Nitinol Stent Research Articles

A new domestic self-expanding nitinol stent: in vivo preclinical study

Objective. To evaluate the results of implantation of a new domestic self-expanding nitinol stent in experimental animals. Materials and methods. Experimental implantations of a self-expanding nitinol stent were performed in the common iliac artery of three Vietnamese Pot-bellied pigs. In the postoperative period, all animals received dual antiplatelet therapy for 3 months. Vital signs were also assessed throughout the observation period. After 3 months, the animals underwent control angiography and ultrasound examination of the iliofemoral segment, followed by withdrawal from the experiment by euthanasia. The next step was a macroscopic and histological analysis of the stented areas of the vessels. Results. The observation period of the animals was 3 months. Throughout the entire observation period, vital signs in all animals remained within normal values. The results of control angiography and ultrasound examination after 3 months demonstrated patency, as well as the absence of significant in-stent stenoses in two pigs. One animal showed signs of in-stent restenosis. The results of macroscopic and histological analysis showed signs of damage to the subendothelial layer, as well as myointimal hyperplasia. These changes were especially pronounced in the animal with restenosis. Our analysis showed that the presented results were due to excessive oversizing of the implanted stents (20–30 %). Conclusion. Our proposed self-expanding nitinol stent, in general, showed satisfactory results in the in vivo experiment. Nevertheless, it should be borne in mind that severe stent oversizing can cause excessive neointimal proliferation, which, in turn, will lead to the development of restenosis in the long-term postoperative period. In this regard, it is necessary to carry out an additional series of implantation of the presented stent to the experimental animals with less oversizing in order to determine its optimal values for this particular stent model.

Past and Recent Progress on Metallic Digestive Tract Stents.

The implantation of digestive tract stents at various lesion sites can effectively improve digestive tract patency, opening up an excellent treatment method for diseases that are currently incurable or resistant to conventional surgery. Digestive tract stents have been extensively studied and widely used worldwide due to their unique advantages of simple implantation, low trauma, satisfactory effect, and low complication rate. Among the various types of stents, metallic stents have been developed to improve surgical efficacy due to their excellent mechanical properties and are constantly being improved. This review provides an overview of the design and development of conventional nonbiodegradable metallic digestive tract stents such as nitinol (NiTi alloy), stainless steel, and cobalt-based alloy stents. Furthermore, biodegradable metallic stents for the digestive tract, such as magnesium-based, iron-based, and zinc-based stents, are described. This paper also evaluates the advantages and disadvantages of existing metallic digestive stents as well as future research directions and challenges in the development of metallic digestive tract stents.

Series of implantation of a new domestic self-expanding nitinol stent in vivo: prototype development

Series of implantation of a new domestic self-expanding nitinol stent in vivo: prototype development

Effectiveness of Adjunctive Drug Therapy to Endoscopic Stenting in Liver Cirrhosis Complicated by Refractory Variceal Bleeding

AIM OF THE STUDY. Comparative clinical analysis of the efficacy of terlipressin and octreotide as additional drug therapy to mechanical hemostasis with nitinol stent in patients with liver cirrhosis complicated by bleeding from esophageal varices refractory to endoscopic treatment.MATERIAL AND METHODS. Thirty-one patients with liver cirrhosis complicated by esophageal variceal bleeding refractory to endoscopic treatment , in whose complex treatment program, as a first-line life­saving measure, hemostasis with a self-expanding hemostasis was performed nitinol stent were randomly assigned to two groups. In group A, 20 patients were treated with terlipressin as an adjuvant to mechanical hemostasis, and in group B, 11 patients were treated with octreotide. Unpaired Student’s t-test was used for statistical analysis of the results. Graphs for assessing the survival function of patients for 8 weeks after the end of treatment were constructed using the Kaplan-Meier method.RESULTS. In the acute observation period terlipressin and octreotide were equally effective in treating refractory variceal bleeding. In the subacute observation period, the administration of octreotide was generally accompanied by a greater number of side effects (54.5%) than terlipressin (30.0%) (p=0.453). In the remote observation period, 8-week survival in the group of patients receiving terlipressin was higher than in the group of patients receiving octreotide.CONCLUSION. Terlipressin is as effective as octreotide as an adjunct to endoscopic stenting in drug therapy for liver cirrhosis complicated by esophageal variceal bleeding refractory to endoscopic treatment. At the same time, terlipressin has a greater effect than octreotide on reducing 8-week mortality, which approaches statistical significance. In this regard, terlipressin may be the vasoactive drug of choice in acute refractory variceal bleeding.

Thermo-expandable intraprostatic nitinol stents in the treatment of bladder outlet obstruction: a consecutive case series.

In high-risk patients, prostatic stents may alleviate obstruction at the prostate level. Since 2020 we have used thermo-expandable intraprostatic nitinol stents. Here we document outcomes through the first years with the procedure. We reviewed patients who had undergone stent treatment between May 2020 and October 2023. Patient and procedural data, urinary symptoms, complications and side effects were recorded. Descriptive statistics were used to summarize outcomes and we evaluated predictors of success and complications using robust multiple regression analyses. We included 52 consecutive patients with a median age of 82 years (range 71-96) and a median Charlson Comorbidity Index of 6 (3-11). Forty-seven men used indwelling catheters, two used clean intermittent catheterization, and three had severe lower urinary tract symptoms. Stents were placed under general anesthesia, sedation, and local anesthesia in 39, 4, and 9 men, respectively. The median treatment time was 14 min (range 8-40). One complication, in the form of an infection requiring IV antibiotics, occurred. Subsequently, 45 men (87%) were able to void spontaneously without bothersome symptoms. After a median of 11 (2-44) months, 8 men had their stents removed due to recurring symptoms. This gives an overall success rate of 37/52 patients (71%). No predictors of success or complications were identified. Thermo-expandable intraprostatic nitinol stents demonstrate a high success rate with a low risk of complications and may serve as an alternative to permanent or intermittent catheterization for men who are unable or unwilling to undergo flow-improving surgery.

A clinical case of acute intestinal obstruction as a result of dislocation of the esophageal self-expanding nitinol stent

INTRODUCTION: Covered esophageal self-expanding stents are often used to palliate dysphagia in patients with unresectable esophageal and gastric cardia cancer. Migration of an esophageal stent is a common occurrence in these patients. One of rare complications that can be caused by stent dislocation is intestinal obstruction. The article describes a case of intestinal obstruction in result of migration of a fully covered nitinol esophageal stent. Patient K., 53 years old, was admitted to hospital in a severe condition with complaints of vomiting, abdominal pain and stool retention that had persisted for four days. The patient refused esophagogastroduodenoscopy. A plain abdominal X-ray did not reveal any free gas. In the mesogastrium, numerous pneumatized loops of small intestine with horizontal fluid levels were identified. For life indications, the patient, after preoperative preparation was taken to the emergency operating room; resection of the terminal part of small intestine was performed with placement of an ileostomy and gastrostomy. Taking into account difficulties of diagnosis (refusal of esophagogastroduodenoscopy by the patient and low informative value of X-ray examination), severity of the patient’s condition (due to a malignant neoplasm and intestinal obstruction), anatomical peculiarities (location of the esophageal stent 30 cm from the ileocecal angle, which would complicate potential application of enteroenteroanastomosis), the chosen tactics was to refuse application of enteroenteroanastomosis and exteriorize ileostomy and gastrostomy. CONCLUSION: Acute intestinal obstruction is a threatening complication of migration of an esophageal stent. Patients with placed esophageal stents require careful monitoring, use of a sparing diet and additional methods of stent fixation, which will help reduce the frequency of stent migration and associated complications.

Post Neck Radiation Cancer Carotid Pseudoaneurysm Blowouts with Viabahn Stent Placement

Carotid Blowout Syndrome (CBS) is a critical and often fatal complication associated with head and neck malignancies. CBS is characterized by three stages: threatened, impending, and acute rupture/hemorrhage. The condition is notably linked with a history of radiotherapy for head and neck cancers, with an incidence of approximately 3-4% among those who have received such treatment. Historically, surgical management of CBS has involved open surgical ligation. However, advancements in endovascular techniques, including endovascular destructive procedures (e.g., coil embolization) and reconstructive procedures (e.g., carotid artery stenting), have become increasingly prevalent. This report presents two cases where a self-expandable PTFE-coated nitinol stent with a heparin coating (Viabahn; Gore and Associates) was utilized in the treatment of CBS.

Manufacturing, Processing, and Characterization of Self-Expanding Metallic Stents: A Comprehensive Review.

This paper aims to review the State of the Art in metal self-expanding stents made from nitinol (NiTi), showing shape memory and superelastic behaviors, to identify the challenges and the opportunities for improving patient outcomes. A significant contribution of this paper is its extensive coverage of multidisciplinary aspects, including design, simulation, materials development, manufacturing, bio/hemocompatibility, biomechanics, biomimicry, patency, and testing methodologies. Additionally, the paper offers in-depth insights into the latest practices and emerging trends, with a special emphasis on the transformative potential of additive manufacturing techniques in the development of metal stents. By consolidating existing knowledge and highlighting areas for future innovation, this review provides a valuable roadmap for advancing nitinol stents.

Treatment of recurrent ureteral stricture after kidney transplantation with nitinol stent

Introduction. Urological complications make up a significant percentage in the structure of kidney graft loss and patient death in the early and long-term period after transplantation. The most common urological complication in the long-term period is ureter or anastomotic stricture, which, according to various authors, occurs in 0.9–34%. However, now there is no consensus in the treatment for recurrent strictures.Case report. We have presented a clinical case of successful treatment for the stricture of the ureterovesical anastomosis after kidney transplant from a brain-dead donor. During the first year after kidney transplantation, after two reconstructive surgeries and repeated placement of plastic stents, the patient was diagnosed with recurrent stricture of the ureterovesical anastomosis, and therefore a coated nitinol ureteral stent was implanted.Conclusion. This clinical case report demonstrates the feasibility of effectively using a nitinol stent in the treatment of recurrent strictures of the ureterovesical anastomosis after kidney transplantation. In some cases, this technique can be considered as an alternative to repeated surgical interventions. Further studies are needed to determine a more precise treatment algorithm.

Role of Multistate Models to Predict Patency, Limb Salvage, and Survival: New Concepts to Analyse Data in Peripheral Arterial Disease

In peripheral arterial disease, patency, limb salvage, and survival rates are mostly reported using Kaplan-Meier analyses. When comparing different revascularisation techniques, these methods have limitations in analysing complex patient flows over time. This study aimed to present, illustrate, and discuss new concepts based on multistate models of analysing outcome parameters in peripheral arterial disease. Previously published data from a single centre, randomised controlled trial (RCT) with 218 cases that underwent either vein bypass surgery (bypass group, n = 109) or nitinol stent angioplasty (stent group, n = 109) of long femoropopliteal lesions were re-analysed using non-homogeneous Markov models. A step by step description of the concepts of states, state space, definitions, and illustration of transition probability curves as well as the benefits of multistate models is given. The RCT was registered at ISRCTN.com (ISRCTN18315574). Transition probability curves over time showed similar patterns in the bypass and stent groups. Significant differences in the transition probabilities were found for transitions from primary patency as well as secondary patency to end of patency. The transition probability for patients with preserved primary patency at 24 months who moved to end of patency at 48 months was 19.9% in the stent group vs. 6.4% in the bypass group (p < .001). The proposed method can answer important questions, such as: Did patients after femoropopliteal stenting with preserved primary patency at two years lose their patency more quickly within the following years compared with bypass surgery? and Did stent patients after a re-intervention to maintain patency at one year lose their patency more quickly compared with bypass surgery within the following years? Completely new research questions can now be raised and answered to optimise treatment and follow up strategies; this might lead to better identification of subgroups at higher risk of clinical deterioration following revascularisation procedures.

Percutaneous Metallic Stents in Malignant Biliary Obstruction: Comparison of Nitinol and Wall Stents.

Palliation of malign biliary obstruction is important which is commonly carried out by percutaneous biliary stenting. Our primary aim with this study was assessment of performance of wall stents, and nitinol stents for the palliation of malign biliary obstruction. The medical records of 157 patients who underwent biliary stenting in our department between January 1, 1995, and December 31, 2005, were retrospectively analyzed. Technical success, treatment success, mortality in the first 30days, minor, and major complications were evaluated and compared among the wall stent, and the nitinol stent groups in all patients which constituted the primary study endpoints. Additionally, stent patency, and mean patient survival times after stent implantation were evaluated in patients for whom follow-up information could be obtained. A total of 213 metallic stents were placed in 157 patients. Wall stent was placed in 83 of the patients with mean age, and SD of 60.4 and 13.5. Nitinol stent was placed in 74 of the patients with mean age of 57.8, and SD of 15.5. Gender ratio was equal in both groups. Biliary stent dysfunction was observed in 13 patients in each of nitinol, and wall stent groups throughout the study period. There was no statistical difference among re-occlusion rates (p = 0.91). For the nitinol stent group median primary patencytime was 119days (90-185days CI 95%), and for the wall stent group median primary patencytime was 81days (60-150days CI 95%). Nitinol stents, and wall stents are safe options that can be safely used in the percutaneous treatment of malignant biliary obstruction with similar treatment and therapeutic success, low complication rates, and patency times that can extend beyond expected survival times.

Newly Designed, Self-Expanding Large-Bore Nitinol Stents for Symptomatic Central Venous Stenosis: Technical and Long-Term Clinical Outcome.

To retrospectively analyze the technical and long-term clinical outcome of angioplasty and stenting using the Venovo™ venous stent for the treatment of malignant and benign superior vena cava (SVC) occlusive disease. Consecutive patients treated with the Venovo™ venous stent for SVC occlusive disease were included. SVC obstruction symptoms were classified according to the Kishi score. The Wilcoxon signed-rank test was used for testing significance of changes. Technical success, defined as correct placement of the stent, completely covering and re-expanding the obstruction, between groups was tested using the Fisher exact test. Overall survival was calculated using the Kaplan-Meier method. Fifty-five patients underwent stent insertion for symptomatic benign (n = 13; 24%) or malignant (n = 42; 76%) SVC occlusive disease. A significant drop in Kishi score, mean 3.91 before versus mean 1.02 after the procedure (P < 0.0001), was observed. In one patient (1.8%), an additional balloon-expandable stent was needed to manage incomplete expansion of the nitinol stent. In one patient, a procedure-related lung embolic complication was noted. Early thrombotic occlusion of the stent occurred in one patient. Late symptomatic restenosis occurred in 3 patients. Overall primary stent patency and primary-assisted stent patency were 86% (95% CI 66-95) and97% (95% CI 83-100) at 1-year follow-up and 98% (95% CI 87-100), 98% (87-100) at 2-year follow-up, respectively. In this retrospective analysis, angioplasty and stent placement using the Venovo™ venous stent is safe and clinically effective for the treatment of both benign and malignant SVC occlusive disease. Reintervention for symptomatic restenosis is rare.

Ultrasound-guided nitinol stent implantation to treat early restenosis of arteriovenous fistula: A 69-case study with 1-year outcome.

To investigate the feasibility, methods and effects of interventional ultrasound in nitinol stent implantation to treat early restenosis after percutaneous transluminal angioplasty (PTA) in autogenous arteriovenous fistula (AVF). From April 2018 to December 2021, 69 patients with early restenosis of AVF received ultrasound-guided nitinol stent implantation (UNSI) and were followed-up. Imaging features of the stent and procedure by ultrasound were observed. The technical success rate, clinical success rate and incidence of complications were recorded and counted. Target lesion primary patency (TLPP), access circuit primary patency (ACPP) and access circuit secondary patency (ACSP) were estimated. Ultrasonography can show the structure of the stent and guide the stenting process clearly. Both the technical and clinical success rates were 100%. Thirty-one patients had in-stent restenosis (ISR), which was treated by plain balloon (PB) PTA or drug coated balloon (DCB) PTA. The TLPP at 3, 6, 12 and 24 months were 100.0%, 94.2%, 63.4% and 39.6%, respectively. The ACPP at 3, 6, 12 and 24 months were 98.6%, 91.6%, 60.2% and 35.2%, respectively. The ACSP at 3, 6, 12 and 24 months were 98.6%, 98.6%, 95.6% and 93.8%, respectively. The TLPP of ISR after DCB PTA at 3, 6 and 12 months were 100.0%, 100.0% and 93.6%, respectively. This pilot study indicates ultrasonography can accurately guide nitinol stent implantation in AVF and this technique is a feasible and minimally invasive treatment for early restenosis after PTA with good short- and medium-term patency. DCB PTA may be used to deal with the ISR and is a way to prolong the patency of nitinol stent.

Clinical Outcomes of Transradial vs Nontransradial Aortoiliac Endovascular Therapy

BackgroundThe introduction of radial-specific equipment has made transradial (TR) aortoiliac (AI) endovascular therapy (EVT) more convenient. ObjectivesThe authors aimed to investigate the perioperative outcomes of the TR approach in patients undergoing AI EVT for symptomatic peripheral artery disease. MethodsThe COMFORT (Contemporary Strategy for Aortoiliac Intervention) registry was a prospective, multicenter, observational study enrolling patients with symptomatic peripheral artery disease undergoing AI EVT between January 2021 and June 2023. The primary outcome was perioperative complications, whereas the secondary outcomes included core laboratory–evaluated residual stenosis >30%, time to hemostasis, time to ambulation, 30-day patency, and 30-day limb symptoms. These outcomes were compared between TR and non-TR AI EVT after propensity score matching. ResultsThe TR approach was selected for 231 of the 947 patients (24.3%). The TR approach was chosen more in patients with a higher ankle-brachial index, chronic total occlusion, aortic lesion, bare nitinol stent implantation, and plain angioplasty, whereas it was chosen less in patients with dialysis, a history of AI EVT, chronic limb-threatening ischemia, bilateral calcification, and simultaneous infrainguinal EVT (all P < 0.05). After propensity score matching, the incidence of perioperative complications did not differ significantly between the groups (TR group: 6.0% vs non-TR group: 5.1%; P = 0.69). The proportions of residual stenosis, 30-day patency, and 30-day limb symptoms were not significantly different (all P > 0.05); however, the time to hemostasis and the time to ambulation were shorter in the TR group (both P < 0.05). ConclusionsNon-TR AI EVT and TR AI EVT using radial-specific equipment were associated with a similar risk of perioperative complications. The TR approach helps shorten the time required for hemostasis and ambulation.

Nickel allergy in a patient after nitinol stent placement

We report a case involving a patient who developed a polymorphic rash and prurigo lesions on the limbs and anterior thorax, accompanied by an urticarial reaction on the back, following the endovascular placement of a femoral and iliac nitinol stent for critical limb ischemia. Patch testing identified a nickel allergy. The patient responded well to corticosteroid therapy, showing significant clinical improvement. This report discusses the epidemiology, pathophysiology, and clinical implications of nickel allergy, particularly in the context of using nickel-alloy stents.

Long-Term Preclinical Evaluation of a Permanent Stent Developed for the Human Eustachian Tube.

The Eustachian tube (ET) is a bottleneck when it comes to middle ear (ME) health. If its function is impaired, this can lead to serious consequences for the patient, such as hearing problems or deafness. Therefore, this study investigated a tapered nitinol stent (3-5 mm × 14 mm) for the human ET as a potential new permanent treatment for chronic Eustachian tube dysfunction (ETD) and thus ME ventilation disorders. The self-expanding stent was inserted unilaterally into the ET of 24 sheep with observation periods of 3, 6, and 12 months. Local tissue effects and the safety of the stent insertion were analyzed based on regular endoscopic checks, weekly tympanometry measurements, final imaging, and histological examinations. The animals showed no stent-related health restrictions. However, the individual anatomy and stenting procedure had an influence on the results. The tissue reaction in the endoscopic examinations was mild even though no concomitant antibiotics were administered. After all three monitoring periods, stented ETs had a significantly larger ET lumen than the non-stented contralateral ETs. However, tissue growth was detected in the stent. Overall, the first long-term study on an ET stent showed that the tapered ET stent could be a promising treatment option for ETD.

Static and dynamic behaviours of a self-expanding nitinol stent real contact area within a PTFE catheter: A multiscale approach

Current research on self-expanding super-elastic nitinol stents is mainly focused on designing geometries suited to the human venous and arterial systems. This study specifically considers a patented one-piece double cross-sectional stent designed to address venous stenosis affecting the vena cava, iliac veins, and their bifurcations. Before its placement within the vein, numerous tribological challenges arise as the stent slides along the guide-wire (so-called catheter). These are mainly connected to the lack of knowledge related to (i) its frictional behaviour and (ii) the level of contact pressure linked to the unknown real contact area between the compressed stent and the polytetrafluoroethylene (PTFE) catheter.This paper describes an original multi-scale approach, based on the Persson’s contact theory, that allows determination of (i) the contact pressure, (ii) the evolution of the real contact area, and (iii) the shear stresses at the interface during the stent sliding. A topographical optimization criterion will finally be provided, enabling control of both friction and stick–slip phenomena at the stent-catheter interface.

Effect of bioprosthetic leaflet anisotropy on stent dynamics of Transcatheter Aortic Valve Replacement devices

The assessment of stent fatigue in Transcatheter Aortic Valve Replacement (TAVR) systems is critical for the design of next-generation devices, both in vitro and in vivo. The mechanical properties of the bioprosthetic heart valves (BHVs) have a significant impact on the fatigue life of the metallic stent and thus must be taken into consideration when evaluating new TAVR device designs. This study aims to investigate the relationship between BHV anisotropic behaviour and the asymmetric deflections of the stent frame observed during in vitro testing.An explicit dynamics finite element model of the nitinol stent with attached bioprosthetic valve leaflets was developed to evaluate the deflections of the TAVR device under haemodynamic loading. Our results demonstrate that pericardium behaviour plays a dominant role in determining stent frame deflection. The anisotropic behaviour of the leaflets, resulting from collagen fibre orientation, affects the extent of deflection encountered by each commissure of the frame. This leads to asymmetric variation in frame deflection that can influence the overall fatigue life of the nitinol stent. This study highlights the importance of considering both the flexible nature of the metallic stent as well as the leaflet anisotropic behaviour in the design and fatigue assessment of TAVR systems.

The Role of Internal Carotid Artery Stent in the Management of Skull Base Paragangliomas.

Background: After two decades from its introduction in the lateral skull base paraganglioma surgery, the indications and results of preoperative internal carotid artery stenting should be critically assessed. Materials and Methods: Monocentric retrospective study on 26 patients affected by head and neck paragangliomas (19 tympanojugular paragangliomas, 4 carotid body paragangliomas, 3 vagal paragangliomas) preoperatively treated with internal carotid artery stents between 2008 and 2023. The preoperative findings, the intraoperative complications and the final surgical results were analyzed. Results: The stent complication rate was less than 3.1%. Self-expanding highly flexible intracranial nitinol stents were applied. In all cases, it was possible to completely mobilize the internal carotid artery and perform a vascular dissection of the tumor. Gross total tumor resection was possible in 85% of cases. The median follow up was 7.83 y (SD +/- 3.93 y). No local recurrence was observed. Conclusions: The preoperative vascular stent facilitates tumor dissection from the internal carotid artery without risk of vascular damage, helping the surgeon to achieve surgical radicality. The vascular stent is indicated in the case of revision surgeries, circumferential involvement of the vessel and in cases with non-insufficient intracerebral crossflow. Procedural complications, temporary antiplatelet therapy and delay of surgery are the limitations of the procedure.

Study of the Structure of Hyperbranched Polyglycerol Coatings and Their Antibiofouling and Antithrombotic Applications.

While blood-contacting materials are widely deployed in medicine in vascular stents, catheters, and cannulas, devices fail in situ because of thrombosis and restenosis. Furthermore, microbial attachment and biofilm formation is not an uncommon problem for medical devices. Even incremental improvements in hemocompatible materials can provide significant benefits for patients in terms of safety and patency as well as substantial cost savings. Herein, a novel but simple strategy is described for coating a range of medical materials, that can be applied to objects of complex geometry, involving plasma-grafting of an ultrathin hyperbranched polyglycerol coating (HPG). Plasma activation creates highly reactive surface oxygen moieties that readily react with glycidol. Irrespective of the substrate, coatings are uniform and pinhole free, comprising O─C─O repeats, with HPG chains packing in a fashion that holds reversibly binding proteins at the coating surface. In vitro assays with planar test samples show that HPG prevents platelet adhesion and activation, as well as reducing (>3 log) bacterial attachment and preventing biofilm formation. Ex vivo and preclinical studies show that HPG-coated nitinol stents do not elicit thrombosis or restenosis, nor complement or neutrophil activation. Subcutaneous implantation of HPG coated disks under the skin of mice shows no evidence of toxicity nor inflammation.