scholarly journals Effect of Valve Height on the Opening and Closing Performance of the Aortic Valve Under Aortic Root Dilatation

2021 ◽  
Vol 12 ◽  
Author(s):  
Qianwen Hou ◽  
Guimei Liu ◽  
Ning Liu ◽  
Honghui Zhang ◽  
Zhuoran Qu ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Contact Force ◽  
Aortic Root ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Element Analysis ◽  
Aortic Root Dilatation ◽  
Valve Opening ◽  
Three Dimensional Models ◽  
Opening And Closing

Patients with aortic valve disease can suffer from valve insufficiency after valve repair surgery due to aortic root dilatation. The paper investigates the effect of valve height (Hv) on the aortic valve opening and closing in order to select the appropriate range of Hv for smoother blood flow through the aortic valve and valve closure completely in the case of continuous aortic root dilatation. A total of 20 parameterized three-dimensional models of the aortic root were constructed following clinical surgical guidance. Aortic annulus diameter (DAA) was separately set to 26, 27, 28, 29, and 30 mm to simulate aortic root dilatation. HV value was separately set to 13.5, 14, 14.5, and 15 mm to simulate aortic valve alterations in surgery. Time-varying pressure loads were applied to the valve, vessel wall of the ascending aorta, and left ventricle. Then, finite element analysis software was employed to simulate the movement and mechanics of the aortic root. The feasible design range of the valve size was evaluated using maximum stress, geometric orifice area (GOA), and leaflet contact force. The results show that the valve was incompletely closed when HV was 13.5 mm and DAA was 29 or 30 mm. The GOA of the valve was small when HV was 15 mm and DAA was 26 or 27 mm. The corresponding values of the other models were within the normal range. Compared with the model with an HV of 14 mm, the model with an HV of 14.5 mm could effectively reduce maximum stress and had relatively larger GOA and less change in contact force. As a result, valve height affects the performance of aortic valve opening and closing. Smaller HV is adapted to smaller DAA and vice versa. When HV is 14.5 mm, the valve is well adapted to the dilatation of the aortic root to enhance repair durability. Therefore, more attention should be paid to HV in surgical planning.

Three-dimensional aortic root reconstruction derived from rotational angiography for transcatheter balloon-expandable aortic valve implantation guidance

2014 ◽  
Vol 176 (3) ◽  
pp. 1318-1320 ◽  
Author(s):  
Mariam Samim ◽  
Pierfrancesco Agostoni ◽  
Freek Nijhoff ◽  
Ricardo P.J. Budde ◽  
Alferso C. Abrahams ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Aortic Root ◽  
Three Dimensional ◽  
Rotational Angiography ◽  
Aortic Valve Implantation ◽  
Valve Implantation

scholarly journals Finite Element Analysis of Needle Insertion Angle in Insulin Therapy

2019 ◽  
Vol 16 (4) ◽  
pp. 7512-7523
Author(s):  
Syakirah Mohamed Amin ◽  
Muhammad Hanif Ramlee ◽  
Hadafi Fitri Mohd Latip ◽  
Gan Hong Seng ◽  
Mohammed Rafiq Abdul Kadir
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Insulin Therapy ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Needle Insertion ◽  
Stress And Strain ◽  
Medical Doctors ◽  
Element Analysis ◽  
Biomechanical Evaluation

Millions in the world suffering diabetes mellitus depends on insulin therapy to control their blood glucose level daily. However, the painful daily injections they need to take could lead to other complications if it is not done correctly. To date, it is suggested by many researchers and medical doctors that the needles should be inserted at any angles of 90º or 45º. Nevertheless, this recommendation has not been supported by clinical or biomechanical evaluation. Hence, this study evaluates the needle insertion for insulin therapy to find the favourable angles in order to reduce injury and pain onto the skin. Finite element analysis was done by  simulating the injection of three-dimensional (3D) needle model into a 3D skin model. The insertions were simulated at two different angles, which are 45ºand 90º with two different lengths of needles; 4 mm and 6 mm. This study concluded the favourable angle for 4 mm needle to be 90º while 6 mm needle was best to be inserted at 45º as these angles exerted the least maximum stress and strain onto the skin.

scholarly journals Numerical simulation of a transcatheter aortic heart valve under application-related loading

2018 ◽  
Vol 4 (1) ◽  
pp. 185-189
Author(s):  
Sylvia Pfensig ◽  
Sebastian Kaule ◽  
Robert Ott ◽  
Carolin Wüstenhagen ◽  
Michael Stiehm ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Aortic Valve ◽  
Minimally Invasive ◽  
Heart Valve ◽  
Aortic Root ◽  
Constitutive Law ◽  
Ar Model ◽  
Valve Prosthesis ◽  
Target Region ◽  
Opening And Closing

AbstractFor the treatment of severe symptomatic aortic valve stenosis, minimally invasive heart valve prostheses have more recently become the lifesaving solution for elderly patients with high operational risk and thus, are often implanted in patients with challenging aortic root configuration. A correct prosthesis deployment and stent adaption to the target region is essential to ensure optimal leaflet performance and long-term prosthesis function. The objective of this study was the development of a suitable in silico setup for structural numerical simulation of a transcatheter aortic valve (TAV) in different cases of clinical relevance. A transcatheter valve prosthesis comprising an unpressurized trileaflet heart valve and an adapted stent configuration was designed. An aortic root (AR) model was developed, based on microcomputed tomography of a native healthy specimen. Using the finite-element analysis (FEA), various loading cases including prosthesis biomechanics with valve opening and closing under physiological pressure ratios throughout a cardiac cycle, prosthesis crimping as well as crimping and release into the developed AR model were simulated. Hyperelastic constitutive law for polymeric leaflet material and superelasticity of shape memory alloys for the self-expanding Nitinol stent structure were implemented into the FEA setup. Calculated performance of the valve including the stent structure demonstrated enhanced leaflet opening and closing as a result of stent deformation and redirected loading. Crimping and subsequent release into the AR model as well as the stent adaption to the target region after expansion proved the suitability of the TAV design for percutaneous application. FEA represented a useful tool for numerical simulation of an entire minimally invasive heart valve prosthesis in relevant clinical scenarios.

scholarly journals Comparative Evaluation of Biomechanical Performance of Titanium and Stainless Steel Mini Implants at Different Angulations in Maxilla: A Finite Element Analysis

2019 ◽  
Vol 53 (3) ◽  
pp. 197-205
Author(s):  
Kshitij Hemant Sabley ◽  
Usha Shenoy ◽  
Sujoy Banerjee ◽  
Pankaj Akhare ◽  
Ananya Hazarey ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Titanium Implant ◽  
Titanium Implants ◽  
Element Analysis ◽  
Mini Implants ◽  
The Difference ◽  
Tractional Forces ◽  
Three Dimensional Models

Objective: To assess and compare the tensions and deformations (stresses and strains) generated after application of two types of forces (traction and torsion) in miniscrews of two different materials (titanium and stainless steel) placed at five different angulations. Materials and Methods: Three-dimensional models of the posterior maxillary area and the mini-implants were constructed using computer-aided design software program (CATIA P3 V5-6 R2015 B26 / 2016; Dassault Systèmes). Titanium and stainless steel materials were used for miniscrews. The area constructed was in between the maxillary second premolar and first molar. The models with mini-implants were inserted at five different angulations (30°, 45°, 60°, 75° and 90°). Torsional and tractional forces were applied on these implants, and the models were solved using ANSYS 10.0. Stress generated in implant and in the cortical and cancellous bones was evaluated and compared at all the five angulations. Results: Stress generated in stainless steel mini-implant during torsional and linear force application was less when compared with titanium mini-implant. Also, stress generated in implants of both materials increased as the angle increased from 30° to 90°. Difference in stress generated by stainless steel implant in the cortical bone for both linear and torsional forces was less when compared with titanium implant, whereas for cancellous bone, the difference was insignificant at all the angles. Conclusion: Irrespective of angles, difference in stress generated in stainless steel implants and titanium implants for both the forces was not significant, and hence, stainless steel implants can be used effectively in a clinical setting.

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.

Thermomechanical Transient Analysis and Conceptual Optimization of a First Stage Bucket

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Alfonso Campos-Amezcua ◽  
Zdzislaw Mazur-Czerwiec ◽  
Armando Gallegos-Muñoz
Keyword(s):  
Transient Analysis ◽  
Computational Models ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Thermomechanical Analysis ◽  
Element Analysis ◽  
Simulation Techniques ◽  
Calculated Stress ◽  
Three Dimensional Models ◽  
Almost All

This paper presents a thermomechanical analysis of a first stage bucket during a gas turbine startup. This analysis uses two simulation techniques, computational fluid dynamics (CFD) for the conjugate heat transfer and flow analysis, and finite element analysis (FEA) for the thermostructural analysis. Computational three-dimensional models were developed using two commercial codes, including all elements of the real bucket to avoid geometric simplifications. An interface was developed to transfer the three-dimensional behavior of bucket temperatures during turbine startup from CFD analysis to subsequent FEA analysis, imposing them as a thermal load. This interface virtually integrates the computational models, although they have different grids. The results of this analysis include temperature evolution and related stresses, as well as the thermomechanical stresses and zones where they are present. These stresses are dominated by thermal mechanisms, so a new temperature startup curve is proposed where the maximum calculated stress decline around 100 MPa, and almost all stresses are lower throughout the transient analysis. The results are compared with experimental data reported in the literature obtaining acceptable approximation.

scholarly journals Aortic root reconstruction with preservation of native aortic valve and sinuses in aortic root dilatation with aortic regurgitation

1999 ◽  
Vol 117 (6) ◽  
pp. 1151-1156 ◽  
Author(s):  
Jacques A.M. van Son ◽  
Roberto Battellini ◽  
Marco Mierzwa ◽  
Thomas Walther ◽  
Rüdiger Autschbach ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Aortic Regurgitation ◽  
Aortic Root ◽  
Native Aortic Valve ◽  
Aortic Root Dilatation

scholarly journals Effect of apical portion of T-, sloped L-, and reversed L-closing loops on their force systems

2016 ◽  
Vol 87 (1) ◽  
pp. 104-110 ◽  
Author(s):  
Paiboon Techalertpaisarn ◽  
Antheunis Versluis
Keyword(s):  
Three Dimensional ◽  
Vertical Force ◽  
Element Analysis ◽  
Force System ◽  
Apical Portion ◽  
Beam Elements ◽  
Force Ratio ◽  
Force Systems ◽  
Three Dimensional Models ◽  
Apical Loop

ABSTRACT Objective: To investigate the effect of the position of the apical portion of closing loops on the force system at both loop ends. Materials and Methods: T-loops were compared with backward-sloped L-loops (SL) and reversed L-loops (RL). SL-loops were directed toward the anterior side; RL-loops were directed toward the posterior side. Loop response to loop pulling was determined with finite element analysis at six positions of the apical loop portion for 12-mm interbracket distance and 8-mm loop length and height. Three-dimensional models of the closing loops were created using beam elements with the properties of stainless steel. Loop responses (horizontal load/deflection, vertical force, and moment-to-force ratio) at both loop ends were calculated as well as at 100 g and 200 g activation forces. Results: T-, SL-, and RL-loops with the same position of the apical portion showed approximately the same force system at both loop ends. This behavior was found across the investigated range through which the loops were moved (interbracket center to posterior bracket). Conclusions: The center of the apical portion determined the force system of the closing loops regardless of the position of the loop legs. The centers of the apical portion of the T-, SL-, and RL-loops acted like V-bend positions.

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