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Comparative analyses of blood flow through mechanical trileaflet and bileaflet aortic valves

Pawlikowski Marek, Nieroda Anna

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 2

141--152

EN

The primary aim of the present study was to compare the bileaflet and trileaflet aortic valves’ performance during uniform blood flow model and boundary conditions. The secondary aim of the study was to determine the effect of Newtonian/non-Newtonian fluid flow assumption on blood flow directly behind the trileaflet valve. Methods: The geometrical model of the whole system consist of the left ventricle, fragment of the aorta and mechanical valves. A representation of pulsatile flow was obtained by measuring blood flow velocity (Doppler ultrasound examination). We have assumed turbulent blood flow. We considered two blood models, Newtonian and non-Newtonian (Carreau model). The valves’ performance was assessed using the reduced stress in the valves, the shear stress in the aortic wall, flow velocity field and the effective orifice area. Results: The maximum von Mises stress for the bileaflet valve leaflets was 0.3 MPa and for the trileaflet valve – 0.06 MPa. The maximum flow velocity for the bileaflet valve was 4.52 m/s for 40° and for the trileaflet valve – 5.74 m/s. Higher shear stress was present in the bileaflet (151.5 Pa) than for the trileaflet valve (49.64 Pa). Conclusions: The results indicate that central blood jet for the trileaflet valve contributes to more physiological blood flow and decreases the risk of haemolysis. The central flow minimises the risk of leaflet dislocation. In addition, lower stresses extend the durability of the valve. However, the trileaflet valve geometry has also disadvantages, for instance, small peripheral streams or relatively low effective orifice area.

2

Dynamic analysis of the aortic valve functioning

Patralski Krzysztof

Journal of Theoretical and Applied Mechanics

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2020

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Vol. 58 nr 4

853--869

EN

The aim of the paper was to recognize the influence of mechanical factors on the movement of the leaflets. Mechanical stimuli may have a positive effect on remodeling the leaflet material to adapt its structure to a changing load. A model of the valve functioning process was developed. A geometric model similar to the construction of a natural valve was adopted. The hybrid process of the liquid-solid interaction problem was described. The interaction process was modeled. The problem was formulated with the Galerkin FEM method. Numerical analyses of a single valve work cycle and the calcification process of aortic valve bioprostheses were performed.

3

The interaction of laser radiation with tissue in the aspect of generating the process of decellularization in the preparation of animal origin autologous tissue

Kopernik Magdalena, Major Roman, Lis Grzegorz, Wilczek Piotr, Lis Maciej, Imbir Gabriela, Chrouda Abir, Mzyk Aldona, Ostrowski Roman, Sanak Marek

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 1

67--77

EN

Purpose: The aim of the work was to create an appropriate substrate for organ transplantation using bioactive tissue-based scaffold populated by cells of the graft recipient. The purpose of the modeling was to investigate the mechanical effects of wave loading of aortic and pulmonary tissue material. Methods: The biological properties of tissues of aortic and pulmonary valves were modified by the process of decellularization. The host cells were removed by various physical methods with focus on minimal degradation of the extracellular matrix. Thus, the decellularization process was controlled by histological methods. The tissue decellularization process was simulated by finite element modelling. Results: The mechanical results represented by a displacement at the center of the sample were coherent and the heterogeneity of the distribution of the caves on the surface of the samples was confirmed, both by experiment and in the simulation by the alternate occurrence of local minima and maxima. The latter results from the uneven removal of cells from the effect of the wave causing decellularization were also predicted by the numerical model. Laser radiation had a destructive effect on the components of the extracellular matrix (e.g., collagen and elastic fibers), mainly depending on the fluence and number of pulses in a single exposure. Conclusions: The differences between the valve tissue materials were shown, and the impact of the process of decellularization on the properties of the tissues was analyzed. It should be emphasized that due to low absorption and high scattering, laser radiation can deeply penetrate the tissue, which allows for effective decellularization process in the entire volume of irradiated tissue.

4

FEA of displacements and stresses of aortic heart valve leaflets during the opening phase

Bialas O., Żmudzki J.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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Vol. 92, nr 1-2

29--35

EN

Purpose: Modelling of biomechanical behaviour of heart valve materials aids improvement of biofunctional feature. The aim of the work was assessment of influence of material thickness of leaflets of artificial aortic valve on displacements and stresses during opening phase using finite element analysis (FEA). Design/methodology/approach: The model of aortic valve was developed on the basis of average anatomical valve shapes and dimensions. Nonlinear dynamic large displacements analysis with assumption of isotropic linear elastic material behaviour was used in simulation (Solidworks). The modulus of elasticity of 5.0 MPa was assumed and Poisson ratio set to 0.45. The rigidly supported leaflets was loaded by pressure increasing in the range 0-55 mmHg in time 0.1 s. Leaflets with material thickness 0.13 and 0.15 and 0.17 mm were analysed. The thickness was simulated with shell finite elements. Findings: The highest stresses were observed in the areas of fixation of the leaflets near the scaffold and were lower than dangerous value of fatigue of polyurethanes. Increasing the thickness of valve leaflet material in the range of 40 micrometres resulted in reduction of the valve outlet by almost 10 percent. Research limitations/implications: The FEA was limited to the isotropic linear-elastic behaviour of the material albeit can be used to assess leaflet deformation during dynamic load. Practical implications: Leaflets design may be start from efficient FEA which helps estimation of material impact on stress and fold formation which can affect local blood flow. Originality/value: Aortic heart valve leaflet material can be initially tested in dynamic conditions during opening phase with using FEA.

5

Fluid-Structure Interaction Modeling of Aortic Valve Stenosis at Different Heart Rates

Bahraseman H. G., Languri E. M., Yahyapourjalaly N., Espino D. M.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 3

11--20

EN

Purpose: This paper proposes a model to measure the cardiac output and stroke volume at different aortic stenosis severities using a fluid–structure interaction (FSI) simulation at rest and during exercise. Methods: The geometry of the aortic valve is generated using echocardiographic imaging. An Arbitrary Lagrangian–Eulerian mesh was generated in order to perform the FSI simulations. Pressure loads on ventricular and aortic sides were applied as boundary conditions. Results: FSI modeling results for the increment rate of cardiac output and stroke volume to heart rate, were about 58.6% and –14%, respectively, at each different stenosis severity. The mean gradient of curves of cardiac output and stroke volume to stenosis severity were reduced by 57% and 48%, respectively, when stenosis severity varied from healthy to critical stenosis. Conclusions: Results of this paper confirm the promising potential of computational modeling capabilities for clinical diagnosis and measurements to predict stenosed aortic valve parameters including cardiac output and stroke volume at different heart rates.

6

Remodelling of material structure in aortic valve leaflet

Patralski K., Konderla P.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 2

63--72

EN

Purpose: The goal of this study is to model changes in fibre content in aortic valve leaflet material due to mechanical stimuli. Methods: The fibre remodelling process is associated with the redistribution of the internal forces acting in the shell. The process is characterized by the occurrence of extreme stresses and strains. The load distribution function is asymmetrical. The optimization problem has been assigned the task of transferring the load imposed on the leaflet. The density of the fibres per unit surface of the middle shell was assumed to be proportional to the shell thickness, which means that fibre density along the normal direction is constant over the entire shell. Results: The model of valve leaflet loading is the distribution of the pressure generated on the leaflet shell surface by the flowing fluid. The algorithm for the redistribution of the leaflet material mass made it possible to distinguish two regions of enhanced thickness in the leaflet shell. One was localized between the commissures along the leaflet attachment, the other one in the middle part of the leaflet at the level of the commissures. A reduction in shell thickness is observed in the middle part of the leaflet, above the point of its attachment to the aorta. Conclusions: The distribution of the thickness field obtained corroborates the findings of the study reported elier. Our study on the remodelling of the valve leaflet entailed the application of the stress criterion, which visibly upgraded the functioning of the valve by improving its mechanical and hemodynamic parameters.

7

Numerical modelling of the opening process of the three-coating aortic valve

Kopernik M., Nowak J.

Archives of Mechanics

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2009

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Vol. 61, nr 3-4

171-193

EN

Numerical modelling of the three-coating human aortic valve is the objective of the paper. The proposed approach is used to select the material properties and the thickness of outer coating of the valve, which are required to obtain the proper work of the valve, which in the present paper is considered as the opening process. Following the previously developed model of the monocoating lea?et of the natural human aortic valve, the model of three-coating valve is prepared. Finite element method (FEM) and sensitivity analysis are used to solve the formulated and selected problems. Two methods of estimation of the valve opening process in numerical models are elaborated on the basis of experimental studies.

8

Fizyczne i numeryczne modelowanie jednowarstwowego płatka zastawki aortalnej

Kopernik M., Nowak J.

Mechanik

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2008

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R. 81, nr 11

958-958

PL

Omówiono opracowanie modelu jednowarstwowego płatka zastawki aortalnej, co pozwala zaprojektować protezę zastawki pracującej docelowo w organizmie człowieka. Opisano kształt zastawki serca, sformułowano podstawowe wymagania stawiane protezom zastawek oraz przybliżono mechanizm otwierania się zastawki serca. Następnie omówiono model elementów skończonych zaproponowany dla zastawki serca, warunki brzegowe i wyniki uzyskane z przeprowadzonych symulacji. Przedstawiono najbardziej charakterystyczne rozkłady naprężeń w płatku zastawki oraz jego przemieszczenia. Analizę wrażliwości wykonano dla modelu zastawki względem jego kluczowych parametrów: kształtu i materiału.

EN

Discussed is a model of monolayer cusp of aortic valve, which will make it possible to design the valve prosthesis for open-ended mounting in human body. The most specific pattern of stress distribution in the cusp of valve and its movements are presented.

9

The analysis of heart valve dysfunction and effectiveness of disc-designed prostheses

Shilko S. V., Hizhenok V. F., Kuzminsky Yu. G., Salivonchik S. P.

Acta of Bioengineering and Biomechanics

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2003

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Vol. 5, nr 2

53-62

EN

The function of heart (in good condition and in poor condition) and hemodynamic characteristics of mechanical prosthetic cardiac valves influencing hemolysis and blood coagulation have been investigated. The solid-state models of disc-designed prosthetic cardiac valves have been constructed. The finite element analysis of blood velocity and pressure at direct and inverse blood flows has shown better characteristics of bi-leaflet valves. The advantage of the numerical modelling is in the possibility of thorough description of blood flow with determination of turbulence and depression zones for different sizes, curvature and ultimate opening angle of leafs. It allows minimising hydraulic resistance, thrombus formation and hemolysis-preserving high reliability of valve closing. The individual design of valve is discussed and aimed at improving a valve function by creating the blood flow twisting.