scholarly journals TAVI-Mimic for testing of heart valve leaflet materials in physiological loading situations

2021 ◽  
Vol 7 (2) ◽  
pp. 570-573
Author(s):  
Joschka Finck ◽  
Jan Oldenburg ◽  
Thomas Kuske ◽  
Niels Grabow ◽  
Klaus-Peter Schmitz ◽  
...  
Keyword(s):  
Aortic Valve ◽  
3D Printing ◽  
Heart Valve ◽  
Valve Leaflet ◽  
Radial Load ◽  
Element Analysis ◽  
Physiological Loading ◽  
Durability Testing

Abstract The loading situation of the aortic valve is complex, complicating the identification of innovative approaches for heart valve leaflet materials, e.g. for transcatheter aortic valve implantation (TAVI). Materials engineering experiments allow for screening of materials but especially for durability testing, the consideration of physiological loads is vital/critical for the suitability-assessment of innovative leaflet materials. For this reason, a framework structure for the testing of leaflet materials in physiological loading (TAVI-Mimic) was developed. The exemplary use case for the TAVI-Mimic was a test for calcification propensity of pericardium during durability testing. The TAVI-Mimic was designed as a fourparted frame, based on previous work of our group. The leaflet material can be attached between inner and outer shells without sewing. In a second step, the TAVI-Mimic was optimized regarding radial load-deformation in comparison to a commercial TAVI by means of finite element analysis (FEA) and hydrodynamic characterization in a pulse duplicator system. Mechanical properties dependent on water uptake of different materials for 3D-printing of the TAVI-Mimic were investigated. After optimization, TAVI-Mimics were equipped with glutaraldehyde-fixated pericardial tissue and prototypes were calcified by using a heart valve durability tester and a metastable calcification-liquid, developed in earlier studies. The development of the TAVI-Mimic using FEA and experiments was successful, leading to a radial load dependent deformation of 0.6 mm which correlates with commercial TAVI. Two methacrylic photopolymers were identified for 3D-printing of the TAVI-Mimic and prototypes attached with pericardial tissue were manufactured. Pericardium TAVI-Mimics were calcified in vitro for one week and an average calciumphosphate precipitate of 0.34- 0.54 mg/cm² was measured. The optimization of the TAVR-Mimic led to an improved load-dependent behaviour compared to a commercial prosthesis while testing. The calcification method, combining the TAVI-Mimic, the metastable calcification solution and the durability tester enabled a successfully calcification of pericardial tissue, approaching the in vivo situation.

scholarly journals Fluid-structure interaction of heart valve dynamics in comparison to finite-element analysis

2018 ◽  
Vol 4 (1) ◽  
pp. 259-262 ◽  
Author(s):  
Finja Borowski ◽  
Michael Sämann ◽  
Sylvia Pfensig ◽  
Carolin Wüstenhagen ◽  
Robert Ott ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Heart Valve ◽  
Elastic Behavior ◽  
Valve Prosthesis ◽  
Arbitrary Lagrangian Eulerian ◽  
Element Analysis ◽  
Valve Dynamics ◽  
Valve Opening ◽  
Valve Prostheses

AbstractAn established therapy for aortic valve stenosis and insufficiency is the transcatheter aortic valve replacement. By means of numerical simulation the valve dynamics can be investigated to improve the valve prostheses performance. This study examines the influence of the hemodynamic properties on the valve dynamics utilizing fluidstructure interaction (FSI) compared with results of finiteelement analysis (FEA). FEA and FSI were conducted using a previously published aortic valve model combined with a new developed model of the aortic root. Boundary conditions for a physiological pressurization were based on measurements of ventricular and aortic pressure from in vitro hydrodynamic studies of a commercially available heart valve prosthesis using a pulse duplicator system. A linear elastic behavior was assumed for leaflet material properties and blood was specified as a homogeneous, Newtonian incompressible fluid. The type of fluid domain discretization can be described with an arbitrary Lagrangian-Eulerian formulation. Comparison of significant points of time and the leaflet opening area were used to investigate the valve opening behavior of both analyses. Numerical results show that total valve opening modelled by FEA is faster compared to FSI by a factor of 5. In conclusion the inertia of the fluid, which surrounds the valve leaflets, has an important influence on leaflet deformation. Therefore, fluid dynamics should not be neglected in numerical analysis of heart valve prostheses.

Spline Based Microstructural Mapping for Soft Biological Tissues: Application to Aortic Valves

2013 ◽  
Author(s):  
A. Aggarwal ◽  
V. S. Aguilar ◽  
C. H. Lee ◽  
G. Ferrari ◽  
J. H. Gorman ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Computer Aided Design ◽  
Biological Tissues ◽  
Mechanical Tests ◽  
Aortic Valves ◽  
Element Analysis ◽  
Tissue Microstructure ◽  
Forward And Inverse Modeling

Splines are the standard tools in computer aided design for geometric representations and have been recently integrated into the finite element analysis of structures and fluids [1]. As the biomedical engineering is making progress, there is a need for an integrated tool for expanding the geometrical representation to include the microstructural details specific to soft tissue, e.g. fiber alignment, orientation, crimp and stiffness. In this work, a spline-based method is presented for aortic valves which facilitates mapping of the fiber structure from any aortic valve specimen to any other aortic valve geometry through a common parameter space. This techniques also has the ability to calculate mean tissue microstructure of representative population. Also strain and pre-strain from in-vivo state to the in-vitro state, where all the mechanical tests are done, are calculated for forward and inverse modeling of aortic valves.

Tissue-Engineered Heart Valve on Acellular Aortic Valve Scaffold: In-Vivo Study

2003 ◽  
Vol 11 (2) ◽  
pp. 153-156 ◽  
Author(s):  
Dong-E Zhao ◽  
Ruo-Bing Li ◽  
Wei-Yong Liu ◽  
Gang Wang ◽  
Shi-Qiang Yu ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Aortic Valve ◽  
Heart Valve ◽  
Extraction Process ◽  
Enzymatic Extraction ◽  
Aortic Valves ◽  
Tissue Engineered Heart Valve ◽  
Cellular Components

The feasibility of constructing a tissue-engineered heart valve on an acellular porcine aortic valve leaflet was evaluated. A detergent and enzymatic extraction process was developed to remove the cellular components from porcine aortic valves. The acellular valve leaflets were seeded for 7 days in vitro with cells from canine arterial wall and endothelial cells. The constructs were implanted into the lumens of 6 canine abdominal aortas to assess the reconstruction of the valve leaflets. It was found that all cellular components had been removed from the porcine aortic valves. The valve leaflets were completely reconstructed at the end of the 10th week in vivo. Scanning electron microscopy showed that the valve leaflets were partially covered with endothelial cells. It was concluded that porcine aortic valves can be decellularized by the detergent and enzymatic extraction process and it is feasible to construct a tissue-engineered heart valve in vivo on an acellular valve scaffold.

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

2019 ◽  
Vol 1-2 (92) ◽  
pp. 29-35
Author(s):  
O. Bialas ◽  
J. Żmudzki
Keyword(s):  
Aortic Valve ◽  
Heart Valve ◽  
Poisson Ratio ◽  
Elastic Behaviour ◽  
Valve Leaflet ◽  
Element Analysis ◽  
Linear Elastic ◽  
Material Thickness ◽  
Aortic Heart Valve ◽  
Opening Phase

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.

scholarly journals Design, development, testing at ISO standards and in vivo feasibility study of a novel polymeric heart valve prosthesis

2020 ◽  
Vol 8 (16) ◽  
pp. 4467-4480
Author(s):  
Joanna R. Stasiak ◽  
Marta Serrani ◽  
Eugenia Biral ◽  
James V. Taylor ◽  
Azfar G. Zaman ◽  
...  
Keyword(s):  
Heart Valve ◽  
Feasibility Study ◽  
Heart Valve Prosthesis ◽  
Valve Prosthesis ◽  
Design Development ◽  
Iso Standards ◽  
Bench Testing ◽  
Bioprosthetic Valves

A novel polymeric heart valve shows durability equivalent to 25 years in accelerated bench testing, in vitro hydrodynamics equivalent to existing bioprosthetic valves; and good performance in a small acute feasibility study in sheep.

scholarly journals Engineering Silicone Rubbers for In Vitro Studies: Creating AAA Models and ILT Analogues With Physiological Properties

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
T. J. Corbett ◽  
B. J. Doyle ◽  
A. Callanan ◽  
M. T. Walsh ◽  
T. M. McGloughlin
Keyword(s):  
In Vitro Studies ◽  
In Vivo Studies ◽  
Aortic Tissue ◽  
Element Analysis ◽  
Future Design ◽  
Change Behavior ◽  
Physiological Properties ◽  
Diameter Change

In vitro studies of abdominal aortic aneurysm (AAA) have been widely reported. Frequently mock artery models with intraluminal thrombus (ILT) analogs are used to mimic the in vivo AAA. While the models used may be physiological, their properties are frequently either not reported or investigated. This study is concerned with the testing and characterization of previously used vessel analog materials and the development of new materials for the manufacture of AAA models. These materials were used in conjunction with a previously validated injection molding technique to manufacture AAA models of ideal geometry. To determine the model properties (stiffness (β) and compliance), the diameter change of each AAA model was investigated under incrementally increasing internal pressures and compared with published in vivo studies to determine if the models behaved physiologically. A FEA study was implemented to determine if the pressure-diameter change behavior of the models could be predicted numerically. ILT analogs were also manufactured and characterized. Ideal models were manufactured with ILT analog internal to the aneurysm region, and the effect of the ILT analog on the model compliance and stiffness was investigated. The wall materials had similar properties (Einit 2.22 MPa and 1.57 MPa) to aortic tissue at physiological pressures (1.8 MPa (from literature)). ILT analogs had a similar Young’s modulus (0.24 MPa and 0.33 MPa) to the medial layer of ILT (0.28 MPa (from literature)). All models had aneurysm sac compliance (2.62–8.01×10−4/mm Hg) in the physiological range (1.8–9.4×10−4/mm Hg (from literature)). The necks of the AAA models had similar stiffness (20.44–29.83) to healthy aortas (17.5±5.5 (from literature)). Good agreement was seen between the diameter changes due to pressurization in the experimental and FEA wall models with a maximum difference of 7.3% at 120 mm Hg. It was also determined that the inclusion of ILT analog in the sac of the models could have an effect on the compliance of the model neck. Ideal AAA models with physiological properties were manufactured. The behavior of these models due to pressurization was predicted using finite element analysis, validating this technique for the future design of realistic physiological AAA models. Addition of ILT analogs in the aneurysm sac was shown to affect neck behavior. This could have implications for endovascular AAA repair due to the importance of the neck for stent-graft fixation.

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