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A Computational Framework Examining the Mechanical Behaviour of Bare and Polymer-Covered Self-Expanding Laser-Cut Stents. Cardiovasc Eng Technol 2021; 13:466-480. [PMID: 34850370 DOI: 10.1007/s13239-021-00597-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 11/16/2021] [Indexed: 01/22/2023]
Abstract
PURPOSE Polymer covered stents have demonstrated promising clinical outcomes with improved patency rates compared to traditional bare-metal stents. However, little is known on the mechanical implication of stent covering. This study aims to provide insight into the role of a polymeric cover on the biomechanical performance of self-expanding laser-cut stents through a combined experimental-computational approach. METHODS Experimental bench top tests were conducted on bare and covered versions of a commercial stent to evaluate the radial, axial and bending response. In parallel, a computational framework with a novel covering strategy was developed that accurately predicts stent mechanical performance. Different stent geometries and polymer materials were also considered to further improve understanding on covered stent mechanics. RESULTS Results show that stent covering causes increased initial axial stiffness and up to 60% greater radial resistive force at small crimp diameters as the cover folds and self-contacts. The incorporation of a cover allows stent designs without interconnecting struts, thereby providing improved flexibility without compromising radial force. It was also shown that use of a stiffer PET polymeric covering material caused significant alterations to the radial and axial response, with the initial axial stiffness increasing six-fold and the maximum radial resistive force increasing four-fold compared to a PTFE-PU covered stent. CONCLUSION This study demonstrates that stent covering has a substantial effect on the overall stent mechanical performance and highlights the importance of considering the mechanical properties of the combined cover and stent.
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Liu Y, Liu P, Song Y, Li S, Shi Y, Quan K, Yu G, Li P, An Q, Zhu W. A heparin-rosuvastatin-loaded P(LLA-CL) nanofiber-covered stent inhibits inflammatory smooth-muscle cell viability to reduce in-stent stenosis and thrombosis. J Nanobiotechnology 2021; 19:123. [PMID: 33926468 PMCID: PMC8086342 DOI: 10.1186/s12951-021-00867-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/20/2021] [Indexed: 11/10/2022] Open
Abstract
Background An endovascular covered-stent has unique advantages in treating complex intracranial aneurysms; however, in-stent stenosis and late thrombosis have become the main factors affecting the efficacy of covered-stent treatment. Smooth-muscle-cell phenotypic modulation plays an important role in late in-stent stenosis and thrombosis. Here, we determined the efficacy of using covered stents loaded with drugs to inhibit smooth-muscle-cell phenotypic modulation and potentially lower the incidence of long-term complications. Methods Nanofiber-covered stents were prepared using coaxial electrospinning, with the core solution prepared with 15% heparin and 20 µM rosuvastatin solution (400: 100 µL), and the shell solution prepared with 120 mg/mL hexafluoroisopropanol. We established a rabbit carotid-artery aneurysm model, which was treated with covered stents. Angiography and histology were performed to evaluate the therapeutic efficacy and incidence rate of in-stent stenosis and thrombosis. Phenotype, function, and inflammatory factors of smooth-muscle cells were studied to explore the mechanism of rosuvastatin action in smooth-muscle cells. Result Heparin–rosuvastatin-loaded nanofiber scaffold mats inhibited the proliferation of synthetic smooth-muscle cells, and the nanofiber-covered stent effectively treated aneurysms in the absence of notable in-stent stenosis. Additionally, in vitro experiments showed that rosuvastatin inhibited the smooth-muscle-cell phenotypic modulation of platelet-derived growth factor-BB induction and decreased synthetic smooth-muscle-cell viability, as well as secretion of inflammatory cytokines. Conclusion Rosuvastatin inhibited the abnormal proliferation of synthetic smooth-muscle cells, and heparin–rosuvastatin-loaded covered stents reduced the incidence of stenosis and late thrombosis, thereby improving the healing rates of stents used for aneurysm treatment. Graphic abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s12951-021-00867-8.
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Affiliation(s)
- Yingjun Liu
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Neurosurgical Institute of Fudan University, Shanghai, China.,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China.,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China
| | - Peixi Liu
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Neurosurgical Institute of Fudan University, Shanghai, China.,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China.,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China
| | - Yaying Song
- Department of Neurology, Renji Hospital of Shanghai Jiao Tong University, Shanghai, China.,Neuroscience and Neuroengineering Research Center, Med-X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Sichen Li
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Neurosurgical Institute of Fudan University, Shanghai, China.,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China.,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China
| | - Yuan Shi
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Neurosurgical Institute of Fudan University, Shanghai, China.,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China.,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China
| | - Kai Quan
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Neurosurgical Institute of Fudan University, Shanghai, China.,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China.,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China
| | - Guo Yu
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Neurosurgical Institute of Fudan University, Shanghai, China.,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China.,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China
| | - Peiliang Li
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China. .,Neurosurgical Institute of Fudan University, Shanghai, China. .,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China. .,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China.
| | - Qingzhu An
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China. .,Neurosurgical Institute of Fudan University, Shanghai, China. .,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China. .,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China.
| | - Wei Zhu
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China. .,Neurosurgical Institute of Fudan University, Shanghai, China. .,Shanghai Clinical Medical Center of Neurosurgery, Shanghai, China. .,Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Shanghai, China.
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Giuliodori A, Hernández JA, Fernandez-Sanchez D, Galve I, Soudah E. Numerical modeling of bare and polymer-covered braided stents using torsional and tensile springs connectors. J Biomech 2021; 123:110459. [PMID: 34022531 DOI: 10.1016/j.jbiomech.2021.110459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 04/12/2021] [Accepted: 04/13/2021] [Indexed: 09/30/2022]
Abstract
Computational modeling of braided stents using the finite element (FE) method has become an essential tool in the design and development of these medical devices. One of the most challenging issues in such a task is representing in an accurate manner the interaction between the interlacing wires. With the goal of achieving a compromise between accuracy and computational affordability, we propose a new approach consisting in using 1D FE formulations equipped with torsional springs at the crossover points of the wires. In the case of covered braided stents, the model is enriched with a set of tensile springs (defined in the longitudinal direction), aimed at capturing the stiffening effect of the polymeric membrane. The predictive capabilities of the proposed model are evaluated using data of our own experimental tests, as well as data from other tests in the literature. The simulations demonstrate that the proposed model is able to predict the (markedly nonlinear) behavior of stents when subjected to radial and axial cycle loads, with errors at the end of the compression stage ranging from 0.5% to 10% in all cases.
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Affiliation(s)
- Agustina Giuliodori
- Centre Internacional de Métodes Numérics en Enginerya, CIMNE, Barcelona, Spain; Universitat Politécnica de Catalunya, UPC, Barcelona, Spain.
| | - Joaquín A Hernández
- Centre Internacional de Métodes Numérics en Enginerya, CIMNE, Barcelona, Spain; E.S. d'Enginyeries Industrial, Aeroespacial i Audiovisual de Terrassa, Technical University of Catalonia, C/ Colom, 11, Terrassa 08222, Spain
| | | | | | - Eduardo Soudah
- Centre Internacional de Métodes Numérics en Enginerya, CIMNE, Barcelona, Spain; Universitat Politécnica de Catalunya, UPC, Barcelona, Spain
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McKenna CG, Vaughan TJ. A finite element investigation on design parameters of bare and polymer-covered self-expanding wire braided stents. J Mech Behav Biomed Mater 2021; 115:104305. [PMID: 33454463 DOI: 10.1016/j.jmbbm.2020.104305] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 12/02/2020] [Accepted: 12/29/2020] [Indexed: 02/07/2023]
Abstract
Self-expanding covered braided stents are routinely used across a diverse range of clinical applications, but few computational studies have attempted to replicate their complex behaviour. In this study, a computational framework was developed to predict the functional performance of bare and covered self-expanding wire braided stents, with a systematic evaluation on the effect of various braid and cover parameters presented. Simulated radial force and kink deformation tests show good agreement to experimental data for covered braided stents across a range of braid angles and cover thicknesses. Our results demonstrate that braid angle is a key governing parameter that dictates the radial and kink performance of both bare-metal and covered wire braided stents. It was also demonstrated that addition of a polymeric cover to a wire braided stent causes a stiffer radial response across all braid angles, particularly when thicker and/or stiffer covering systems were considered. This study represents the first experimentally-validated computational model for covered wire braided stent systems and has excellent potential to be used in future design of these devices for a range of applications.
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Affiliation(s)
- Ciara G McKenna
- Biomechanics Research Centre (BioMEC), Biomedical Engineering, School of Engineering, College of Science and Engineering, National University of Ireland Galway, Galway, Ireland
| | - Ted J Vaughan
- Biomechanics Research Centre (BioMEC), Biomedical Engineering, School of Engineering, College of Science and Engineering, National University of Ireland Galway, Galway, Ireland.
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Parallelized microfluidic diatom accumulation assay to test fouling-release coatings. Biointerphases 2018; 13:041007. [PMID: 30021446 DOI: 10.1116/1.5034090] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Assessing the efficiency of the next generation of protective marine coatings is highly relevant for their optimization. In this paper, a parallelized microfluidic testing device is presented to quantify the accumulation of a model organism (Navicula perminuta) under constant laminar flow. Using automated microscopy in conjunction with image analysis, the adhesion densities on the tested surfaces could be determined after exposure to a flow of suspended algae for 90 min. The optimized protocol for the assay is presented, and the reproducibility of the densities of attached diatoms was verified on four identical surfaces (self-assembled dodecanethiol monolayers). A set of well-characterized self-assembled monolayers with different chemical terminations was used to validate the performance of the assay and its capability to discriminate diatom accumulation on different surface chemistries under dynamic conditions. The observed trends are in good agreement with previously published results obtained in single channel accumulation and detachment assays. To demonstrate the practical relevance of the dynamic experiment, diatom attachment on four technically relevant silicone coatings with different fouling-release properties could clearly be distinguished.
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Samami H, Pan J. Detection of degradation in polyester implants by analysing mode shapes of structure vibration. J Mech Behav Biomed Mater 2016; 62:299-309. [PMID: 27235780 DOI: 10.1016/j.jmbbm.2016.05.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 11/27/2022]
Abstract
This paper presents a numerical study on using vibration analysis to detect degradation in degrading polyesters. A numerical model of a degrading plate sample is considered. The plate is assumed to degrade following the typical behaviour of amorphous copolymers of polylactide and polyglycolide. Due to the well-known autocatalytic effect in the degradation of these polyesters, the inner core of the plate degrades faster than outer surface region, forming layers of materials with varying Young׳s modulus. Firstly the change in molecular weight and corresponding change in Young׳s modulus at different times are calculated using the mathematical models developed in our previous work. Secondly the first four mode shapes of transverse vibration of the plate are calculated using the finite element method. Finally the curvature of the mode shapes are calculated and related to the spatial distribution of the polymer degradation. It is shown that the curvature of the mode shapes can be used to detect the onset and distribution of polymer degradation. The level of measurement accuracy required in an experiment is presented to guide practical applications of the method. At the end of this paper a demonstration case of coronary stent is presented showing how the method can be used to detect degradation in an implant of sophisticated structure.
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Affiliation(s)
- Hassan Samami
- Department of Engineering, University of Leicester, Leicester, UK
| | - Jingzhe Pan
- Department of Engineering, University of Leicester, Leicester, UK.
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Imani SM, Goudarzi AM, Ghasemi SE, Kalani A, Mahdinejad J. Analysis of the stent expansion in a stenosed artery using finite element method: application to stent versus stent study. Proc Inst Mech Eng H 2015; 228:996-1004. [PMID: 25406228 DOI: 10.1177/0954411914556788] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In this article, finite element method is used to investigate the mechanical behavior of a stent and to determine the biomechanical interaction between the stent and the artery in a stenting procedure. The main objective of this study is to reach to a model close to a real condition of coronary stent placement. Unlike most of the models proposed in the literature, all the steps of the deployment of a stent in the stenotic vessel (i.e. pressure increasing, constant load pressure and pressure decreasing) are simulated in this article to show the behavior of the stent in different stages of implantation. The results indicate that the first step of deployment, that is, pressure increasing, plays a main role in the success of stent implantation. So that, in order to compare the behavior of different types of stents, it is sufficient to compare their behavior at the end of pressure increasing step. In order to show the application of the findings in stent versus stent studies, three commercially available stents (the Palmaz-Schatz, Multi-Link and NIR stents) are modeled and their behavior is compared at the end of pressure increasing step. The effect of stent design on the restenosis rate is investigated. According to the findings, the possibility of restenosis is lower for Multi-Link and NIR stents in comparison with Palmaz-Schatz stent which is in good agreement with clinical results. Therefore, the testing methodology outlined here is proposed as a simple and economical alternative for "stent versus stent" complicated clinical trials.
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Affiliation(s)
- S Misagh Imani
- Department of Mechanical Engineering, Sari Branch, Islamic Azad University, Sari, Iran
| | - A M Goudarzi
- Department of Mechanical Engineering, Babol University of Technology, Babol, Iran
| | - S E Ghasemi
- Young Researchers and Elite Club, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
| | - A Kalani
- Bushehr University of Medical Sciences, Bushehr, Iran
| | - J Mahdinejad
- Department of Mechanical Engineering, Sari Branch, Islamic Azad University, Sari, Iran
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Schiavone A, Zhao L, Abdel-Wahab A. Effects of material, coating, design and plaque composition on stent deployment inside a stenotic artery—Finite element simulation. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2014; 42:479-88. [DOI: 10.1016/j.msec.2014.05.057] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 04/18/2014] [Accepted: 05/29/2014] [Indexed: 01/19/2023]
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Weaver JD, Ku DN. A Study on the Effects of Covered Stents on Tissue Prolapse. J Biomech Eng 2012; 134:024505. [DOI: 10.1115/1.4006199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Polyvinyl alcohol (PVA) cryogel covered stents may reduce complications from thrombosis and restenosis by decreasing tissue prolapse. Finite element analysis was employed to evaluate the effects of PVA cryogel layers of varying thickness on tissue prolapse and artery wall stress for two common stent geometries and two vessel diameters. Additionally, several PVA cryogel covered stents were fabricated and imaged with an environmental scanning electron microscope. Finite element results showed that covered stents reduced tissue prolapse up to 13% and artery wall stress up to 29% with the size of the reduction depending on the stent geometry, vessel diameter, and PVA cryogel layer thickness. Environmental scanning electron microscope images of expanded covered stents showed the PVA cryogel to completely cover the area between struts without gaps or tears. Overall, this work provides both computational and experimental evidence for the use of PVA cryogels in covered stents.
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Affiliation(s)
- Jason D. Weaver
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 315 Ferst Dr., Room 2119, Atlanta, GA 30332
| | - D. N. Ku
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 315 Ferst Dr., Room 2307, Atlanta, GA 30332
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Martin D, Boyle FJ. Computational structural modelling of coronary stent deployment: a review. Comput Methods Biomech Biomed Engin 2011; 14:331-48. [DOI: 10.1080/10255841003766845] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Wang Y, Betts DE, Finlay JA, Brewer L, Callow ME, Callow JA, Wendt DE, DeSimone JM. Photocurable Amphiphilic Perfluoropolyether/Poly(ethylene glycol) Networks for Fouling-Release Coatings. Macromolecules 2011. [DOI: 10.1021/ma102271t] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yapei Wang
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Douglas E. Betts
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | | | - Lenora Brewer
- Cal Poly, San Luis Obispo, Biological Sciences Department, San Luis Obispo, California 93407, United States
| | | | | | - Dean E. Wendt
- Cal Poly, San Luis Obispo, Biological Sciences Department, San Luis Obispo, California 93407, United States
| | - Joseph M. DeSimone
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
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Larrabide I, Kim M, Augsburger L, Villa-Uriol MC, Rüfenacht D, Frangi AF. Fast virtual deployment of self-expandable stents: method and in vitro evaluation for intracranial aneurysmal stenting. Med Image Anal 2010; 16:721-30. [PMID: 20627664 DOI: 10.1016/j.media.2010.04.009] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2009] [Revised: 04/04/2010] [Accepted: 04/28/2010] [Indexed: 11/28/2022]
Abstract
INTRODUCTION Minimally invasive treatment approaches, like the implantation of percutaneous stents, are becoming more popular every day for the treatment of intracranial aneurysms. The outcome of such treatments is related to factors like vessel and aneurysm geometry, hemodynamic conditions and device design. For this reason, having a tool for assessing stenting alternatives beforehand is crucial. METHODOLOGY The Fast Virtual Stenting (FVS) method, which provides an estimation of the configuration of intracranial stents when released in realistic geometries, is proposed in this paper. This method is based on constrained simplex deformable models. The constraints are used to account for the stent design. An algorithm for its computational implementation is also proposed. The performance of the proposed methodology was contrasted with real stents released in a silicone phantom. RESULTS In vitro experiments were performed on the phantom where a contrast injection was performed. Subsequently, corresponding Computational Fluid Dynamics (CFD) analyzes were carried out on a digital replica of the phantom with the virtually released stent. Virtual angiographies are used to compare in vitro experiments and CFD analysis. Contrast time-density curves for in vitro and CFD data were generated and used to compare them. CONCLUSIONS Results of both experiments resemble very well, especially when comparing the contrast density curves. The use of FVS methodology in the clinical environment could provide additional information to clinicians before the treatment to choose the therapy that best fits the patient.
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Affiliation(s)
- Ignacio Larrabide
- Networking Biomedical Research Center on Bioengineering, Biomaterials and Nanomedicine, Barcelona, Spain.
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Treatment of carotid siphon aneurysms by use of the Willis stent graft: an angiographic and histopathological study. Eur Radiol 2010; 20:1974-84. [DOI: 10.1007/s00330-010-1738-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2009] [Revised: 11/24/2009] [Accepted: 12/16/2009] [Indexed: 10/19/2022]
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Development of novel covered stents using salmon collagen. J Artif Organs 2009; 12:61-6. [DOI: 10.1007/s10047-008-0446-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 11/27/2008] [Indexed: 10/21/2022]
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Kim JH, Kang TJ, Yu WR. Mechanical modeling of self-expandable stent fabricated using braiding technology. J Biomech 2008; 41:3202-12. [DOI: 10.1016/j.jbiomech.2008.08.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 08/10/2008] [Accepted: 08/11/2008] [Indexed: 11/17/2022]
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Li MH, Zhu YQ, Fang C, Wang W, Zhang PL, Cheng YS, Tan HQ, Wang JB. The feasibility and efficacy of treatment with a Willis covered stent in recurrent intracranial aneurysms after coiling. AJNR Am J Neuroradiol 2008; 29:1395-400. [PMID: 18436616 PMCID: PMC8119161 DOI: 10.3174/ajnr.a1096] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 02/25/2008] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Aneurysm recurrence is an innate problem after coiling, and the recurrence rate is higher in complicated aneurysms. We evaluated the feasibility and efficacy of using the Willis covered stent in treating recurrent aneurysms after coil embolization. MATERIALS AND METHODS Eight aneurysms in 8 patients treated with detachable coils had confirmed recurrent aneurysms: 3 giant, 1 large, 1 dissecting, and 3 small wide-necked. The recurrent aneurysms involved C3 in 1 patient, C4 in 1, C7 in 5, and V4 in 1. A total of 11 covered stents were implanted into 8 target arteries. Follow-up angiography was performed 1-16 months after the procedure. Clinical follow-up data were collected and retrospectively analyzed, grading as fully recovered, improved, unchanged, or aggravated. RESULTS Willis covered stent placement succeeded technically in all of the aneurysms. No technique-related adverse event occurred. Total occlusion was achieved immediately in 6 aneurysms, and a small endoleak was observed in 2 aneurysms. No mortality or morbidity occurred during or after the procedures, including during the follow-up period. Follow-up angiograms revealed that all 8 of the recurrent aneurysms were completely isolated, and 8 parent vessels kept patency, except 1 with mild stenosis. Clinical neurologic symptoms fully resolved in 5 patients, improved in 1, and were unchanged in 2 at the end of the follow-up period. CONCLUSIONS In this small study with a middle-term follow-up, the Willis covered stent was used safely and effectively to occlude recurred aneurysms after coiling. Longer-term follow-up and additional clinical experience are needed to fully determine the safety and efficacy of the device.
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Affiliation(s)
- M-H Li
- Department of Diagnostic and Interventional Radiology, Sixth Affiliated People's Hospital, Shanghai Jiao Tong University, Shanghai, China
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Welch T, Eberhart RC, Chuong CJ. Characterizing the expansive deformation of a bioresorbable polymer fiber stent. Ann Biomed Eng 2008; 36:742-51. [PMID: 18264765 DOI: 10.1007/s10439-008-9455-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 01/29/2008] [Indexed: 10/22/2022]
Abstract
Polymeric vascular stents must employ other strategies than malleable deformation, as generally practiced with metal stents, to expand and withstand compressive stresses in situ. The stent expansion strategy must further consider induced flow perturbations and wall stresses that may injure the vessel wall and promote thrombogenesis. Analyzing the stresses furled stents undergo during balloon-assisted expansion is an important first step in achieving a better understanding of stent-wall mechanical interactions, thereby to improve stent function. To this end, we performed finite element (FE) analysis of the balloon-induced unfurling of an internally coiled, bioresorbable polymeric stent employing a 3D FE solid model of a 120 degrees symmetric stent segment and a large deformation finite strain formulation. Uni-axial tensile testing of stent fiber elastic to plastic yielding provided the mechanical property information, and the von Mises criterion was employed to establish the elastic-plastic transition in the FE model. The model was validated with pressure and deformation measurements obtained during stent expansion tests. The internal coils of this inner coil-outer coil design twisted as the stent expanded, leading to plastic yielding at the point of tangency of the inner and outer coils. The remaining stent fiber portions underwent elastic bending. Cross-sections revealed only the outside surface layer of the coiled fiber underwent plastic yielding. The interior elastic fiber was supported by this plastic shell. The analysis suggests that during balloon-induced expansion, local plastic yielding in torsion "sets" the stent fibers, imparting high radial collapse resistance. The results further suggest that the stent exerts non-uniform mechanical forces on the vessel wall during expansion.
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Affiliation(s)
- Tre Welch
- Bioengineering Department, University of Texas at Arlington, Box 19138, Arlington, TX 76019, USA
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De Beule M, Mortier P, Carlier SG, Verhegghe B, Van Impe R, Verdonck P. Realistic finite element-based stent design: The impact of balloon folding. J Biomech 2008; 41:383-9. [DOI: 10.1016/j.jbiomech.2007.08.014] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Accepted: 08/29/2007] [Indexed: 11/30/2022]
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Narracott AJ, Lawford PV, Gunn JPG, Hose DR. Balloon folding affects the symmetry of stent deployment: experimental and computational evidence. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2007; 2007:3069-73. [PMID: 18002642 DOI: 10.1109/iembs.2007.4352976] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The level of restenosis following coronary artery stenting may be related to the deployed stent geometry. This study investigated the influence of two balloon folding patterns (;C' and ;S' shaped) on stent deployment. In vitro stent expansion showed ;S' shape folding produced more uniform expansion than ;C' shape folding. A numerical contact model (NCM) was developed to study the detail of load transfer between balloon and stent. Finite element analysis of the Palmaz-Schatz 204C stent provided a composite non-linear material model for the NCM. Agreement between the predicted final stent geometry and experimental results was strongly dependent on the frictional coefficient between the stent and balloon. We conclude that non-uniform contact may contribute to the asymmetry of deployed stents reported clinically.
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Affiliation(s)
- Andrew J Narracott
- Academic Unit of Medical Physics, University of Sheffield, I floor, Royal Hallamshire Hospital, Glossop Road, Sheffield, S10 2JF, UK.
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Raamachandran J, Jayavenkateshwaran K. Modeling of stents exhibiting negative Poisson's ratio effect. Comput Methods Biomech Biomed Engin 2007; 10:245-55. [PMID: 17671858 DOI: 10.1080/10255840701198004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Intravascular stents are metallic scaffolding structures deployed in the stenotic arteries to restore the lumen for the blood flow to the down stream tissues. Most stents are balloon expandable and are deployed from its crimped state through a balloon catheter. The efficacy of the stenting procedure mainly depends on the way the stent is deployed. Both numerical and experimental evaluations show that almost all the present day stents undergo the most undesirable effects namely: (i) longitudinal foreshortening: the axial contraction in the length, and (ii) dogboning: flaring of the distal edges, during the radial expansion of the stents. Due to the foreshortening effect, clinicians are forced to select stents longer than the plaque. Still, the final length of the stent depends on the amount of radial expansion, which is subjective during the procedure. This paper introduces a new stent model called "Murugan", which exhibits negative Poisson's ratio effect. That is, the stent may have zero axial contraction or can have extension when under radial expansion. The presence of hyperelastic balloon and the stent-balloon friction is also considered to study their effects in mechanical properties of the stents under consideration. Free expansion analysis is done using finite element method (FEM) to compare the new stent model with the present day stent geometries.
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Affiliation(s)
- J Raamachandran
- Solid Mechanics Group, Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai, Tamilnadu 600 036, India.
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