镍钛形状记忆合金血管内支架组织相容性实验研究

将锥形记忆合金支架分别植入６只猪右侧髂动脉。用以研究镍钛形状记忆合金血管内支架生物相容性，支架植入前入植入后８个月，观测动物血常规，肝肾功能以及毛发中镍钛元素含量，均无明显变化（Ｐ〉０．０５），支架植入后８个月处死动物，全身重要脏器（肝、脾、肾、肺、心、脑等）病理学检查结构正常，无淋巴细胞和单核细胞浸润，支架植入部位上游血管壁内膜光滑，内皮细胞结构正常，内弹力板完整，支架植入段为完整肉芽组织阻塞，     

Self-expanding stents in transjugular intrahepatic portosystemic shunt: experience with nitinol Strecker stents

The aim of our study was to evaluate the performance and efficacy of a new self-expanding stent (nitinol Strecker stent) in the transjugular intrahepatic portosystemic shunt (TIPS) procedure. We have successfully placed 64 nitinol Strecker stents in 48 patients. The average portosystemic gradient decreased from 22 to 11 mm Hg. Balloon dilatation was necessary in 12 of 35 angiographically controlled cases at 5 days (34%), because of incomplete stent expansion, small thrombi within the stent or obstruction. At 1–6 months stent malfunctions occurred in 8 of 23 patients who underwent control angiography (34%) and at 6–24 months in 6 of 7 patients (85%). Rebleeding occurred in 2 of 39 patients (follow-up > 1 month) (5%) and temporary crises of de novo encephalopathy were observed in 11 of 48 patients (23%). Refractory ascites completely resolved in 4 of 6 patients (66%) and improved in the remaining 2 cases. Compared with other self-expanding stents, nitinol Strecker stents seem to be equally effective in TIPS; no increase in complication rate was observed, either clinical or stent-related. Correspondence to: P. Rossi     

A comparison of balloon- and self-expanding stents

This paper summarizes some of the key differences between self-expanding and balloon-expanding stents, aligning engineering and design differences with clinical performance. While neither type of stent can be considered universally superior, the differences are significant enough to make each type more appropriate in specific circumstances. Many of the differences concern long-term outcome, for which there is still insufficient data.     

Effect of Slip Time in Forming Neo‐Esophageal Stenosis After Replacement of a Thoracic Esophagus With Nitinol Artificial Esophagus

Attempts have been made to investigate the effect of slip time of nitinol artificial esophagus for forming neo‐esophageal stenosis after replacement of a thoracic esophagus with nitinol artificial esophagus in 20 experimental pigs. The pigs whose slip time was less than 90 days postoperatively had severe dysphagia (Bown's III) immediately after they were fed, and the dysphagia aggravated gradually later on (Bown's III–IV). The pigs whose slip time was more than 90 days postoperatively had mild/moderate dysphagia (Bown's I–II) immediately after they were fed, and the dysphagia relieved gradually later on (Bown's II‐I‐0). The ratios between the diameter of neo‐esophagus in different slip time and normal esophagus were 25% (at 2 months postoperatively), 58% (at 4 months postoperatively), and 93% (at 6 months postoperatively), respectively. The relationship between nitinol artificial esophagus slip time and neo‐esophageal stenosis showed a positive correlation. After replacement of a thoracic esophagus with nitinol artificial esophagus, the artificial esophageal slip time not only affected the original diameter of the neo‐esophagus immediately, but also affected the neo‐esophageal scar stricture forming process later on. The narrowing of neo‐esophagus is caused by overgrowth of scar tissue. But there is the positive correlation between artificial esophagus slip time and neo‐esophageal stenosis, so this can be a way of overcoming neo‐esophageal stenosis by delaying slip time of artificial esophagus.     

Design Method of a Foldable Ventricular Assist Device for Minimally Invasive Implantation

To date, ventricular assist devices (VADs) have become accepted as a therapeutic solution for end‐stage heart failure patients when a donor heart is not available. Newer generation VADs allow for a significant reduction in size and an improvement in reliability. However, the invasive implantation still limits this technology to critically ill patients. Recently, expandable/deployable devices have been investigated as a potential solution for minimally invasive insertion. Such a device can be inserted percutaneously via peripheral vessels in a collapsed form and operated in an expanded form at the desired location. A common structure of such foldable pumps comprises a memory alloy skeleton covered by flexible polyurethane material. The material properties allow elastic deformation to achieve the folded position and withstand the hydrodynamic forces during operation; however, determining the optimal geometry for such a structure is a complex challenge. The numerical finite element method (FEM) is widely used and provides accurate structural analysis, but computation time is considerably high during the initial design stage where various geometries need to be examined. This article details a simplified two‐dimensional analytical method to estimate the mechanical stress and deformation of memory alloy skeletons. The method was applied in design examples including two popular types of blade skeletons of a foldable VAD. Furthermore, three force distributions were simulated to evaluate the strength of the structures under different loading conditions experienced during pump operation. The results were verified with FEM simulations. The proposed two‐dimensional method gives a close stress and deformation estimation compared with three‐dimensional FEM simulations. The results confirm the feasibility of such a simplified analytical approach to reveal priorities for structural optimization before time‐consuming FEM simulations, providing an effective tool in the initial structural design stage of foldable minimally invasive VADs.     

Self-Expandable nitinol stent for cardiovascular applications: canine and human experience

The initial experimental and clinical experience with the cardiovascular self-expandable Nitinol stent (vascular and coronary versions) is described. The stent is designed as a helical coil with two terminal balls that are used for restraining it on the delivery catheter. Upon release, the stent self-expands immediately. A temporary stent version continues with a long wire that can be removed by pulling it as a straight wire through a small profile catheter. The stent uncoils in its own groove upon removal, a relatively atraumatic procedure. The stents have been studied in dogs and in peripheral arteries in patients. The results show a transient nonocclusive proliferative response to the stent that is maximal at 3–6 mo. The removability of the permanent stent has been proven in dogs. The preliminary results in patients are encouraging and demonstrate its feasibility for permanent and potentially temporary arterial support. © 1994 Wiley-Liss,Inc..     

双侧无铆型房间隔缺损封堵器的实验研究

目的在犬房间隔缺损(ASD)模型上评价双侧无铆型ASD封堵器的疗效、安全性和生物相容性。方法自行设计封堵器是由镍钛合金丝编织成的网状结构,外形呈双盘状,其左房面平整,右房面中间凹陷,中央有与推送杆相接的连接袢,内衬有三层聚酯膜。犬ASD模型建立采用房间隔穿刺结合球囊扩张方法,模拟临床经导管封堵ASD过程,闭合人工制备的ASD。用心脏超声观察封堵器位置及封堵器对右、左房室瓣功能的影响。术后1、2、3、6个月分别处死动物行组织学检查,观察封堵器周围及表面的组织学反应。结果8条犬成功制作ASD模型并封堵,超声显示封堵器位置固定良好,不影响右、左房室瓣功能。各观察时间点肉眼见所有封堵器表面光滑均覆有薄层的新生内膜。3个月后封堵器表面完全内皮化,光镜和电镜检查显示封堵器置入部位周围组织无明显的炎症反应。6个月扫描电镜观察金属丝无腐蚀。HE染色显示肺、肝、脾、肾、胰等组织无血栓栓塞、炎症表现。结论双侧无铆型ASD封堵器操作简便、使用安全及有良好的生物相容性,提示自制的ASD封堵器将可安全地应用于临床。     

Transcatheter mitral valve replacement: tissue in-growth after 4 weeks

Open in a separate window OBJECTIVESTissue reaction to transcatheter mitral valve replacement in the mitral annulus remains to be elucidated.METHODSTrileaflet porcine pericardial valves were sewn onto self-expanding d-shaped nitinol stents, which were delivered transapically and in an off-pump fashion into the mitral position of 10 pigs. After at least 4 weeks of follow-up, gross pathological assessment and histological examination were performed. The specimens were stained with Movat’s pentachrome, Elastica-van-Gieson and von Kossa staining. The leucocytes, B cells, T cells or macrophages were detected by specific immunohistochemical staining.RESULTSProper stent positioning in the mitral annulus was achieved in 9/10 animals. Nine of 10 animals survived the desired observation period. In all but one, the mitral valve stent was well integrated into the left atrium and perpendicularly embedded into the annulus by 85 ± 24%. One animal had minor fractures in the nitinol struts and another animal showed tearing of 1 of 4 tethers. Histological examination demonstrated no major tissue reaction with the nitninol struts but well-preserved overall structures around the mitral annulus in 8/9 cases.CONCLUSIONSThis is the first report demonstrating good in-growth of transcatheter-delivered anatomically shaped mitral valve stents after at least 4 weeks of follow-up. Histological examination demonstrated progressive healing and neointimalization.     

The OTSC® Proctology clip system for anorectal fistula closure: the ‘Anal Fistula Claw’: Case report

Abstract

Surgical treatment of high or complex anal fistulas often renders unsatisfying results. This is the report of the first successful closure of such anal fistula using a special Nitinol clip and applicator, the OTSC® Proctology system (Ovesco AG, Tuebingen, Germany): A 54-year old female patient was suffering from a high transsphincteric anal fistula. After seton drainage of the fistula for ten weeks, the fistula track was debrided using a special fistula brush. After transanal clip release from the applicator, the internal fistula opening was adequately closed by the clip. Eight months after clip closure the fistula had healed and the clip was removed using the OTSC® Proctology Clip Cutter. Fistula closure using the OTSC® Proctology system represents a promising sphincter-preserving minimally invasive procedure.     

A rare life-threatening complication of migrated nitinol self-expanding metallic stent (Ultraflex)

The use of self-expanding metallic stents (SEMS) as esophageal endoprosthesis represents an advancement in the palliation of dysphagia from unresectable esophageal carcinoma. However, the problem of stent migration persists. Although most migrated stents have a benign outcome, complications do occur. Rare reports of intestinal obstruction have been confined to the stiff plastic and stainless-steel stents. We report the first case of intestinal obstruction secondary to the pliable Nitinol SEMS (Ultraflex) migration.