scholarly journals Effect of non-linear leaflet material properties on aortic valve dynamics - A coupled fluid-structure approach

2021 ◽  
pp. 123-136 ◽  
Author(s):  
Armin Amindari ◽  
Kadir Kırkköprü ◽  
İrfan levent Saltık ◽  
Emin Sünbüloğlu
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Flow Field ◽  
Material Properties ◽  
Complex Structure ◽  
Fluid Structure ◽  
Non Linear ◽  
Stress Levels ◽  
Systolic Phase ◽  
Simulation Results

Due to complex structure of aortic valve (AV) leaflets and its strong interaction with the blood flow field, realistic and accurate modeling of the valve deformations comes with many challenges. In this study, we aimed to investigate the effect of AV material properties on the valve deformations, by implementing different non-linear properties of the AV leaflets in three different material models. In the computations, we captured the dynamics between the leaflet deformations and blood flow field variations by using an iterative implicit fluid-structure interaction (FSI) approach. By comparison of the FSI simulation results of these three models, the effects of hyperelasticity and anisotropy on the valve deformations have been studied in detail. The simulation results reveal the fact that the material characteristics strongly affect the deformation characteristics of the leaflets in the systolic phase. The material anisotropy stabilizes the leaflet movements during the systolic phase, which helps decreasing the flutters of the leaflets during the peak jet blood flow. Similarly, it has been observed that the hyperelastic behavior yields an increase in the valve opening area during systolic phase which prevents the risk of excessive work of the heart due to high pressure difference. Furthermore, simulation results indicate that the stress levels in hyperelastic model are much lower, compared to the stress levels in linear elastic one. This suggests that the non-linear material character of the leaflets decreases the risk of calcification.

Modeling of aortic valve stenosis using fluid-structure interaction method

Perfusion ◽  
2021 ◽  
pp. 026765912199854
Author(s):  
Mohammad Javad Ghasemi Pour ◽  
Kamran Hassani ◽  
Morteza Khayat ◽  
Shahram Etemadi Haghighi
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Relaxation Phase ◽  
Exercise Condition ◽  
Time Dependent Domain ◽  
Comparison Of The Results

Background and objectives: Fluid structure interaction (FSI) is defined as interaction of the structures with contacting fluids. The aortic valve experiences the interaction with blood flow in systolic phase. In this study, we have tried to predict the hemodynamics of blood flow through a normal and stenotic aortic valve in two relaxation and exercise conditions using a three-dimensional FSI method. Methods: The aorta valve was modeled as a three-dimensional geometry including a normal model and two others with 25% and 50% stenosis. The geometry of the aortic valve was extracted from CT images and the models were generated by MMIMCS software and then they were implemented in ANSYS software. The pulsatile flow rate was used for all cases and the numerical simulations were conducted based on a time-dependent domain. Results: The obtained results including the velocity, pressure, and shear stress contours in different systolic time sequences were explained and discussed. The maximum blood flow velocity in relaxation phase was obtained 1.62 m/s (normal valve), 3.78 m/s (25% stenosed valve), and 4.73 m/s (50% stenosed valve). In exercise condition, the maximum velocities are 2.86, 4.32, and 5.42 m/s respectively. The maximum blood pressure in relaxation phase was calculated 111.45 mmHg (normal), 148.66 mmHg (25% stenosed), and 164.21 mmHg (50% stenosed). However, the calculated values in exercise situation were 129.57, 163.58, and 191.26 mmHg. The validation of the predicted results was also conducted using existing literature. Conclusions: We believe that such model are useful tools for biomechanical experts. The further studies should be done using experimental data and the data are implemented on the boundary conditions for better comparison of the results.

Fluid-Structure Interaction Simulation of Blood Flow Inside a Diseased Left Ventricle With Obstructive Hypertrophic Cardiomyopathy in Early Systole

2009 ◽  
Author(s):  
Ahmad Moghaddaszade-Kermani ◽  
Peter Oshkai ◽  
Afzal Suleman
Keyword(s):  
Blood Flow ◽  
Hypertrophic Cardiomyopathy ◽  
Left Ventricle ◽  
Fluid Structure Interaction ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Ventricular Pressure ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Systolic Phase

Mitral-Septal contact has been proven to be the cause of obstruction in the left ventricle with hypertrophic cardiomyopathy (HC). This paper presents a study on the fluid mechanics of obstruction using two-way loosely coupled fluid-structure interaction (FSI) methodology. A parametric model for the geometry of the diseased left ventricular cavity, myocardium and mitral valve has been developed, using the dimensions extracted from magnetic resonance images. The three-element Windkessel model [1] was modified for HC and solved to introduce pressure boundary condition to the aortic aperture in the systolic phase. The FSI algorithm starts at the beginning of systolic phase by applying the left ventricular pressure to the internal surface of the myocardium to contract the muscle. The displacements of the myocardium and mitral leaflets were calculated using the nonlinear finite element hyperelastic model [2] and subsequently transferred to the fluid domain. The fluid mesh was moved accordingly and the Navier-Stokes equations were solved in the laminar regime with the new mesh using the finite volume method. In the next time step, the left ventricular pressure was increased to contract the muscle further and the same procedure was repeated for the fluid solution. The results show that blood flow jet applies a drag force to the mitral leaflets which in turn causes the leaflet to deform toward the septum thus creating a narrow passage and possible obstruction.

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.

Flow Field Analysis and Numerical Simulation for Pipe with Tee on Fluid-Structure Coupling

2012 ◽  
Vol 503-504 ◽  
pp. 768-771
Author(s):  
Zhong Bin Liu ◽  
Feng Luo ◽  
Tao Zeng ◽  
Hui Wu
Keyword(s):  
Flow Field ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Main Flow ◽  
Field Analysis ◽  
Fluid Structure ◽  
Coulomb Failure ◽  
Flow Field Analysis ◽  
Simulation Results ◽  
Graphics Software

Y-shaped tee is modeled by three-dimensional graphics software and its flow field is analyzed and numerical simulated by CFD software. The mechanical stability of Y-shaped tee in the work process is analyzed by fluid-structure coupling. The results show that the pressure of water is gradually decreased and the velocity of water is gradually increased as the main flow is near Y-shaped tee; the branch of pipeline exits the largest failure risk by the coulomb failure expression. Simulation results are consistent to the practice, which provides important theoretical basis for improving and optimization of Y-shaped tee.

scholarly journals The Comparison of Different Constitutive Laws and Fiber Architectures for the Aortic Valve on Fluid–Structure Interaction Simulation

2021 ◽  
Vol 12 ◽  
Author(s):  
Li Cai ◽  
Ruihang Zhang ◽  
Yiqiang Li ◽  
Guangyu Zhu ◽  
Xingshuang Ma ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Fluid Structure Interaction ◽  
Constitutive Laws ◽  
Constitutive Law ◽  
Mechanical Behaviors ◽  
Windkessel Model ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Non Linear ◽  
Constitutive Parameters

Built on the hybrid immersed boundary/finite element (IB/FE) method, fluid–structure interaction (FSI) simulations of aortic valve (AV) dynamics are performed with three different constitutive laws and two different fiber architectures for the AV leaflets. An idealized AV model is used and mounted in a straight tube, and a three-element Windkessel model is further attached to the aorta. After obtaining ex vivo biaxial tensile testing of porcine AV leaflets, we first determine the constitutive parameters of the selected three constitutive laws by matching the analytical stretch–stress relations derived from constitutive laws to the experimentally measured data. Both the average error and relevant R-squared value reveal that the anisotropic non-linear constitutive law with exponential terms for both the fiber and cross-fiber directions could be more suitable for characterizing the mechanical behaviors of the AV leaflets. We then thoroughly compare the simulation results from both structural mechanics and hemodynamics. Compared to the other two constitutive laws, the anisotropic non-linear constitutive law with exponential terms for both the fiber and cross-fiber directions shows the larger leaflet displacements at the opened state, the largest forward jet flow, the smaller regurgitant flow. We further analyze hemodynamic parameters of the six different cases, including the regurgitant fraction, the mean transvalvular pressure gradient, the effective orifice area, and the energy loss of the left ventricle. We find that the fiber architecture with body-fitted orientation shows better dynamic behaviors in the leaflets, especially with the constitutive law using exponential terms for both the fiber and cross-fiber directions. In conclusion, both constitutive laws and fiber architectures can affect AV dynamics. Our results further suggest that the strain energy function with exponential terms for both the fiber and cross-fiber directions could be more suitable for describing the AV leaflet mechanical behaviors. Future experimental studies are needed to identify competent constitutive laws for the AV leaflets and their associated fiber orientations with controlled experiments. Although limitations exist in the present AV model, our results provide important information for selecting appropriate constitutive laws and fiber architectures when modeling AV dynamics.

scholarly journals Aortic Valve Geometry Modeling – Review

2016 ◽  
Vol 16 (4) ◽  
pp. 29-37 ◽  
Author(s):  
K. Dawidowska
Keyword(s):  
Computer Simulation ◽  
Aortic Valve ◽  
Diagnostic Imaging ◽  
Research Methods ◽  
Material Properties ◽  
Valve Leaflet ◽  
Geometry Modeling ◽  
Aortic Valve Leaflet ◽  
Simulation Results ◽  
Valve Operation

Abstract The present work is a review of publications covering computer simulation of aortic valve operation and material properties of aortic valve components studies. Particular attention is paid to the anisotropy of material and geometric properties. The methods of geometric models developing by using specified research methods and/or diagnostic imaging devices are presented. The microstructure of the aortic valve is also described and its impact on material properties definition introduced. The various ways of describing the aortic valve leaflet anisotropic properties are mentioned. Often exploited simplifications and their impact on the simulation results is also presented.

Modified Septal Myectomy Using a Curved Knife for Left Ventricular Septal Hypertrophy

2014 ◽  
Vol 17 (5) ◽  
pp. 269
Author(s):  
Shinya Takahashi ◽  
Taiichi Takasaki ◽  
Futoshi Tadehara ◽  
Takahiro Taguchi ◽  
Keijiro Katayama ◽  
...  
Keyword(s):  
Blood Flow ◽  
Chest Pain ◽  
Aortic Valve ◽  
Cross Section ◽  
Left Ventricular ◽  
Chest Discomfort ◽  
Septal Myectomy ◽  
Asymmetric Septal Hypertrophy ◽  
Septal Hypertrophy ◽  
Septal Myocardium

An 86-year-old woman presented with chest pain and discomfort. Echocardiography revealed severe aortic valve stenosis and asymmetric septal hypertrophy. Aortic valve replacement and myectomy were performed using a curved knife. The blade was U-shaped in cross-section, and was curved upward along the long axis. Hypertrophic septal myocardium was removed along the long axis of the left ventricle (LV), and a groove for blood flow was constructed. The patient was discharged uneventfully without recurrence of her chest discomfort. Our result suggested that a curved knife is a reasonable option for transaortic septal myectomy in patients with obstructive LV hypertrophy.

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