冠状动脉支架膨胀行为的有限元分析

冠状动脉支架作为经皮穿刺冠状动脉成形术中保持病变血管畅通的核心器件,其在手术过程中受球囊作用的扩张特性以及球囊撤出后的反弹行为对支架植入术的成功有着重要的影响。利用有限元的方法系统地研究了专利支架设计,其筋的尺寸变化和支架扩张尺度的不同对支架膨胀行为的影响。结果显示,增加支架筋的宽度或厚度提高了使支架迅速扩张所需的临界内压力,支架轴向长度的变化只与其结构和最终膨胀状态紧密相关。在结构一定的情况下,支架所用材料可能是影响支架反弹指标的主要因素。模型校核和SEM观察表明,有限元模拟可以在一定程度上替代支架原型测试工作。     

交变磁场诱导冠状动脉支架的升温

背景:对于药物涂层支架的安全性问题目前尚存在争议。磁诱导热疗可以利用交变磁场诱导磁介质升温,对局部病灶进行热疗。由于心脏支架多以不锈钢、镍、铬等合金材料构成,因此具备在磁场下的升温条件,并且目前国内外尚无通过磁诱导心脏支架升温的相关报道。目的:观察不同冠状动脉支架在交变磁场下的升温情况。探讨磁场强度、磁场频率、磁场方向及支架的材质对冠状动脉支架升温的影响规律。方法:将不同材质冠状动脉支架(316L型、镍钛合金、钴铬合金)置于交变磁场中,调节磁场参数(场强、频率)和支架长轴与磁场方向的夹角,观察上述因素对交变磁场诱导冠状动脉支架升温的影响。结果与结论:支架材料对磁场诱导升温有显著影响,并以316L型支架升温效果最好;随着支架长轴与磁场方向所成角度的增大,升温效果明显降低;随着交变磁场频率及电流强度增加温度升高更明显。     

冠脉支架设计的材料适应性研究

目的 基于一种确定的冠脉支架设计,分析不同材料的适应性,建立支架设计-材料选择的评价方法。 方法针对可能应用的 5 种支架材料,利用有限元数值模拟方法分析支架在血管中的扩张性能,考察支架设计和材料的安全性及可用性。 针对不可降解材料重点考察支架在长期植入后的耐疲劳性能;对可降解材料分析其降解过程中 的支撑力变化,明确支架所能提供的支撑力的规律。 结果 针对确定的冠脉支架设计,模拟显示 316L 不锈钢和L605 钴铬合金支架的径向回弹率分别是 26% 和 19% ,轴向缩短率分别为 0. 22% 和 0. 28% ,最大等效应力分别为551. 2、829. 1 MPa,疲劳动态安全系数分别为 1. 36 和 1. 67,针对可降解材料 AZ31 镁合金、铁和左旋聚乳酸(PLLA),基于该设计的支架的模拟破坏时间分别为 30 h 和 180、270 d。 结论 基于本文的支架设计,L605 钴铬合金具有最佳的扩张性能和耐疲劳性能,可以满足临床需求。 相较于 AZ31 的快速降解破坏,铁支架和 PLLA 支架的力学性能接近,但仍需结构优化后才能满足临床需求。 有限元数值模拟,尤其是扩张性能和耐疲劳性能分析,可以有效模拟支架力学行为,并为支架制造材料选择和设计优化提供依据。     

球扩式介入主动脉瓣膜支架的抗迁移力学行为

目的 研究球扩式主动脉瓣膜支架植入后的抗迁移力学行为。 方法 建立球扩式瓣膜支架介入主动脉瓣膜后的抗迁移力学模型,采用数值模拟方法研究不同瓣环椭圆率、摩擦因数、瓣膜支架材料及自体瓣叶钙化情况对瓣膜支架抗迁移力的影响规律。 结果 当主动脉瓣环椭圆率为 0. 2、0. 3、0. 4、0. 5 时,对应的最大抗迁移力分别为12. 37、10. 94、8. 50、4. 75 N;当摩擦因数为 0. 1、0. 2、0. 3 时,瓣膜支架的最大抗迁移力分别为 8. 98、11. 00、13. 10 N;L605 钴铬合金制成的瓣膜支架的锚定性要优于 316L 不锈钢制成瓣膜支架的锚定性,其对应的最大抗迁移力分别为 13. 10、9. 82 N;当自体瓣叶发生钙化时,最大抗迁移力为 13. 1 N,而未钙化时最大抗迁移力仅为 5. 51 N,相比而言降低了 57. 9% 。 结论 随着主动脉瓣瓣环椭圆率不断增大,瓣膜支架的锚定性逐渐降低;随着瓣膜支架与组织间的摩擦因数不断增大,最大抗迁移力也不断增大;L605 钴铬合金制成的瓣膜支架比 316L 不锈钢制成瓣膜支架的锚定性能优异;瓣膜发生钙化情况下瓣膜支架的锚定性要优于未发生钙化时的锚定性。 研究结果为抗迁移瓣膜支架的结构设计和临床选择提供重要的科学依据。     

雷帕霉素洗脱钴基合金支架系统

上海微创医疗器械(集团)有限公司自主设计研发FIREKINGFISHER?冠脉雷帕霉素洗脱钴基合金支架系统,由球囊扩张型冠脉支架、钴铬合金载药涂层和支架输送系统组成。IREKINGFISHER?药物洗脱支架保留了前代产品FIREBIRD2?支架平台设计的基础上,对其输送系统进行优化,在保持球囊扩张性能不变的基础上,进一步赋予产品良好的通过性和推送性,进而提高支架在病变部位通过性。球囊内管内层含氟,导丝走形更爽滑支架钴基合金平台,支架壁薄但仍能提供良好的径向支撑力,具有优良的抗疲劳和抗腐蚀性,X线显影佳,由于其为非磁性材料适于MRI检查。     

纤维蛋白原对模拟人工体液中不锈钢腐蚀行为的影响

在模拟人工体液PBS溶液中采用电化学测试技术考察了纤维蛋白原对冠状动脉支架用SUS316L和SUS317L不锈钢腐蚀行为的影响。结果表明：纤维蛋白原的存在增大了介质对材料的浸蚀性。在含纤维蛋白原的溶液中,试样的自腐蚀电位负移,维钝电流密度增大,点蚀击穿电位（Eb)降低。并利用扫描电镜观察了吸附现象,发现吸附的纤维蛋白原呈白色条状,不连续地分布在材料表面。     

医用316L不锈钢接骨板固定股骨的有限元方法分析

目的用三维有限元方法对医用316L不锈钢接骨板、螺钉及股骨进行应力计算,最终分析316L不锈钢接骨板对股骨的应力遮挡效应.方法首先建立医用316L不锈钢接骨板、螺钉及股骨的三维几何模型;网格划分后建立对应的三维有限元模型;在定义材料属性的基础上,加载边界条件,对站立位状态下的接骨板及螺钉强度进行有限元计算,同时分析股骨应力遮挡问题.结果通过对螺钉未加压状态和加压状态下股骨所受应力与站立位时正常股骨应力的对比,得出医用316L不锈钢接骨板及螺钉对股骨的应力遮挡效应.结论医用316L不锈钢接骨板及螺钉对股骨产生明显的应力遮挡效应,仅靠螺钉加压对应力遮挡效应的降低作用有限.本文建立的接骨板对股骨应力遮挡的分析方法可广泛应用于其他骨骼骨折应力遮挡的分析.     

生物医学用金属材料耐体液腐蚀研究概况

前言对生物医学用金属材料耐体液腐蚀的要求很高。在一般工程技术应用中,把腐蚀速度为25.4微米/年的材料称为耐蚀性极好的材料。但在医学上,要求金属材料的腐蚀速度等于或少于2.54微米/年。即对耐蚀性要求提高10倍以上。金属材料移植到人体后,经常出现腐蚀现象。文献〔1〕引证Scales等人的研究结果指出:18/8不锈钢器件平均有36%的界面发生腐蚀。316L不锈钢组合件缝隙腐蚀达91%。钴-铬合金、钛合金也产生缝隙腐     

三种心血管支架用金属材料的表面特性与生物相容性

考察了316L不锈钢、NiTi合金和TLM钛合金的表面特性、血液相容性和内皮化能力,以筛选心血管支架材料。结果表明,316L不锈钢具有较好的血液相容性,内皮细胞生长良好,但耐蚀性差;NiTi合金的耐蚀性和血液相容性优良,内皮细胞生长状况良好。TLM合金由生物相容性元素组成,其耐蚀性好,但表面粗糙度较高,亲水性差,影响了材料的血液相容性和内皮化能力。作为心血管支架材料,三种材料中NiTi合金具有最好的生物相容性。     

316L不锈钢冠状动脉支架再狭窄研究进展

支架植入术是解决经皮冠状动脉血管形成术(PTCA)后再狭窄的有效途径,但支架植入后 仍存在一定程度的再狭窄。本文详细阐述了临床上常用的316L不锈钢冠状动脉支架植入后再狭窄的机 理及其改性研究进展。     

球囊配置对冠状动脉支架扩张和回弹行为的影响

探讨不同球囊配置对冠状动脉支架扩张和回弹行为的影响,以期从球囊配置的角度为球囊 支架系统的有限元模拟策略及优化设计提供一定的指导。采用SolidWorks建立Cypher支架模型及4种Raptor球囊模型(无褶、三褶、六褶和六褶锥形末端球囊模型),使用Hypermesh软件进行各模型的网格划分,应用Abaqus Explicit模块完成不同球囊 支架系统的扩张和回弹模拟。结合制造商提供的压力 直径顺应性曲线验证模拟结果的合理性,并引入“狗骨头”率、轴向缩短率及径向回弹率等3个参数评估不同球囊 支架系统模拟效果的优劣。结果表明,无褶球囊 支架系统在较低压力下扩张明显,各项参数较其他球囊 支架系统很大;六褶球囊 支架系统相较三褶在扩张中的压力 直径顺应性曲线更接近制造商提供的数据,且轴向缩短率（6.1%）和径向回弹率（1.9%）也均优于三褶;六褶锥形末端球囊 支架系统由于与导管间的连接使得“狗骨头”率（12.0%）和轴向缩短率（3.85%）明显降低。对于球囊 支架系统的有限元模拟,在支架的初级设计阶段可以采用理想的无褶球囊模型进行支架的扩张模拟,但考虑支架的瞬态行为和最终定位时,球囊的褶皱和锥形末端设计等几何特征不可忽略;在球囊 支架系统的优化设计中,球囊褶数可以从三褶调整为六褶,更有益于支架的均匀扩张。     

Mesenchymal stem cell seeding promotes reendothelialization of the endovascular stent

This study is designed to make a novel cell seeding stent and to evaluate reendothelialization and anti-restenosis after the stent implantation. In comparison with cell seeding stents utilized in previous studies, Mesenchymal stem cells (MSCs) have advantages on promoting of issue repair. Thus it was employed to improve the reendothelialization effects of endovascular stent in present work. MSCs were isolated by density gradient centrifugation and determined as CD29(+) CD44(+) CD34(-) cells by immunofluorescence and immunocytochemistry; gluten and polylysine coated stents were prepared by ultrasonic atomization spray, and MSCs seeded stents were made through rotation culture according to the optimized conditions that were determined in previous studies. The results from animal experiments, in which male New Zealand white rabbits were used, show that the reendothelialization of MSCs coated stents can be completed within one month; in comparison with 316L stainless steel stents (316L SS stents) and gluten and polylysine coated stents, the intimal hyperplasia and in-stent restenosis are significantly inhibited by MSCs coated stents. Endovascular stent seeded with MSCs promotes reendothelialization and inhibits the intimal hyperplasia and in-stent restenosis compared with the 316L SS stents and the gluten and polylysine coated stents.     

The Stress–Strain Behavior of Coronary Stent Struts is Size Dependent

Coronary stents are used to re-establish the vascular lumen and flow conditions within the coronary arteries; the typical thickness of a stent strut is 100 m, and average grain sizes of approximately 25 m exist in stainless steel stents. The purpose of this study is to investigate the effect of strut size on the stress strain behavior of 316 L stainless steel. Other materials have shown a size dependence at the micron size scale; however, at present there are no studies that show a material property size dependence in coronary stents. Electropolished stainless steel stent struts within the size range of 60–500 m were tensile tested. The results showed that within the size range of coronary stent struts a size dependent stress–strain relationship is required to describe the material. Finite element models of the final phase of fracture, i.e., void growth models, explained partially the reason for this size effect. This study demonstrated that a size based stress–strain relationship must be used to describe the tensile behavior material of 316 L stainless steel at the size scale of coronary stent struts. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr, 8780Rb, 8719Uv     

Effects of overexpansion on stents' recoil, symmetry/asymmetry, and neointimal hyperplasia in aortas of hypercholesterolemic rabbits.

BACKGROUND: It is not known whether overexpansion modifies stent recoil, symmetric distribution of struts, and neointimal hyperplasia. OBJECTIVES: The objectives were (a) to evaluate whether stent overexpansion modifies the geometric configuration of the stent in the arterial wall, (b) to determine the relationship between overexpansion and stent recoil, and (c) to evaluate the relationship between the distribution of struts and neointimal hyperplasia. METHODS: Twenty tubular stainless steel 316L stents (3.0 and 3.5 mm in diameter) were implanted at 20 and 10 atm, respectively, in the abdominal aorta of New Zealand rabbits fed a hypercholesterolemic diet (1% cholesterol). Sham operations were also performed in seven animals. Eight weeks after implantation or sham operation, an intravascular ultrasound (IVUS) study was performed to measure stent recoil and aid in stent classification (symmetric or asymmetric) according to strut distribution. The degree of injury and neointimal hyperplasia were also evaluated in hematoxylin-eosin stained sections. RESULTS: The symmetry/asymmetry of stents assessed by IVUS, as well as the neointimal hyperplasia, was similar in both groups. Stent recoil was significantly greater in the 3.0-mm stent (overexpanded) group (0.28+/-0.02 mm), as compared with stent recoil in the 3.5-mm stent group (0.10+/-0.01 mm, P<.05). The neointimal hyperplasia in histological slices, independent of the implant technique, was predominantly in zones with higher strut concentration as compared with zones with fewer struts. CONCLUSIONS: Stent overexpansion enhanced stent recoil and did not modify symmetric and asymmetric strut distribution. Neointimal hyperplasia was not modified by the implant technique. Interestingly, significant hyperplasia was observed in locations with greater strut concentration, independent of overexpansion.     

Bioresorbable polymeric stents: current status and future promise

Metal stents and, more recently, polymer-coated metal stents are used to stabilize dissections, eliminate vessel recoil, and guide remodeling after balloon angioplasty and other treatments for arterial disease. Bioresorbable polymeric stents are being developed to improve the biocompatibility and the drug reservoir capacity of metal stents, and to offer a transient alternative to the permanent metallic stent implant. Following a brief review of metal stent technology, the emerging class of expandable, bioresorbable polymeric stents is described, with emphasis on developments in the authors' laboratory.     

Studying the non-uniform expansion of a stent influenced by the balloon

Non-uniform expansion of cardiovascular stents, which exists widely in experiments, has a large influence on stent safety, but has seldom been studied in depth until now. In this paper we use a folded balloon with friction to expand a stent through finite element method (FEM), and study how this influences non-uniform expansion of the stent. The simulations were carried out using ABAQUES software. The results show that the stent expands non-uniformly only when the fold and friction are considered together in the FEM model. The extent of non-uniformity during expansion increases with rising friction coefficient values; with the same friction coefficient but different stent locations on the balloon the extent of non-uniform deformation is different. On the other hand, compared to a tri-folded balloon, a six-folded balloon clearly decreases the expansive non-uniformity, which means that by increasing the number of the folded parts of balloon the stent expands more uniformly.     

Review: Bioresorbable polymeric stents: current status and future promise

Metal stents and, more recently, polymer-coated metal stents are used to stabilize dissections, eliminate vessel recoil, and guide remodeling after balloon angioplasty and other treatments for arterial disease. Bioresorbable polymeric stents are being developed to improve the biocompatibility and the drug reservoir capacity of metal stents, and to offer a transient alternative to the permanent metallic stent implant. Following a brief review of metal stent technology, the emerging class of expandable, bioresorbable polymeric stents is described, with emphasis on developments in the authors' laboratory.     

Process of prototyping coronary stents from biodegradable Fe–Mn alloys

Biodegradable stents are considered to be a recent innovation, and their feasibility and applicability have been proven in recent years. Research in this area has focused on materials development and biological studies, rather than on how to transform the developed biodegradable materials into the stent itself. Currently available stent technology, the laser cutting-based process, might be adapted to fabricate biodegradable stents. In this work, the fabrication, characterization and testing of biodegradable Fe–Mn stents are described. A standard process for fabricating and testing stainless steel 316L stents was referred to. The influence of process parameters on the physical, metallurgical and mechanical properties of the stents, and the quality of the produced stents, were investigated. It was found that some steps of the standard process such as laser cutting can be directly applied, but changes to parameters are needed for annealing, and alternatives are needed to replace electropolishing.     

砷涂层支架置入后的血管组织相容性

背景：研究认为,三氧化二砷可以抑制血管平滑肌细胞的增殖,促进其凋亡,那么砷对血管平滑肌细胞的增生是否也有同样的抑制作用,砷涂层血管支架能否与血管组织相容,早期较好地被血管内膜覆盖或达到减少内膜过度增生的作用？ 目的：观察砷涂层血管支架的血管组织相容性。 方法：取大耳白家兔14只,随机分为2组,分别在腹主动脉处植入砷涂层316 L不锈钢支架和316 L不锈钢裸支架,植入28 d后结扎支架部位血管的远端和近端,取下支架部位的血管行苏木精-伊红染色,光镜检查。 结果与结论：①大体观察：支架处的血管外径稍大于相邻处血管的外径,呈扩张状态,无肉眼可见的血栓,切开支架,支架表面可见光滑的新生内膜形成,新生内膜表面光滑。②光镜观察：支架丝位于血管的中层,中层平滑肌被压,支架丝周边,血管内膜平滑肌增生,使血管内膜增厚。支架丝的血管腔面可见新生的血管内膜形成并覆盖支架丝,支架丝与血管组织之间可见一薄层黑色物质,为涂层药物砷及其化合物,证明砷涂层支架可以被血管组织覆盖,具有良好的血管组织相容性。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：