM-1 and the recruitment of monocytic cells (MOMA-2+) in neointimal lesions in vivo. ConclusionOur findings show that systemic sirolimus treatment effectively prevents SMC and EC proliferation in vivo without directly affecting these cells. Instead, sirolimus prevents neointima formation and re-endothelialization by attenuating the inflammatory response after injury with secondary effects on SMC and EC proliferation. Thus, despite a similar net effect, the mechanisms of systemic sirolimus treatment are largely different from the local effects achieved after application of sirolimus-eluting stents.

Trans-tracheostomy repair of tracheo-esophageal fistula under endoscopic view in a 75-year-old woman

Tracheo-esophageal fistula is a life-threatening condition for fatal pulmonary complications. Surgery is the treatment of choice. Unfortunately, the most of patients are unfit for surgery and in these cases there is no a standardized management. Herein, we reported a clinical case of a 75-year-old-woman with a tracheoesophageal fistula related to tracheostomy. The fistula was localized 3.5 cm below the vocal folds and extended 3 cm distally. The patient's poor clinical condition contraindicated surgery while the characteristics of fistula prevented any successfully endoscopic repair with standard methods as application of fibrin glue, clipping, or stenting. Thus, we performed a minimally invasive procedure as trans-tracheotomy closure of the fistula under endoscopic view. Under general anesthesia, the patient was intubated with a rigid bronchoscopy. The cannula was removed and a standard needle-holder was inserted through the tracheotomy. The tear was closed from the distal to the proximal ends with interrupted stitch. Following, a Montgomery T tube was inserted to protect the suture and maintain the air-way patency. At the last follow-up (7 months after the procedure), the patient was alive and tolerated a full diet.

Evaluation of wrought Zn-Al alloys (1, 3, and 5 wt % Al) through mechanical and in vivo testing for stent applications.

Special high grade zinc and wrought zinc-aluminum (Zn-Al) alloys containing up to 5.5 wt % Al were processed, characterized, and implanted in rats in search of a new family of alloys with possible applications as bioabsorbable endovascular stents. These materials retained roll-induced texture with an anisotropic distribution of the second-phase Al precipitates following hot-rolling, and changes in lattice parameters were observed with respect to Al content. Mechanical properties for the alloys fell roughly in line with strength (190-240 MPa yield strength; 220-300 MPa ultimate tensile strength) and elongation (15-30%) benchmarks, and favorable elastic ranges (0.19-0.27%) were observed. Intergranular corrosion was observed during residence of Zn-Al alloys in the murine aorta, suggesting a different corrosion mechanism than that of pure zinc. This mode of failure needs to be avoided for stent applications because the intergranular corrosion caused cracking and fragmentation of the implants, although the composition of corrosion products was roughly identical between non- and Al-containing materials. In spite of differences in corrosion mechanisms, the cross-sectional reduction of metals in murine aorta was nearly identical at 30-40% and 40-50% after 4.5 and 6 months, respectively, for pure Zn and Zn-Al alloys. Histopathological analysis and evaluation of arterial tissue compatibility around Zn-Al alloys failed to identify areas of necrosis, though both chronic and acute inflammatory indications were present. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 245-258, 2018.

Application of self-expanding titanium nickelide stents of Belorussian manufacture in the treatment of stenotic colorectal cancer

Application of self-expanding titanium nickelide stents of Belorussian manufacture in the treatment of stenotic colorectal cancer

Novel Strategy of Stents in Thyroid Mass: A Case Series Reporto f Managing Severely Dyspnoeic Patients

Background: Tracheal and bronchial stenosis are a life-threatening condition causing difficulty in breathing and even severe respiratory distress. Patients with severe dyspnea were addressed in the insertion of silicone tracheobronchial stents using rigid bronchoscopy method and they exhibited symptomatic improvement as well as rise in the oxygen saturation. The bronchial stents were applicable to many extensive malignant airway stenosis patients, such as esophageal cancer, lung cancer and laryngeal cancer. But effectiveness of bronchial stents for thyroid cancer is not certain. Case presentation: We reported on 3 emergency patients with a thyroid mass, referring to our hospital because of grade 4 dyspnea according to the American Thoracic Society shortness of breath. The main clinical symptoms were severe dyspnea and stridor. The radiographic examination and tomographic examination showed the narrowing and displacement of the trachea. Bronchial stents were employed in these 3 patients before undergoing thyroid surgery. And these patients’ thyroid surgeries were successful. Conclusion: In our study, we applied the bronchial stents to thyroid mass patients with dyspnea and the operation was successful. So, we found that application of bronchial stents may provide a new strategy to dyspnoeic patients with huge thyroid mass.

Rapamycin-loaded nanoporous α-Fe2O3 as an endothelial favorable and thromboresistant coating for biodegradable drug-eluting Fe stent applications.

Iron and its alloys can be potentially employed to fabricate advanced degradable cardiovascular stents due to their excellent mechanical and biocompatibility properties. However, their clinical applications are hindered by their inherent slow degradation rate, the formation of thrombosis and in-stent restenosis. In this study, vertically oriented and orderly arranged α-Fe2O3 (hematite) nanotubes with diameters ranging from 30 nm to 70 nm were successfully fabricated on iron substrates using an anodic oxidation approach. These nanotubular coatings acted as drug depots by being loaded with anti-proliferation drug rapamycin to accelerate the re-endothelialization process and being coated by PLGA through a simple spin-coating process to control the drug release rate. The static immersion test showed that the 50 nm-Fe2O3 nanotube arrays displayed a faster corrosion rate than pristine Fe, and the PLGA coating effectively reduced the initial burst release of the loaded drug and extended the rapamycin release time to 30 days. The CCK-8 assay and immunofluorescence staining analysis results indicated that the endothelial cells (ECs) on the coated samples showed higher cell viability than the vascular smooth muscle cells (VSMCs), with possible outcomes to promote re-endothelialization and decrease VSMC proliferation. In addition, the surface modified iron exhibited very good hemocompatibility. The current findings suggested that fabricating rapamycin-loaded and PLGA coated Fe2O3 nanotubes on a pure iron surface may be a promising method to improve the corrosion rate and accelerate the re-endothelialization of the iron for biodegradable cardiovascular stent applications.

Conceptual design investigation on applicable mesh structures for medical stent applications

Conceptual design investigation on applicable mesh structures for medical stent applications

Research progress and application of the aortic taper angle

Endovascular repair has gained worldwide popularity for the treatment of aortic dissection and aortic aneurysm. The non-tapered stents are selected usually. The aortic diameters vary in different level. High incidence of distal stent-induced complications is closely related to the aortic taper angle. According to several published studies, the aortic taper angle could be evaluated by establishing geometric model. Applications of tapered stents can significantly reducing the incidence of distal stent-induced complications. This review summaries the latest researches in the studies of the progress and the application of the aortic taper angle and the tapered stents, providing a reference for endovascular stent-graft selecting in the treatment of aortic dissection and aortic aneurysm. Key words: Aneurysm, dissecting; Stents; Angioplasty; Taper angle; Aortic diameter

Pros and cons of Danis stent application in esophageal bleeding

Aim. A critical analysis of world clinical experience of endoscopic hemostasis with self-expanding nitinol Danis stents application in acute bleeding from esophageal varices.Methods. Literature data of last 10 years about self-expanding nitinol Danis stents application at the peak of esophageal bleeding or in high risk of its recurrence were analyzed.Results. The advantages of Danis stent include minimal injury, good tolerance by the patient, providing physiological drainage of saliva and the possibility of fluid and food intake through the mouth, possibility of a repeated endoscopic inspection of the esophagus and stomach after the application of the stent, reducing the risk of aspiration pneumonia, the impossibility of removal or displacement by the patient in agitation. According to most authors, Danis stent allows saving time to get ready for safe transjugular intrahepatic portocaval shunt (TIPS), surgical intervention or liver transplantation. This time should be used for performing all procedures necessary to stabilize the patient’s condition and clarify the nature of the existing pathology. Disadvantages include high risk of migration from the esophagus into the stomach with loss of its plugging function, limitation for treatment of only esophageal varices, development of small erosions or ulcers on the mucous membrane of the esophagus after removal of the stent. When Danis stent was used as a final method of treatment in patients who do not fit for TIPS or liver transplant, the mortality rate reached 50%.Conclusion. To date, it is not yet clarified whether endoscopic hemostasis with self-expanding nitinol Danis stents should be firmly used in the treatment algorithm of patients with variceal bleeding; confirmation of initial clinical results in further comparative randomized controlled trials is necessary.

Novel Ti-Ta-Hf-Zr alloys with promising mechanical properties for prospective stent applications.

Titanium alloys are receiving increasing research interest for the development of metallic stent materials due to their excellent biocompatibility, corrosion resistance, non-magnetism and radiopacity. In this study, a new series of Ti-Ta-Hf-Zr (TTHZ) alloys including Ti-37Ta-26Hf-13Zr, Ti-40Ta-22Hf-11.7Zr and Ti-45Ta-18.4Hf-10Zr (wt.%) were designed using the d-electron theory combined with electron to atom ratio (e/a) and molybdenum equivalence (Moeq) approaches. The microstructure of the TTHZ alloys were investigated using optical microscopy, XRD, SEM and TEM and the mechanical properties were tested using a Vickers micro-indenter, compression and tensile testing machines. The cytocompatibility of the alloys was assessed using osteoblast-like cells in vitro. The as-cast TTHZ alloys consisted of primarily β and ω nanoparticles and their tensile strength, yield strength, Young’s modulus and elastic admissible strain were measured as being between 1000.7–1172.8 MPa, 1000.7–1132.2 MPa, 71.7–79.1 GPa and 1.32–1.58%, respectively. The compressive yield strength of the as-cast alloys ranged from 1137.0 to 1158.0 MPa. The TTHZ alloys exhibited excellent cytocompatibility as indicated by their high cell viability ratios, which were close to that of CP-Ti. The TTHZ alloys can be anticipated to be promising metallic stent materials by virtue of the unique combination of extraordinarily high elastic admissible strain, high mechanical strength and excellent biocompatibility.

A chemical stability study of trimethylsilane plasma nanocoatings for coronary stents

Trimethylsilane (TMS) plasma nanocoatings were deposited onto stainless steel coupons in direct current (DC) and radio frequency (RF) glow discharges and additional NH3/O2 plasma treatment to tailor the coating surface properties. The chemical stability of the nanocoatings were evaluated after 12 week storage under dry condition (25 °C) and immersion in simulated body fluid (SBF) at 37 °C. It was found that nanocoatings did not impact surface roughness of underlying stainless steel substrates. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to characterize surface chemistry and compositions. Both DC and RF nanocoatings had Si- and C-rich composition; and the O- and N-contents on the surfaces were substantially increased after NH3/O2 plasma treatment. Contact angle measurements showed that DC-TMS nanocoating with NH3/O2 treatment generated very hydrophilic surfaces. DC-TMS nanocoatings with NH3/O2 treatment showed minimal surface chemistry change after 12 week immersion in SBF. However, nitrogen functionalities on RF-TMS coating with NH3/O2 post treatment were not as stable as in DC case. Cell culture studies revealed that the surfaces with DC coating and NH3/O2 post treatment demonstrated substantially improved proliferation of endothelial cells over the 12 week storage period at both dry and wet conditions, as compared to other coated surfaces. Therefore, DC nanocoatings with NH3/O2 post treatment may be chemically stable for long-term properties, including shelf-life storage and exposure to the bloodstream for coronary stent applications.

気道ステントの外科治療への応用( 「気道ステントをめぐる諸問題-pros and cons」)

気道ステントの外科治療への応用( 「気道ステントをめぐる諸問題-pros and cons」)

Biodegradable airway stents in infants – Potential life-threatening pitfalls

ObjectiveThe solution of severe tracheobronchial obstructions in early childhood means a great challenge. Biodegradable stents were intended to be a minimally invasive temporary solution which may decrease the number of interventions and limit the possible complications of stenting procedures. However, our first experiences have brought out a new, - especially in childhood - potentially life-threatening complication of this concept. MethodsFive SX-ELLA biodegradable polydioxanone stents was applied in three patients because of severe tracheobronchial obstruction: congenital tracheomalacia (7 day-old), acquired tracheomalacia (10 month-old), and congenital trachea-bronchomalacia (10 month-old). ResultsThe breathing of all children improved right after the procedure. We observed degradation of the stent from the 5th postoperative week which resulted in large intraluminar fragments causing significant airway obstruction: one patient died of severe pneumonia, the other baby required urgent bronchoscopy to remove the obstructing ‘foreign body’ from the trachea. In the third case repeated stent placements successfully maintained the tracheal lumen. ConclusionsPolydioxanone stents may offer an alternative to metallic or silastic stents for collapse or external compression of the trachea in children; however, large decaying fragments mean a potential risk especially in the small size pediatric airway. The fragmentation of the stent, which generally starts in the 4–6 postoperative weeks, may create large sharp pieces. These may be anchored to the mucosa and covered by crust leading to obstruction. As repeated interventions are required, we do not consider the application of biodegradable stents unambiguously advantageous.

Deployment of a Bulk Metallic Glass-Based Self-Expandable Stent in a Patient-Specific Descending Aorta.

The emergence of bulk metallic glasses (BMGs) has been tantalizing in biomedical applications such as development of novel cardiovascular stents. Numerous investigations have confirmed the superior functional properties and biocompatibility of BMGs over conventional crystalline alloys as stent materials. However, a detailed understanding of the mechanical behavior of BMG-based stents during different stages of their application is still scarce. Here, by quantitative finite element analyses (FEA), we explore the deployment process of a BMG-based self-expandable stent in a patient specific descending aorta to evaluate the arterial stresses and the vessel deformation during the stent deployment. We further benchmark the performance of the BMG based stent by comparing the deployment results both with the results of a similar nitinol based stent and the experimental failure strength of the human arteries. Our detailed analyses confirm that the proposed BMG stent can be safely deployed in the artery without vessel overstretching and mechanical failure, preventing unexpected vessel injuries and resultant pathological responses. Our findings would be insightful for further investigations toward realization of novel BMG-based stent applications.

Biomaterial-Based Approaches to Address Vein Graft and Hemodialysis Access Failures.

Veins used as grafts in heart bypass or as access points in hemodialysis exhibit high failure rates, thereby causing significant morbidity and mortality for patients. Interventional or revisional surgeries required to correct these failures have been met with limited success and exorbitant costs, particularly for the US Centers for Medicare & Medicaid Services. Vein stenosis or occlusion leading to failure is primarily the result of neointimal hyperplasia. Systemic therapies have achieved little long-term success, indicating the need for more localized, sustained, biomaterial-based solutions. Numerous studies have demonstrated the ability of external stents to reduce neointimal hyperplasia. However, successful results from animal models have failed to translate to the clinic thus far, and no external stent is currently approved for use in the US to prevent vein graft or hemodialysis access failures. This review discusses current progress in the field, design considerations, and future perspectives for biomaterial-based external stents. More comparative studies iteratively modulating biomaterial and biomaterial-drug approaches are critical in addressing mechanistic knowledge gaps associated with external stent application to the arteriovenous environment. Addressing these gaps will ultimately lead to more viable solutions that prevent vein graft and hemodialysis access failures.