Geometry Governs Mechanics of Cardiovascular Stents

2009 ◽  
Author(s):  
Graeham R. Douglas ◽  
Tho Wei Tan ◽  
Tim Bond ◽  
A. Srikantha Phani
Keyword(s):  
Arterial Wall ◽  
Mechanical Response ◽  
Neointimal Hyperplasia ◽  
Stent Migration ◽  
Contributing Factors ◽  
Poisson Effect ◽  
Element Analysis ◽  
Cardiovascular Stents ◽  
Stent Restenosis ◽  
Longitudinal Strains

Cardiovascular stents are tubular lattice structures implanted into a stenosed artery to provide adequate lumen support and promote circulation. Commonly encountered complications are stent migration, NeoIntimal Hyperplasia (NIH), and damage to the arterial wall. Central to all these problems is the mechanical response of a stent to forces operating in situ including stent-artery interaction. The influence of geometry or repetitive pattern of the stent upon its mechanical response is the subject of this study. We focus on damage to the arterial wall caused by the stent which can lead to eventual in-stent restenosis. Stent-artery compliance mismatch and longitudinal strain due to Poisson effect are hypothesized as the main contributing factors to restenosis. Finite Element Analysis (FEA) is employed to compare radial compliance and longitudinal strains of different stent geometries. Existing geometrical calculations in the literature [1] are applied to stents of different geometries to compute a non-dimensional NIH index. The main finding is that hybrid lattice stent designs exhibit negligible longitudinal strains (Poisson effect) as the stent expands/contracts during each Cardiac cycle. Wall stresses can be minimized though a careful tailoring of stent geometry.

Performance of Self-Expanding Nitinol Stent in a Curved Artery: Impact of Stent Length and Deployment Orientation

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Shijia Zhao ◽  
Linxia Gu ◽  
Stacey R. Froemming
Keyword(s):  
Neointimal Hyperplasia ◽  
Wall Stress ◽  
Stent Migration ◽  
Clinical Implications ◽  
Stent Deployment ◽  
Element Analysis ◽  
Nitinol Stent ◽  
Curved Artery ◽  
Stent Length ◽  
The Impact

The primary aim of this work was to investigate the performance of self-expanding Nitinol stents in a curved artery through finite element analysis. The interaction between a PROTÉGÉTM GPSTM self-expanding Nitinol stent and a stenosed artery, as well as a sheath, was characterized in terms of acute lumen gain, stent underexpansion, incomplete stent apposition, and tissue prolapse. The clinical implications of these parameters were discussed. The impact of stent deployment orientation and the stent length on the arterial wall stress distribution were evaluated. It was found that the maximum principal stress increased by 17.46%, when the deployment orientation of stent was varied at a 5 deg angle. A longer stent led to an increased contact pressure between stent and underlying tissue, which might alleviate the stent migration. However, it also caused a severe hinge effect and arterial stress concentration correspondingly, which might aggravate neointimal hyperplasia. The fundamental understanding of the behavior of a self-expanding stent and its clinical implications will facilitate a better device design.

Continuous Subcutaneous Angiopeptin Treatment Significantly Reduces Neointimal Hyperplasia in a Porcine Coronary In-Stent Restenosis Model

Circulation ◽  
1997 ◽  
Vol 95 (2) ◽  
pp. 449-454 ◽  
Author(s):  
Mun K. Hong ◽  
Kenneth M. Kent ◽  
Roxana Mehran ◽  
Gary S. Mintz ◽  
Fermin O. Tio ◽  
...  
Keyword(s):  
Neointimal Hyperplasia ◽  
Stent Restenosis ◽  
In Stent Restenosis

Endovascular treatment of aortic coarctation with a novel BeGraft aortic stent in children and young adults: a single-centre experience with short-term follow-up results

2021 ◽  
pp. 1-8
Author(s):  
Murat Muhtar Yılmazer ◽  
Gamze Vuran ◽  
Timur Meşe ◽  
Barış Güven ◽  
Cüneyt Zihni ◽  
...  
Keyword(s):  
Abdominal Aorta ◽  
Aortic Coarctation ◽  
Paediatric Population ◽  
Stent Migration ◽  
Long Term Results ◽  
Single Centre ◽  
Surgical Closure ◽  
Stent Restenosis ◽  
Stent Diameter

Abstract Objectives: We present our experience and outcomes with the BeGraft in the treatment of aortic coarctation in a predominantly paediatric population. Methods: This study includes a retrospective analysis of patients who had Begraft aortic stent implantation between 2018 and 2020 from a single centre. Results: The BeGraft aortic stent was used in 11 patients (7 males, 4 females) with a median age of 14 (13–21) years and a median weight of 65 (46–103) kg. Coarctation was native in five patients and recurrent in six patients. Median stent diameter and length were 16 mm and 38 mm, respectively. The median peak-to-peak pressure was 30 (12–55) mmHg before the procedure and 5 (0–17) mmHg after the procedure. The stenting procedure was successful in 10 of the 11 patients. Stent migration to the abdominal aorta occurred on post-procedure day 1 in the 21-year-old patient, who had previously undergone surgical closure of the ventricular septal defect and balloon angioplasty for coarctation. After repositioning failed, the stent was safely fixed in the abdominal aorta. Strut distortion also occurred during balloon retrieval in one patient, but no aneurysm or in-stent restenosis was observed at 1-year follow-up. The patients were followed for a median of 14 (4–25) months and none required redilation. Conclusions: Our initial results demonstrated that the BeGraft aortic stent effectively reduced the pressure gradient in selected native and recurrent cases. Despite advantages such as a smaller sheath and low profile, more experience and medium- to long-term results are needed.

scholarly journals Discrete element analysis of the punching behaviour of a secured drapery system: from laboratory characterization to idealized in situ conditions

2021 ◽  
Author(s):  
Antonio Pol ◽  
Fabio Gabrieli ◽  
Lorenzo Brezzi
Keyword(s):  
Mechanical Response ◽  
Steel Wire ◽  
Discrete Element ◽  
Wire Mesh ◽  
Steel Plates ◽  
Loading Conditions ◽  
Element Analysis ◽  
In Situ Conditions ◽  
Wire Meshes

AbstractIn this work, the mechanical response of a steel wire mesh panel against a punching load is studied starting from laboratory test conditions and extending the results to field applications. Wire meshes anchored with bolts and steel plates are extensively used in rockfall protection and slope stabilization. Their performances are evaluated through laboratory tests, but the mechanical constraints, the geometry and the loading conditions may strongly differ from the in situ conditions leading to incorrect estimations of the strength of the mesh. In this work, the discrete element method is used to simulate a wire mesh. After validation of the numerical mesh model against experimental data, the punching behaviour of an anchored mesh panel is investigated in order to obtain a more realistic characterization of the mesh mechanical response in field conditions. The dimension of the punching element, its position, the anchor plate size and the anchor spacing are varied, providing analytical relationships able to predict the panel response in different loading conditions. Furthermore, the mesh panel aspect ratio is analysed showing the existence of an optimal value. The results of this study can provide useful information to practitioners for designing secured drapery systems, as well as for the assessment of their safety conditions.

scholarly journals Multifunctional Biodegradable Vascular PLLA Scaffold with Improved X-ray Opacity, Anti-Inflammation, and Re-Endothelization

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1979
Author(s):  
Ho In Lee ◽  
Yun Heo ◽  
Seung-Woon Baek ◽  
Da-Seul Kim ◽  
Duck Hyun Song ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Inflammatory Responses ◽  
Neointimal Hyperplasia ◽  
Film Surface ◽  
High Mechanical Property ◽  
X Ray ◽  
Stent Restenosis ◽  
X Ray Computed ◽  
Hydrolysis Of

Poly(L-lactic acid) (PLLA) has been used as a biodegradable vascular scaffold (BVS) material due to high mechanical property, biodegradability, and biocompatibility. However, acidic byproducts from hydrolysis of PLLA reduce the pH after the surrounding implanted area and cause inflammatory responses. As a result, severe inflammation, thrombosis, and in-stent restenosis can occur after implantation by using BVS. Additionally, polymers such as PLLA could not find on X-ray computed tomography (CT) because of low radiopacity. To this end, here, we fabricated PLLA films as the surface of BVS and divided PLLA films into two coating layers. At the first layer, PLLA film was coated by 2,3,5-triiodobenzoic acid (TIBA) and magnesium hydroxide (MH) with poly(D,L-lactic acid) (PDLLA) for radiopaque and neutralization of acidic environment, respectively. The second layer of coated PLLA films is composed of polydopamine (PDA) and then cystamine (Cys) for the generation of nitric oxide (NO) release, which is needed for suppression of smooth muscle cells (SMCs) and proliferation of endothelial cells (ECs). The characterization of the film surface was conducted via various analyses. Through the surface modification of PLLA films, they have multifunctional abilities to overcome problems of BVS effectively such as X-ray penetrability, inflammation, thrombosis, and neointimal hyperplasia. These results suggest that the modification of biodegradable PLLA using TIBA, MH, PDA, and Cys will have important potential in implant applications.

Scanner influence on the mechanical response of QCT-based finite element analysis of long bones

2019 ◽  
Vol 86 ◽  
pp. 149-159 ◽  
Author(s):  
Yekutiel Katz ◽  
Gal Dahan ◽  
Jacob Sosna ◽  
Ilan Shelef ◽  
Evgenia Cherniavsky ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanical Response ◽  
Long Bones ◽  
Element Analysis

scholarly journals PS202. Durable Effect of Nitric Oxide at Inhibiting Neointimal Hyperplasia Is due to Modulation of Cellular Populations Throughout the Arterial Wall

2010 ◽  
Vol 51 (6) ◽  
pp. 71S-72S
Author(s):  
Ashley Vavra ◽  
Janet Martinez ◽  
Vanessa R. Lee ◽  
Bo Fu ◽  
Qun Jiang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Arterial Wall ◽  
Neointimal Hyperplasia

Analysis of Passive Filling With Fibrotic Myocardial Infarction

2015 ◽  
Author(s):  
Fulufhelo Masithulela
Keyword(s):  
Myocardial Infarction ◽  
Structural Changes ◽  
Strain Energy Function ◽  
Transversely Isotropic ◽  
Magnetic Resonance Images ◽  
Cardiac Contraction ◽  
Diastolic Filling ◽  
Element Analysis ◽  
Infarcted Heart ◽  
Longitudinal Strains

Cardiovascular diseases account for one third of all deaths worldwide, more than 33% of which are related to ischemic heart disease, involving a myocardial infarction (MI). Following myocardial infarction, the injured region and ventricle undergo structural changes which are thought to be caused by elevated stresses and reduction of strains in the infarcted wall. The fibrotic phase is defined as the period when the amount of new collagen and number of fibroblasts rapidly increase in the infarcted tissue. We studied through finite element analysis the mechanics of the infarcted and remodeling rat heart during diastolic filling. Biventricular geometries of healthy and infarcted rat hearts reconstructed from magnetic resonance images were imported in Abaqus©. The passive myocardium was modelled as a nearly incompressible, hyperelastic, transversely isotropic material represented by the strain energy function W = ½C(eQ − 1) with Q = bfE112 + bt(E222 + E332 + E322) + bfs(E122 + E212 + E132 + E312). Material parameters were obtained from literature [1]. As boundary conditions, the circumferential and longitudinal displacements at the base were set to zero. The radial displacements at the base were left free. A linearly increasing pressure from 0 to 3.80 kPa and 0.86 kPa, respectively, was applied to the endocardial surfaces of left and right ventricle. Average radial, circumferential and longitudinal strains during passive filling were −0.331, 0.135, 0.042 and −0.250, −0.078 and 0.046 for the healthy heart and the infarcted heart, respectively. The average radial, circumferential and longitudinal stresses were −1.196 kPa, 3.87 kPa in the healthy heart and 0.424 kPa and −1.90 kPa, 8.74 kPa and 1.69 kPa in the infarcted heart. The strains were considerable lower in the infarcted heart compared to the health heart whereas stresses were higher in the presence of an infarct compared to the healthy case. The results of this study indicate the feasibility of the models developed for a more comprehensive assessment of mechanics of the infarcted ventricle including extension to account for cardiac contraction.

scholarly journals Association of seven renin angiotensin system gene polymorphisms with restenosis in patients following coronary stenting

2017 ◽  
Vol 18 (1) ◽  
pp. 147032031668877 ◽  
Author(s):  
Min Zhu ◽  
Minjun Yang ◽  
Jiangbo Lin ◽  
Huanhuan Zhu ◽  
Yifei Lu ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Angiotensin Converting Enzyme ◽  
Neointimal Hyperplasia ◽  
Renin Angiotensin System ◽  
Coronary Stenting ◽  
Converting Enzyme ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Stent Restenosis ◽  
In Stent Restenosis

Background and objective: Percutaneous coronary intervention, despite being effective for coronary revascularization, causes in-stent restenosis due to neointimal hyperplasia in a large number of patients. The renin-angiotensin system is involved in neointimal hyperplasia. This study sought to evaluate seven gene polymorphisms of key renin-angiotensin system components, including angiotensinogen, angiotensin-converting enzyme and angiotensin II type 1a receptors, and their associations with in-stent restenosis in patients with coronary artery disease following coronary stenting. Methods and results: Three hundred and fifty-two patients undergoing coronary drug-eluting stent implantation were recruited. Seventy-five patients (21.3%) were diagnosed as restenosis by angiography. Genotyping for angiotensin-converting enzyme insertion/deletion demonstrated a significant association of angiotensin-converting enzyme DD genotype with the occurrence of restenosis. Direct DNA sequencing revealed no association of angiotensinogen (M235T, G217A, G152A, G-6A, and A-20C) or angiotensin II type I receptor A1166C polymorphisms with in-stent restenosis. However, angiotensin II type 1a A1166C polymorphism was significantly associated with increased susceptibility to restenosis in a subgroup of patients aged more than 60 years. Conclusion: Thus, our study suggests that genetic polymorphisms of angiotensin-converting enzyme insertion/deletion are associated with in-stent restenosis in coronary artery disease patients following coronary stenting.

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