Crimping and deployment of metallic and polymeric stents -- finite element modelling

Schiavone, Alessandro; Qiu, Tianyang; Zhao, Liguo

doi:10.20517/2574-1209.2016.03

Cited by 40 publications

(35 citation statements)

References 34 publications

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“…The model was calibrated by taking the average stress-stretch curves that were measured and obtained from 13 patients (Holzapfel et al, 2005). The calibrated parameter values for the HGO model were given in our previous paper (Schiavone et al, 2017) and the simulated longitudinal and circumferential stress-stretch responses of three layers were in excellent agreement with the experimental results (Schiavone et al, 2017). For the hypocellular plaque, the first order hyper elastic Ogden strain energy potential (Ogden, 1972) was used here, and material parameters were calibrated against test data (Loree et al, 1994) and given in Zahedmanesh and Lally (2009).…”

Section: Constitutive Models For Plaque-arterymentioning

confidence: 99%

Effect of two-year degradation on mechanical interaction between a bioresorbable scaffold and blood vessel

Qiu

Abunassar

et al. 2018

Journal of the Mechanical Behavior of Biomedical Materials

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This paper aims to evaluate the mechanical behaviour of a bioresorbable polymeric coronary scaffold using finite element method, focusing on scaffold-artery interaction during degradation and vessel remodelling. A series of nonlinear stress-strain responses was constructed to match the experimental measurement of radial stiffness and strength for polymeric scaffolds over 2-year in-vitro degradation times. Degradation process was modelled by incorporating the change of material property as a function of time. Vessel remodelling was realised by changing the size of artery-plaque system manually, according to the clinical data in literature. Over degradation times, stress on the scaffold tended to increase firstly and then decreased gradually, corresponding to the changing yield stress of the scaffold material; whereas the stress on the plaque and arterial layers showed a continuous decrease. In addition, stress reduction was also observed for scaffold, plaque and artery in the simulations with the consideration of vessel remodelling. For the first time, the work offered insights into mechanical interaction between a bioresorbable scaffold and blood vessel during two-year in-vitro degradation, which has significance in assisting with further development of bioresorbable implants for treating cardiovascular diseases.

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Section: Constitutive Models For Plaque-arterymentioning

confidence: 99%

Effect of two-year degradation on mechanical interaction between a bioresorbable scaffold and blood vessel

Qiu

Abunassar

et al. 2018

Journal of the Mechanical Behavior of Biomedical Materials

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“…Open and closed cell design: general shape of the stent (coil, tubular mesh, slotted tube) and bridging between rings (peak-to-peak, peak-to-valley, and mid-strut-to-mid-strut connections) can influence flexibility, radial strength and scaffolding (ability to support tissue; thus, preventing prolapse) [233]. Slotted tube stents design can be either open or closed cells.…”

Section: Mechanical Aspects Of Stentsmentioning

confidence: 99%

“…By simply not performing holes (drug reservoirs) in the crown, the maximum equivalent plastic strain was reduced by 9% and the strain distribution was spread out even more uniformly than the case. Schiavone et al [233] compared the mechanical performance of metal (Xience) and bioresorbable polymer (Elixir) stents during the process of crimping and deployment. High levels of stresses were observed in both stents following their deployment in the artery showing maximum von Mises stresses in the U-bend areas with a value of 935 MPa for Xience and 95 MPa for Elixir stent.…”

Section: Mechanical Aspects Of Stentsmentioning

confidence: 99%

Recent Advances in Manufacturing Innovative Stents

et al. 2020

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Cardiovascular diseases are the most distributed cause of death worldwide. Stenting of arteries as a percutaneous transluminal angioplasty procedure became a promising minimally invasive therapy based on re-opening narrowed arteries by stent insertion. In order to improve and optimize this method, many research groups are focusing on designing new or improving existent stents. Since the beginning of the stent development in 1986, starting with bare-metal stents (BMS), these devices have been continuously enhanced by applying new materials, developing stent coatings based on inorganic and organic compounds including drugs, nanoparticles or biological components such as genes and cells, as well as adapting stent designs with different fabrication technologies. Drug eluting stents (DES) have been developed to overcome the main shortcomings of BMS or coated stents. Coatings are mainly applied to control biocompatibility, degradation rate, protein adsorption, and allow adequate endothelialization in order to ensure better clinical outcome of BMS, reducing restenosis and thrombosis. As coating materials (i) organic polymers: polyurethanes, poly(ε-caprolactone), styrene-b-isobutylene-b-styrene, polyhydroxybutyrates, poly(lactide-co-glycolide), and phosphoryl choline; (ii) biological components: vascular endothelial growth factor (VEGF) and anti-CD34 antibody and (iii) inorganic coatings: noble metals, wide class of oxides, nitrides, silicide and carbide, hydroxyapatite, diamond-like carbon, and others are used. DES were developed to reduce the tissue hyperplasia and in-stent restenosis utilizing antiproliferative substances like paclitaxel, limus (siro-, zotaro-, evero-, bio-, amphi-, tacro-limus), ABT-578, tyrphostin AGL-2043, genes, etc. The innovative solutions aim at overcoming the main limitations of the stent technology, such as in-stent restenosis and stent thrombosis, while maintaining the prime requirements on biocompatibility, biodegradability, and mechanical behavior. This paper provides an overview of the existing stent types, their functionality, materials, and manufacturing conditions demonstrating the still huge potential for the development of promising stent solutions.

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“…Figure 17a demonstrates the von Mises stress for crimping to 1.5 mm (A) and expansion (B). Stresses were localized in the U-bend regions of the scaffold, common for polymeric stents (Schiavone et al 2017). The stage of elastic recoil saw a stress decrease from 161 MPa to 102.4 MPa.…”

Section: Computational and Mathematical Modelling Of Br Scaffoldsmentioning

confidence: 99%

Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress

Naseem

Zhao

Liu

et al. 2017

Mech Adv Mater Mod Process

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Stents are commonly used in medical procedures to alleviate the symptoms of coronary heart disease, a prevalent modern society disease. These structures are employed to maintain vessel patency and restore blood flow. Traditionally stents are made of metals such as stainless steel or cobalt chromium; however, these scaffolds have known disadvantages. An emergence of transient scaffolds is gaining popularity, with the structure engaged for a required period whilst healing of the diseased arterial wall occurs. Polymers dominate a medical device sector, with incorporation in sutures, scaffolds and screws. Thanks to their good mechanical and biological properties and their ability to degrade naturally. Polylactic acid is an extremely versatile polymer, with its properties easily tailored to applications. Its dominance in the stenting field increases continually, with the first polymer scaffold gaining FDA approval in 2016. Still some challenges with PLLA bioresorbable materials remain, especially with regard to understanding their mechanical response, assessment of its changes with degradation and comparison of their performance with that of metallic drug-eluting stent. Currently, there is still a lack of works on evaluating both the pre-degradation properties and degradation performance of these scaffolds. Additionally, there are no established material models incorporating non-linear viscoelastic behaviour of PLLA and its evolution with in-service degradation. Assessing these features through experimental analysis accompanied by analytical and numerical studies will provide powerful tools for design and optimisation of these structures endorsing their broader use in stenting. This overview assesses the recent studies investigating mechanical and computational performance of poly(l-lactic) acid and its use in stenting applications.

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Crimping and deployment of metallic and polymeric stents -- finite element modelling

Cited by 40 publications

References 34 publications

Effect of two-year degradation on mechanical interaction between a bioresorbable scaffold and blood vessel

Effect of two-year degradation on mechanical interaction between a bioresorbable scaffold and blood vessel

Recent Advances in Manufacturing Innovative Stents

Experimental and computational studies of poly-L-lactic acid for cardiovascular applications: recent progress

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