scholarly journals CFD Modelling of Abdominal Aortic Aneurysm on Hemodynamic Loads Using a Realistic Geometry with CT

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Eduardo Soudah ◽  
E. Y. K. Ng ◽  
T. H. Loong ◽  
Maurizio Bordone ◽  
Uei Pua ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Arterial Wall ◽  
Wall Stress ◽  
Asymmetry Index ◽  
Geometric Parameters ◽  
Cfd Modelling ◽  
Finite Elements Analysis ◽  
Abdominal Aortic

The objective of this study is to find a correlation between the abdominal aortic aneurysm (AAA) geometric parameters, wall stress shear (WSS), abdominal flow patterns, intraluminal thrombus (ILT), and AAA arterial wall rupture using computational fluid dynamics (CFD). Real AAA 3D models were created by three-dimensional (3D) reconstruction of in vivo acquired computed tomography (CT) images from 5 patients. Based on 3D AAA models, high quality volume meshes were created using an optimal tetrahedral aspect ratio for the whole domain. In order to quantify the WSS and the recirculation inside the AAA, a 3D CFD using finite elements analysis was used. The CFD computation was performed assuming that the arterial wall is rigid and the blood is considered a homogeneous Newtonian fluid with a density of 1050 kg/m3and a kinematic viscosity of4×10-3Pa·s. Parallelization procedures were used in order to increase the performance of the CFD calculations. A relation between AAA geometric parameters (asymmetry index (β), saccular index (γ), deformation diameter ratio (χ), and tortuosity index (ε)) and hemodynamic loads was observed, and it could be used as a potential predictor of AAA arterial wall rupture and potential ILT formation.

scholarly journals The Role of Geometric Parameters in the Prediction of Abdominal Aortic Aneurysm Wall Stress

2010 ◽  
Vol 39 (1) ◽  
pp. 42-48 ◽  
Author(s):  
E. Georgakarakos ◽  
C.V. Ioannou ◽  
Y. Kamarianakis ◽  
Y. Papaharilaou ◽  
T. Kostas ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Geometric Parameters ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Abdominal Aortic Aneurysm Wall

Abstract 297: Segmental Aortic Stiffening is a Mechanism Driving Early Abdominal Aortic Aneurysm Pathogenesis

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Uwe Raaz ◽  
Alexander M Zöllner ◽  
Ryuji Toh ◽  
Futoshi Nakagami ◽  
Isabel N Schellinger ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Aortic Wall ◽  
Ex Vivo ◽  
Wall Stress ◽  
Finite Elements Analysis ◽  
External Application ◽  
Abdominal Aortic ◽  
Aneurysm Growth ◽  
Aortic Stiffening

Stiffening of the aortic wall is a phenomenon consistently observed in abdominal aortic aneurysm (AAA). However, its role in AAA pathophysiology is largely undefined. Using an established murine elastase-induced AAA model, we demonstrate that segmental aortic stiffening (SAS) precedes aneurysm growth. Finite elements analysis (FEA)-based wall stress calculations reveal that early stiffening of the aneurysm-prone aortic segment leads to axial (longitudinal) stress generated by cyclic (systolic) tethering of adjacent, more compliant wall segments. Interventional stiffening of AAA-adjacent segments (via external application of surgical adhesive) significantly reduces aneurysm growth. These changes correlate with reduced segmental stiffness of the AAA-prone aorta (due to equalized stiffness in adjacent aortic segments), reduced axial wall stress, decreased production of reactive oxygen species (ROS), attenuated elastin breakdown, and decreased expression of inflammatory cytokines and macrophage infiltration, as well as attenuated apoptosis within the aortic wall. Cyclic pressurization of stiffened aortic segments ex vivo increases the expression of genes related to inflammation and extracellular matrix (ECM) remodeling. Finally, human ultrasound studies reveal that aging, a significant AAA risk factor, is accompanied by segmental infrarenal aortic stiffening. The present study introduces the novel concept of segmental aortic stiffening (SAS) as an early pathomechanism generating aortic wall stress and thereby triggering AAA growth. Therefore monitoring SAS by ultrasound might help to better identify patients at risk for AAA disease and better predict the susceptibility of small AAA to further growth. Moreover our results suggest that interventional mechanical stiffening of the AAA-adjacent aorta may be further tested as a novel treatment option to limit early AAA growth.

scholarly journals In vivo analysis of mechanical wall stress and abdominal aortic aneurysm rupture risk

2002 ◽  
Vol 36 (3) ◽  
pp. 589-597 ◽  
Author(s):  
Mark F. Fillinger ◽  
M.L. Raghavan ◽  
Steven P. Marra ◽  
Jack L. Cronenwett ◽  
Francis E. Kennedy
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Aneurysm Rupture ◽  
Rupture Risk ◽  
Abdominal Aortic Aneurysm Rupture ◽  
Abdominal Aortic ◽  
In Vivo Analysis

An Automated Methdology for Investigating the Correlation Between Abdominal Aortic Aneurysm Wall Stress and Risk of Rupture

2001 ◽  
Author(s):  
Madhavan L. Raghavan ◽  
Mark F. Fillinger ◽  
Steven P. Marra ◽  
Francis E. Kennedy
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Aneurysm Rupture ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Risk Of Rupture ◽  
Scan Data ◽  
Biomechanical Approach

Abstract Clinical experience with regard to predicting abdominal aortic aneurysm (AAA) rupture has shown that although AAA diameter is a good indicator, there are likely other risk factors. Some researchers have explored a biomechanical approach to predicting aneurysm rupture risk [1,2] based on the hypothesis that aneurysm rupture occurs when the mechanical stresses in the aortic wall exceed the wall failure strength. Therefore, knowledge of wall stresses in a particular AAA may help identify impending rupture. Recently, researchers have used patients’ abdominal CT scan data and blood pressure to estimate in-vivo AAA wall stresses [3]. In the present project, an improved automated methodology is used to predict AAA wall stress. The underlying correlation between mechanical stress and aneurysm wall rupture is also investigated.

Wall Stress Studies of Abdominal Aortic Aneurysm in a Clinical Model

2001 ◽  
Vol 15 (3) ◽  
pp. 355-366 ◽  
Author(s):  
Mano J. Thubrikar ◽  
Jihad Al-Soudi ◽  
Francis Robicsek
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Clinical Model ◽  
Stress Studies ◽  
Abdominal Aortic

Abstract 3718: MMP-12 Inhibitor Reduces Severity of ANGII-induced Aortic Abdominal Aneurysms in apoE−/− Mice

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Dawn A Savio ◽  
Anita R Halpern ◽  
Yuchuan Wu ◽  
Wei Li ◽  
Joseph Sypek ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Vascular Wall ◽  
Inflammatory Disorder ◽  
Gene Markers ◽  
Genetic Ablation ◽  
Macrophage Recruitment ◽  
Aneurysm Formation ◽  
Abdominal Aortic

Abdominal aortic aneurysm (AAA) is an inflammatory disorder characterized by local connective tissue degradation, macrophage recruitment and infiltration leading to aortic dilation and rupture. Aneurysms of the abdominal aorta represent a significant cardiovascular risk for which inflammation plays an integral role in the defined pathology. Genetic ablation of metalloprotease-12 (MMP-12) eliminates metalloelastase activity and attenuates aneurysm formation in apoE−/− mice. In the current study, a selective MMP-12 inhibitor, WAY-644 was evaluated in the well-established murine model of ANGII-induced aneurysm formation. This inhibitor displays activity for murine MMP-12, IC50 = 6.3 nM by FRET analysis, with low crossreactivity for other MMPs (exception MMP-8), and has established in vivo efficacy in inflammation models. Coadministration of WAY-644 to hyperlipidemic apoE−/− mice during ANGII infusion (1.44 mg/kg) for 28d alters the severity of AngII-induced AAAs as measured by changes in abdominal aortic wet weights and typical AAA classification. As expected, plasma MMP-12 protease activity measured by FRET analysis was inhibited. RNA profiling of abdominal aortic aneurysm tissue characterizes ANGII-induced AAA expansion driven by macrophage infiltration, destructive MMP production and attenuation by MMP-12 inhibition. The transcription of a subset of proinflammatory genes activated with ANGII treatment was repressed by the inhibitor. These genes include quantitative markers of macrophage accumulation in the vessel wall, CD68, MCP1/CCL2, CCR2, MMP-12, and Csf1. Associated reductions in gene markers for inflammation and oxidative stress, ie., heme oxidase (HO), nitric oxide synthase (nos2), Ikbkb, and Stat3 also correlate with MMP-12 antagonism. These changes occur in the absence of lipid changes (TC or TG), or quantitative changes in aortic arch lesions in the ANGII-infused animals. The findings support a mechanism whereby MMP-12 metalloelastase inactivation reduces macrophage recruitment to aneurysmal lesion sites, to lessen activated-macrophage expression of proinflammatory cytokines that figure prominently in vascular wall destruction and the pathogenesis of AAAs.

The influence of 3D geometry on abdominal aortic aneurysm wall stress

2006 ◽  
Vol 39 ◽  
pp. S273-S274
Author(s):  
Y. Papaharilaou ◽  
J. Ekaterinaris ◽  
E. Karatsis
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
3D Geometry ◽  
Abdominal Aortic Aneurysm Wall

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.

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