scholarly journals The Effect of Pentagalloyl Glucose on the Wall Mechanics and Inflammatory Activity of Rat Abdominal Aortic Aneurysms

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Mirunalini Thirugnanasambandam ◽  
Dan T. Simionescu ◽  
Patricia G. Escobar ◽  
Eugene Sprague ◽  
Beth Goins ◽  
...  
Keyword(s):  
Biological Markers ◽  
Wall Stress ◽  
Treated Group ◽  
Untreated Group ◽  
Aortic Aneurysms ◽  
Inflammatory Activity ◽  
Element Analysis ◽  
Abdominal Aortic ◽  
Pentagalloyl Glucose ◽  
And Biological Markers

An abdominal aortic aneurysm (AAA) is a permanent localized expansion of the abdominal aorta with mortality rate of up to 90% after rupture. AAA growth is a process of vascular degeneration accompanied by a reduction in wall strength and an increase in inflammatory activity. It is unclear whether this process can be intervened to attenuate AAA growth, and hence, it is of great clinical interest to develop a technique that can stabilize the AAA. The objective of this work is to develop a protocol for future studies to evaluate the effects of drug-based therapies on the mechanics and inflammation in rodent models of AAA. The scope of the study is limited to the use of pentagalloyl glucose (PGG) for aneurysm treatment in the calcium chloride rat AAA model. Peak wall stress (PWS) and matrix metalloproteinase (MMP) activity, which are the biomechanical and biological markers of AAA growth and rupture, were evaluated over 4 weeks in untreated and treated (with PGG) groups. The AAA specimens were mechanically characterized by planar biaxial tensile testing and the data fitted to a five-parameter nonlinear, hyperelastic, anisotropic Holzapfel–Gasser–Ogden (HGO) material model, which was used to perform finite element analysis (FEA) to evaluate PWS. Our results demonstrated that there was a reduction in PWS between pre- and post-AAA induction FEA models in the treatment group compared to the untreated group using either animal-specific or average material properties. However, this reduction was not statistically significant. Conversely, there was a statistically significant reduction in MMP-activated fluorescent signal between pre- and post-AAA induction models in the treated group compared to the untreated group. Therefore, the primary contribution of this work is the quantification of the stabilizing effects of PGG using biomechanical and biological markers of AAA, thus indicating that PGG could be part of a new clinical treatment strategy that will require further investigation.

Use of the Photoelastic Method to Determine the Wall Stress in Realistic Abdominal Aortic Aneurysm Models

2011 ◽  
Author(s):  
Barry J. Doyle ◽  
Anthony Callanan ◽  
John Killion ◽  
Timothy M. McGloughlin
Keyword(s):  
Wall Stress ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Western World ◽  
Photoelastic Method ◽  
Element Analysis ◽  
Abdominal Aortic ◽  
The Us ◽  
Numerical Tools

Abdominal aortic aneurysms (AAAs) remain a significant cause of death in the Western world with over 15,000 deaths per year in the US linked to AAA rupture. Recent research [1] has questioned the use of maximum diameter as a definitive risk parameter as it is now believed that alternative factors may be important in rupture-prediction. Wall stress was shown to be a better predictor than diameter of rupture [1], with biomechanics-based rupture indices [2,3] and asymmetry also reported to have potential clinical applicability [4]. However, the majority of numerical methods used to form these alternative rupture parameters are without rigorous experimental validation, and therefore may not be as accurate as believed. Validated experiments are required in order to convince the clinical community of the worth of numerical tools such as finite element analysis (FEA) in AAA risk-prediction. Strain gauges have been used in the past to determine the strain on an AAA [5], however, the photoelastic method has also proved to be a useful tool in AAA biomechanics [6]. This paper examines the approach using three medium-sized patient-specific AAA cases at realistic pressure loadings.

Abdominal Aortic Aneurysm: From Clinical Imaging to Realistic Replicas

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Sergio Ruiz de Galarreta ◽  
Aitor Cazón ◽  
Raúl Antón ◽  
Ender A. Finol
Keyword(s):  
Wall Thickness ◽  
Physiological Stress ◽  
Ex Vivo ◽  
Casting Process ◽  
Aortic Aneurysms ◽  
Optical Methods ◽  
Patient Specific ◽  
Uniaxial Tensile ◽  
Element Analysis ◽  
Abdominal Aortic

The goal of this work is to develop a framework for manufacturing nonuniform wall thickness replicas of abdominal aortic aneurysms (AAAs). The methodology was based on the use of computed tomography (CT) images for virtual modeling, additive manufacturing for the initial physical replica, and a vacuum casting process and range of polyurethane resins for the final rubberlike phantom. The average wall thickness of the resulting AAA phantom was compared with the average thickness of the corresponding patient-specific virtual model, obtaining an average dimensional mismatch of 180 μm (11.14%). The material characterization of the artery was determined from uniaxial tensile tests as various combinations of polyurethane resins were chosen due to their similarity with ex vivo AAA mechanical behavior in the physiological stress configuration. The proposed methodology yields AAA phantoms with nonuniform wall thickness using a fast and low-cost process. These replicas may be used in benchtop experiments to validate deformations obtained with numerical simulations using finite element analysis, or to validate optical methods developed to image ex vivo arterial deformations during pressure-inflation testing.

Dose-dependent effect of ANG II-receptor antagonist on myocyte remodeling in rat cardiac hypertrophy

1997 ◽  
Vol 273 (4) ◽  
pp. H1824-H1831 ◽  
Author(s):  
Masakazu Obayashi ◽  
Masafumi Yano ◽  
Michihiro Kohno ◽  
Shigeki Kobayashi ◽  
Taketo Tanigawa ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Receptor Antagonist ◽  
Pressure Overload ◽  
Wall Stress ◽  
Treated Group ◽  
Left Ventricular ◽  
Abdominal Aortic ◽  
Significant Difference ◽  
And Function ◽  
Vehicle Treated Group

The goal of this study was to examine the effect of an angiotensin II type 1 (AT1)-receptor antagonist (TCV-116) on left ventricular (LV) geometry and function during the development of pressure-overload LV hypertrophy. A low (LD; 0.3 mg ⋅ kg−1 ⋅ day−1) or a high (HD; 3.0 mg ⋅ kg−1 ⋅ day−1) dose of TCV-116 was administered to abdominal aortic-banded rats over 4 wk, and hemodynamics and morphology were then evaluated. In both LD and HD groups, peak LV pressures were decreased to a similar extent compared with the vehicle-treated group but stayed at higher levels than in the sham-operated group. In the LD group, both end-diastolic wall thickness (3.08 ± 0.14 mm) and myocyte width (13.3 ± 0.1 μm) decreased compared with those in the vehicle-treated group (3.67 ± 0.19 mm and 15.3 ± 0.1 μm, respectively; both P < 0.05). In the HD group, myocyte length was further decreased (HD: 82.6 ± 2.6, LD: 94.1 ± 2.9 μm; P < 0.05) in association with a reduction in LV midwall radius (HD: 3.36 ± 0.12, LD: 3.60 ± 0.14 mm; P < 0.05) and peak midwall fiber stress (HD: 69 ± 8, LD: 83 ± 10 × 103dyn/cm2; P < 0.05). There was no significant difference in cardiac output among all groups. The AT1-receptor antagonist TCV-116 induced an inhibition of the development of pressure-overload hypertrophy. Morphologically, not only the width but also the length of myocytes was attenuated with TCV-116, leading to a reduction of midwall radius and hence wall stress, which in turn may contribute to a preservation of cardiac output.

scholarly journals A Methodology for the Derivation of Unloaded Abdominal Aortic Aneurysm Geometry With Experimental Validation

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Santanu Chandra ◽  
Vimalatharmaiyah Gnanaruban ◽  
Fabian Riveros ◽  
Jose F. Rodriguez ◽  
Ender A. Finol
Keyword(s):  
Finite Element ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Stress Component ◽  
Wall Stress ◽  
Patient Specific ◽  
Element Analysis ◽  
Nodal Surface ◽  
Abdominal Aortic ◽  
Peak Wall Stress

In this work, we present a novel method for the derivation of the unloaded geometry of an abdominal aortic aneurysm (AAA) from a pressurized geometry in turn obtained by 3D reconstruction of computed tomography (CT) images. The approach was experimentally validated with an aneurysm phantom loaded with gauge pressures of 80, 120, and 140 mm Hg. The unloaded phantom geometries estimated from these pressurized states were compared to the actual unloaded phantom geometry, resulting in mean nodal surface distances of up to 3.9% of the maximum aneurysm diameter. An in-silico verification was also performed using a patient-specific AAA mesh, resulting in maximum nodal surface distances of 8 μm after running the algorithm for eight iterations. The methodology was then applied to 12 patient-specific AAA for which their corresponding unloaded geometries were generated in 5–8 iterations. The wall mechanics resulting from finite element analysis of the pressurized (CT image-based) and unloaded geometries were compared to quantify the relative importance of using an unloaded geometry for AAA biomechanics. The pressurized AAA models underestimate peak wall stress (quantified by the first principal stress component) on average by 15% compared to the unloaded AAA models. The validation and application of the method, readily compatible with any finite element solver, underscores the importance of generating the unloaded AAA volume mesh prior to using wall stress as a biomechanical marker for rupture risk assessment.

Abstract 348: A Novel Self Expanding Stent Technology for treatment of Aortic Aneurysms - Finite Element Analysis

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Mark Arokiaraj
Keyword(s):  
Wall Stress ◽  
Radial Force ◽  
Aortic Aneurysms ◽  
Element Analysis ◽  
Cell Width ◽  
Nitinol Stent ◽  
Aneurysm Wall ◽  
Hyper Elastic ◽  
Peak Wall Stress ◽  
Aneurysm Model

Background: To investigate a novel self-expanding Nitinol stent model in treatment of aortic aneurysms. Methods: A novel large self-expanding Nitinol stent method was designed with strut thickness of 70µM x 70µM width and it was deployed in a virtual aneurysm model of 6cm wide x 6cm long fusiform hyper-elastic anisotropic model. At cell width of 9mm, there was no buckling of the deployed stent. The peak wall stress and stress-strain properties of the aortic aneurysm wall; and the adjacent normal segments of aorta were studied at various pressures with or without stent. The radial force of the stents was tested after parametric variations. A prototype 300µM x 150µM stent with cell width of 9mm was evaluated similarly for maximal stress distribution after embedding in the aortic wall and with a tissue overgrowth of 1mm over the stent. Results: The 300µM x 150µM stent reduced the peak wall stress by 70% in the aneurysm and 50% reduction in compliance after a tissue overgrowth of 1mm over the stent struts. Conclusions: There is potential for a novel Nitinol based self-expanding stent in the therapy of aortic aneurysms.

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