scholarly journals Fluid-Structure Interaction in Abdominal Aortic Aneurysms: Effect of Haematocrit

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 11 ◽  
Author(s):  
Yorgos Stergiou ◽  
Athanasios Kanaris ◽  
Aikaterini Mouza ◽  
Spiros Paras
Keyword(s):  
Blood Flow ◽  
Dynamic Behavior ◽  
Blood Viscosity ◽  
Arterial Wall ◽  
Fluid Structure Interaction ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Abdominal Aortic

The Abdominal Aortic Aneurysm (AAA) is a local dilation of the abdominal aorta and it is a cause for serious concern because of the high mortality associated with its rupture. Consequently, the understanding of the phenomena related to the creation and the progression of an AAA is of crucial importance. In this work, the complicated interaction between the blood flow and the AAA wall is numerically examined using a fully coupled Fluid-Structure Interaction (FSI) method. The study investigates the possible link between the dynamic behavior of an AAA and the blood viscosity variations attributed to the haematocrit value, while it also incorporates the pulsatile blood flow, the non-Newtonian behavior of blood and the hyperelasticity of the arterial wall. It was found that blood viscosity has no significant effect on von Mises stress magnitude and distribution, whereas there is a close relation between the haematocrit value and the Wall Shear Stress (WSS) magnitude in AAAs. This WSS variation can possibly alter the mechanical properties of the arterial wall and increase its growth rate or even its rupture possibility. The relationship between haematocrit and dynamic behavior of an AAA can be helpful in designing a patient specific treatment.

scholarly journals Fluid-Structure Interaction in Abdominal Aortic Aneurysms: Effect of Haematocrit

2018 ◽  
Author(s):  
Yorgos G. Stergiou ◽  
Athanasios G. Kanaris ◽  
Aikaterini A. Mouza ◽  
Spiros V. Paras
Keyword(s):  
Blood Flow ◽  
Blood Viscosity ◽  
Arterial Wall ◽  
Dynamic Behaviour ◽  
Fluid Structure Interaction ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Abdominal Aortic

The Abdominal Aortic Aneurysm (AAA) is a local dilation of the abdominal aorta and it is a cause for serious concern because of the high mortality associated with its rupture. Consequently, the understanding of the phenomena related to the creation and the progression of an AAA is of crucial importance. In this work the complicated interaction between the blood flow and the AAA wall is numerically examined using a fully coupled Fluid-Structure Interaction (FSI) method. The study investigates the possible link between the dynamic behaviour of an AAA and the blood viscosity variations attributed to the haematocrit value, while it also incorporates the pulsatile blood flow, the non-Newtonian behaviour of blood and the hyperelasticity of the arterial wall. It was found that blood viscosity has no significant effect on von Mises stress magnitude and distribution, whereas there is a close relation between the haematocrit value and the Wall Shear Stress (WSS) magnitude in AAAs. This WSS variation can possibly alter the mechanical properties of the arterial wall and increase its growth rate or even its rupture possibility. The relationship between haematocrit and dynamic behaviour of an AAA can be helpful in designing a patient specific treatment.

Fluid-structure interaction in abdominal aortic aneurysms: Structural and geometrical considerations

2015 ◽  
Vol 26 (04) ◽  
pp. 1550038 ◽  
Author(s):  
Yaser Mesri ◽  
Hamid Niazmand ◽  
Amin Deyranlou ◽  
Mahmood Reza Sadeghi
Keyword(s):  
Wall Thickness ◽  
Arterial Wall ◽  
Fluid Structure Interaction ◽  
Wall Stress ◽  
Aortic Aneurysms ◽  
Material Behavior ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Abdominal Aortic ◽  
Iliac Bifurcation

Rupture of the abdominal aortic aneurysm (AAA) is the result of the relatively complex interaction of blood hemodynamics and material behavior of arterial walls. In the present study, the cumulative effects of physiological parameters such as the directional growth, arterial wall properties (isotropy and anisotropy), iliac bifurcation and arterial wall thickness on prediction of wall stress in fully coupled fluid-structure interaction (FSI) analysis of five idealized AAA models have been investigated. In particular, the numerical model considers the heterogeneity of arterial wall and the iliac bifurcation, which allows the study of the geometric asymmetry due to the growth of the aneurysm into different directions. Results demonstrate that the blood pulsatile nature is responsible for emerging a time-dependent recirculation zone inside the aneurysm, which directly affects the stress distribution in aneurismal wall. Therefore, aneurysm deviation from the arterial axis, especially, in the lateral direction increases the wall stress in a relatively nonlinear fashion. Among the models analyzed in this investigation, the anisotropic material model that considers the wall thickness variations, greatly affects the wall stress values, while the stress distributions are less affected as compared to the uniform wall thickness models. In this regard, it is confirmed that wall stress predictions are more influenced by the appropriate structural model than the geometrical considerations such as the level of asymmetry and its curvature, growth direction and its extent.

Effects of Turbulent Blood Flow on Abdominal Aortic Aneurysms: A Fluid-Structure Interaction Study

2013 ◽  
Author(s):  
Shengmao Lin ◽  
Linxia Gu
Keyword(s):  
Blood Flow ◽  
Effective Means ◽  
Fluid Structure Interaction ◽  
Wall Stress ◽  
Aortic Aneurysms ◽  
Infrarenal Aorta ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aneurysm Wall ◽  
Abdominal Aortic

Abdominal aortic aneurysm (AAA), local dilations of the infrarenal aorta, is the 13th leading cause of mortality in US. Various tools have been used to investigate the effect of blood flow on the mechanics of AAA, which might predict its fracture potential, a life-threaten event. The modeling techniques are gaining popularity, including the partially or fully coupled fluid-structure interaction method (p-FSI and f-FSI, respectively) and the static computational solid stress (CSS) analyses. In the present study, comparison among the above mentioned three computational methods were performed to identify the effective means to characterize the effects of pulsatile turbulent blood flow on predicting the stress distribution on AAA. Results have shown that ignorance of blood flow in simulation will underestimate the wall stress calculation and the flexibility of aneurysm wall has a large impact in simulating the blood through the AAA.

scholarly journals Ultrasound-Based Fluid-Structure Interaction Modeling of Abdominal Aortic Aneurysms Incorporating Pre-stress

2021 ◽  
Vol 12 ◽  
Author(s):  
Judith H. C. Fonken ◽  
Esther J. Maas ◽  
Arjet H. M. Nievergeld ◽  
Marc R. H. M. van Sambeek ◽  
Frans N. van de Vosse ◽  
...  
Keyword(s):  
Fluid Structure Interaction ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Risk Indicator ◽  
Rupture Risk ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Abdominal Aortic

Currently, the prediction of rupture risk in abdominal aortic aneurysms (AAAs) solely relies on maximum diameter. However, wall mechanics and hemodynamics have shown to provide better risk indicators. Patient-specific fluid-structure interaction (FSI) simulations based on a non-invasive image modality are required to establish a patient-specific risk indicator. In this study, a robust framework to execute FSI simulations based on time-resolved three-dimensional ultrasound (3D+t US) data was obtained and employed on a data set of 30 AAA patients. Furthermore, the effect of including a pre-stress estimation (PSE) to obtain the stresses present in the measured geometry was evaluated. The established workflow uses the patient-specific 3D+t US-based segmentation and brachial blood pressure as input to generate meshes and boundary conditions for the FSI simulations. The 3D+t US-based FSI framework was successfully employed on an extensive set of AAA patient data. Omitting the pre-stress results in increased displacements, decreased wall stresses, and deviating time-averaged wall shear stress and oscillatory shear index patterns. These results underline the importance of incorporating pre-stress in FSI simulations. After validation, the presented framework provides an important tool for personalized modeling and longitudinal studies on AAA growth and rupture risk.

scholarly journals Image-Guided Fluid-Structure Interaction Simulation of Transvalvular Hemodynamics: Quantifying the Effects of Varying Aortic Valve Leaflet Thickness

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 119 ◽  
Author(s):  
Anvar Gilmanov ◽  
Alexander Barker ◽  
Henryk Stolarski ◽  
Fotis Sotiropoulos
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Heart Valve ◽  
Fluid Structure Interaction ◽  
Maximum Velocity ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Orifice Area ◽  
Fluid Structure ◽  
Structure Interaction

When flow-induced forces are altered at the blood vessel, maladaptive remodeling can occur. One reason such remodeling may occur has to do with the abnormal functioning of the aortic heart valve due to disease, calcification, injury, or an improperly-designed prosthetic valve, which restricts the opening of the valve leaflets and drastically alters the hemodynamics in the ascending aorta. While the specifics underlying the fundamental mechanisms leading to changes in heart valve function may differ from one cause to another, one common and important change is in leaflet stiffness and/or mass. Here, we examine the link between valve stiffness and mass and the hemodynamic environment in aorta by coupling magnetic resonance imaging (MRI) with high-resolution fluid–structure interaction (FSI) computational fluid dynamics to simulate blood flow in a patient-specific model. The thoracic aorta and a native aortic valve were re-constructed in the FSI model from the MRI data and used for the simulations. The effect of valve stiffness and mass is parametrically investigated by varying the thickness (h) of the leaflets (h = 0.6, 2, 4 mm). The FSI simulations were designed to investigate systematically progressively higher levels of valve stiffness by increasing valve thickness and quantifying hemodynamic parameters known to be linked to aortopathy and valve disease. The computed results reveal dramatic differences in all hemodynamic parameters: (1) the geometric orifice area (GOA), (2) the maximum velocity V max of the jet passing through the aortic orifice area, (3) the rate of energy dissipation E ˙ diss ( t ) , (4) the total loss of energy E diss , (5) the kinetic energy of the blood flow E kin ( t ) , and (6) the average magnitude of vorticity Ω a ( t ) , illustrating the change in hemodynamics that occur due to the presence of aortic valve stenosis.

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