Stent Mesh Research Articles

Characteristics of Stents for Pipe Flows with an Aneurysmal Model

Recently, endovascular therapy with microcoils and stents has started for the treatment of aneurysmal diseases. This study explores assessments of stent characteristics for pipe flows with a model of an aneurysmal sac in vitro. The operating fluid is the water, and three kinds of stents are adopted in the range of Reynolds number in human blood flows. As assessment parameters for stent characteristics, the pipe friction coefficient for the stent is considered as well as fineness and thickness of the stent mesh. The velocity fields within the aneurysmal model have been measured by means of PIV, and the distributions of shear stress and flow patterns have been investigated. The results have indicated that stents with the finer or the thinner meshes, or stents with the smaller pipe friction coefficient have blockage effects against flows into the aneurysmal model.

TRANSECTION OF METAL STENTS USING ARGON PLASMA COAGULATION

Background: Placement of self-expandable metallic stents has become the preferred palliative treatment for patients with unresectable malignant biliary obstruction. Metallic stents provide longer patency compared with plastic stents. Distal malposition or migration of metallic stents sometimes occurs, but it is often difficult to remove them. We evaluated the efficacy and safety of argon plasma coagulation (APC), and the optimum conditions for cutting metallic stents (Wallstent). Methods: We wrapped porcine small intestines around a metallic Wallstent with and without silicon lining membrane (Permulume®), leaving the distal portion unwrapped to resemble the protrusion of the biliary metallic stent from the ampulla of Vater. APC irradiation was applied to the metallic stent at 1 cm from the edge of the wrapped small intestine at 30, 60 and 99 watts (W) for 3 or 6 s. Results: Metallic Wallstent with the silicone-based membrane Permalume® was cut at 30 W power, whereas more than 60 W power was required to cut the bare metallic wire. The irradiation of APC (flow rate at 2.0 L/min) at 30 W to the covered metallic stent transected the metallic mesh stent not only under dry but also under wet conditions (moisturized stent). Irradiation of APC caused no gross damage to the small intestines irrespective of the power applied and duration of irradiation. Conclusions: Our results suggest that APC is efficacious and safe for endoscopic sectioning of wire mesh stents at low power (30 W) without gross damage to the surrounding pancreaticobiliary tissues.

A Randomized Prospective Comparison of Self-Expandable Plastic Stents and Partially Covered Self-Expandable Metal Stents in the Palliation of Malignant Esophageal Dysphagia

Self-expanding metal stents (SEMS) provide effective palliation in patients with malignant dysphagia, although severe complications and mortality may result. We performed a prospective controlled trial to compare a new self-expanding polyester mesh stent (Polyflex) with SEMS (Ultraflex). One hundred one patients with unresectable esophageal carcinoma were randomized to placement of a Polyflex (N=47) or a partially covered Ultraflex (N=54) stent. Patients with esophagogastric junction (EGJ) malignancy were excluded. Placement was successful in 46 (98%) patients with the Polyflex and 54 (100%) patients with the Ultraflex stent. In one patient, the Polyflex stent could not be placed. After 1 wk, dysphagia was improved by at least 1 grade in 100% of the Polyflex group and in 94% of the Ultraflex group. Major complications were observed in 48% of the Polyflex group and 33% of the Ultraflex group. Intraprocedural perforation occurred in 1 Polyflex and 1 Ultraflex patient. Two Polyflex patients had postprocedural hemorrhage. Twenty (44%) patients with a Polyflex stent and 18 (33%) with an Ultraflex stent had recurrent dysphagia because of tumor overgrowth, stent migration, hyperplastic granulomatous reaction, or food bolus impaction. Multivariate analysis showed a significantly higher complication rate with Polyflex than with Ultraflex stents (odds ratio 2.3, 95% CI 1.2-4.4). However, median survival was 134 days with Polyflex and 122 days with Ultraflex stents (P=NS). No difference was seen in palliation of dysphagia between the two stents. Significantly more complications, especially late stent migration, were observed in the Polyflex group.

External Stenting with a New Polyester Mesh Reduces Neointimal Hyperplasia of Vein Grafts in a Sheep Model

External stents placed around vein grafts have demonstrated effectiveness in reducing neointimal hyperplasia by preventing distension of the thin-walled vein grafts when exposed to arterial pressure. However, the ideal stent material has yet to be defined. The following study investigates the short- and long-term effects of an innovative polyester mesh stent designed with optimized adaptation of circumferential compliance. Following in vitro definition of the ideal macro-porous polyester stent material, a total of 12 sheep underwent implantation of bilateral carotid artery vein graft bypasses. In six sheep, the short term outcome (four weeks of implantation) was investigated by comparing the newly-designed stent to native veins, micro-porous PTFE stent grafts and metallic Biocompound stents (BCGs). Flow volume and graft diameter were measured prior to explantation. Grafts were evaluated histologically with respect to morphometry and immunoassaying. In the long-term group (6-month implantation time), the polyester stent was compared to native veins. All stents effectively prevented dilatation of the graft. Perfused vessel diameters of the polyester veins were 8.3+/-0.6 mm. BCG as well as PTFE veins showed diameter reduction to 7.4+/-0.7 mm (p<0.05) and 7.8+/-0.4 mm (p<0.05), respectively. Both in the short and long terms, the new polyester stent led to significantly higher reduction of neointimal hyperplasia and luminal encroachment compared to the native vessel. It proved superior to PTFE stenting, while the Biocompound material failed to prove efficacy. It was demonstrated that the new macro-porous polyester mesh stent reduced neointimal hyperplasia more effectively than other commercially available stents.

Multi-link Vision and MiniVision stent registry in Asian patients with coronary artery disease: a prospective, multi-center study

Recent studies have showed that the fine mesh stents are associated with a significant reduction in both clinical and angiographic re-stenosis of the coronary arteries. To maintain a very satisfactory radio-opacity using the stents, Guidant of the USA has designed a new type of bare metal stents (BMS)-Multi-link (ML) Vision/ML MiniVision stents. The clinical outcomes of Asian patients with coronary artery disease (CAD) after implanting the Multi-link Vision or MiniVision stent were investigated in this study. An observational, prospective, multi-center, non-randomized post marketing registry was conducted to demonstrate the efficacy of the BMS-ML Vision/ML MiniVision stents. The primary end point of the registry was clinical target lesion revascularization (TLR) at a 6-month follow-up. The major secondary end points included the rate of major adverse cardiac events (MACE) and serious adverse events (SAE) in hospital and at 6 months; and the rate of clinical TLR as a function of the type of angina. A total of 429 Asian people with 449 lesions from 14 centers were selected for this study. The average reference diameter of the lesions was (3.0 +/- 0.5) mm, and the mean length was (15.7 +/- 5.0) mm. The successful rate of the procedure was 99.3%. Twenty-five percent of the lesions were treated by direct stenting without pre-dilation. Eighty-six percent of the lesions were implanted with ML Vision stent. After the 6-month follow-up, the rate of clinical TLR was 1.4%. The MACE, SAE and target vessel revascularization (TVR) were 6.8%, 3.5% and 1.4% respectively. The current registry showed the excellent 6-month clinical outcomes of ML Vision/ML MiniVision stents in Asian patients with CAD.

Application of Self-Expandable Metal Stents for Ureteroileal Anastomotic Strictures: Long-Term Results

We report our long-term experience with the management of benign ureteroileal anastomotic strictures using self-expandable metal stents. A total of 16 male and 2 female patients with a mean+/-SD age of 72+/-7 years (range 66 to 78) with benign fibrotic strictures at the site of ureteroileal anastomosis underwent implantation of self-expandable metal stents with a nominal diameter of 6 to 8 mm. A total of 24 ureteroileal conduits were treated. The external nephrostomy tubes were removed after fluoroscopic validation of ureteral patency. Patients were followed with blood biochemistry, ultrasonography, urography and/or virtual endoscopy. Retrograde external-internal catheter insertion through the cutaneous stoma was performed in cases of recalcitrant stricture. The technical success rate of ureteroileal stricture crossing and stenting was 100% (24 of 24 cases). Mean followup was 21 months (range 7 to 50). The clinical success rate during the immediate post-stenting period was 70.8% (17 of 24 cases). The 1 and 4-year primary patency rates were 37.8% and 22.7%, respectively. Secondary interventions included repeat balloon dilation in 15 ureters, of which 8 also underwent subsequent coaxial stent placement. The 1 and 4-year secondary patency rates were 64.8% and 56.7%, respectively. Except in 2 patients who died external-internal Double-J catheters continued to be inserted retrograde in 6 ureteroileal conduits. They are periodically exchanged to prevent mucous inspissation and stent encrustation. Metal stents served as the definitive treatment for stricture in more than half of the cases, whereas in the remainder the stents allowed the uncomplicated and regular exchange of Double-J catheters in retrograde fashion. This combined, less invasive treatment for ureteroileal anastomotic strictures may help patients avoid surgical revision and preserve quality of life.

The Niti-S Oesophageal Stent Reduces Migration Rates in the Palliation of Malignant Dysphagia

Background: Self-expanding metal mesh stents (SEMS) are frequently used in the palliation of malignant dysphagia. Our Unit has significant experience of both the Ultraflex stent (Boston Scientific, Natick, Mass) and the Niti-S stent (Taewong Medical, Seoul, Korea). A comparative study was conducted to determine the frequency of stent-related complications with the use of Ultraflex and Niti-S stents in one institution. Methods: Between April 2003 and June 2006 135 patients required SEMS insertion for the palliation of malignant oesophageal obstruction. Individuals received either an Ultraflex (n = 72) or a Niti-S (n = 63) stent. The incidence of complications including retrosternal pain, bleeding, perforation, tumour in-growth or over-growth, migration and 30-day mortality was compared. Results: The age, gender distribution, tumour length, stent length and number of days in hospital after stent insertion were similar between the two groups (median (interquartile range)). The number of patients with retrosternal pain, haematemesis, perforation, bolus obstruction, tumour in-growth or over-growth, and 30-day mortality were also similar. However, the incidence of stent migration was significantly less in the Niti-S stent group. Distal oesophageal and oesophago-gastric junction (OGJ) tumours accounted for 82% of patients receiving an Ultraflex stent and 81% of patients receiving a Niti-S stent. Ultraflex stent migration only occurred in distal oesophageal or junctional cases. Conclusion: The Niti-S stent has design features aimed at reducing stent migration and tumour in-growth. This study has demonstrated a significantly reduced migration rate when compared with the Ultraflex stent with no increase in morbidity or mortality. This finding was sustained even in the distal third and OGJ cancers where the risk of migration is greatest. There was a trend towards reduced tumour in-/over-growth. This study supports the development of a prospective randomised trial. Tabled 1 Ultrafex (n = 72) Niti-S (n = 63) p value Age (years) 74 (62-84) 76 (64-83) n/s Male:female 45:27 44:19 n/s Tumour length (cm) 6 (5-8) 6 (5-9) n/s Distal oesophageal tumour 35 26 n/s OGJ tumour 24 25 n/s Stent length (cm) 9 (7-12) 8 (8-12) n/s Post-stent stay (days) 3 (2-4) 3 (2-5) n/s Tumour in-/over-growth 14 9 n/s Stent migration (all tumours) 8 0 0.02 Stent migration (distal oesophageal tumour) 3 0 n/a Stent migration (OGJ tumour) 5 0 n/a 30-day mortality 2 0 n/a n/s - not significant. n/a - not applicable (numbers too small) Open table in a new tab n/s - not significant. n/a - not applicable (numbers too small)

Computational Approach to Estimating the Effects of Blood Properties on Changes in Intra-stent Flow

In this study various blood rheological assumptions are numerically investigated for the hemodynamic properties of intra-stent flow. Non-newtonian blood properties have never been implemented in blood coronary stented flow investigation, although its effects appear essential for a correct estimation and distribution of wall shear stress (WSS) exerted by the fluid on the internal vessel surface. Our numerical model is based on a full 3D stent mesh. Rigid wall and stationary inflow conditions are applied. Newtonian behavior, non-newtonian model based on Carreau-Yasuda relation and a characteristic newtonian value defined with flow representative parameters are introduced in this research. Non-newtonian flow generates an alteration of near wall viscosity norms compared to newtonian. Maximal WSS values are located in the center part of stent pattern structure and minimal values are focused on the proximal stent wire surface. A flow rate increase emphasizes fluid perturbations, and generates a WSS rise except for interstrut area. Nevertheless, a local quantitative analysis discloses an underestimation of WSS for modelisation using a newtonian blood flow, with clinical consequence of overestimate restenosis risk area. Characteristic viscosity introduction appears to present a useful option compared to rheological modelisation based on experimental data, with computer time gain and relevant results for quantitative and qualitative WSS determination.

NUMERICAL ANALYSIS OF THE FLUID DYNAMICS IN A HELICAL STENT

Motivation: The implantation of a stent into a native coronary artery represents a bold intrusion of a totally foreign substance into the circulatory system. Although most of the clinically implanted coronary stents are uneventful in patients, many however failed due to disturbed flow caused by the stent. It is always desirable to continuously carry out research that may eventually lead to the development of an ideal stent for the future. Methods: The flow dynamics of a simple helical stent is numerically analyzed by computational fluid dynamics (CFD), (CFD-ACE+ 2004, ESI-CFD INC., USA). Based on the physiological character of coronary artery, the parameters of helical stent, pitch, roughness, leading angle, and diameter are manipulated to derive flow information of wall shear stress, pressure distribution, and vortices. Results and Conclusions: The results show that the flow is dominated by the contact geometry between the blood flow and the wall when the wall of stent is thick. Swirling flow is also observed when the helical stent is implanted into the artery with large wall effect and small screw angle. At the same stent thickness, the helical stent exhibits larger wall shear stress than mesh stent. Endothelium proliferation is thus expected to decrease.

Self-deployable origami stent grafts as a biomedical application of Ni-rich TiNi shape memory alloy foil

This paper describes the design, manufacturing and properties of a new type of stent graft, the origami stent graft. Unlike conventional stent grafts which consist of a wire mesh stent and a covering membrane, the new origami stent graft is made from a single foldable foil with hill and valley folds. The Ni-rich titanium/nickel (TiNi) shape memory alloy (SMA) foil made by the newly developed ultrafine laminates method was used in order to produce the stent graft. The pattern of folds on the foil was produced by negative photochemical etching. The deployment of the stent graft is achieved either by SMA effect at the body temperature or by making use of property of superelasticity. A number of prototypes of the stent graft, which are the same size as standard oesophageal and aortal stent grafts, have been produced successfully. It was demonstrated that the stent graft deploy as expected.

Pathology of Stented Common Carotid Aneurysm in Dogs

To elucidate focal successive histological responses of the neck of wide-necked aneurysm after single stent implantation and stent-assisted coiling, an experimental wide-necked aneurysm model was surgically created in bilateral common carotid arteries of adult dogs. Balloon-expandable porous stents were positioned across the aneurysm necks on both sides. The aneurysm cavity of one side was additionally loosely coiled with Gugliemi detachable coils after stent implantation. The dogs were followed up with ultrasonography and angiography, then sacrificed at two days, one month, and one year and the aneurysm specimen was subjected to macro, micro, and electron microscopic observation. Stent implantation and coiling was successful in eight dogs. This investigation observed that single stent implantation slowed down the blood flow within the aneurysm, but barely induced thrombosis within the aneurysm. There was neointima formation over the stent mesh without thrombus within the aneurysm cavity, but it did not cover the whole aneurysm neck at one year.Aneurysms treated with stent-assisted coiling showed thrombosis within the aneurysms and neointima formation over the whole aneurysm orifice. These results suggest that the neointima could develop over bare stent filament without thrombus within the aneurysm cavity, coils could enhance thrombosis within the aneurysm cavity and facilitate neointima formation over the aneurysm orifice. Stent-assisted coiling may be an alternative option for the treatment of wide-necked aneurysms.

Cryoplasty for the Treatment of Femoropopliteal Arterial Disease: Will Freezing Solve the Problem of Cold Feet?

IN patients with symptomatic femoropopliteal arterial disease, percutaneous transluminal angioplasty (PTA) has been established as the first-line treatment for the majority of atherosclerotic lesions. A significant drawback of the procedure is the high rate of recurrent stenosis, which usually develops during the first 12 months after treatment (1). Initial failure of PTA caused by elastic recoil or hemodynamically relevant dissection can be managed by the implantation of stents, but clinical and experimental studies have shown that angioplasty triggers multiple cellular and molecular mechanisms that lead to a cascade of events that eventually results in increased vascular smooth muscle cell proliferation, synthesis of extracellular matrix, and consecutive formation of neointimal hyperplasia with luminal narrowing. Although stents may dramatically improve the appearance immediately after angioplasty, they have yet failed to show superior long-term efficacy, as intimal hyperplasia is even more pronounced after stent implantation than after PTA alone (2,3). In this respect, the search for new techniques and devices dedicated to endovascular management of peripheral artery disease is a contemporary issue and has to be continued. Each year, a vast number of experimental and clinical studies are performed to test refinements of current balloon/stent systems or to explore new and more innovative techniques for transluminal treatment of femoropopliteal obstructions. However, most of the new devices and strategies fail to show significant improvements in long-term outcome when finally introduced into clinical practice. Recanalization techniques like atherectomy (rotational and directional), excimer laser–assisted angioplasty, or subintimal angioplasty mainly address the appearance of the vessel immediately after angioplasty. Transluminal removal of the atherosclerotic plaque and/or creation of a subintimal channel results in a wider lumen (or neolumen) with a relatively smooth surface, while the profound vessel wall trauma of balloon angioplasty is avoided (4–7). However, the efficacy of these techniques in terms of reduction of neointimal hyperplasia has not been determined for treatment of femoropopliteal arterial disease. The same is true for cutting balloon angioplasty, which represents a modification of conventional balloon dilation. The cutting blades of the balloon make controlled longitudinal incisions into the plaque and reduce the force needed to dilate the vessel. This is thought to result in lower rates of dissection and to trigger a more benign course of arterial healing as a result of the limited stretch injury. Although cutting balloon angioplasty has been positively evaluated in the coronary circulation, there are few reports about its use for peripheral vessels (8). During the past two decades, nearly all available stent designs— mostly variations of balloon-expandable devices and thermal or self-expanding cobalt or nickel titanium alloy (ie, nitinol) systems—have been used at the femoropopliteal level for salvage of PTA or even off-label primary treatment. However, in randomized studies, stents have generally failed to prove a significant benefit when evaluated versus PTA alone (9). The fact that the stent design can have significant impact on neointimal thickness independently of the extent of stretch injury has been demonstrated by Garasic et al (10), thereby finding that the optimal structure for these devices might be a key requirement for restenosis prevention. Recent investigations have highlighted the various forces that affect a stent when implanted into the femoropopliteal artery. In this territory, a combination of stresses like longitudinal extension, torsion, flexion at the popliteal level, and muscle compression in the adductor channel are encountered that may significantly influence long-term success (11). Newer generations of nitinol self-expanding coil and mesh stents, which seem to provide the necessary flexibility in multiple dimensions, appear to have a positive impact on femoropopliteal patency, but this notion has not been confirmed in a randomized setting (12–14). Fabric-covered From the Department of Radiology, University Clinics Schleswig-Holstein, Campus Kiel, Arnold-Heller Str. 9, 24105 Kiel, Germany. Address correspondence to T.J.; E-mail: jahnke@medscape.com

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Endoscopic Deployment of Jostent Selfx for Malignant Hilar Biliary Stricture: A Pilot Study

Endoscopic Deployment of Jostent Selfx for Malignant Hilar Biliary Stricture: A Pilot Study Hirofumi Kawamoto, Takashi Nakanishi, Osamu Mizuno, Etsuji Ishida, Tsuneyoshi Ogawa, Yuko Okamoto, Hirotoshi Fukatsu, Yasushi Shiratori Objectives: The JoStent SelfX stent (Abbott Vascular Devices, Redwood City, California, USA) is manufactured from a nickel-titanium alloy (nitinol) with a high degree of flexibility and elasticity. The JoStent SelfX also offers a wide stent mesh, thin delivery shaft, and good pushability. Therefore, the JoStent SelfX in endoscopic deployment of partial stent-in-stent procedure may be useful in case of the hilar biliary stricture. This pilot study was conducted to evaluate the procedure of stent deployment and its short-term stent efficacy. Methods: Between March 2003 and October 2004, 17 patients (male: female 9:8, mean age 67 year old, mean observation period 146 days) with malignant hilar biliary stricture admitted to our hospital were enrolled. The patients consisted of 11 patients with hilar bile duct carcinoma, 3 with gallbladder carcinoma, and one each patient with pancreas, colon, and hepatocellular carcinoma. All patients received JoStent SelfX endoscopically. The first stent was inserted into the left lateral segment as the stent mesh space was widest at the branching. After finding the right biliary branch through the stent mesh using Naviguide (Olympus, Tokyo, Japan), the second stent was inserted into this branch as a partial stent-in-stent procedure. This procedure was termed as ‘‘L-R pattern’’. When the patients had Bismuth type 4 stricture with large tumor in the left hepatic lobe or left portal vein obstruction, the first stent was inserted into the right posterior segment and the second stent was inserted into anterior branch. This procedure was termed as ‘‘Ra-p pattern’’. Results: Classifying the pattern of stenosis according to Bismuth classification, 1 patient had type 2 stenosis, 3 patients type 3 stenosis, and 13 patients type 4 stenosis. Of these, the L-R pattern deployment was performed in 11 patients and the Ra-p pattern deployment in 6 patients. On the intention-to-treat basis, the L-R pattern deployment was not achieved in 1 patient due to the failure of passing guidewire through the stenosis. Thus, the success rate of deployment was 94% (16/17). The Ra-p deployment was performed to this patient. Conclusion: The JoStent SelfX is a suitable metallic stent to deploy in the hilar biliary stricture in partial stent-in-stent procedure. T1274 Prospective Randomized Controlled Trial of Endoscopic Sphincterotomy Compared with Endoscopic Papillary Balloon Dilatation for Bile Duct Stones: Late Complications After Stone Removal Yutaka Komatsu, Naotaka Fujita, Hiroyuki Maguchi, Ichiro Yasuda, Osamu Hasebe, Yoshinori Igarashi, Akihiko Murakami, Hidekazu Mukai, Tsuneshi Fujii, Kenji Yamao, Kensei Maeshiro Aim: To compare long term complications of the two treatments, endoscopic sphincterotomy (EST) and endoscopic papillary balloon dilation (EPBD), for bile duct stones, including stone recurrence. Methods: From March 2000 to March 2001, a randomized controlled trial was carried out involving 11 institutions. Two hundred eighty two patients who had bile duct stones less than 14 mm in minimum diameter on X-ray images were included in this study. Patients were randomized to EST or EPBD treatment groups. Follow-up data were collected by personal interview or telephone every year. Even if biliary events had not occurred, blood examination, abdominal ultrasound, MRCP and/or ERCP were performed to assess asymptomatic stone recurrence, as available. The clinical outcome after stone removal in three years was evaluated using Kaplan-Meier analysis supplemented by the log lank test. Results: See Table. Conclusion: Overall incidence of late complications in the EST group was higher than that in the EPBD group. Stone recurrence in the EST group was also more frequent than in the EPBD group. Furthermore, a higher rate of asymptomatic stone recurrence in EST group was proved by follow-up MRCP and/or ERCP. Further long-term follow-up study will elucidate the efficacy of both procedures. Abstracts

New guide wire technique for stent placement through an occluded self‐expandable metal stent: The hairpin technique

Self-expandable metal stents (SEMS) for malignant biliary strictures sometimes occlude, requiring the insertion of another stent. When a guide wire is advanced conventionally through the proximal portion of an occluded SEMS, the guide wire sometimes penetrates the stent mesh. The present study reports a new guide wire insertion technique that prevents this problem from occurring. In this new method of advancing a guide wire, the tip is not straight but bent into a curve. Because the advancing end of the guidewire is rounded like a hairpin, it cannot penetrate the stent mesh. Before cannulation, the flexible tip of the guide wire is extended out of the tip of the cannula in the descending duodenum and then cannulation is carried out as the flexible tip makes a hairpin curve. The guide wire with a maintained hairpin curve is advanced through the proximal end of the SEMS. The hairpin curve pops open and the guide wire straightens out when the guide wire has passed through the SEMS. After that, a second stent can be inserted over the guide wire. This technique has been utilized 14 times for occluded SEMS in 10 patients between June 2001 and September 2003. In all patients the technique served to ensure access to the biliary tree and successful placement of a second stent. This new hairpin guide wire technique was effective in preventing the guide wire from penetrating the stent mesh and, therefore contributed to successful stent placement within occluded SEMS.

BIOCOMPATIBILITY OF NITINOL AND STAINLESS STEEL IN THE BLADDER: AN EXPERIMENTAL STUDY

We tested the biocompatibility of nitinol, a nickel titanium alloy, and stainless steel (SS) as bladder implant materials. Rats received a nitinol implant, an SS implant or were sham controls. Two, 3, 6 and 8 weeks following implantation 24-hour voiding behavior studies were performed to investigate bladder irritation. All animals were sacrificed 8 weeks after implantation and a sample of urine was aspirated for culture. The bladders were examined by light microscopy and scanning electron microscopy (SEM). No visible encrustations or infections were noted in urine. Voiding frequency in the light period 6 weeks after implantation was significantly decreased in the 2 implant groups compared with sham controls. There were no other significant differences in frequency or mean volume per void in the light or dark periods at any time point. Light microscopy demonstrated similar implant tissue effects in all groups with little or no inflammation or fibrosis. Under SEM all implants showed a brittle, amorphous coating devoid of cells. The transition between the urothelium mucosa and the rod was smoother for SS than for nitinol, suggesting an affinity of SS for mucosa. In all nitinol rods discontinuity was present between the mucosa and rod. Nitinol and SS do not cause more irritation than the effects of surgery alone and the 2 materials seem to be biocompatible in the bladder. Nitinol may be more inert than SS based on SEM results.

Benign Esophagorespiratory Fistula Complicated by Deep Impaction of Stent Mesh in the Esophageal Wall

The placement of self-expandable metallic stents is widely accepted as a treatment for malignant esophagorespiratory fistulas [1] [2]. In contrast, there is ongoing discussion about the use of metallic stents for temporary treatment of benign and potentially reversible esophageal disorders, because after only a few weeks stent retrieval may already be difficult [2] [3] [4].

メッシュ型人工気管の力学特性

Many studies have been made to develop artificial tracheas with good biocompatibility and mechanical performance. We have designed a new type of mesh-type artificial tracheas. The basic frame of the specimens was composed of a mesh cylinder and stent attached to the outside of the cylinder. We have demonstrated from the mechanical tests that artificial tracheas with ring-type stents are stiffer than those with spiral-type stents. Artificial tracheas with arc-shaped shaped stents are half as stiff as artificial tracheas with whole ring stents. We have compared the mechanical properties of mesh-type artificial tracheas with nylon ring stents and those of canine tracheas, and have found the proper number of rings per unit length for the mesh-type artificial tracheas.

Integrin Profile and In Vivo Homing of Human Smooth Muscle Progenitor Cells

Recently, we identified circulating smooth muscle progenitor cells (SPCs) in human peripheral blood. The integrin profile of such progenitors is currently unknown and may affect their in vivo homing characteristics. In this study, we determined the integrin profile of vascular progenitors and SPC adhesion to extracellular matrix (ECM) proteins in vitro and in vivo. SPCs and endothelial progenitor cells (EPCs) were isolated from peripheral blood of healthy human subjects, and expression of surface integrins and adhesion to several vascular ECM proteins were determined. Homing of SPCs in vivo to specific ECM protein was determined by intracoronary infusion of fluorescent SPCs into porcine coronary arteries containing a fibronectin-coated mesh stent. SPCs had high expression of beta1 integrin, moderate expression of alpha1, low levels of alpha(v)beta3, and did not express alpha(v)beta5, beta2, alpha2beta1, or alpha4beta1 integrins. In contrast, EPCs had high expression of alpha2beta1, alpha(v)beta3, alpha(v)beta5, beta1, and alpha1 and minimal expression of alpha4beta1. Moreover, SPCs showed increased adherence to fibronectin and collagen type I compared with vitronectin, consistent with their integrin profile, and demonstrated a similar degree of in vivo attachment to fibronectin-coated mesh. These data for the first time show a spectrum of integrin expression on vascular progenitors and suggest the potential importance of integrins in mediating adherence of SPCs to specific ECM both in vitro and in vivo.

Glue Embolization of Aneurysm after Stenting in Canine Carotid Arteries - Technical Feasibility

Purpose: Coiling or infusion of embolic materials into a wide necked aneurysm can be performed with stenting. The purpose of our study is to assess the technical feasibility of aneurysm treatment with glue embolization after stenting. Materials and Methods: We used four Wallstents for surgically repairing eight canine carotid aneurysms. After confirmation of the aneurysms on the angiogram, we introduced a 6-7 F guiding catheter in order to deploy the stents. After stenting, we passed a microcatheter into the aneurysm lumen through the stent mesh. 28% glue was slowly injected until the glue cast completely filled the lumen. We evaluated the passage of a microcatheter through the stent meshwork, formation of the glue cast and the stents’ability to protection for any leakage of glue. The follow-up angiogram was obtained for two dogs, one to three times until 8 weeks, and then we sacrificed the dogs and performed pathologic examinations. Results: Stenting was successful in all cases except one in which the vessel was occluded because the stent was not completely expanded within the lumen. The microcatheter could not pass through the stent mesh in one aneurysm. The two week follow-up angiogram showed complete occlusion of the aneurysm and a patent carotid lumen in a case after successful stenting and glue embolization without distal migration of glue. Tungsten in the glue was noted to migrate out of aneurysm into the soft tissue of the neck. Histopathologic examination showed successful obliteration and stable organization of the aneurysmal lumen with ingrowth of fibroblasts and a foreign body reaction. In contrast, the aneurysms without the glue embolization being performed showed partially thrombosed aneurysmal lumens that became smaller and indistinct on the 8 week follow-up angiograms. Histopathologic examination showed a disorganized thrombus with numerous recanalizations. Conclusion: Glue embolization after stenting could be performed for aneurysm without distal migration of the glue or gluing of the catheter. This concept appears to be useful for applications to the further research and the treatment of aneurysm.