scholarly journals In Vitro Degradation Behaviours of PDO Monofilament and Its Intravascular Stents with Braided Structure

2016 ◽  
Vol 16 (2) ◽  
pp. 80-89 ◽  
Author(s):  
Cong-er Wang ◽  
Pei-hua Zhang
Keyword(s):  
Mechanical Properties ◽  
Vascular Wall ◽  
Radial Force ◽  
Temporary Increase ◽  
Crystalline Region ◽  
Bending Rigidity ◽  
Intravascular Stents ◽  
Braided Structure ◽  
Intravascular Stent

Abstract Biodegradable intravascular stent has attracted more and more focus in recent years as an effective solution for angiostenosis. Ideal stents were expected to exhibit sufficient radial force to support the vascular wall, while suitable flexibility for the angioplasty. After vascular remodeling, stents should be degraded into small molecular and be eliminated from human body, causing no potential risk. In this paper, poly-p-dioxanone (PDO) monofilament was braided into net structure with four different braiding density, two of which exhibited sufficient radial force larger than 30 kPa, and three of which showed the bending rigidity within 11.7–88.1 N•mm2. The degradation behaviors of monofilaments and stents have been observed for 16 weeks. The findings obtained indicate that degradation first occurred in morphology region, which induced temporary increase of crystallinity, monofilament bending rigidity and stent mechanical properties. During this period, monofilament tends to be hard and brittle and lost its tensile properties. Then the crystalline region was degraded and stent mechanical properties decreased. All the results reveal that the PDO intravascular stents with braided structure were able to afford at least 10 weeks of sufficient support to the vascular wall.

Preparation and In Vitro Degradation of PDO Intravascular Stents with Braided Structure

2014 ◽  
Vol 906 ◽  
pp. 238-245 ◽  
Author(s):  
Cong R. Wang ◽  
Hui Jun Xu ◽  
Pei Hua Zhang
Keyword(s):  
Mechanical Properties ◽  
Compression Strength ◽  
Short Term ◽  
In Vitro Degradation ◽  
Intravascular Stents ◽  
Degradation Behaviors ◽  
Braided Structure ◽  
Original Strength ◽  
Good Compression

In this paper, in vitro degradation behaviors of the PDO monofilaments and the stents were studied. The mechanical properties,morphology observation and Differential Scanning Calorimeter (DSC) of PDO monofilaments were determined, as well as the compression strength of the stents. The experimental results showed that the PDO monofilaments contained half of its original strength after 6 weeks degradation and lost its strength in the 10thweek. DSC outcomes showed that the crystalline regions of PDO havent been hydrolyzed after 16 weeks of degradation. The stents demonstrated good compression behaviors for 12 weeks and therefore can be utilized in short-term application.

Design and characterization of PDO biodegradable intravascular stents

2016 ◽  
Vol 87 (16) ◽  
pp. 1968-1976 ◽  
Author(s):  
Cong-er Wang ◽  
Pei-hua Zhang
Keyword(s):  
Mechanical Properties ◽  
Recovery Rate ◽  
Degradation Process ◽  
Radial Force ◽  
Fabrication Process ◽  
International Standards ◽  
Intravascular Stents ◽  
Shortening Rate ◽  
Degradation Properties

Two novel biodegradable intravascular stents (BIS) with different structures are introduced. Braiding-structural BIS and Z-structural BIS were fabricated from polydioxanone (PDO) monofilament by a hand-braiding method with a perforated mold, imitating commercial stents that have been used clinically. The fabrication process of these two BIS is described and stent parameters, mechanical properties, and degradation properties are reported. The findings reveal that Z-structural BIS have higher porosity, smaller longitudinal shortening rate, and higher radial force and recovery rate compared with the braiding-structural stent. During the degradation process, braiding-structural BIS maintained their mechanical properties higher than international standards for 12 weeks, while Z-structural stents maintained them for 16 weeks.

Mechanical Analysis of Heterogeneous, Atherosclerotic Human Aorta

1998 ◽  
Vol 120 (5) ◽  
pp. 602-607 ◽  
Author(s):  
D. Beattie ◽  
C. Xu ◽  
R. Vito ◽  
S. Glagov ◽  
M. C. Whang
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Strain Energy ◽  
Vascular Wall ◽  
Mechanical Analysis ◽  
Human Aorta ◽  
Stress And Strain ◽  
Optimization Strategy

An experimental technique was developed to determine the finite strain field in heterogeneous, diseased human aortic cross sections at physiologic pressures in vitro. Also, the distributions within the cross sections of four histologic features (disease-free zones, lipid accumulations, fibrous intimal tissue, and regions of calcification) were quantified using light microscopic morphometry. A model incorporating heterogeneous, plane stress finite elements coupled the experimental and histologic data. Tissue constituent mechanical properties were determined through an optimization strategy, and the distributions of stress and strain energy in the diseased vascular wall were calculated. Results show that the constituents of atherosclerotic lesions exhibit large differences in their bilinear mechanical properties. The distributions of stress and strain energy in the diseased vascular wall are strongly influenced by both lesion structure and composition. These results suggest that accounting for heterogeneities in the mechanical analysis of atherosclerotic arterial tissue is critical to establishing links between lesion morphology and the susceptibility of plaque to mechanical disruption in vivo.

Clinical Results and Mechanical Properties of the Carotid CGUARD Double-Layered Embolic Prevention Stent

2016 ◽  
Vol 24 (1) ◽  
pp. 130-137 ◽  
Author(s):  
Christian Wissgott ◽  
Wolfram Schmidt ◽  
Christoph Brandt-Wunderlich ◽  
Peter Behrens ◽  
Reimer Andresen
Keyword(s):  
Mechanical Properties ◽  
Double Layer ◽  
Clinical Results ◽  
Radial Force ◽  
Bending Stiffness ◽  
Lesion Length ◽  
Collapse Pressure ◽  
Stent System ◽  
In Vitro Investigation

Purpose: To report early clinical outcomes with a novel double-layer stent for the internal carotid artery (ICA) and the in vitro investigation of the stent’s mechanical properties. Methods: A prospective single-center study enrolled 30 consecutive patients (mean age 73.1±6.3 years; 21 men) with symptomatic (n=25) or high-grade (n=5) ICA stenosis treated with the new double-layer carotid CGUARD Embolic Prevention System (EPS) stent, which has an inner open-cell nitinol design with an outer closed-cell polyethylene terephthalate layer. The average stenosis of the treated arteries was 84.1%±7.9% with a mean lesion length of 16.6±2.1 mm. In the laboratory, 8×40-mm stents where tested in vitro with respect to their radial force during expansion, the bending stiffness of the stent system and the expanded stent, as well as the collapse pressure in a thin and flexible sheath. The wall adaptation was assessed using fluoroscopy after stent release in step and curved vessel models. Results: The stent was successfully implanted in all patients. No peri- or postprocedural complications occurred; no minor or major stroke was observed in the 6-month follow-up. The bending stiffness of the expanded stent was 63.1 N·mm2 and (not unexpectedly) was clearly lower than that of the stent system (601.5 N·mm2). The normalized radial force during expansion of the stent to 7.0 mm, consistent with in vivo sizing, was relatively high (0.056 N/mm), which correlates well with the collapse pressure of 0.17 bars. Vessel wall adaptation was harmonic and caused no straightening of the vessel after clinical application. Conclusion: Because of its structure, the novel CGUARD EPS stent is characterized by a high flexibility combined with a high radial force and very good plaque coverage. These first clinical results demonstrate a very safe implantation behavior without any stroke up to 6 months after the procedure.

scholarly journals Structural Design of Mechanical Property for Biodegradable Polymeric Stent

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Yunbo Wei ◽  
Minjie Wang ◽  
Danyang Zhao ◽  
Hongxia Li ◽  
Yifei Jin
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Design Method ◽  
Ring Structure ◽  
Mechanical Tests ◽  
Radial Force ◽  
Element Analysis ◽  
Stent Expansion ◽  
Supporting Ring

How to improve stent mechanical properties is a key issue for designing biodegradable polymeric stents (BPSs). In this study, a new design method of BPS was proposed based on the force analysis of supporting rings and bridges during stent implantation, and a novel BPS called open C-shaped stent (OCS) with superior comprehensive mechanical properties was developed accordingly. The key mechanical properties including radial force, radial recoil, and axial foreshortening of the OCS have been comprehensively studied and compared with those of the Abbott BVS using finite element analysis (FEA). In addition, the effects of the stent geometries on these mechanical properties have also been discussed in detail. Besides, in vitro mechanical tests including stent expansion and planar compression experiments have been performed to verify the simulation results. Based on the FEA results, it is found that the radial force and radial recoil of the designed OCS are 30% higher and 24% lower than those of the BVS, respectively. Meanwhile, the OCS is not shortened during expansion. Radial force and radial recoil are mainly dependent on the supporting ring structure, and the utilization of designed unequal-height supporting ring (UHSR) can effectively improve these two properties. Axial foreshortening is mainly determined by the bridge geometry as well as the connecting position of the bridge with the adjacent supporting rings. It is feasible to improve the axial foreshortening by using the bridges with a curved structure and locating the connecting position in the middle of the straight section of the supporting elements. The rationality of the proposed OCS and the effectiveness of the finite element method have been verified by in vitro experiments.

scholarly journals Experimental evaluation of stent retrievers’ mechanical properties and effectiveness

2016 ◽  
Vol 9 (3) ◽  
pp. 257-263 ◽  
Author(s):  
Paolo Machi ◽  
Franck Jourdan ◽  
Dominique Ambard ◽  
Cedric Reynaud ◽  
Kyriakos Lobotesis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Vessel Wall ◽  
Large Diameter ◽  
Mechanical Tests ◽  
Radial Force ◽  
Functional Tests ◽  
Clot Removal ◽  
Stent Retrievers ◽  
Thrombus Removal

BackgroundFive randomized controlled trials recently appeared in the literature demonstrating that early mechanical thrombectomy in patients with acute ischemic stroke is significantly related to an improved outcome. Stent retrievers are accepted as the most effective devices for intracranial thrombectomy.ObjectiveTo analyze the mechanical properties of stent retrievers, their behavior during retrieval, and interaction with different clots and to identify device features that might correlate with the effectiveness of thrombus removal.Materials and methodsAll stent retrievers available in France up to June 2015 were evaluated by mechanical and functional tests aimed at investigating the variation of their radial force and their behavior during retrieval. Devices were also tested during in vitro thrombectomies using white and red experimental thrombi produced with human blood. Functional tests and in vitro thrombectomies were conducted using a rigid 3D printed vascular model.ResultsMechanical tests showed a variation in radial force during retrieval for each stent. A constant radial force during retrieval was related to continuous cohesion over the vessel wall and a higher rate of clot removal efficacy. All stent retrievers failed when interacting with white large thrombi (diameter ≥6 mm).ConclusionsNone of the tested devices were effective in removing white clots of large diameter (≥6 mm). Constant radial force during retrieval allows constant cohesion to the vessel wall and pressure over the clot; such features allow for a higher rate of clot removal.

scholarly journals A realistic way to investigate the design, and mechanical properties of flow diverter stents

2021 ◽  
Author(s):  
Prasanth Velvaluri ◽  
Mariya Pravdivtseva ◽  
Johannes Hensler ◽  
Fritz Wodarg ◽  
Olav Jansen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flow Diverter ◽  
Radial Force ◽  
Cell Area ◽  
Flow Properties ◽  
4D Flow ◽  
Flow Mri ◽  
Mechanical Devices ◽  
First Time

Purpose: Braided flow diverters (FD) are highly sophisticated, delicate, and intricate mechanical devices used to treat intracranial aneurysms and thus saving lives. Testing such devices in vitro, however, remains an unsolved challenge. Here, we evaluate methods that access flow, design, and mechanical properties in vitro. Methods: Flow properties, cell porosity, and cell area were evaluated by placing FDs in patient-derived, 3D printed models of human vasculature. 4D flow MRI was used to measure fluid dynamics. Laser microscopy was used to measure porosity and cell area with the top of aneurysm sac cut off for the model. New testing methods were developed to investigate the bending, circumferential, and longitudinal radial force continuously over varying diameters. Results: The placement and flow properties of the FD in the vasculature models were successfully measured by MRI, although artifacts occurred. The setup to measure porosity and cell area inside of the model proved successful. The newly discussed methods allowed us to measure the indicated forces, to our knowledge for the first time, continuously. Conclusion: Modern and specifically tailored techniques, some of which were presented here for the first time, allow detailed insights into the flow and mechanical properties of braided flow diverter stents.

scholarly journals Carbamylation of elastic fibers is a molecular substratum of aortic stiffness

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Manon Doué ◽  
Anaïs Okwieka ◽  
Alexandre Berquand ◽  
Laëtitia Gorisse ◽  
Pascal Maurice ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cardiovascular Diseases ◽  
Aortic Stiffness ◽  
Molecular Mechanisms ◽  
Elastic Fiber ◽  
Plasma Concentrations ◽  
Vascular Wall ◽  
Elastic Fibers ◽  
Fiber Morphology

AbstractBecause of their long lifespan, matrix proteins of the vascular wall, such as elastin, are subjected to molecular aging characterized by non-enzymatic post-translational modifications, like carbamylation which results from the binding of cyanate (mainly derived from the dissociation of urea) to protein amino groups. While several studies have demonstrated a relationship between increased plasma concentrations of carbamylated proteins and the development of cardiovascular diseases, molecular mechanisms explaining the involvement of protein carbamylation in these pathological contexts remain to be fully elucidated. The aim of this work was to determine whether vascular elastic fibers could be carbamylated, and if so, what impact this phenomenon would have on the mechanical properties of the vascular wall. Our experiments showed that vascular elastin was carbamylated in vivo. Fiber morphology was unchanged after in vitro carbamylation, as well as its sensitivity to elastase degradation. In mice fed with cyanate-supplemented water in order to increase protein carbamylation within the aortic wall, an increased stiffness in elastic fibers was evidenced by atomic force microscopy, whereas no fragmentation of elastic fiber was observed. In addition, this increased stiffness was also associated with an increase in aortic pulse wave velocity in ApoE−/− mice. These results provide evidence for the carbamylation of elastic fibers which results in an increase in their stiffness at the molecular level. These alterations of vessel wall mechanical properties may contribute to aortic stiffness, suggesting a new role for carbamylation in cardiovascular diseases.

The Role of Stent Design and Polymers in Safety Outcomes – A Review

2012 ◽  
Vol 8 (1) ◽  
pp. 63
Author(s):  
Carlo Zivelonghi ◽  
Giulia Geremia ◽  
Michele Pighi ◽  
Flavio Ribichini ◽  
◽  
...  
Keyword(s):  
Clinical Performance ◽  
Drug Carrier ◽  
Chemical Properties ◽  
Vascular Wall ◽  
Radial Force ◽  
Vascular Trauma ◽  
Polymer Composition ◽  
Drug Eluting Stent ◽  
Stent Design ◽  
Drug Elution

Each component of a drug-eluting stent (DES) contributes to the safety of the device. Continuous efforts are being dedicated to the search of the optimal compromise between facility of use, safety and long-term efficacy. Shorter balloons reduce the vascular trauma beyond the stent struts; the metallic composition of the stent platform and the platform itself interact with the vascular wall in a long-lasting equilibrium between radial force, vessel patency and reparative cellular regrowth. The modality of drug elution is largely regulated by the chosen drug carrier, rather than by the chemical properties of the drug itself. Drug elution can be accomplished by permanent polymers that remain in the vessel wall forever, by biodegradable polymers that leave the naked metallic structure behind after their complete absorption, or even by direct release of the drug from stent reservoirs. The clinical performance of DESs has been exhaustively assessed in a large number of studies that have showed rapid and continuous improvements, from the first-generation DESs to the latest devices, based on substantial changes in stent design and polymer composition.

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