Self-expanding Stainless Steel Research Articles

Results of Palliative Stenting in Malignant Superior Vena Cava Syndrome Analyzing Self-Expanding Stainless Steel and Nitinol Venous Bare Metal Stents.

The purpose was to analyze the technical, clinical, and survival outcomes of our patients with malignant superior cava vein syndrome (SVCS) treated with endovascular approach and analyze the efficacy of different stent types used. It is an observational, retrospective, single-center study. From 2006 to 2023, 42 patients (32 male, 10 female, mean age 62 years, age range, 41-87 years) underwent percutaneous stent placement for malignant SVCS. One stainless steel stent (Wallstent) and 2 venous nitinol stent type (Sinus-XL, Venovo) were used. Follow-up mean was 276 days. A total of 53 stents were deployed. Clinical success was 97.6% in less 24 hours. Technical success was achieved in 97.6%. No complications were found except 1 patient died during the procedure due to stent migration and atrial dissociation (2.3%). Overall intraprocedural stent migration rate was 11.9% (18.8% stainless steel stent, 9.6% nitinol stent, p>0.05). Overall survival rates were 87.8%, 41.99%, and 34.12%, and overall primary patency rates were 100%, 93.3%, 91.6% at 1, 6, and 12 months, respectively. Endovascular treatment is a safe and effective therapeutic option for SVCS with high technical and clinical success rates and low complication and recurrence rates. The malignant superior cava vein syndrome is a rare clinical entity treated classically with radiation and chemotherapy with a slower response, or surgical bypass, which is an aggressive surgical technique. Endovascular treatment offers a low-invasive technique with quick clinical resolution and good permeability results. However, further studies are lacking to deal with procedure technical characteristics, stent type used, technical complications, and medium- and long-term patency studies. This study aims to evaluate all these items, analysing self-expanding stainless steel and nitinol venous bare metal stents, and add value to endovascular treatment, confirming the good results of this technique.

Deformation mechanics of self-expanding venous stents: Modelling and experiments

Deformation properties of venous stents based on braided design, chevron design, Z design, and diamond design are compared using in vitro experiments coupled with analytical and finite element modelling. Their suitability for deployment in different clinical contexts is assessed based on their deformation characteristics. Self-expanding stainless steel stents possess superior collapse resistance compared to Nitinol stents. Consequently, they may be more reliable to treat diseases like May-Thurner syndrome in which resistance against a concentrated (pinching) force applied on the stent is needed to prevent collapse. Braided design applies a larger radial pressure particularly for vessels of diameter smaller than 75% of its nominal diameter, making it suitable for a long lesion with high recoil. Z design has the least foreshortening, which aids in accurate deployment. Nitinol stents are more compliant than their stainless steel counterparts, which indicates their suitability in veins. The semi-analytical method presented can aid in rapid assessment of topology governed deformation characteristics of stents and their design optimization.

Combined stent placement and high dose PGE1 drip infusion for chronic occlusion of the superficial femoral artery as a modality to salvage chronic critical limb ischemia

Purpose To assess the initial effect, short-term patency, and limb salvage rates of combined stent placement and high-dose prostaglandin E-1 (PGE1) drip infusion for chronic occlusion of the superficial femoral artery (SFA). Materials and methods A total of 15 arteriosclerotic occlusive lesions of the SFA were treated in 11 consecutive patients (mean age: 78.4 years old). All cases were of category 4 or 5, based on the criteria of the Society of Vascular Surgery and Intermittent Society for Cardiovascular Surgery (SVC/ISCVS). In all cases a self-expandable stainless steel stent was implanted. PGE1 treatment was started 3–5 days before stent placement and continued for 7–10 days after the intervention. The technical success, limb salvage outcomes, patency rates, and complications were examined. Results In all cases, the technical success rate of the procedure was 100%. After stent implantation, the clinical status of all cases was improved by at least +2, and major amputation was not required in any cases. The 12-month primary, secondary patency rates, and limb salvage rate were 57%, 100%, and 100%, respectively. Conclusion Combined stent placement and high-dose PGE1 drip infusion is a treatment of choice for salvaging the lower limb of a patient with chronic critical ischemia.

Drug-Eluting Biodegradable Poly-D/L-Lactic Acid Vascular Stents:An Experimental Pilot Study

To evaluate in vivo a new drug-eluting biodegradable vascular stent with respect to biocompatibility, neointimal hyperplasia formation, and reliability. Self-expanding biodegradable poly-96L/4D-lactic acid (PLA) stents with 2 drugs (PLA + dexamethasone [DEX] and PLA + simvastatin [SIM]) and 2 different coatings (PLA + P(D,L)LA and PLA + polycaprolactone [PCL]) were compared with a self-expanding stainless steel Wallstent. The stents were implanted in both common iliac arteries of 8 pigs. Prior to sacrifice at 1 month, angiography was performed to determine patency. Specimens were harvested for quantitative histomorphometry; vascular injury and inflammation scores were assigned to the stented iliac segments. All stented arteries were angiographically patent. The mean luminal diameter (3.05 mm) and area (30.36 mm2) of DEX-eluting PLA stents were decreased compared to other stents (PLA + P(D,L)LA: 3.66 mm and 43.92 mm2; PLA + SIM: 4.21 mm and 56.48 mm2; PLA + PCL: 4.19 mm and 54.64 mm2; Wallstent: 5.01 mm and 81.19 mm2). Wallstents and DEX-eluting PLA stents induced minimal intimal hyperplasia: PLA + DEX: 0.16 mm, PLA + P(D,L)LA: 0.35 mm, PLA + SIM: 0.33 mm, PLA + PCL: 0.29 mm, and Wallstent: 0.18 mm. The vascular injury scores demonstrated only mild vascular trauma for all stents. Only mild to moderate inflammatory reaction was noted around stent struts with a vascular inflammation score. Biodegradable polymer stents appear to be biocompatible and reliable, causing minimal neointimal hyperplasia. Furthermore, the new biodegradable poly-D/L-lactic acid stent can be used as a local drug delivery vehicle. The DEX-eluting PLA stent reduces neointimal hyperplasia. The findings show a need for further investigation to prove the efficacy and safety of this new biodegradable drug-eluting stent.

Elective Stent-Graft Treatment of Aortic Dissections

To retrospectively review 8 years' experience with stent-graft treatment of aortic dissections at a single institution. Forty-six patients (31 men; mean age 59 years, range 38-88) underwent stent-graft treatment for 9 Stanford type A and 37 type B aortic dissections (9 acute phase, 13 subacute, 24 chronic). Custom-designed self-expanding stainless steel Z stents covered with polytetrafluoroethylene were used (n=20) until low-profile modular stent-grafts became available for percutaneous delivery (n=26). Endovascular stent-graft deployment was technically successful in 44 (96%) patients; the 2 failed cases owing to intraprocedural migration and graft torsion were converted to surgery. There were 5 type I endoleaks for a clinical success (entry tear exclusion) of 85% (39/46). Complications included 3 cases of transient renal failure, 2 puncture site pseudoaneurysms, 1 guidewire-induced new intimal tear (converted), and 2 cases of stent-induced saccular aneurysms (1 converted). Follow-up at a mean 34 months (range 12-96) showed complete resolution of the thoracic false lumen in 14 (74%) of 19 acute/subacute patients treated successfully; 3 (16%) showed a reduced thoracic false lumen diameter. In the 23 chronic-phase patients treated successfully, 8 (35%) had complete resolution of the thoracic false lumen, and 11 (48%) showed size reduction. Enlargement of the abdominal aortic false lumen due to persistent flow into re-entry tear(s) occurred in 3 (13%). Stent-graft treatment is a feasible and effective treatment modality in aortic dissection. However, close follow-up is mandatory to monitor new intimal tear, saccular aneurysms, or enlargement of the abdominal aortic false lumen.

NICKEL-TITANIUM SHAPE MEMORY ALLOY MEMOKATH 051 URETERAL STENT FOR MANAGING LONG-TERM URETERAL OBSTRUCTION: 4-YEAR EXPERIENCE

We present our 4-year experience with the thermo-expandable shape memory alloy Memokath 051 stent (Engineers and Doctors of Copenhagen, Copenhagen, Denmark) for managing long-term ureteral obstruction. We used a nickel-titanium shape memory alloy ureteral stent to treat 28 patients 29 to 86 years old (mean age 59.2). Ureteral obstruction was caused by malignancy in 18 cases and by recurrent benign disease in 10. A total of 37 stents were inserted from November 1996 to November 2000 using general anesthesia. Mean followup was 19.3 months (range 3 to 35). Upper tract decompression was achieved in all cases. Currently 15 stents are functional in 13 patients, while 8 patients died with a total of 13 functioning stents in place. In 7 patients 9 stents were removed for various reasons. There has been no radiological evidence of encrustation to date. No patient has been rehospitalized with stent related sepsis pain or hematuria, resulting in improved quality of life. This stent seems to provide a significant benefit over conventional Double-J (Medical Engineering Corp., New York, New York) and other metallic stents. Its remarkable thermal memory permits removal, a feature that until recently was not available in any other metallic ureteral stent. Durable and complication-free decompression of the upper tract can be achieved with the Memokath 051.

Elective Endovascular Treatment of Descending Thoracic Aortic Aneurysms and Chronic Dissections with Stent-Grafts

To report our experience of endovascular stent-graft placement in patients with descending thoracic aortic dissections and aneurysms and to evaluate the feasibility, safety, and clinical outcomes of the treatment. Stent-grafts were placed in the descending thoracic aortas of 23 patients with saccular aneurysms (n = 11) and Stanford type B chronic aortic dissections of the descending thoracic and abdominal aorta (n = 12). All stent-grafts were individually constructed of self-expandable stainless steel stents covered with polytetrafluoroethylene. Vascular access was achieved through the femoral artery in all patients. Clinical status of each patient was monitored and postoperative CT was performed within 1 month of the procedure and at 3-12-month intervals after the procedures. Successful exclusion of the primary entry tears of dissections and the inlets of saccular aneurysms was achieved in all but two patients with aortic dissection. The overall technical success rate was 91.3% (dissection: 10 of 12 = 83%; aneurysm: 11 of 11 = 100%). All patients in whom technical success was achieved showed complete thrombosis and significant decrease in diameter of the thoracic false lumen (preoperative: 5.3 cm +/- 0.9; postoperative: 4.3 cm +/- 0.9; P = .004) or aneurysm sac (preoperative: 5.3 cm +/- 1.7; postoperative: 2.8 cm +/- 2.5; P = .001). In addition, five patients demonstrated complete resolution of the dissected thoracic false lumen (n = 2) and aneurysm sac (n = 3). However, in all patients with aortic dissection, the abdominal aorta was not significantly changed in size (P = .302) and shape and their false lumen flows remained persistent. Immediate postoperative complications were detected in 12 patients (52%); 10 had fever, leukocytosis, and elevation of C-reactive protein, another had wound infection, and another had transient abdominal pain. Three patients died 2, 3, and 12 months after the procedure: one from septic shock, another from underlying mediastinitis, and the other from an unexplained cause. The remaining 20 patients were well after the procedure (1-9 days; mean, 3 days), without any stent-graft-related complications or discomfort (follow up period: 10-65 mo; mean: 25.1 mo +/- 15.6). The cumulative survival rate after the stent graft was 100% at 30 days and 91% at 12 months. For treatment of aortic dissection and saccular aneurysm of the descending thoracic aorta, endovascular stent-graft repair may be a technically feasible and effective treatment modality.

気道・食道のステント治療 食道癌による食道狭窄のステント治療

The purpose of this study was to evaluate the results of esophageal stents implanted in patients with inoperable esophageal carcinoma. From May 1984 to February 2000, 81 patients with inoperable carcinoma of the esophagus were treated by placement of 51 plastic prostheses and 30 metallic stents. The plastic prostheses consisted of 30 silicone stents, 19 polyurethane stents and 2 polyuronide stents in our series. Twenty-nine of the 30 patients treated with metallic stents were treated with Ultraflex (a self-expanding nitinol stent) and one case with Wallstent (a self-expanding stainless steel stent). The overall rate of palliation of dysphagia with the esophageal stents was 86% in our series. The rate of successful palliation for 31 cases with tracheoesophageal fistula was 90%. There were no differences between the plastic prosthesis group and metallic stent group in these rates. The overall median survival time after treatment with stent was 54 days. There was no difference between the stent groups in survival curves by the Kaplan-Meier method. Complaints of sore throat were much more common in the plastic prosthesis group than in the metallic stent group, and that was the only statistically difference between the two groups in terms of complications after the insertion of the stents (p < 0.05). This might have been due to the fact that the metallic stent was slimer than the plastic prosthesis at the insertion point.

Intraoperative stenting of the internal carotid artery after unsuccessful eversion endarterectomy

Stenting Of The Internal Carotid Artery (ICA) Has Been Shown To Be Feasible In Atherosclerotic Lesions, In Restenosis After Carotid Endarterectomy, And In Spontaneous Carotid Dissections. To Correct An Intimal Flap That Detached Distal Occlusion Of The Ica After Eversion Carotid Endarterectomy, As Shown With Intraoperative Completion Angiography, We Successfully Used Stenting Of The Ica With A Self-EXPANDABLE Stainless Steel Stent Placed During Surgery Through The Common Carotid Artery. (J Vasc Surg 1999;30:355-6.)

Endovascular stent graft repair of aortopulmonary fistula

Two patients who had aortopulmonary fistula of postoperative origin with hemoptysis underwent successful repair by means of an endovascular stent graft procedure. One patient had undergone repeated thoracotomies two times, and the other one time to repair anastomotic aneurysms of the descending aorta after surgery for Takayasu's arteritis. A self-expanding stainless steel stent covered with a Dacron graft was inserted into the lesion through the external iliac or femoral artery. The patients recovered well, with no signs of infection or recurrent hemoptysis 8 months after the procedure. Endovascular stent grafting may be a therapeutic option for treating patients with aortopulmonary fistula. (J Vasc Surg 1999;29:557-60.)

Stent endoprosthesis for obstructing colorectal cancers

Purpose of this study was to assess stent endoprosthesis for colorectal cancer (SECC) as an adjuvant to operative preparation in patients with obstructing colorectal cancers. A self-expanding stainless steel stent was inserted in 15 patients with obstructing colorectal cancers under colonoscopic observation and fluoroscopic control. Following successful SECC, the colon was mechanically prepared using polyethylene glycol. Definitive surgical treatment then was undertaken. All 12 patients in whom the stent had been successfully placed recovered intestinal transit and tolerated mechanical preparation. A satisfactory preparation was confirmed during the operation. Two perforations and one dislocation were encountered. SECC is a new method for operative preparation of patients with obstructing colorectal cancers, which may reduce morbidity and mortality associated with this difficult problem.

The effect of an intraluminal stent on neointimal hyperplasia at an end-to-side polytetrafluoroethylene graft arterial anastomosis

Anastomotic neointimal hyperplasia plays a significant role in the late failure of infrainguinal prosthetic arterial bypass grafts. Previous work from our laboratory revealed that placing a stent across an end-to-end arterio-arterial anastomosis resulted in an increase in the luminal area as well as in the intimal thickness (IT) at the anastomotic level. This study was designed to evaluate the effects on neointimal hyperplasia when a stent is placed across an end-to-side polytetrafluoroethylene (PTFE) graft arterial anastomosis. A canine model of an end-to-side anastomosis was developed using a 12 x 6 mm polytetrafluoroethylene aortobi-iliac graft. A self-expanding stainless steel Wallstent was placed across one randomly selected distal anastomosis leaving the opposite side as a control. Dogs were sacrificed at 4 and 12 weeks. At sacrifice, the graft and intact anastomoses were pressure-perfusion fixed with glutaraldehyde. Sections of each distal graft, anastomosis, and recipient artery were obtained for analysis. Computer images of each section were digitized to determine the luminal area and the mean IT. The data were analyzed statistically using univariate repeated measures of analysis of variance. One animal died prior to early sacrifice. Eight of 10 graft limbs remained patent at sacrifice. Of the 2 limbs that occluded, one was stented and one was nonstented. At 4 weeks, stented graft limbs had significantly greater IT at the proximal stent level (mean difference between control and stented sides 0.163 mm +/- 0.054, P = 0.01). Stented and nonstented anastomoses had similar luminal area and IT at other levels where sections were taken. At 12 weeks, control limbs had significantly greater IT at the anastomotic level compared to the 4-week measurements (mean difference 12 weeks versus 4 weeks 0.185 mm +/- 0.06, P = 0.006). In the stented limbs, IT at the anastomotic level had stabilized and was not significantly thicker than at 4 weeks. The control limbs had greater IT at the anastomotic level than the stented limbs (mean difference between controls and stented sides at 12 weeks 0.091 mm +/- 0.044, P = 0.06). At the proximal end of the stent, IT progressed significantly between the 4th and 12th weeks (mean difference 12 weeks versus 4 weeks 0.155 mm +/- 0.06, P = 0.02). The IT at the proximal end of the stent at 12 weeks was significantly greater than the IT at a comparable level in the controls (mean difference stent versus control 0.132 mm +/- 0.05, P = 0.04). The luminal area in the control limbs was significantly greater than in the stented anastomoses at levels corresponding to either end of the stent (mean difference at proximal end 4.163 mm2 +/- 1.633, P = 0.01; mean difference at distal end 7.192 mm2 +/- 1.633, P = 0.0005). However, there was no difference in luminal area at the anastomotic level. We conclude that the presence of an intraluminal stent alters the siting and degree of anastomotic neointimal hyperplasia in a canine model of an end-to-side anastomosis resulting in translocation of the intimal hyperplastic response to the proximal graft stent interface in a magnitude similar to that which would normally be found at the anastomosis.

Endoscopic Retrieval of a Self-Expanding Stainless Steel Stent from the Common Bile Duct

Endoscopic Retrieval of a Self-Expanding Stainless Steel Stent from the Common Bile Duct

Self-expanding Stents in the Treatment of Tracheobronchial Obstruction

The self-expandable stainless steel stents (Gianturco, William Cook, Bjaeverskov, Denmark) used extensively in biliary ducts and the vascular system have recently been modified for use in the tracheobronchial tree. Between March 1991 and September 1992, six patients with unresectable tracheobronchial and mediastinal diseases were treated with the placement of one or more self-expanding stents under direct vision with a fiberoptic bronchoscope. All patients had been intubated for severe respiratory insufficiency. In all cases, immediate relief of respiratory symptoms was achieved and all patients were extubated 1 or 2 days after stent placement. Tolerance of the stents was excellent. No patient complained of pain, discomfort, or foreign body sensation. No infection or obstruction of the stents was observed. The chest roentgenogram and the bronchoscopies performed during follow-up have shown no change in the position of the stents. Our results seem promising since these devices provide effective palliation of airway obstructions and are well tolerated.

Self-expanding stainless steel stent application in rectosigmoid stricture

In recent years, several reports on the experimental and clinical applications of the Gianturco stent (self-expanding stainless steel stent) have been published. However, to our knowledge, the use of stents in rectosigmoid strictures has not been reported. We used self-expanding stainless steel stents to dilate rectosigmoid strictures caused by nonresectable recurrent neoplasm. Insertion and dilation (sigmoid colon and rectum) in two patients were successful. Accordingly, these patients were able to maintain bowel activity and avoid palliative loop colostomy. We believe that this procedure is effective for nonresectable rectosigmoid stricture due to recurrent neoplasm.

Malignant biliary obstruction: treatment with self-expandable stainless steel endoprosthesis.

Metal endoprostheses of the Wallstent type were successfully inserted percutaneously and endoscopically in 80 consecutive patients with malignant obstructive biliary stenoses, who were followed for up to 18 months. The indication for treatment was jaundice due to malignant biliary obstruction. Repeat radiological investigations were performed if the patient had symptoms suggesting stent occlusion. After stent implantation, 88% of patients demonstrated a serum bilirubin decrease by more than 50%. We observed a 15% rate of serious complications, including a 10% rate of cholangitis with septicemia. There were no cases of stent migration or occlusion due to encrustation of bile. Recurrent jaundice occurred in 17.5% of patients due to progressive tumor growth after 3-10 months. In 5 of these patients, tumor overgrowth was redilated and/or restented. Of the 80 patients, 34% are alive after 2-12 months (mean: 242 days); of these, two-thirds are free of jaundice. Sixty-six percent of patients died between 3 days and 1.5 years (mean: 133 days). Although autopsy investigations revealed the possibility of tumor growth onto the inner surface of the stent, through the mesh of the endoprosthesis, no stent occlusion by tumor ingrowth into the lumen occurred. Self-expandable stainless steel endoprostheses provide good palliation in patients with malignant obstructive jaundice.

Historical overview on the development and characteristics of stents and future outlooks.

The history and development of endovascular stents is described beginning with the Maass double helix spiral prosthesis, the first stent used in human clinical trials in the early 80s. This is followed by a description of the three main groups of stent techniques: the shape memory alloy stents, the balloon-expandable stents, and the self-expanding stainless steel stents. Requirements and new trends for improving clinical results in the future complete this text.

Successful stenting of a life threatening pulmonary arterial stenosis.

A 35 year old woman with multiple pulmonary arterial stenoses and occlusions was admitted with increasingly severe breathlessness. Balloon angioplasty of a life threatening stenosis in a remaining pulmonary artery branch was attempted on two occasions but without success. When a self-expanding stainless steel stent was inserted at the site of stenosis after a further angioplasty acute localised pulmonary oedema developed as blood flow distal to the lesion increased considerably. This was followed by a slow and dramatic improvement in the patient's condition. She no longer required an urgent transplant and resumed an active life.

Reduction in thrombus formation by placement of endovascular stents at endarterectomy sites in baboon carotid arteries.

Although antithrombotic therapies with aspirin, dipyridamole, and heparin have decreased thrombo-occlusive events, they have not abolished these complications. Endovascular mechanical support, first reported by Dotter in 1969, has been proposed as a means to reduce both acute and chronic vessel closure by providing a supporting framework for the disrupted and sometimes dissected arterial wall. To determine the effects of placing self-expanding stainless steel wire endoprostheses on the accumulation of thrombus at sites of carotid artery endarterectomy we measured platelet deposition continuously for 90 minutes and at 24 and 48 hours by gamma camera imaging of autologous 111In-labeled platelets in six stented and nonstented endarterectomized baboons that received heparin but no antiplatelet agents. At nonstented endarterectomy sites 5.36 +/- 1.25 x 10(8), 4.78 +/- 0.98 x 10(8), and 4.55 +/- 0.81 x 10(8) platelets per cm were deposited at 30, 60, and 90 minutes, respectively. In contrast, stented endarterectomy sites accumulated 0.99 +/- 0.31 x 10(8), 0.66 +/- 0.33 x 10(8), and 0.80 +/- 0.36 x 10(8) platelets per cm at 30 minutes (p = 0.02), 60 minutes (p = 0.004), and 90 minutes (p = 0.002), respectively. Platelet deposition remained reduced at 24 and 48 hours in stented endarterectomized carotid arteries (ECAs) when assessed as a ratio between net radioactivity in the endarterectomized region versus whole blood radioactivity (p = 0.006 and p = 0.009, respectively). Both stented and nonstented ECAs remained patent acutely, although two of six nonstented ECAs occluded by 30 days. By comparison 11 of 14 nonstented ECAs remained patent in another group of control animals. Scanning electron microscopy of control and stented arteries at 30 days demonstrated equivalently confluent endothelium. We postulate that endovascular stents reduce the thrombogenic effects of flap formation, tearing, dissection, and vasospasm in ECAs.

Self-expandable stainless steel endoprostheses for treatment of malignant bile duct obstruction.

The Wallstent biliary endoprosthesis is a mesh of stainless steel that is delivered percutaneously over a 7-French catheter but expands to achieve a 1-cm lumen when released across a bile-duct stricture. The small transhepatic track required makes insertion easier, less painful, and probably safer when compared with plastic stents, and the large internal lumen reduces the rate of occlusion by encrusted bile. Wallstent endoprostheses were inserted under local anesthesia in 41 consecutive patients with malignant obstructive jaundice. Biliary drainage was considered the treatment of choice in all of these patients. The diagnosis was based on biopsy results in 32 patients and on radiologic appearances in nine. The patients were followed up in outpatient clinics for 16 months and had repeated radiologic examinations only if they had symptoms suggesting stent occlusion. No cases of hemobilia due to damaged hepatic vessels occurred. Two patients had septicemia treated with antibiotics. Three patients had recurrent jaundice due to growth of tumor below or above the stents. Endoprosthesis migration was not seen. No cases of stent occlusion due to encrustation of bile occurred. The median survival of patients was 105 days (range, 10-545 days). Our experience shows that Wallstent endoprostheses can be inserted with little discomfort for the patient and with relatively few complications. They provide good palliation in patients with malignant obstructive jaundice.