Mechanical Properties and Microstructure of Intraluminal Thrombus From Abdominal Aortic Aneurysm

2001 ◽  
Vol 123 (6) ◽  
pp. 536-539 ◽  
Author(s):  
David H. J. Wang ◽  
Michel Makaroun ◽  
Marshall W. Webster ◽  
David A. Vorp
Keyword(s):  
Constitutive Model ◽  
Wall Stress ◽  
Uniaxial Tensile ◽  
Intraluminal Thrombus ◽  
Material Parameters ◽  
Uniaxial Tensile Testing ◽  
Abdominal Aortic ◽  
Significant Difference ◽  
Two Parameter ◽  
Luminal Region

Accurate estimation of the wall stress distribution in an abdominal aortic aneurysm (AAA) may prove clinically useful by predicting when a particular aneurysm will rupture. Appropriate constitutive models for both the wall and the intraluminal thrombus (ILT) found in most AAA are necessary for this task. The purpose of this work was to determine the mechanical properties of ILT within AAA and to derive a more suitable constitutive model for this material. Uniaxial tensile testing was carried out on 50 specimens, including 14 longitudinally oriented and 14 circumferentially oriented specimens from the luminal region of the ILT, and 11 longitudinally oriented and 11 circumferentially oriented specimens from the medial region. A two-parameter, large-strain, hyperelastic constitutive model was developed and used to fit the uniaxial tensile testing data for determination of the material parameters. Maximum stiffness and strength were also determined from the data for each specimen. Scanning electron microscopy (SEM) was conducted to study the regional microstructural difference. Our results indicate that the microstructure of ILT differs between the luminal, medial, and abluminal regions, with the luminal region stronger and stiffer than the medial region. In all cases, the constitutive model fit the experimental data very well R2>0.98. No significant difference was found for either of the two material parameters between longitudinal and circumferential directions, but a significant difference in material parameters, stiffness, and strength between the luminal and medial regions was determined p<0.01. Therefore, our results suggest that ILT is an inhomogeneous and possibly isotropic material. The two-parameter, hyperelastic, isotropic, incompressible material model derived here for ILT can be easily incorporated into finite element models for simulation of wall stress distribution in AAA.

A Large Strain Hyperelastic Constitutive Model for Intraluminal Thrombus From Abdominal Aortic Aneurysm

1999 ◽  
Author(s):  
David H. J. Wang ◽  
Michel S. Makaroun ◽  
Marshall W. Webster ◽  
David A. Vorp
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Constitutive Model ◽  
Large Strain ◽  
Constitutive Models ◽  
Wall Stress ◽  
Accurate Estimation ◽  
Elastic Model ◽  
Intraluminal Thrombus ◽  
Abdominal Aortic

Abstract Rupture of abdominal aortic aneurysm (AAA) occurs when the wall stress acting on the dilated aortic wall exceeds the strength of the tissue. Therefore, accurate estimation of the wall stress distribution in AAA may be a clinically useful tool to predict their rupture. A majority of AAA contains a laminated, stationary, intraluminal thrombus (ILT) (Harter et al., 1982). Previous investigations have shown that ILT may significantly alter the wall stress acting on AAA (Inzoli et al., 1993; Mower et al., 1997; Stringfellow et al., 1987; Vorp et al., 1998; Di Martino et al., 1998). However, all of those studies used a simplified linear elastic model for ILT. This is inappropriate and can lead to inaccuracies since both AAA wall and contained ILT undergo large deformation during the cardiac cycle (Vorp et al., 1996). Therefore, to accomplish accurate stress analysis of AAA, appropriate constitutive models for both the wall and ILT are necessary. Our group has previously proposed a finite strain constitutive model for the AAA wall (Raghavan et al., in press). The purpose of this work was to derive a more suitable constitutive model and the associated mechanical properties for the ILT within AAA.

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.

Effect of Intraluminal Thrombus on Wall Stress and Growth Rate of Abdominal Aneurysms

2010 ◽  
Author(s):  
Lambert Speelman ◽  
E. Marielle H. Bosboom ◽  
Geert Willem H. Schurink ◽  
Jaap Buth ◽  
Marcel Breeuwer ◽  
...  
Keyword(s):  
Risk Estimation ◽  
Wall Stress ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Intraluminal Thrombus ◽  
Abdominal Aortic ◽  
Risk Of Rupture ◽  
Peak Wall Stress ◽  
Higher Sensitivity ◽  
Main Factor

In the decision for surgical repair of abdominal aortic aneurysms (AAAs), the risk of rupture is weighed carefully against the risk of the surgical procedure. Currently, AAA diameter is the main factor that determines the decision for surgery. However, in rupture risk estimation AAA wall stress has higher sensitivity and specificity than maximum diameter [1]. Moreover, peak wall stress was higher for ruptured than for non-ruptured or asymptomatic AAAs [2, 3].

Effect of Variations in Intraluminal Thrombus Constitutive Properties on Abdominal Aortic Aneurysm Wall Stress: A Parametric Study

2001 ◽  
Author(s):  
Elena S. Di Martino ◽  
David H. J. Wang ◽  
Alberto Redaelli ◽  
Michel S. Makaroun ◽  
David A. Vorp
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Parametric Study ◽  
Wall Stress ◽  
Transverse Diameter ◽  
Intraluminal Thrombus ◽  
Arterial Blood ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Constitutive Parameters

Abstract The prevalence of abdominal aortic aneurysm (AAA) is growing together with population age, being 8.8% in a population above 65 years according to a recent study [1]. Deciding between elective surgical repair of AAA and watchful management is a complex issue due to the lack of reliable rupture risk indices. The maximum transverse diameter of AAA is most commonly used in clinical practice to base this decision. From a biomechanical viewpoint, AAA rupture is related to the balance between the stresses acting on the wall and strength of the wall tissue. Many different factors contribute to the stress within the aortic aneurysm wall, including the presence of intraluminal thrombus (ILT) [2–5], the local surface curvature [6] and material characteristics of the AAA wall [7], and the presence of local “stress concentrators” due to calcifications or local thinning. As regards the ILT, its role with respect to aneurysm wall stresses has given rise to many hypotheses. Some studies show that the pressure inside the thrombus is not reduced with respect to the arterial blood pressure, some, including studies from the authors, state a possible protective role [2–5]. Previously in our laboratory, a nonlinear, hyperelastic constitutive model was developed for ILT, and the parameters for which were determined through ex-vivo experimentation [8]. The purpose of this study was to investigate the reliability of using the same population-mean values of ILT constitutive parameters for estimates of wall stress distribution in all AAA. For this, we performed a parametric study in which the ELT constitutive parameters were varied within a physiological range and aortic wall stresses were evaluated.

Age-Related Differences in the Biaxial Biomechanical Behavior of Human Abdominal Aorta

2002 ◽  
Author(s):  
Jonathan P. Vande Geest ◽  
Michael S. Sacks ◽  
David A. Vorp
Keyword(s):  
Tensile Testing ◽  
Mechanical Response ◽  
Uniaxial Tensile ◽  
Aortic Tissue ◽  
Orthogonal Direction ◽  
Biomechanical Behavior ◽  
Uniaxial Tensile Testing ◽  
Age Related ◽  
Abdominal Aortic ◽  
Biomechanical Response

The biomechanical response of abdominal aortic tissue to uniaxial loading conditions has been reported previously [1]. This testing identified the uniaxial mechanical response of aortic tissue to specimens oriented in the longitudinal and circumferential directions, but did not provide significant evidence for the isotropy or anisotropy of this tissue. The information taken from uniaxial tensile testing is insufficient for the characterization of the multi-axial mechanical response of aortic tissue. In particular, the uniaxial response of a biological tissue in a given direction does not incorporate the effects of loading in an orthogonal direction. For these reasons, there exists a need for an enhanced description of the mechanical response of aortic tissue to loading in multiple planar directions. For the current investigation, biaxial tensile testing was performed on normal abdominal aortic tissue in order to gain insight into the anisotropy and age related differences of the biomechanical response of this tissue.

Intraluminal Thrombus in AAA Wall Stress Analysis

2007 ◽  
Author(s):  
Lambert Speelman ◽  
Evelyne A. van Dam ◽  
Gerrit W. M. Peters ◽  
E. Marielle M. Bosboom ◽  
Marcel C. M. Rutten ◽  
...  
Keyword(s):  
Stress Analysis ◽  
Software Package ◽  
Software Tool ◽  
Wall Stress ◽  
Rupture Risk ◽  
Medical Systems ◽  
Intraluminal Thrombus ◽  
Abdominal Aortic ◽  
Ct Data

In previous research abdominal aortic aneurysm (AAA) wall stress analysis has proven to be more accurate in rupture risk prediction than the clinically used diameter criterion [1]. Together with Philips Medical Systems (Best, NL), a clinical software tool is created that automatically derives the AAA geometry from patient CT data and performs AAA wall stress analysis (Hemodyn package). Using this software package, the role of intraluminal thrombus (ILT) in AAA wall stress analysis is evaluated in this study.

scholarly journals Impact of poroelasticity of intraluminal thrombus on wall stress of abdominal aortic aneurysms

2012 ◽  
Vol 11 (1) ◽  
pp. 62 ◽  
Author(s):  
Stanislav Polzer ◽  
T Gasser ◽  
Bernd Markert ◽  
Jiri Bursa ◽  
Pavel Skacel
Keyword(s):  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Intraluminal Thrombus ◽  
Abdominal Aortic

BIOMECHANICAL PROPERTIES OF MESHES FOLLOWING IMPLANTATION IN THE RAT ABDOMINAL WALL MODEL

2016 ◽  
Vol 16 (03) ◽  
pp. 1650036
Author(s):  
NATASHA UDPA ◽  
SHAMA IYER ◽  
SEAN P. MCDONOUGH ◽  
YINGXIN GAO
Keyword(s):  
Mechanical Strength ◽  
Abdominal Wall ◽  
Polypropylene Mesh ◽  
Biomechanical Properties ◽  
Uniaxial Tensile ◽  
Collagen Deposition ◽  
Collagen Types ◽  
Wall Model ◽  
Uniaxial Tensile Testing ◽  
Significant Difference

The objective of our study was to (1) evaluate mesh strength and collagen incorporation after 4 and 12 weeks of implantation in a rat abdominal wall model and (2) determine the relationship between collagen deposition and mechanical strength of a chitosan-coated polypropylene mesh. We implanted 0.5% chitosan-coated polypropylene mesh (PPM), collagen-coated PPM (PelvitexTM; C.R. Bard), and PPM (Avaulta Solo[Formula: see text]; C.R. Bard) using a rat abdominal defect model. Mechanical properties were determined from uniaxial tensile testing and collagen deposition of each mesh was evaluated 4 and 12 weeks post-implantation. We found that after implantation, the neo tissue of Ch-PPM is stiffer than the commercially available meshes. We also observed no significant difference in the ratio of collagen types I/III between mesh samples at 4 weeks or 12 weeks. We found no relationship between the ratio of collagen types I/III and the mechanical strength of mesh samples after implantation. The increased stiffness with chitosan coating could be due to increased muscle tissue ingrowth.

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