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Gunasekera S, de Silva C, Ng O, Thomas S, Varcoe R, Barber T. Stenosis to stented: decrease in flow disturbances following stent implantation of a diseased arteriovenous fistula. Biomech Model Mechanobiol 2024; 23:453-468. [PMID: 38063956 DOI: 10.1007/s10237-023-01784-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Accepted: 10/14/2023] [Indexed: 03/26/2024]
Abstract
The arteriovenous fistula (AVF) is commonly faced with stenosis at the juxta-anastomotic (JXA) region of the vein. Implantation of a flexible nitinol stent across the stenosed JXA has led to the retention of functioning AVFs leading to the resulting AVF geometry being distinctly altered, thereby affecting the haemodynamic environment within it. In this study, large eddy simulations of the flow field within a patient-specific AVF geometry before and after stent implantation were conducted to detail the change in flow features. Although the diseased AVF had much lower flow rates, adverse flow features, such as recirculation zones and swirling flow at the anastomosis, and jet flow at the stenosis site were present. Larger velocity fluctuations (leading to higher turbulent kinetic energy) stemming from these flow features were apparent in the diseased AVF compared to the stented AVF. The unsteadiness at the stenosis created large regions of wall shear stress (WSS) fluctuations downstream of the stenosis site that were not as apparent in the stented AVF geometry. The larger pressure drop across the diseased vein, compared to the stented vein, was primarily caused by the constriction at the stenosis, potentially causing the lower flow rate. Furthermore, the WSS fluctuations in the diseased AVF could lead to further disease progression downstream of the stenosis. The change in bulk flow unsteadiness, pressure drop, and WSS behaviour confirms that the haemodynamic environment of the diseased AVF has substantially improved following the flexible stent implantation.
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Affiliation(s)
- Sanjiv Gunasekera
- School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia.
| | - Charitha de Silva
- School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Olivia Ng
- School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Shannon Thomas
- Department of Vascular Surgery, Prince of Wales Hospital, Randwick, NSW, 2031, Australia
| | - Ramon Varcoe
- Department of Vascular Surgery, Prince of Wales Hospital, Randwick, NSW, 2031, Australia
| | - Tracie Barber
- School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia
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Bańka P, Wybraniec M, Bochenek T, Gruchlik B, Burchacka A, Swinarew A, Mizia-Stec K. Influence of Aortic Valve Stenosis and Wall Shear Stress on Platelets Function. J Clin Med 2023; 12:6301. [PMID: 37834945 PMCID: PMC10573628 DOI: 10.3390/jcm12196301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 09/19/2023] [Accepted: 09/26/2023] [Indexed: 10/15/2023] Open
Abstract
Aortic valve stenosis (AS) is a common heart valve disease in the elderly population, and its pathogenesis remains an interesting area of research. The degeneration of the aortic valve leaflets gradually progresses to valve sclerosis. The advanced phase is marked by the presence of extracellular fibrosis and calcification. Turbulent, accelerated blood flow generated by the stenotic valve causes excessive damage to the aortic wall. Elevated shear stress due to AS leads to the degradation of high-molecular weight multimers of von Willebrand factor, which may involve bleeding in the mucosal tissues. Conversely, elevated shear stress has been associated with the release of thrombin and the activation of platelets, even in individuals with acquired von Willebrand syndrome. Moreover, turbulent blood flow in the aorta may activate the endothelium and promote platelet adhesion and activation on the aortic valve surface. Platelets release a wide range of mediators, including lysophosphatidic acid, which have pro-osteogenic effects in AS. All of these interactions result in blood coagulation, fibrinolysis, and the hemostatic process. This review summarizes the current knowledge on high shear stress-induced hemostatic disorders, the influence of AS on platelets and antiplatelet therapy.
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Affiliation(s)
- Paweł Bańka
- First Department of Cardiology, School of Medicine in Katowice, Medical University of Silesia, 40-635 Katowice, Poland
| | - Maciej Wybraniec
- First Department of Cardiology, School of Medicine in Katowice, Medical University of Silesia, 40-635 Katowice, Poland
| | - Tomasz Bochenek
- First Department of Cardiology, School of Medicine in Katowice, Medical University of Silesia, 40-635 Katowice, Poland
| | - Bartosz Gruchlik
- First Department of Cardiology, School of Medicine in Katowice, Medical University of Silesia, 40-635 Katowice, Poland
| | - Aleksandra Burchacka
- First Department of Cardiology, School of Medicine in Katowice, Medical University of Silesia, 40-635 Katowice, Poland
| | - Andrzej Swinarew
- Faculty of Science and Technology, University of Silesia in Katowice, 40-007 Katowice, Poland
- Department of Swimming and Water Rescue, Institute of Sport Science, The Jerzy Kukuczka Academy of Physical Education, 40-065 Katowice, Poland
| | - Katarzyna Mizia-Stec
- First Department of Cardiology, School of Medicine in Katowice, Medical University of Silesia, 40-635 Katowice, Poland
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The effect of turbulence modelling on the assessment of platelet activation. J Biomech 2021; 128:110704. [PMID: 34482226 DOI: 10.1016/j.jbiomech.2021.110704] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 07/24/2021] [Accepted: 08/16/2021] [Indexed: 11/21/2022]
Abstract
Pathological platelet activation by abnormal shear stresses is regarded as a main clinical complication in recipients of cardiovascular mechanical devices. In order to improve their performance computational fluid dynamics (CFD) are used to evaluate flow fields and related shear stresses. CFD models are coupled with mathematical models that describe the relation between fluid dynamics variables, and in particular shear stresses, and the platelet activation state (PAS). These models typically use a Lagrangian approach to compute the shear stresses along possible platelet trajectories. However, in the case of turbulent flow, the choice of the proper turbulence closure is still debated for both concerning its effect on shear stress calculation and Lagrangian statistics. In this study different numerical simulations of the flow through a mechanical heart valve were performed and then compared in terms of Eulerian and Lagrangian quantities: a direct numerical simulation (DNS), a large eddy simulation (LES), two Reynolds-averaged Navier-Stokes (RANS) simulations (SST k-ω and RSM) and a "laminar" (no turbulence modelling) simulation. Results exhibit a large variability in the PAS assessment depending on the turbulence model adopted. "Laminar" and RSM estimates of platelet activation are about 60% below DNS, while LES is 16% less. Surprisingly, PAS estimated from the SST k- ω velocity field is only 8% less than from DNS data. This appears more artificial than physical as can be inferred after comparing frequency distributions of PAS and of the different Lagrangian variables of the mechano-biological model of platelet activation. Our study indicates how much turbulence closures may affect platelet activation estimates, in comparison to an accurate DNS, when assessing blood damage in blood contacting devices.
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Ozden K, Yazicioglu Y, Sert C. Simulation of turbulence induced sound generation inside stenosed femoral artery models with different severities and eccentricities. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2021; 208:106253. [PMID: 34273673 DOI: 10.1016/j.cmpb.2021.106253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 06/17/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND AND OBJECTIVES Recent developments of low-cost, compact acoustic sensors, advanced signal processing tools and powerful computational resources allow researchers design new scoring systems for acoustic detection of arterial stenoses. In this study, numerical simulations of blood flow inside stenosed arteries are performed to understand the effect of stenosis severity and eccentricity on the turbulence induced wall pressure fluctuations and the generated sound. METHODS Axisymmetric and eccentric elliptic stenoses of five different severities are generated inside a 6.4 mm diameter femoral artery model. Large eddy simulations of pulsatile, non-Newtonian blood flow are performed using the open source software OpenFOAM. RESULTS Post-stenotic turbulence activity is found to be almost zero for 50 and 60% severities. For severities of 75% and more, turbulent kinetic energy rises significantly with increasing severity. The location of the highest turbulence activity on the vessel wall from the stenosis exit decreases with increasing severity. The maximum level of turbulent kinetic energy seen in 95% severity models is about 9 and 31 times higher than that of 87% and 75% models, respectively. Spectrum of wall pressure fluctuations show that 50 and 60% axisymmetric models are almost silent. The spectrum starts to get richer with 75% severity, and the fluctuation intensity increases with severity. Compared to the axisymmetric models, more activity is observed in the 0-150 Hz band for the 50 and 60% eccentric models. Axial extent of the acoustically active region is also longer in them. Converting wall pressure data into sound revealed that murmurs that can be considered as signs of vascular stenosis are obtained for models with 75% and higher severity. CONCLUSIONS Sound patterns generated from simulation results are similar to the typical sounds obtained by Doppler ultrasonography, and present distinct characters. Together with a sensor technology that can measure these sounds from within the stenosed artery, they can be processed and used for the purpose of non-invasive diagnosis. Computational fluid dynamics studies that simulate large number of cases with different stenosis severities and morphologies will play a critical role in developing the necessary sound databases, which can be used to train new diagnostic devices.
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Affiliation(s)
- Kamil Ozden
- Roketsan Missile Industries Inc., Elmadag, Ankara 06780, Turkey.
| | - Yigit Yazicioglu
- Department of Mechanical Engineering, Middle East Technical University, Ankara 06800, Turkey.
| | - Cuneyt Sert
- Department of Mechanical Engineering, Middle East Technical University, Ankara 06800, Turkey.
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Jhun CS, Newswanger R, Cysyk JP, Ponnaluri S, Good B, Manning KB, Rosenberg G. Dynamics of Blood Flows in Aortic Stenosis: Mild, Moderate, and Severe. ASAIO J 2021; 67:666-674. [PMID: 33164999 PMCID: PMC8093327 DOI: 10.1097/mat.0000000000001296] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Supraphysiologic high shear stresses created in calcific aortic stenosis (AS) are known to cause hemostatic abnormalities, however, the relationship between the complex blood flows over the severity of AS and hemostatic abnormalities still remains unclear. This study systematically characterized the blood flow in mild, moderate, and severe AS. A series of large eddy simulations (LES) validated by particle image velocimetry were performed on physiologically representative AS models with a peak physiologic flow condition of 18 liter per minute. Time-accurate velocity fields, transvalvular pressure gradient, and laminar viscous-and turbulent (or Reynolds) shear stresses (RSSmax) were evaluated for each degree of severity. The peak velocities of mild, moderate, and severe AS were on the order of 2.0, 4.0, and 8.0 m/s, respectively. Jet velocity in severe AS was highly skewed with extremely high velocity (as high as 8 m/s) and mainly traveled through the posterior aortic wall up to the aortic arch while still carrying a relatively high velocity, that is, >4 m/s. The mean laminar viscous wall shear stresses (WSS) for mild, moderate, and severe AS were on the order of 40, 100, and 180 Pa, respectively. The RSSmax were on the order of 260, 490, and 2,500 Pa for mild, moderate, and severe AS, respectively. This study may provide a link between altered flows in AS and hemostatic abnormalities such as acquired von Willebrand syndrome and hemolysis, thus, help diagnosing and timing of the treatment.
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Affiliation(s)
- Choon-Sik Jhun
- Department of Surgery, The Pennsylvania State University, College of Medicine, Hershey, PA
| | - Raymond Newswanger
- Department of Surgery, The Pennsylvania State University, College of Medicine, Hershey, PA
| | - Joshua P. Cysyk
- Department of Surgery, The Pennsylvania State University, College of Medicine, Hershey, PA
| | - Sailahari Ponnaluri
- Department of Biomedical Engineering, College of Engineering, The Pennsylvania State University, University Park, PA
| | - Bryan Good
- Department of Biomedical Engineering, College of Engineering, The Pennsylvania State University, University Park, PA
| | - Keefe B. Manning
- Department of Biomedical Engineering, College of Engineering, The Pennsylvania State University, University Park, PA
| | - Gerson Rosenberg
- Department of Surgery, The Pennsylvania State University, College of Medicine, Hershey, PA
- Department of Biomedical Engineering, College of Engineering, The Pennsylvania State University, University Park, PA
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Comprehensive In Vitro Study of the Flow Past Two Transcatheter Aortic Valves: Comparison with a Severe Stenotic Case. Ann Biomed Eng 2019; 47:2241-2257. [DOI: 10.1007/s10439-019-02289-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/10/2019] [Indexed: 11/25/2022]
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Zmijanovic V, Mendez S, Moureau V, Nicoud F. About the numerical robustness of biomedical benchmark cases: Interlaboratory FDA's idealized medical device. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e02789. [PMID: 27021351 DOI: 10.1002/cnm.2789] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 03/15/2016] [Accepted: 03/16/2016] [Indexed: 06/05/2023]
Abstract
The need for reliable approaches in numerical simulations stands out as a critical issue for the development and optimization of cardiovascular biomedical devices. This led the US Food and Drug Administration to undertake a programme of validation of computational fluid dynamics methods for transitional and turbulent flows. In the current investigation, large-eddy simulation is used to simulate the flow in the first benchmark medical device, and results are confronted to the existing laboratory experiments. This idealized medical device has the particularity to feature transition to turbulence after a sudden expansion. The effects of numerical parameters and low-level inlet perturbations are investigated. Results indicate a considerable impact of numerical aspects on the prediction of the location of the transition to turbulence. The study also demonstrates that injecting small perturbations at the inflow greatly improves the streamwise velocity estimation in the transition region and substantially contributes to the robustness of the flow statistical data. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Vladeta Zmijanovic
- Institute of Montpellier Alexander Grothendieck - CNRS UMR5149 and University of Montpellier, Montpellier, 34095, France
| | - Simon Mendez
- Institute of Montpellier Alexander Grothendieck - CNRS UMR5149 and University of Montpellier, Montpellier, 34095, France
| | - Vincent Moureau
- CORIA, CNRS, INSA and University of Rouen, Saint-Etienne-du-Rouvray, 76801, France
| | - Franck Nicoud
- Institute of Montpellier Alexander Grothendieck - CNRS UMR5149 and University of Montpellier, Montpellier, 34095, France
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