EFFECTS OF BALLOON LENGTH AND COMPLIANCE ON VASCULAR STENT EXPANSION

Vascular stents are used to dilate arteries that are narrowed or clogged by plaque. However, in-stent restenosis is still one of the major causes of the clinical failure. It is believed that vessel trauma imposed during stent deployment is closely correlated to restenosis. Clinical observations show that the longitudinal and axial geographic miss in pre/post-dilation are responsible for the vessel trauma. The interactions between the stent-strut and the artery are difficult to measure in vivo or clinically and reported results are very limited. A numerical approach that leverages on computing power can provide new insights into the stent implantation process. In this study, the effects of balloon length and compliance that play important roles during stent expansion were investigated. Areas in the vessels with high stress concentrations were identified as these were weaknesses that might have a high possibility of vascular injury. Two different types of numerical models were constructed: a simplified model that considered only the balloon and stent and a more comprehensive model that consisted of the balloon, stent, plaque, and artery. Virtual stent implantation trials were simulated and the phenomena of stent recoil, dogboning and foreshortening were observed and examined. It was found that balloons which were slightly longer than the stent and less compliance would be more likely to eliminate dogboning. Furthermore, a new parameter, namely the Ectropion angle, was introduced to describe the turning effect of the stent end in situations when dogboning could not adequately characterize this phenomenon. The present study could provide guidance for the placement of stents by clinical practitioners.

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Modeling of the Onset, Propagation, and Interaction of Multiple Cracks Generated From Corrosion Pits by Using Peridynamics

Journal of Engineering Materials and Technology ◽

10.1115/1.4036443 ◽

2017 ◽

Vol 139 (4) ◽

Cited By ~ 13

Author(s):

Dennj De Meo ◽

Luigi Russo ◽

Erkan Oterkus

Keyword(s):

Structural Damage ◽

Crack Nucleation ◽

Numerical Models ◽

Measurement Techniques ◽

High Stress ◽

Numerical Approach ◽

Multiple Cracks ◽

Numerical Instabilities ◽

Corrosion Pits ◽

Crack Transition

High stress regions around corrosion pits can lead to crack nucleation and propagation. In fact, in many engineering applications, corrosion pits act as precursor to cracking, but prediction of structural damage has been hindered by lack of understanding of the process by which a crack develops from a pit and limitations in visualization and measurement techniques. An experimental approach able to accurately quantify the stress and strain field around corrosion pits is still lacking. In this regard, numerical modeling can be helpful. Several numerical models, usually based on finite element method (FEM), are available for predicting the evolution of long cracks. However, the methodology for dealing with the nucleation of damage is less well developed, and, often, numerical instabilities arise during the simulation of crack propagation. Moreover, the popular assumption that the crack has the same depth as the pit at the point of transition and by implication initiates at the pit base has no intrinsic foundation. A numerical approach is required to model nucleation and propagation of cracks without being affected by any numerical instability and without assuming crack initiation from the base of the pit. This is achieved in the present study, where peridynamics (PD) theory is used in order to overcome the major shortcomings of the currently available numerical approaches. Pit-to-crack transition phenomenon is modeled, and nonconventional and more effective numerical frameworks that can be helpful in failure analysis and in the design of new fracture-resistant and corrosion-resistant materials are presented.

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A tough endothelium-like dressing for vascular stents

10.21203/rs.3.rs-431076/v1 ◽

2021 ◽

Author(s):

Yin Chen ◽

Peng Gao ◽

Lu Huang ◽

Xing Tan ◽

Ningling Zhou ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Surface Engineering ◽

De Novo ◽

Neointimal Hyperplasia ◽

Muscle Cells ◽

Vascular Stents ◽

Stent Restenosis ◽

In Stent Restenosis

Abstract Vascular stent is viewed as one of the greatest advancements in interventional cardiology. However, current approved stents suffer from in-stent restenosis associated with neointimal hyperplasia or stent thrombosis. To address this issue, we developed an endothelium-like (EL) dressing for vascular stents inspired by the importance and biological functions of native endothelium for cardiovascular system. Our EL dressing is based on a de novo designed hydrogel that is mechanically tough and could preserve integrity on stents during angioplasty. Due to its physiochemical similarities to subendothelial extracellular matrix, the EL dressing facilitated the adhesion and growth of endothelial cells. Besides, it is non-thrombotic and capable of inhibiting smooth muscle cells thanks to the capacity to catalyze nitric oxide generation. Transcriptome analysis further unraveled the EL dressing could modulate the inflammatory response and induce the relaxation of smooth muscle cells, while potentially promoting angiogenesis by stimulating the expression of angiogenic factors. In vivo study demonstrated vascular stents encapsulated by it promoted rapid restoration of native endothelium and persistently suppressed in-stent restenosis in both leporine and swine models. We expect such EL dressing will open a new avenue to the surface engineering of vascular implants for better clinical outcomes.

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In vivo intramuscular fascicle-aponeuroses dynamics of the human medial gastrocnemius during plantarflexion and dorsiflexion of the foot

Journal of Applied Physiology ◽

10.1152/japplphysiol.91598.2008 ◽

2009 ◽

Vol 107 (4) ◽

pp. 1276-1284 ◽

Cited By ~ 49

Author(s):

David D. Shin ◽

John A. Hodgson ◽

V. Reggie Edgerton ◽

Shantanu Sinha

Keyword(s):

Gastrocnemius Muscle ◽

Imaging Techniques ◽

High Stress ◽

Proximal Region ◽

Pennation Angle ◽

Medial Gastrocnemius ◽

Stress Concentrations ◽

Fascicle Length ◽

Medial Gastrocnemius Muscle

Velocity-encoded phase-contrast magnetic resonance (MR) imaging techniques and a computer-controlled MR-compatible foot pedal device were used to investigate the medial gastrocnemius muscle and aponeurosis deformations during passive and active eccentric movements of the plantarflexors. Intrafascicular strain, measured as the ratio of strain in the fascicle segment at its insertion to strain at its origin, was nonuniform along the proximodistal axis of the muscle ( P < 0.01), progressively increasing from the proximal to distal direction. The high intrafascicular strain regions appeared to correlate with the muscle regions that are likely to encounter high stress concentrations, i.e., the regions where the muscle physiological cross section decreases close to the tendons. The architectural gear ratio, i.e., the mechanical amplification ratio of fascicle length displacement to that of tendon/aponeuroses in a pennate muscle, also exhibited significant regional differences, with the highest ratios in the proximal region of the muscle accompanied by a higher initial pennation angle and a larger range of fascicular rotation about the origin. Values close to unity in the distal region of the muscle suggest that the aponeurosis separation may decrease in this region. Fascicle length and pennation angle changes were significantly influenced by force generation in the muscle, probably due to a shortening of the loaded muscle fibers relative to a passive condition. Overall, our data illustrate significant proximodistal intramuscular heterogeneity as supported by a regionally variable end-to-end strain ratio of fascicles and angle changes in the medial gastrocnemius muscle during passive and active ankle movements. These observations emphasize the need to reassess current conceptual models of muscle-tendon mechanics.

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Location-Specific Comparison Between a 3D In-Stent Restenosis Model and Micro-CT and Histology Data from Porcine In Vivo Experiments

Cardiovascular Engineering and Technology ◽

10.1007/s13239-019-00431-4 ◽

2019 ◽

Vol 10 (4) ◽

pp. 568-582 ◽

Cited By ~ 2

Author(s):

P. S. Zun ◽

A. J. Narracott ◽

C. Chiastra ◽

J. Gunn ◽

A. G. Hoekstra

Keyword(s):

Experimental Data ◽

In Silico ◽

Computational Models ◽

Tissue Growth ◽

Micro Ct ◽

Stent Deployment ◽

Stent Restenosis ◽

In Stent Restenosis ◽

Good Agreement

Abstract Background Coronary artery restenosis is an important side effect of percutaneous coronary intervention. Computational models can be used to better understand this process. We report on an approach for validation of an in silico 3D model of in-stent restenosis in porcine coronary arteries and illustrate this approach by comparing the modelling results to in vivo data for 14 and 28 days post-stenting. Methods This multiscale model includes single-scale models for stent deployment, blood flow and tissue growth in the stented vessel, including smooth muscle cell (SMC) proliferation and extracellular matrix (ECM) production. The validation procedure uses data from porcine in vivo experiments, by simulating stent deployment using stent geometry obtained from micro computed tomography (micro-CT) of the stented vessel and directly comparing the simulation results of neointimal growth to histological sections taken at the same locations. Results Metrics for comparison are per-strut neointimal thickness and per-section neointimal area. The neointimal area predicted by the model demonstrates a good agreement with the detailed experimental data. For 14 days post-stenting the relative neointimal area, averaged over all vessel sections considered, was 20 ± 3% in vivo and 22 ± 4% in silico. For 28 days, the area was 42 ± 3% in vivo and 41 ± 3% in silico. Conclusions The approach presented here provides a very detailed, location-specific, validation methodology for in silico restenosis models. The model was able to closely match both histology datasets with a single set of parameters. Good agreement was obtained for both the overall amount of neointima produced and the local distribution. It should be noted that including vessel curvature and ECM production in the model was paramount to obtain a good agreement with the experimental data.

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ARTERIAL WALL MECHANICS AND CLINICAL IMPLICATIONS AFTER CORONARY STENTING: COMPARISONS OF THREE STENT DESIGNS

International Journal of Applied Mechanics ◽

10.1142/s1758825112500135 ◽

2012 ◽

Vol 04 (02) ◽

pp. 1250013 ◽

Cited By ~ 9

Author(s):

LINXIA GU ◽

SHIJIA ZHAO ◽

STACEY R. FROEMMING

Keyword(s):

Stress Distributions ◽

Cobalt Chromium ◽

Stress Concentrations ◽

Stent Deployment ◽

Stress Variation ◽

Stent Restenosis ◽

Arterial Wall Mechanics ◽

The Impact ◽

The Relationship ◽

In Stent Restenosis

The goal of this work is to quantitatively assess the relationship between the reported restenosis rates and stent induced arterial stress or strain parameters through finite element method. The impact of three stent designs (Palmaz–Schatz stent, Express stent, and Multilink Vision stent) on the arterial stress distributions were characterized. The influences of initial stent deployment location, stent-tissue friction, and plaque properties on the arterial stresses were also investigated. Higher arterial stresses were observed at the proximal end of the plaque. The Multilink–Vision stent induced lesser stress concentrations due to the high stiffness of the Cobalt Chromium material and thinner strut thickness. The stent-induced arterial stress concentrations were positively correlated with the reported in-stent restenosis rates, with a correlation coefficient of 0.992. Stent deployment initiated at the center of the lumen led to less arterial stress variation, while deployment closer to the thinner edge of the plaque causes higher arterial stresses. The friction between the stent and tissue was found to contribute to larger stress alternations for the plaque only. Increased plaque stiffness resulted in a reduced arterial stress concentration and clinical restenosis rate. Results presented herein suggested that arterial stresses serve as a comprehensive index factor to predict the occurrence of in-stent restenosis, which will facilitate the new stent design and surgical planning.

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Current Use of Intravascular Ultrasound in Coronary Artery Disease

Clinical Medicine Insights Therapeutics ◽

10.4137/cmt.s18472 ◽

2016 ◽

Vol 8 ◽

pp. CMT.S18472 ◽

Cited By ~ 1

Author(s):

Ahmed Hassan ◽

Tomotaka Dohi ◽

Hiroyuki Daida

Keyword(s):

Intravascular Ultrasound ◽

Fibrous Tissue ◽

Intervention Strategy ◽

Coronary Intervention ◽

Visual Assessment ◽

Coronary Plaque ◽

Stent Deployment ◽

Stent Restenosis ◽

Stent Expansion ◽

Predominant Component

Recently, most coronary interventions rely on visual assessment of the coronary lesions using angiography with all known inherent limitations. Intravascular ultrasound (IVUS) allows for the evaluation of the coronary pathology to obtain information about both the extent and nature of atherosclerotic plaque; thus, planning the intervention strategy is based on objective data. Following the advent of gray-scale IVUS, several modes had been developed to study coronary plaque composition, thus determining the predominant component of the plaque, fibrous tissue, lipid-necrotic core, or calcium, and the intervention strategy. After intervention, IVUS plays an important role in optimizing the results after stent deployment regarding stent expansion and apposition to reduce the incidence of both stent thrombosis and in-stent restenosis. This review discusses the basic role of IVUS in evaluating plaque structure and parameters to optimize results after coronary intervention in light of recent evidence.

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Recent advances to accelerate re-endothelialization for vascular stents

Journal of Tissue Engineering ◽

10.1177/2041731417731546 ◽

2017 ◽

Vol 8 ◽

pp. 204173141773154 ◽

Cited By ~ 33

Author(s):

Tarek M Bedair ◽

Mahmoud A ElNaggar ◽

Yoon Ki Joung ◽

Dong Keun Han

Keyword(s):

Cardiovascular Diseases ◽

Surface Chemistry ◽

Surface Topography ◽

Stent Implantation ◽

Driving Force ◽

Large Body ◽

Vascular Stents ◽

Stent Restenosis ◽

The World ◽

In Stent Restenosis

Cardiovascular diseases are considered as one of the serious diseases that leads to the death of millions of people all over the world. Stent implantation has been approved as an easy and promising way to treat cardiovascular diseases. However, in-stent restenosis and thrombosis remain serious problems after stent implantation. It was demonstrated in a large body of previously published literature that endothelium impairment represents a major factor for restenosis. This discovery became the driving force for many studies trying to achieve an optimized methodology for accelerated re-endothelialization to prevent restenosis. Thus, in this review, we summarize the different methodologies opted to achieve re-endothelialization, such as, but not limited to, manipulation of surface chemistry and surface topography.

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