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Ristow I, Riedel C, Lenz A, Well L, Adam G, Panuccio G, Kölbel T, Bannas P. Current Imaging Strategies in Patients with Abdominal Aortic Aneurysms. ROFO-FORTSCHR RONTG 2024; 196:52-61. [PMID: 37699431 DOI: 10.1055/a-2119-6448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
BACKGROUND An abdominal aortic aneurysm (AAA) is defined as a localized dilatation of the abdominal aorta of ≥ 3 cm. With a prevalence of 4-8 %, AAA is one of the most common vascular diseases in Western society. Radiological imaging is an elementary component in the diagnosis, monitoring, and treatment planning of AAA patients. METHOD This is a narrative review article on preoperative imaging strategies of AAA, incorporating expert opinions based on the current literature and standard-of-care practices from our own center. Examples are provided to illustrate clinical cases from our institution. RESULTS AND CONCLUSION Radiological imaging plays a pivotal role in the initial diagnosis and monitoring of patients with AAA. Ultrasound is the mainstay imaging modality for AAA screening and surveillance. Contrast-enhanced CT angiography is currently considered the gold standard for preoperative imaging and image-based treatment planning in AAA repair. New non-contrast MR angiography techniques are robustly applicable and allow precise determination of aortic diameters, which is of critical importance, particularly with regard to current diameter-based surgical treatment guidelines. 3D imaging with multiplanar reformation and automatic centerline positioning enables more accurate assessment of the maximum aortic diameter. Modern imaging techniques such as 4D flow MRI have the potential to further improve individualized risk stratification in patients with AAA. KEY POINTS · Ultrasound is the mainstay imaging modality for AAA screening and monitoring. · Contrast-enhanced CT angiography is the gold standard for preoperative imaging in AAA repair. · Non-contrast MR angiography allows for accurate monitoring of aortic diameters in AAA patients. · Measurement of aortic diameters is more accurate with 3D-CT/MRI compared to ultrasound. · Research seeks new quantitative imaging biomarkers for AAA risk stratification, e. g., using 4D flow MRI.
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Affiliation(s)
- Inka Ristow
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christoph Riedel
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Alexander Lenz
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Lennart Well
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Gerhard Adam
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Giuseppe Panuccio
- German Aortic Center Hamburg, Department of Vascular Medicine, University Medical Center Hamburg-Eppendorf University Heart & Vascular Center, Hamburg, Germany
| | - Tilo Kölbel
- German Aortic Center Hamburg, Department of Vascular Medicine, University Medical Center Hamburg-Eppendorf University Heart & Vascular Center, Hamburg, Germany
| | - Peter Bannas
- Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Sun W, Zheng J, Gao Y. Targeting Platelet Activation in Abdominal Aortic Aneurysm: Current Knowledge and Perspectives. Biomolecules 2022; 12:biom12020206. [PMID: 35204706 PMCID: PMC8961578 DOI: 10.3390/biom12020206] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/21/2022] [Accepted: 01/22/2022] [Indexed: 01/28/2023] Open
Abstract
Abdominal aortic aneurysm (AAA) is a potentially fatal vascular disease that involves complex multifactorial hemodynamic, thrombotic, inflammatory, and aortic wall remodeling processes. However, its mechanisms are incompletely understood. It has become increasingly clear that platelets are involved in pathological processes of vascular diseases beyond their role in hemostasis and thrombosis. Platelet activation with membrane receptors and secreted mediators promotes thrombus formation and the accumulation of inflammatory cells, which may play an important role in the development of AAA by destroying the structural integrity and stability of the vessel wall. Turbulent blood flow in aortic aneurysms promotes platelet activation and aggregation. Platelet count and heterogeneity are important predictive, diagnostic, and prognostic indicators of AAA. We summarize the relationship between platelet activation and AAA development and propose future research directions and possible clinical applications.
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Affiliation(s)
- Weiliang Sun
- Institute of Clinical Medicine Sciences, China-Japan Friendship Hospital, 2 Yinghua Dongjie, Chaoyang District, Beijing 100029, China;
| | - Jingang Zheng
- Department of Cardiology, China-Japan Friendship Hospital, 2 Yinghua Dongjie, Chaoyang District, Beijing 100029, China;
| | - Yanxiang Gao
- Department of Cardiology, China-Japan Friendship Hospital, 2 Yinghua Dongjie, Chaoyang District, Beijing 100029, China;
- Correspondence:
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Pillalamarri NR, Piskin S, Patnaik SS, Murali S, Finol EA. Patient-Specific Computational Analysis of Hemodynamics in Adult Pulmonary Hypertension. Ann Biomed Eng 2021; 49:3465-3480. [PMID: 34799807 DOI: 10.1007/s10439-021-02884-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 10/29/2021] [Indexed: 11/25/2022]
Abstract
Pulmonary hypertension (PH) is a progressive disease characterized by elevated pressure and vascular resistance in the pulmonary arteries. Nearly 250,000 hospitalizations occur annually in the US with PH as the primary or secondary condition. A definitive diagnosis of PH requires right heart catheterization (RHC) in addition to a chest computed tomography, a walking test, and others. While RHC is the gold standard for diagnosing PH, it is invasive and posseses inherent risks and contraindications. In this work, we characterized the patient-specific pulmonary hemodynamics in silico for diverse PH WHO groups. We grouped patients on the basis of mean pulmonary arterial pressure (mPAP) into three disease severity groups: at-risk ([Formula: see text], denoted with A), mild ([Formula: see text], denoted with M), and severe ([Formula: see text], denoted with S). The pulsatile flow hemodynamics was simulated by evaluating the three-dimensional Navier-Stokes system of equations using a flow solver developed by customizing OpenFOAM libraries (v5.0, The OpenFOAM Foundation). Quasi patient-specific boundary conditions were implemented using a Womersley inlet velocity profile and transient resistance outflow conditions. Hemodynamic indices such as spatially averaged wall shear stress ([Formula: see text]), wall shear stress gradient ([Formula: see text]), time-averaged wall shear stress ([Formula: see text]), oscillatory shear index ([Formula: see text]), and relative residence time ([Formula: see text]), were evaluated along with the clinical metrics pulmonary vascular resistance ([Formula: see text]), stroke volume ([Formula: see text]) and compliance ([Formula: see text]), to assess possible spatiotemporal correlations. We observed statistically significant decreases in [Formula: see text], [Formula: see text], and [Formula: see text], and increases in [Formula: see text] and [Formula: see text] with disease severity. [Formula: see text] was moderately correlated with [Formula: see text] and [Formula: see text] at the mid-notch stage of the cardiac cycle when these indices were computed using the global pulmonary arterial geometry. These results are promising in the context of a long-term goal of identifying computational biomarkers that can serve as surrogates for invasive diagnostic protocols of PH.
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Affiliation(s)
- Narasimha R Pillalamarri
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
| | - Senol Piskin
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
- Department of Mechanical Engineering, Istinye University, Istanbul, Turkey
| | - Sourav S Patnaik
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX, USA
| | - Srinivas Murali
- Division of Cardiovascular Medicine, Allegheny Health Network, Pittsburgh, PA, USA
| | - Ender A Finol
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA.
- UTSA/UTHSA Joint Graduate Program in Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX, USA.
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Real-Time Evaluation of Blood Flow Patterns Using AneurysmFlow for an in vivo Abdominal Aortic Aneurysm Model. Ann Vasc Surg 2021; 80:256-263. [PMID: 34752852 DOI: 10.1016/j.avsg.2021.08.044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/18/2021] [Accepted: 08/18/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND Many new tools for abdominal aortic aneurysm (AAA) rupture risk evaluation have been developed. These new tools need detailed hemodynamic information in AAA. However, hemodynamic data obtained from in vivo research are lacking. Thus, the objective of this study was to analyze blood flow patterns in an in vivo AAA model to acquire real-time hemodynamic information using AneurysmFlow, a novel flow evaluation system. METHODS Digital subtraction angiography images of patients who underwent endovascular aneurysm repair were analyzed using the visualization function of the AneurysmFlow to classify blood flow patterns as laminar or turbulent flow. The presence of boundary layer separation was also evaluated. The time taken for contrast medium to travel from the infrarenal aortic neck to aortic bifurcation was acquired to calculate the flow velocity. Associations between characteristics of aneurysm including lumen occupying ratio of intraluminal thrombus (ILT) and the hemodynamic flow pattern were evaluated. RESULTS A total of 37 AAA patients was enrolled. Their blood flow patterns were evaluated using the AneurysmFlow. Logistic regression analyses with lumen occupying ratio of ILT as an independent variable showed that the larger the lumen occupying ratio of ILT, the more likely the aneurysm was to show a laminar pattern (P = 0.03) and the more likely the boundary layer separation would not exist (P = 0.04). The flow velocity from the infrarenal aortic neck to the aortic bifurcation showed a positive association with the lumen occupying ratio of the ILT in linear regression analysis (P < 0.001). CONCLUSION Hemodynamic analysis of AAA with the AneurysmFlow using real-time individual patient models showed different flow patterns and flow velocities depending on ILT. This novel analytic approach using AneurysmFlow has potential to play an important role in obtaining clinically meaningful hemodynamic information of AAA.
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Owen DG, de Oliveira DC, Neale EK, Shepherd DET, Espino DM. Numerical modelling of blood rheology and platelet activation through a stenosed left coronary artery bifurcation. PLoS One 2021; 16:e0259196. [PMID: 34731193 PMCID: PMC8565790 DOI: 10.1371/journal.pone.0259196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 10/14/2021] [Indexed: 01/09/2023] Open
Abstract
Coronary bifurcations are prone to atherosclerotic plaque growth, experiencing regions of reduced wall shear stress (WSS) and increased platelet adhesion. This study compares effects across different rheological approaches on hemodynamics, combined with a shear stress exposure history model of platelets within a stenosed porcine bifurcation. Simulations used both single/multiphase blood models to determine which approach best predicts phenomena associated with atherosclerosis and atherothrombosis. A novel Lagrangian platelet tracking model was used to evaluate residence time and shear history of platelets indicating likely regions of thrombus formation. Results show a decrease in area of regions with pathologically low time-averaged WSS with the use of multiphase models, particularly in a stenotic bifurcation. Significant non-Newtonian effects were observed due to low-shear and varying hematocrit levels found on the outer walls of the bifurcation and distal to the stenosis. Platelet residence time increased 11% in the stenosed artery, with exposure times to low-shear sufficient for red blood cell aggregation (>1.5 s). increasing the risk of thrombosis. This shows stenotic artery hemodynamics are inherently non-Newtonian and multiphase, with variations in hematocrit (0.163-0.617) and elevated vorticity distal to stenosis (+15%) impairing the function of the endothelium via reduced time-averaged WSS regions, rheological properties and platelet activation/adhesion.
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Affiliation(s)
- David G. Owen
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Diana C. de Oliveira
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Emma K. Neale
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Duncan E. T. Shepherd
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Daniel M. Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
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6
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Boyd AJ. Intraluminal thrombus: Innocent bystander or factor in abdominal aortic aneurysm pathogenesis? JVS Vasc Sci 2021; 2:159-169. [PMID: 34617066 PMCID: PMC8489244 DOI: 10.1016/j.jvssci.2021.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 02/20/2021] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Abdominal aortic aneurysms (AAAs) represent a complex multifactorial hemodynamic, thrombotic, and inflammatory process that can ultimately result in aortic rupture and death. Despite improved screening and surgical management of AAAs, the mortality rates have remained high after rupture, and little progress has occurred in the development of nonoperative treatments. Intraluminal thrombus (ILT) is present in most AAAs and might be involved in AAA pathogenesis. The present review examined the latest clinical and experimental evidence for possible involvement of the ILT in AAA growth and rupture. METHODS A literature review was performed after a search of the PubMed database from 2012 to June 2020 using the terms "abdominal aortic aneurysm" and "intraluminal thrombus." RESULTS The structure, composition, and hemodynamics of ILT formation and propagation were reviewed in relation to the hemostatic and proteolytic factors favoring ILT deposition. The potential effects of the ILT on AAA wall degeneration and rupture, including a review of the current controversies regarding the position, thickness, and composition of ILT, are presented. Although initially potentially protective against increased wall stress, increasing evidence has shown that an increased volume and greater age of the ILT have direct detrimental effects on aortic wall integrity, which might predispose to an increased rupture risk. CONCLUSIONS ILT does not appear to be an innocent bystander in AAA pathophysiology. However, its exact role remains elusive and controversial. Despite computational evidence of a possible protective role of the ILT in reducing wall stress, increasing evidence has shown that the ILT promotes AAA wall degeneration in humans and in animal models. Further research, with large animal models and with more chronic ILT is crucial for a better understanding of the role of the ILT in AAAs and for the potential development of targeted therapies to slow or halt AAA progression.
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Affiliation(s)
- April J. Boyd
- Department of Vascular Surgery, University of Manitoba, Winnipeg, Manitoba, Canada
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7
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Thirugnanasambandam M, Canchi T, Piskin S, Karmonik C, Kung E, Menon PG, Avril S, Finol EA. Design, Development, and Temporal Evaluation of a Magnetic Resonance Imaging-Compatible In Vitro Circulation Model Using a Compliant Abdominal Aortic Aneurysm Phantom. J Biomech Eng 2021; 143:1096849. [PMID: 33493273 DOI: 10.1115/1.4049894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Indexed: 11/08/2022]
Abstract
Biomechanical characterization of abdominal aortic aneurysms (AAAs) has become commonplace in rupture risk assessment studies. However, its translation to the clinic has been greatly limited due to the complexity associated with its tools and their implementation. The unattainability of patient-specific tissue properties leads to the use of generalized population-averaged material models in finite element analyses, which adds a degree of uncertainty to the wall mechanics quantification. In addition, computational fluid dynamics modeling of AAA typically lacks the patient-specific inflow and outflow boundary conditions that should be obtained by nonstandard of care clinical imaging. An alternative approach for analyzing AAA flow and sac volume changes is to conduct in vitro experiments in a controlled laboratory environment. In this study, we designed, built, and characterized quantitatively a benchtop flow loop using a deformable AAA silicone phantom representative of a patient-specific geometry. The impedance modules, which are essential components of the flow loop, were fine-tuned to ensure typical intraluminal pressure conditions within the AAA sac. The phantom was imaged with a magnetic resonance imaging (MRI) scanner to acquire time-resolved images of the moving wall and the velocity field inside the sac. Temporal AAA sac volume changes lead to a corresponding variation in compliance throughout the cardiac cycle. The primary outcome of this work was the design optimization of the impedance elements, the quantitative characterization of the resistive and capacitive attributes of a compliant AAA phantom, and the exemplary use of MRI for flow visualization and quantification of the deformed AAA geometry.
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Affiliation(s)
- Mirunalini Thirugnanasambandam
- University of Texas at San Antonio, UTSA/UTHSCSA Joint Graduate Program in Biomedical Engineering, San Antonio, TX 78249
| | - Tejas Canchi
- Department of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
| | - Senol Piskin
- Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249; Department of Mechanical Engineering, Istinye University, Istanbul 34010, Turkey
| | | | - Ethan Kung
- Department of Mechanical Engineering, Clemson University Clemson, SC 29634
| | - Prahlad G Menon
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260
| | - Stephane Avril
- Ecole Nationale Supérieure des Mines, Center for Biomedical and Healthcare Engineering, St-Etienne 75006, France
| | - Ender A Finol
- University of Texas at San Antonio, UTSA/UTHSCSA Joint Graduate Program in Biomedical Engineering, San Antonio, TX 78249; Department of Mechanical Engineering, University of Texas at San Antonio, Room EB 3.04.08 One UTSA Circle, San Antonio, TX 78249
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Owen DG, de Oliveira DC, Qian S, Green NC, Shepherd DET, Espino DM. Impact of side-hole geometry on the performance of hemodialysis catheter tips: A computational fluid dynamics assessment. PLoS One 2020; 15:e0236946. [PMID: 32764790 PMCID: PMC7413473 DOI: 10.1371/journal.pone.0236946] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/16/2020] [Indexed: 12/02/2022] Open
Abstract
Hemodialysis catheters are used to support blood filtration, yet there are multiple fundamentally different approaches to catheter tip design with no clear optimal solution. Side-holes have been shown to increase flow rates and decrease recirculation but have been associated with clotting/increased infection rates. This study investigates the impact of changing the shape, size and number of side-holes on a simple symmetric tip catheter by evaluating the velocity, shear stress and shear rate of inflowing blood. A platelet model is used to examine the residence time and shear history of inflowing platelets. The results show that side-holes improve the theoretical performance of the catheters, reducing the maximum velocity and shear stress occurring at the tip compared to non-side-hole catheters. Increasing the side-hole area improved performance up to a point, past which not all inflow through the hole was captured, and instead a small fraction slowly 'washed-out' through the remainder of the tip resulting in greater residence times and increasing the likelihood of platelet adhesion. An oval shaped hole presents a lower chance of external fibrin formation compared to a circular hole, although this would also be influenced by the catheter material surface topology which is dependent on the manufacturing process. Overall, whilst side-holes may be associated with increased clotting and infection, this can be reduced when side-hole geometry is correctly implemented though; a sufficient area for body diameter (minimising residence time) and utilising angle-cut, oval shaped holes (reducing shear stress and chances of fibrin formation partially occluding holes).
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Affiliation(s)
- David G. Owen
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Diana C. de Oliveira
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Shuang Qian
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Naomi C. Green
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Duncan E. T. Shepherd
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Daniel M. Espino
- Department of Mechanical Engineering, University of Birmingham, Birmingham, United Kingdom
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Fan YN, Ke X, Yi ZL, Lin YQ, Deng BQ, Shu XR, Yang DH, Liao ZY, Nie RQ. Plasma D-dimer as a predictor of intraluminal thrombus burden and progression of abdominal aortic aneurysm. Life Sci 2020; 240:117069. [PMID: 31751582 DOI: 10.1016/j.lfs.2019.117069] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 11/03/2019] [Accepted: 11/13/2019] [Indexed: 10/25/2022]
Abstract
AIM Intraluminal thrombus (ILT) is presented in most abdominal aortic aneurysms (AAAs) and is suggested to promote AAA expansion. D-dimer, a breakdown product in the thrombus remodeling, may have prognostic value for AAA. This study investigated the interrelation between plasma D-dimer level, ILT volume, AAA size and progression. MAIN METHODS This was a retrospective observational study that involved 181 patients with infra-renal AAA. They were divided into small and large AAA groups according to AAA diameter. 24 of them had repeated abdominal computed tomography angiography (CTA) scan and were divided into slow-growing and fast-growing AAA groups according to the median value of AAA growth rate. Baseline and follow-up plasma D-dimer level, maximum diameter of AAA, total infra-renal aortic volume and ILT volume were analyzed. KEY FINDINGS Plasma D-dimer level was positively correlated with ILT volume (R = 0.382, P < 0.001) and maximum diameter of AAA (R = 0.442, P < 0.001). Increasing value of plasma D-dimer was positively associated with the accelerated growth rate of AAA (R = 0.720, P < 0.01). ILT volume showed positive correlation with maximum diameter (R = 0.859, P < 0.001) and growth rate of AAA (R = 0.490, P < 0.05). After adjusting the baseline ILT volume, the positive correlations remained to be statistically significant between plasma D-dimer level and AAA size (R = 0.200, P < 0.05), as well as increasing value of plasma D-dimer and growth rate of AAA (R = 0.642, P < 0.05). SIGNIFICANCE Plasma D-dimer level reflected ILT burden in AAAs. Plasma D-dimer level and ILT volume were positively correlated with AAA size. Increasing value of plasma D-dimer and baseline ILT volume could be predictors of AAA progression.
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Affiliation(s)
- Ying-Nan Fan
- Department of Cardiology, Sun Yat-Sen Memorial Hospital, Sun Yat-sen University, No. 107, Yanjiang Road West, Yuexiu District, Guangzhou 510120, China.
| | - Xiao Ke
- Department of Cardiology, Fuwai Hospital, Chinese Academy of Medical Sciences, Shenzhen (Sun Yat-sen Cardiovascular Hospital, Shenzhen), No. 12, Langshan Road, Nanshan District, Shenzhen 518057, China.
| | - Zhi-Long Yi
- Department of Radiology, Sun Yat-Sen Memorial Hospital, Sun Yat-sen University, No. 107, Yanjiang Road West, Yuexiu District, Guangzhou 510120, China.
| | - Yong-Qing Lin
- Department of Cardiology, Sun Yat-Sen Memorial Hospital, Sun Yat-sen University, No. 107, Yanjiang Road West, Yuexiu District, Guangzhou 510120, China.
| | - Bing-Qing Deng
- Department of Cardiology, Sun Yat-Sen Memorial Hospital, Sun Yat-sen University, No. 107, Yanjiang Road West, Yuexiu District, Guangzhou 510120, China.
| | - Xiao-Rong Shu
- Department of Cardiology, Sun Yat-Sen Memorial Hospital, Sun Yat-sen University, No. 107, Yanjiang Road West, Yuexiu District, Guangzhou 510120, China.
| | - Da-Hao Yang
- Department of Cardiology, Fuwai Hospital, Chinese Academy of Medical Sciences, Shenzhen (Sun Yat-sen Cardiovascular Hospital, Shenzhen), No. 12, Langshan Road, Nanshan District, Shenzhen 518057, China.
| | - Zhi-Yong Liao
- Department of Cardiology, Fuwai Hospital, Chinese Academy of Medical Sciences, Shenzhen (Sun Yat-sen Cardiovascular Hospital, Shenzhen), No. 12, Langshan Road, Nanshan District, Shenzhen 518057, China.
| | - Ru-Qiong Nie
- Department of Cardiology, Sun Yat-Sen Memorial Hospital, Sun Yat-sen University, No. 107, Yanjiang Road West, Yuexiu District, Guangzhou 510120, China.
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Overeem SP, Goudeketting SR, Schuurmann RC, Heyligers JM, Verhagen HJ, Versluis M, de Vries JPP. Assessment of changes in stent graft geometry after chimney endovascular aneurysm sealing. J Vasc Surg 2019; 70:1754-1764. [DOI: 10.1016/j.jvs.2019.02.058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 02/19/2019] [Indexed: 11/24/2022]
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Joly F, Soulez G, Lessard S, Kauffmann C, Vignon-Clementel I. A Cohort Longitudinal Study Identifies Morphology and Hemodynamics Predictors of Abdominal Aortic Aneurysm Growth. Ann Biomed Eng 2019; 48:606-623. [DOI: 10.1007/s10439-019-02375-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 09/24/2019] [Indexed: 12/19/2022]
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Visualizing and quantifying flow stasis in abdominal aortic aneurysms in men using 4D flow MRI. Magn Reson Imaging 2019; 57:103-110. [DOI: 10.1016/j.mri.2018.11.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 11/10/2018] [Accepted: 11/11/2018] [Indexed: 01/24/2023]
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Strongly Coupled Morphological Features of Aortic Aneurysms Drive Intraluminal Thrombus. Sci Rep 2018; 8:13273. [PMID: 30185838 PMCID: PMC6125404 DOI: 10.1038/s41598-018-31637-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 08/15/2018] [Indexed: 01/13/2023] Open
Abstract
Over 75% of abdominal aortic aneurysms harbor an intraluminal thrombus, and increasing evidence suggests that biologically active thrombus contributes to the natural history of these potentially lethal lesions. Thrombus formation depends on the local hemodynamics, which in turn depends on morphological features of the aneurysm and near vasculature. We previously presented a hemodynamically motivated “thrombus formation potential” that predicts where and when thrombus might form. Herein, we combine detailed studies of the three-dimensional hemodynamics with methods of sparse grid collocation and interpolation via kriging to examine roles of five key morphological features of aneurysms on thrombus formation: lesion diameter, axial position, length, curvature, and renal artery position. Computational simulations suggest that maximum diameter is a key determinant of thrombogenicity, but other morphological features modulate this dependence. More distally located lesions tend to have a higher thrombus formation potential and shorter lesions tend to have a higher potential than longer lesions, given the same aneurysmal dilatation. Finally, movement of vortical structures through the infrarenal aorta and lesion can significantly affect thrombogenicity. Formation of intraluminal thrombus within an evolving abdominal aortic aneurysm thus depends on coupled morphological features, not all intuitive, and computational simulations can be useful for predicting thrombogenesis.
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Flow stagnation volume and abdominal aortic aneurysm growth: Insights from patient-specific computational flow dynamics of Lagrangian-coherent structures. Comput Biol Med 2018; 92:98-109. [DOI: 10.1016/j.compbiomed.2017.10.033] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 10/09/2017] [Accepted: 10/28/2017] [Indexed: 12/23/2022]
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Virag L, Wilson JS, Humphrey JD, Karšaj I. Potential biomechanical roles of risk factors in the evolution of thrombus-laden abdominal aortic aneurysms. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:10.1002/cnm.2893. [PMID: 28447404 PMCID: PMC5658277 DOI: 10.1002/cnm.2893] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 02/23/2017] [Accepted: 04/23/2017] [Indexed: 05/22/2023]
Abstract
Abdominal aortic aneurysms (AAAs) typically harbour an intraluminal thrombus (ILT), yet most prior computational models neglect biochemomechanical effects of thrombus on lesion evolution. We recently proposed a growth and remodelling model of thrombus-laden AAAs that introduced a number of new constitutive relations and associated model parameters. Because values of several of these parameters have yet to be elucidated by clinical data and could vary significantly from patient to patient, the aim of this study was to investigate the possible extent to which these parameters influence AAA evolution. Given that some of these parameters model potential effects of factors that influence the risk of rupture, this study also provides insight into possible roles of common risk factors on the natural history of AAAs. Despite geometrical limitations of a cylindrical domain, findings support current thought that smoking, hypertension, and female sex likely increase the risk of rupture. Although thrombus thickness is not a reliable risk factor for rupture, the model suggests that the presence of ILT may have a destabilizing effect on AAA evolution, consistent with histological findings from human samples. Finally, simulations support two hypotheses that should be tested on patient-specific geometries in the future. First, ILT is a potential source of the staccato enlargement observed in many AAAs. Second, ILT can influence rupture risk, positively or negatively, via competing biomechanical (eg, stress shielding) and biochemical (ie, proteolytic) effects. Although further computational and experimental studies are needed, the present findings highlight the importance of considering ILT when predicting aneurysmal enlargement and rupture risk.
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Affiliation(s)
- Lana Virag
- Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Zagreb, Croatia
| | - John S. Wilson
- Department of Radiology, Emory University, Atlanta, GA, USA
| | - Jay D. Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
| | - Igor Karšaj
- Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Zagreb, Croatia
- Address for Correspondence: Igor Karšaj, Ph.D., Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, Zagreb, 10000, Croatia, Phone: +38516168125,
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Boersen JT, Groot Jebbink E, Van de Velde L, Versluis M, Lajoinie G, Slump CH, de Vries JPPM, Reijnen MMPJ. The Influence of Positioning of the Nellix Endovascular Aneurysm Sealing System on Suprarenal and Renal Flow: An In Vitro Study. J Endovasc Ther 2017; 24:677-687. [DOI: https:/doi.org/10.1177/1526602817719465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
Purpose: To examine the influence of device positioning and infrarenal neck diameter on flow patterns in the Nellix endovascular aneurysm sealing (EVAS) system. Methods: The transition of the aortic flow lumen into two 10-mm-diameter stents after EVAS creates a mismatched area. Flow recirculation may affect local wall shear stress (WSS) profiles and residence time associated with atherosclerosis and thrombosis. To examine these issues, 7 abdominal aortic aneurysm flow phantoms were created, including 3 unstented controls and 3 stented models with infrarenal neck diameters of 24, 28, and 32 mm. Stents were positioned within the instructions for use (IFU). Another 28-mm model was created to evaluate lower positioning of the stents outside the IFU (28-mm LP). Flow was visualized using optical particle imaging velocimetry (PIV) and quantified by time-averaged WSS (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) in the aorta at the anteroposterior (AP) midplane, lateral midplane, and renal artery AP midplane levels. Results: Flow in the aorta AP midplane was similar in all models. Vortices were observed in the stented models in the lateral midplane near the anterior and posterior walls. In the 32-mm IFU and 28-mm LP models, a steady state of vortices appeared, with varying location during a cycle. In all models, a low TAWSS (<10−2 Pa) was observed at the anterior wall of the aorta with peak OSI of 0.5 and peak RRT of 104 Pa−1. This region was more proximally located in the stented models. The 24- and 28-mm IFU models showed flow with a higher velocity at the renal artery inflow compared to controls. TAWSS in the renal artery was lower near the orifice in all models, with the largest area in the 24-mm IFU model. OSI and RRT in the renal artery were near zero for all models. Conclusion: EVAS enhances vorticity proximal to the seal zone, especially with lower positioning of the device and in larger neck diameters. Endobags just below the renal artery affect the flow profile in a minor area of this artery in 24- and 28-mm necks, while lower stent positioning does not influence the renal artery flow profile.
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Affiliation(s)
- Johannes T. Boersen
- Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands
- Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
| | - Erik Groot Jebbink
- Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | | | - Michel Versluis
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Guillaume Lajoinie
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | - Cornelius H. Slump
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
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Boersen JT, Groot Jebbink E, Van de Velde L, Versluis M, Lajoinie G, Slump CH, de Vries JPPM, Reijnen MMPJ. The Influence of Positioning of the Nellix Endovascular Aneurysm Sealing System on Suprarenal and Renal Flow: An In Vitro Study. J Endovasc Ther 2017; 24:677-687. [PMID: 28689483 DOI: 10.1177/1526602817719465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE To examine the influence of device positioning and infrarenal neck diameter on flow patterns in the Nellix endovascular aneurysm sealing (EVAS) system. METHODS The transition of the aortic flow lumen into two 10-mm-diameter stents after EVAS creates a mismatched area. Flow recirculation may affect local wall shear stress (WSS) profiles and residence time associated with atherosclerosis and thrombosis. To examine these issues, 7 abdominal aortic aneurysm flow phantoms were created, including 3 unstented controls and 3 stented models with infrarenal neck diameters of 24, 28, and 32 mm. Stents were positioned within the instructions for use (IFU). Another 28-mm model was created to evaluate lower positioning of the stents outside the IFU (28-mm LP). Flow was visualized using optical particle imaging velocimetry (PIV) and quantified by time-averaged WSS (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) in the aorta at the anteroposterior (AP) midplane, lateral midplane, and renal artery AP midplane levels. RESULTS Flow in the aorta AP midplane was similar in all models. Vortices were observed in the stented models in the lateral midplane near the anterior and posterior walls. In the 32-mm IFU and 28-mm LP models, a steady state of vortices appeared, with varying location during a cycle. In all models, a low TAWSS (<10-2 Pa) was observed at the anterior wall of the aorta with peak OSI of 0.5 and peak RRT of 104 Pa-1. This region was more proximally located in the stented models. The 24- and 28-mm IFU models showed flow with a higher velocity at the renal artery inflow compared to controls. TAWSS in the renal artery was lower near the orifice in all models, with the largest area in the 24-mm IFU model. OSI and RRT in the renal artery were near zero for all models. CONCLUSION EVAS enhances vorticity proximal to the seal zone, especially with lower positioning of the device and in larger neck diameters. Endobags just below the renal artery affect the flow profile in a minor area of this artery in 24- and 28-mm necks, while lower stent positioning does not influence the renal artery flow profile.
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Affiliation(s)
- Johannes T Boersen
- 1 Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands.,2 Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
| | - Erik Groot Jebbink
- 1 Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands.,3 Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | | | - Michel Versluis
- 3 Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands.,4 MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Guillaume Lajoinie
- 3 Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | - Cornelius H Slump
- 4 MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
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Barber T. Wall shear stress and near-wall flows in the stenosed femoral artery. Comput Methods Biomech Biomed Engin 2017; 20:1048-1055. [DOI: 10.1080/10255842.2017.1331342] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- T. Barber
- School of Mechanical & Manufacturing Engineering, University of New South Wales, Sydney, Australia
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Raptis A, Xenos M, Georgakarakos E, Kouvelos G, Giannoukas A, Matsagkas M. Hemodynamic Profile of Two Aortic Endografts Accounting for Their Postimplantation Position. J Med Device 2017. [DOI: 10.1115/1.4035687] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Endovascular aneurysm repair (EVAR) is a clinically effective technique for treating anatomically eligible abdominal aortic aneurysms (AAAs), involving the deployment of an endograft (EG) that is designed to prevent blood leakage in the aneurysmal sac. While most EGs have equivalent operating principles, the hemodynamic environment established by different EGs is not necessarily the same. So, to unveil the post-EVAR hemodynamic properties, we need an EG-specific computational approach that currently lacks from the literature. Endurant and Excluder are two EGs with similar pre-installation designs. We assumed that the flow conditions in the particular EGs do not vary significantly. The hypothesis was tested combining image reconstructions, computational fluid dynamics (CFD), and statistics, taking into account the postimplantation position of the EGs. Ten patients with Endurant EGs and ten patients with Excluder EGs were included in this study. The two groups were matched with respect to the preoperative morphological characteristics of the AAAs. The EG models are derived from image reconstructions of postoperative computed tomography scans. Wall shear stress (WSS), displacement force, velocity, and helicity were calculated in regions of interest within the EG structures, i.e., the main body, the upper and lower part of the limbs. Excluder generated higher WSS compared to Endurant, especially on the lower part of the limbs (p = 0.001). Spatial fluctuations of WSS were observed on the upper part of the Excluder limbs. Higher blood velocity was induced by Excluder in all the regions of interest (p = 0.04, p = 0.01, and p = 0.004). Focal points of secondary flow were detected in the main body of Endurant and the limbs of Excluder. The displacement force acting on the lower part of the Excluder limbs was stronger compared to the Endurant one (p = 0.03). The results showed that two similar EGs implanted in similar AAAs can induce significantly different flow properties. The delineation of the hemodynamic features associated with the various commercially available EGs could further promote the personalization of treatment offered to aneurysmal patients and inspire ideas for the improvement of EG designs in the future.
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Affiliation(s)
- Anastasios Raptis
- Cardiovascular Surgery Department, Sector of Surgery, Faculty of Medicine, School of Health Sciences, University of Ioannina, Ioannina 45500, Greece
- Laboratory for Vascular Simulations, Institute of Vascular Diseases, Ioannina 45500, Greece e-mails:
| | - Michalis Xenos
- Department of Mathematics, University of Ioannina, Ioannina 45500, Greece
- Laboratory for Vascular Simulations, Institute of Vascular Diseases, Ioannina 45500, Greece e-mail:
| | - Efstratios Georgakarakos
- Department of Vascular Surgery, “Democritus” Medical School, University Hospital of Alexandroupolis, Alexandroupolis 68100, Greece e-mail:
| | - George Kouvelos
- Department of Vascular Surgery, Faculty of Medicine, University of Thessaly, Larissa 41334, Greece e-mail:
| | - Athanasios Giannoukas
- Department of Vascular Surgery, Faculty of Medicine, University of Thessaly, Larissa 41334, Greece
- Laboratory for Vascular Simulations, Institute of Vascular Diseases, Ioannina 45500, Greece e-mail:
| | - Miltiadis Matsagkas
- Department of Vascular Surgery, Faculty of Medicine, University of Thessaly, Larissa 41334, Greece
- Laboratory for Vascular Simulations, Institute of Vascular Diseases, Ioannina 45500, Greece e-mails:
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Di Achille P, Tellides G, Humphrey J. Hemodynamics-driven deposition of intraluminal thrombus in abdominal aortic aneurysms. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:10.1002/cnm.2828. [PMID: 27569676 PMCID: PMC5332472 DOI: 10.1002/cnm.2828] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 07/06/2016] [Accepted: 08/25/2016] [Indexed: 05/18/2023]
Abstract
Accumulating evidence suggests that intraluminal thrombus plays many roles in the natural history of abdominal aortic aneurysms. There is, therefore, a pressing need for computational models that can describe and predict the initiation and progression of thrombus in aneurysms. In this paper, we introduce a phenomenological metric for thrombus deposition potential and use hemodynamic simulations based on medical images from 6 patients to identify best-fit values of the 2 key model parameters. We then introduce a shape optimization method to predict the associated radial growth of the thrombus into the lumen based on the expectation that thrombus initiation will create a thrombogenic surface, which in turn will promote growth until increasing hemodynamically induced frictional forces prevent any further cell or protein deposition. Comparisons between predicted and actual intraluminal thrombus in the 6 patient-specific aneurysms suggest that this phenomenological description provides a good first estimate of thrombus deposition. We submit further that, because the biologically active region of the thrombus appears to be confined to a thin luminal layer, predictions of morphology alone may be sufficient to inform fluid-solid-growth models of aneurysmal growth and remodeling.
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Affiliation(s)
- P. Di Achille
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
| | - G. Tellides
- Department of Surgery, Yale School of Medicine, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
| | - J.D. Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
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Kelsey LJ, Powell JT, Norman PE, Miller K, Doyle BJ. A comparison of hemodynamic metrics and intraluminal thrombus burden in a common iliac artery aneurysm. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e2821. [PMID: 27509188 DOI: 10.1002/cnm.2821] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 06/06/2016] [Accepted: 07/02/2016] [Indexed: 06/06/2023]
Abstract
Aneurysms of the common iliac artery (CIAA) are typically found in association with an abdominal aortic aneurysm (AAA). Isolated CIAAs, in the absence of an AAA, are uncommon. Similar to AAAs, CIAA may develop intraluminal thrombus (ILT). As isolated CIAAs have a contralateral common iliac artery for comparison, they provide an opportunity to study the hemodynamic mechanisms behind ILT formation. In this study, we compared a large isolated CIAA and the contralateral iliac artery using computational fluid dynamics to determine if hemodynamic metrics correlate with the location of ILT. We performed a comprehensive computational fluid dynamics study and investigated the residence time of platelets and monocytes, velocity fields, time-averaged wall shear stress, oscillatory shear index, and endothelial cell activation potential. We then correlated these data to ILT burden determined with computed tomography. We found that high cell residence times, low time-averaged wall shear stress, high oscillatory shear index, and high endothelial cell activation potential all correlate with regions of ILT development. Our results show agreement with previous hypotheses of thrombus formation in AAA and provide insights into the computational hemodynamics of iliac artery aneurysms.
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Affiliation(s)
- Lachlan J Kelsey
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Perth, WA, Australia
- Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, The University of Western Australia, Crawley, WA, Australia
| | - Janet T Powell
- Vascular Surgery Research Group, Imperial College London, London, UK
| | - Paul E Norman
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Perth, WA, Australia
- School of Surgery, The University of Western Australia, Crawley, WA, Australia
| | - Karol Miller
- Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, The University of Western Australia, Crawley, WA, Australia
- Institute of Mechanics and Advanced Materials, Cardiff University, Cardiff, UK
| | - Barry J Doyle
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Perth, WA, Australia
- School of Mechanical and Chemical Engineering, The University of Western Australia, Crawley, WA, Australia
- British Heart Foundation Centre for Cardiovascular Science, The University of Edinburgh, Edinburgh, UK
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Boersen JT, Groot Jebbink E, Versluis M, Slump CH, Ku DN, de Vries JPPM, Reijnen MMPJ. Flow and wall shear stress characterization after endovascular aneurysm repair and endovascular aneurysm sealing in an infrarenal aneurysm model. J Vasc Surg 2017; 66:1844-1853. [PMID: 28285931 DOI: 10.1016/j.jvs.2016.10.077] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 10/10/2016] [Indexed: 11/17/2022]
Abstract
BACKGROUND Endovascular aneurysm repair (EVAR) with a modular endograft has become the preferred treatment for abdominal aortic aneurysms. A novel concept is endovascular aneurysm sealing (EVAS), consisting of dual endoframes surrounded by polymer-filled endobags. This dual-lumen configuration is different from a bifurcation with a tapered trajectory of the flow lumen into the two limbs and may induce unfavorable flow conditions. These include low and oscillatory wall shear stress (WSS), linked to atherosclerosis, and high shear rates that may result in thrombosis. An in vitro study was performed to assess the impact of EVAR and EVAS on flow patterns and WSS. METHODS Four abdominal aortic aneurysm phantoms were constructed, including three stented models, to study the influence of the flow divider on flow (Endurant [Medtronic, Minneapolis, Minn], AFX [Endologix, Irvine, Calif], and Nellix [Endologix]). Experimental models were tested under physiologic resting conditions, and flow was visualized with laser particle imaging velocimetry, quantified by shear rate, WSS, and oscillatory shear index (OSI) in the suprarenal aorta, renal artery (RA), and common iliac artery. RESULTS WSS and OSI were comparable for all models in the suprarenal aorta. The RA flow profile in the EVAR models was comparable to the control, but a region of lower WSS was observed on the caudal wall compared with the control. The EVAS model showed a stronger jet flow with a higher shear rate in some regions compared with the other models. Small regions of low WSS and high OSI were found near the distal end of all stents in the common iliac artery compared with the control. Maximum shear rates in each region of interest were well below the pathologic threshold for acute thrombosis. CONCLUSIONS The different stent designs do not influence suprarenal flow. Lower WSS is observed in the caudal wall of the RA after EVAR and a higher shear rate after EVAS. All stented models have a small region of low WSS and high OSI near the distal outflow of the stents.
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Affiliation(s)
- Johannes T Boersen
- Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands; Department of Vascular Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands; Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands.
| | - Erik Groot Jebbink
- Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands; Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands
| | - Michel Versluis
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands
| | - Cornelis H Slump
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - David N Ku
- School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Ga
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Hemodynamic Study of Flow Remodeling Stent Graft for the Treatment of Highly Angulated Abdominal Aortic Aneurysm. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2016; 2016:3830123. [PMID: 27247612 PMCID: PMC4876205 DOI: 10.1155/2016/3830123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 03/30/2016] [Accepted: 04/17/2016] [Indexed: 11/18/2022]
Abstract
This study investigates the effect of a novel flow remodeling stent graft (FRSG) on the hemodynamic characteristics in highly angulated abdominal aortic aneurysm based on computational fluid dynamics (CFD) approach. An idealized aortic aneurysm with varying aortic neck angulations was constructed and CFD simulations were performed on nonstented models and stented models with FRSG. The influence of FRSG intervention on the hemodynamic performance is analyzed and compared in terms of flow patterns, wall shear stress (WSS), and pressure distribution in the aneurysm. The findings showed that aortic neck angulations significantly influence the velocity flow field in nonstented models, with larger angulations shifting the mainstream blood flow towards the center of the aorta. By introducing FRSG treatment into the aneurysm, erratic flow recirculation pattern in the aneurysm sac diminishes while the average velocity magnitude in the aneurysm sac was reduced in the range of 39% to 53%. FRSG intervention protects the aneurysm against the impacts of high velocity concentrated flow and decreases wall shear stress by more than 50%. The simulation results highlighted that FRSG may effectively treat aneurysm with high aortic neck angulations via the mechanism of promoting thrombus formation and subsequently led to the resorption of the aneurysm.
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Ou C, Huang W, Yuen MMF. A computational model based on fibrin accumulation for the prediction of stasis thrombosis following flow-diverting treatment in cerebral aneurysms. Med Biol Eng Comput 2016; 55:89-99. [PMID: 27106753 DOI: 10.1007/s11517-016-1501-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 03/27/2016] [Indexed: 01/09/2023]
Abstract
Flow diverters, the specially designed low porosity stents, have been used to redirect blood flow from entering aneurysm, which induces flow stasis in aneurysm and promote thrombosis for repairing aneurysm. However, it is not clear how thrombus develops following flow-diversion treatment. Our objective was to develop a computation model for the prediction of stasis-induced thrombosis following flow-diversion treatment in cerebral aneurysms. We proposed a hypothesis to initiate coagulation following flow-diversion treatment. An experimental model was used by ligating rat's right common carotid artery (RCCA) to create flow-stasis environment. Thrombus formed in RCCA as a result of flow stasis. The fibrin distributions in different sections along the axial length of RCCA were measured. The fibrin distribution predicted by our computational model displayed a trend of increase from the proximal neck to the distal tip, consistent with the experimental results on rats. The model was applied on a saccular aneurysm treated with flow diverter to investigate thrombus development following flow diversion. Thrombus was predicted to form inside the sac, and the aneurysm was occluded with only a small remnant neck remained. Our model can serve as a tool to evaluate flow-diversion treatment outcome and optimize the design of flow diverters.
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Affiliation(s)
- Chubin Ou
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Wei Huang
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Matthew Ming-Fai Yuen
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
- Division of Biomedical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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Aramburu J, Antón R, Borro D, Rivas A, Larraona GS, Ramos JC, Finol EA. A methodology for assessing local bifurcated blood vessel shape variations. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/1/015001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Association of Intraluminal Thrombus, Hemodynamic Forces, and Abdominal Aortic Aneurysm Expansion Using Longitudinal CT Images. Ann Biomed Eng 2015; 44:1502-14. [PMID: 26429788 DOI: 10.1007/s10439-015-1461-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 09/14/2015] [Indexed: 12/22/2022]
Abstract
While hemodynamic forces and intraluminal thrombus (ILT) are believed to play important roles on abdominal aortic aneurysm (AAA), it has been suggested that hemodynamic forces and ILT also interact with each other, making it a complex problem. There is, however, a pressing need to understand relationships among three factors: hemodynamics, ILT accumulation, and AAA expansion for AAA prognosis. Hence this study used longitudinal computer tomography scans from 14 patients and analyzed the relationship between them. Hemodynamic forces, represented by wall shear stress (WSS), were obtained from computational fluid dynamics; ILT accumulation was described by ILT thickness distribution changes between consecutives scans, and ILT accumulation and AAA expansion rates were estimated from changes in ILT and AAA volume. Results showed that, while low WSS was observed at regions where ILT accumulated, the rate at which ILT accumulated occurred at the same rate as the aneurysm expansion. Comparison between AAAs with and without thrombus showed that aneurysm with ILT recorded lower values of WSS and higher values of AAA expansion than those without thrombus. Findings suggest that low WSS may promote ILT accumulation and submit the idea that by increasing WSS levels ILT accumulation may be prevented.
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Doyle B, Sun Z, Jansen S, Norman P. Commentary: Computational Modeling of Contemporary Stent-Grafts. J Endovasc Ther 2015; 22:591-3. [PMID: 26187979 DOI: 10.1177/1526602815590370] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Barry Doyle
- Vascular Engineering, Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, Australia Centre for Cardiovascular Science, University of Edinburgh, UK
| | - Zhonghua Sun
- Discipline of Medical Radiation Sciences, School of Science, Curtin University, Perth, Australia
| | - Shirley Jansen
- Department of Vascular Surgery, Sir Charles Gairdner Hospital, Perth, Australia Harry Perkins Institute for Medical Research, QEII Campus, Perth, Australia School of Public Health, Curtin University, Perth, Australia
| | - Paul Norman
- Vascular Engineering, Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, Australia School of Surgery, The University of Western Australia, Perth, Australia
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Tong J, Holzapfel GA. Structure, Mechanics, and Histology of Intraluminal Thrombi in Abdominal Aortic Aneurysms. Ann Biomed Eng 2015; 43:1488-501. [DOI: 10.1007/s10439-015-1332-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 05/06/2015] [Indexed: 01/08/2023]
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Zhang P, Liu X, Sun A, Fan Y, Deng X. Hemodynamic insight into overlapping bare-metal stents strategy in the treatment of aortic aneurysm. J Biomech 2015; 48:2041-6. [PMID: 25911250 DOI: 10.1016/j.jbiomech.2015.03.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 03/18/2015] [Accepted: 03/22/2015] [Indexed: 10/23/2022]
Abstract
Clinical trials have shown overlapping bare-metal stents provoke effective thrombus clot within the aneurysm sac and shrinkage of the aneurysm by directly regulating the hemodynamics. To gain insight into the hemodynamic mechanism of the technique, three cases of simplified thoracic aortic aneurysm models (with no stent, a single stent and two overlapped stents deployed within the aneurysm sac) were studied and compared in terms of time-varying velocity and shear rate, time-averaged wall shear stress (TAWSS), oscillating shear index (OSI) and relative residence time (RRT). The results demonstrated that the overlapping stents' strategy was more effective in reducing the velocity of blood flow within the aneurysm, especially for the area near the aneurysm wall. Stenting induced a dramatic change trend of shear rate during the cardiac cycle, in which a very high shear rate (>10,000 s(-1)) during the systole and a quite low shear rate (<1000 s(-1)) during the diastole were observed, respectively. Moreover, reduced TAWSS and OSI and elevated RRT values were observed on the aneurysm wall after stent placement. The effects of stenting on the shear rate, TAWSS, OSI and RRT in the aneurysm would be significantly enhanced by two overlapped stents. The present findings therefore indicated that, the overlapping bare-metal stents can isolate the aneurysm effectively and may create a favorable hemodynamic environment provoking platelets activation and aggregation within the aneurysm, which may promote thrombus formation/growth there, hence contribute to degradation of the aneurysm.
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Affiliation(s)
- Peng Zhang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China
| | - Xiao Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
| | - Anqiang Sun
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China
| | - Xiaoyan Deng
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
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30
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Hansen KB, Arzani A, Shadden SC. Mechanical platelet activation potential in abdominal aortic aneurysms. J Biomech Eng 2015; 137:041005. [PMID: 25588057 DOI: 10.1115/1.4029580] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Indexed: 11/08/2022]
Abstract
Intraluminal thrombus (ILT) in abdominal aortic aneurysms (AAA) has potential implications to aneurysm growth and rupture risk; yet, the mechanisms underlying its development remain poorly understood. Some researchers have proposed that ILT development may be driven by biomechanical platelet activation within the AAA, followed by adhesion in regions of low wall shear stress. Studies have investigated wall shear stress levels within AAA, but platelet activation potential (AP) has not been quantified. In this study, patient-specific computational fluid dynamic (CFD) models were used to analyze stress-induced AP within AAA under rest and exercise flow conditions. The analysis was conducted using Lagrangian particle-based and Eulerian continuum-based approaches, and the results were compared. Results indicated that biomechanical platelet activation is unlikely to play a significant role for the conditions considered. No consistent trend was observed in comparing rest and exercise conditions, but the functional dependence of AP on stress magnitude and exposure time can have a large impact on absolute levels of anticipated platelet AP. The Lagrangian method obtained higher peak AP values, although this difference was limited to a small percentage of particles that falls below reported levels of physiologic background platelet activation.
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31
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Raptis A, Xenos M, Dimas S, Giannoukas A, Labropoulos N, Bluestein D, Matsagkas MI. Effect of macroscale formation of intraluminal thrombus on blood flow in abdominal aortic aneurysms. Comput Methods Biomech Biomed Engin 2015; 19:84-92. [DOI: 10.1080/10255842.2014.989389] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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32
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Di Achille P, Tellides G, Figueroa CA, Humphrey JD. A haemodynamic predictor of intraluminal thrombus formation in abdominal aortic aneurysms. Proc Math Phys Eng Sci 2014. [DOI: 10.1098/rspa.2014.0163] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Intraluminal thrombus (ILT) is present in over 75% of all abdominal aortic aneurysms (AAAs) and probably contributes to the complex biomechanics and pathobiology of these lesions. A reliable predictor of thrombus formation in enlarging lesions could thereby aid clinicians in treatment planning. The primary goal of this work was to identify a new phenomenological metric having clinical utility that is motivated by the hypothesis that two basic haemodynamic features must coincide spatially and temporally to promote the formation of a thrombus on an intact endothelium—platelets must be activated within a shear flow and then be presented to a susceptible endothelium. Towards this end, we propose a new thrombus formation potential (TFP) that combines information on the flow-induced shear history experienced by blood-borne particles that come in close proximity to the endothelium with information on both the time-averaged wall shear stress (WSS) and the oscillatory shear index (OSI) that locally affect the endothelial mechanobiology. To illustrate the possible utility of this new metric, we show computational results for 10 carotid arteries from five patients where regions of low WSS and high OSI tend not to be presented with activated platelets (i.e. they have a low TFP), consistent with the thrombo-resistance of the healthy carotid despite its complex haemodynamics. Conversely, we show results for three patients that high TFP co-localizes with regions of observed thin thrombus in AAAs, which contrasts with findings of low TFP for the abdominal aorta of three healthy subjects. We submit that these promising results suggest the need for further consideration of the TFP, or a similar combined metric, as a potentially useful clinical predictor of the possible formation of ILT in AAAs.
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Affiliation(s)
- P. Di Achille
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
| | - G. Tellides
- Department of Surgery, Yale School of Medicine, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
| | - C. A. Figueroa
- Department of Surgery and Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J. D. Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, USA
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33
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Chen CY, Antón R, Hung MY, Menon P, Finol EA, Pekkan K. Effects of intraluminal thrombus on patient-specific abdominal aortic aneurysm hemodynamics via stereoscopic particle image velocity and computational fluid dynamics modeling. J Biomech Eng 2014; 136:031001. [PMID: 24316984 DOI: 10.1115/1.4026160] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Accepted: 12/05/2013] [Indexed: 11/08/2022]
Abstract
The pathology of the human abdominal aortic aneurysm (AAA) and its relationship to the later complication of intraluminal thrombus (ILT) formation remains unclear. The hemodynamics in the diseased abdominal aorta are hypothesized to be a key contributor to the formation and growth of ILT. The objective of this investigation is to establish a reliable 3D flow visualization method with corresponding validation tests with high confidence in order to provide insight into the basic hemodynamic features for a better understanding of hemodynamics in AAA pathology and seek potential treatment for AAA diseases. A stereoscopic particle image velocity (PIV) experiment was conducted using transparent patient-specific experimental AAA models (with and without ILT) at three axial planes. Results show that before ILT formation, a 3D vortex was generated in the AAA phantom. This geometry-related vortex was not observed after the formation of ILT, indicating its possible role in the subsequent appearance of ILT in this patient. It may indicate that a longer residence time of recirculated blood flow in the aortic lumen due to this vortex caused sufficient shear-induced platelet activation to develop ILT and maintain uniform flow conditions. Additionally, two computational fluid dynamics (CFD) modeling codes (Fluent and an in-house cardiovascular CFD code) were compared with the two-dimensional, three-component velocity stereoscopic PIV data. Results showed that correlation coefficients of the out-of-plane velocity data between PIV and both CFD methods are greater than 0.85, demonstrating good quantitative agreement. The stereoscopic PIV study can be utilized as test case templates for ongoing efforts in cardiovascular CFD solver development. Likewise, it is envisaged that the patient-specific data may provide a benchmark for further studying hemodynamics of actual AAA, ILT, and their convolution effects under physiological conditions for clinical applications.
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Peach TW, Ngoepe M, Spranger K, Zajarias-Fainsod D, Ventikos Y. Personalizing flow-diverter intervention for cerebral aneurysms: from computational hemodynamics to biochemical modeling. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2014; 30:1387-1407. [PMID: 25045060 DOI: 10.1002/cnm.2663] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 06/11/2014] [Accepted: 07/07/2014] [Indexed: 06/03/2023]
Abstract
This paper presents the computational modeling of a variety of flow-diverting stents, deployed in a number of patient-specific aneurysm geometries. We consider virtual device deployment and hemodynamics as well as thrombus formation, with the scope to assess pre-operatively the efficacy of specific devices in treating particular aneurysms. An algorithm based on a linear and torsional spring analogy is developed for the fast virtual deployment of stents and similar minimally invasive devices in patient-specific vessel geometries. The virtual deployment algorithm is used to accurately deploy a total of four stent designs in three aneurysm geometries. A variety of different flow-diverting stent designs, representing the commercially available and the entirely novel, are presented, varying in both mesh design and porosity. Transient computational hemodynamics simulations are performed on multiple patient-specific geometries to predict the reduction in aneurysm inflow after the deployment of each device. Further, a thrombosis initiation and growth model is implemented, coupled with the hemodynamic computations. Hemodynamic simulations show large variations in flow reduction between devices and across different aneurysm geometries. The industry standard of flow-diverters with 70% porosity, assumed to offer the best compromise in flexibility and flow reduction, is challenged in at least one aneurysm geometry.
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Affiliation(s)
- T W Peach
- Institute of Biomedical Engineering & Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ
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35
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Arzani A, Suh GY, Dalman RL, Shadden SC. A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms. Am J Physiol Heart Circ Physiol 2014; 307:H1786-95. [PMID: 25326533 DOI: 10.1152/ajpheart.00461.2014] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Abdominal aortic aneurysm (AAA) is often accompanied by in traluminal thrombus (ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2- to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (>0.4) and low TAWSS (<1 dyn/cm(2)) did not appear to coincide with locations of thrombus deposition.
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Affiliation(s)
- Amirhossein Arzani
- Mechanical Engineering, University of California, Berkeley, California; and
| | - Ga-Young Suh
- Division of Vascular Surgery, Stanford University, Stanford, California
| | - Ronald L Dalman
- Division of Vascular Surgery, Stanford University, Stanford, California
| | - Shawn C Shadden
- Mechanical Engineering, University of California, Berkeley, California; and
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36
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Lagrangian postprocessing of computational hemodynamics. Ann Biomed Eng 2014; 43:41-58. [PMID: 25059889 DOI: 10.1007/s10439-014-1070-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 07/11/2014] [Indexed: 10/25/2022]
Abstract
Recent advances in imaging, modeling, and computing have rapidly expanded our capabilities to model hemodynamics in the large vessels (heart, arteries, and veins). This data encodes a wealth of information that is often under-utilized. Modeling (and measuring) blood flow in the large vessels typically amounts to solving for the time-varying velocity field in a region of interest. Flow in the heart and larger arteries is often complex, and velocity field data provides a starting point for investigating the hemodynamics. This data can be used to perform Lagrangian particle tracking, and other Lagrangian-based postprocessing. As described herein, Lagrangian methods are necessary to understand inherently transient hemodynamic conditions from the fluid mechanics perspective, and to properly understand the biomechanical factors that lead to acute and gradual changes of vascular function and health. The goal of the present paper is to review Lagrangian methods that have been used in post-processing velocity data of cardiovascular flows.
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37
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Wilson JS, Humphrey JD. Evolving anisotropy and degree of elastolytic insult in abdominal aortic aneurysms: potential clinical relevance? J Biomech 2014; 47:2995-3002. [PMID: 25086482 DOI: 10.1016/j.jbiomech.2014.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 05/05/2014] [Accepted: 07/02/2014] [Indexed: 12/16/2022]
Abstract
Accurately estimating patient-specific rupture risk remains a primary challenge in timing interventions for abdominal aortic aneurysms (AAAs). By re-analyzing published biaxial mechanical testing data from surgically repaired human AAAs, material anisotropy emerged as a potentially important determinant of patient-specific lesion progression. That is, based on a new classification scheme, we discovered that anisotropic aneurysmal specimens correlated with increased patient age at surgery when compared with more isotropic specimens (79.7 vs. 70.9 years, p<0.002), despite no significant difference in maximum diameter. Furthermore, using an idealized axisymmetric, finite-element growth and remodeling model of AAA progression, we found that both the initial axial extent of elastin loss and ongoing damage to elastin in the shoulder region of the AAA directly affected the degree of anisotropy as the lesion evolved, with more extensive insults increasing the anisotropy. This effect appeared to be mediated by alterations in axial loading and subsequent differences in orientation of deposited collagen fibers. While the observed increased age before surgical intervention may suggest a potential benefit of anisotropic remodeling, future biaxial tests coupled with pre-surgical data on expansion rates and detailed theoretical analyses of the biostability of a lesion as a function of anisotropy will be required to verify its clinical relevance to patient-specific rupture risk.
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Affiliation(s)
- John S Wilson
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - J D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA; Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT 06520, USA.
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38
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Deplano V, Knapp Y, Bailly L, Bertrand E. Flow of a blood analogue fluid in a compliant abdominal aortic aneurysm model: experimental modelling. J Biomech 2014; 47:1262-9. [PMID: 24612986 DOI: 10.1016/j.jbiomech.2014.02.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 02/18/2014] [Accepted: 02/18/2014] [Indexed: 10/25/2022]
Abstract
The aim of this work is to develop a unique in vitro set-up in order to analyse the influence of the shear thinning fluid-properties on the flow dynamics within the bulge of an abdominal aortic aneurysm (AAA). From an experimental point of view, the goals are to elaborate an analogue shear thinning fluid mimicking the macroscopic blood behaviour, to characterise its rheology at low shear rates and to propose an experimental device able to manage such an analogue fluid without altering its feature while reproducing physiological flow rate and pressure, through compliant AAA. Once these experimental prerequisites achieved, the results obtained in the present work show that the flow dynamics is highly dependent on the fluid rheology. The main results point out that the propagation of the vortex ring, generated in the AAA bulge, is slower for shear thinning fluids inducing a smaller travelled distance by the vortex ring so that it never impacts the anterior wall in the distal region, in opposition to Newtonian fluids. Moreover, scalar shear rate values are globally lower for shear thinning fluids inducing higher maximum stress values than those for the Newtonian fluids. Consequently, this work highlights that a Newtonian fluid model is finally inadequate to obtain a reliable prediction of the flow dynamics within AAA.
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Affiliation(s)
- Valérie Deplano
- Aix-Marseille Université, CNRS, Centrale Marseille, IRPHE UMR 7342, F-13384 Marseille, France.
| | - Yannick Knapp
- Université d׳Avignon, LAPEC EA4278, F-84000 Avignon, France
| | - Lucie Bailly
- Aix-Marseille Université, CNRS, Centrale Marseille, IRPHE UMR 7342, F-13384 Marseille, France
| | - Eric Bertrand
- Aix-Marseille Université, CNRS, Centrale Marseille, IRPHE UMR 7342, F-13384 Marseille, France
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39
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Gorring N, Kark L, Simmons A, Barber T. Determining possible thrombus sites in an extracorporeal device, using computational fluid dynamics-derived relative residence time. Comput Methods Biomech Biomed Engin 2014; 18:628-34. [DOI: 10.1080/10255842.2013.826655] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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40
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Bodnár T, Fasano A, Sequeira A. Mathematical Models for Blood Coagulation. FLUID-STRUCTURE INTERACTION AND BIOMEDICAL APPLICATIONS 2014. [DOI: 10.1007/978-3-0348-0822-4_7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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41
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Wilson JS, Virag L, Di Achille P, Karsaj I, Humphrey JD. Biochemomechanics of intraluminal thrombus in abdominal aortic aneurysms. J Biomech Eng 2013; 135:021011. [PMID: 23445056 DOI: 10.1115/1.4023437] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Most computational models of abdominal aortic aneurysms address either the hemodynamics within the lesion or the mechanics of the wall. More recently, however, some models have appropriately begun to account for the evolving mechanics of the wall in response to the changing hemodynamic loads. Collectively, this large body of work has provided tremendous insight into this life-threatening condition and has provided important guidance for current research. Nevertheless, there has yet to be a comprehensive model that addresses the mechanobiology, biochemistry, and biomechanics of thrombus-laden abdominal aortic aneurysms. That is, there is a pressing need to include effects of the hemodynamics on both the development of the nearly ubiquitous intraluminal thrombus and the evolving mechanics of the wall, which depends in part on biochemical effects of the adjacent thrombus. Indeed, there is increasing evidence that intraluminal thrombus in abdominal aortic aneurysms is biologically active and should not be treated as homogeneous inert material. In this review paper, we bring together diverse findings from the literature to encourage next generation models that account for the biochemomechanics of growth and remodeling in patient-specific, thrombus-laden abdominal aortic aneurysms.
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Affiliation(s)
- J S Wilson
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
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42
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Hardman D, Doyle BJ, Semple SIK, Richards JMJ, Newby DE, Easson WJ, Hoskins PR. On the prediction of monocyte deposition in abdominal aortic aneurysms using computational fluid dynamics. Proc Inst Mech Eng H 2013; 227:1114-24. [DOI: 10.1177/0954411913494319] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In abdominal aortic aneurysm disease, the aortic wall is exposed to intense biological activity involving inflammation and matrix metalloproteinase–mediated degradation of the extracellular matrix. These processes are orchestrated by monocytes and rather than affecting the aorta uniformly, damage and weaken focal areas of the wall leaving it vulnerable to rupture. This study attempts to model numerically the deposition of monocytes using large eddy simulation, discrete phase modelling and near-wall particle residence time. The model was first applied to idealised aneurysms and then to three patient-specific lumen geometries using three-component inlet velocities derived from phase-contrast magnetic resonance imaging. The use of a novel, variable wall shear stress-limiter based on previous experimental data significantly improved the results. Simulations identified a critical diameter (1.8 times the inlet diameter) beyond which significant monocyte deposition is expected to occur. Monocyte adhesion occurred proximally in smaller abdominal aortic aneurysms and distally as the sac expands. The near-wall particle residence time observed in each of the patient-specific models was markedly different. Discrete hotspots of monocyte residence time were detected, suggesting that the monocyte infiltration responsible for the breakdown of the abdominal aortic aneurysm wall occurs heterogeneously. Peak monocyte residence time was found to increase with aneurysm sac size. Further work addressing certain limitations is needed in a larger cohort to determine clinical significance.
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Affiliation(s)
- David Hardman
- Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK
| | - Barry J Doyle
- Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK
- Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, The University of Western Australia, Crawley, WA, Australia
| | - Scott IK Semple
- Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK
- Clinical Research Imaging Centre, The University of Edinburgh, Edinburgh, UK
| | - Jennifer MJ Richards
- Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK
- Clinical Research Imaging Centre, The University of Edinburgh, Edinburgh, UK
- Centre of Clinical and Surgical Sciences (Surgery), The University of Edinburgh, Edinburgh, UK
| | - David E Newby
- Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK
- Clinical Research Imaging Centre, The University of Edinburgh, Edinburgh, UK
| | - William J Easson
- Institute for Materials and Processes, School of Engineering and Electronics, The University of Edinburgh, Edinburgh, UK
| | - Peter R Hoskins
- Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK
- Department of Mechanical, Aeronautical and Biomedical Engineering, University of Limerick, Limerick, Ireland
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43
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Hardman D, Semple SI, Richards JMJ, Hoskins PR. Comparison of patient-specific inlet boundary conditions in the numerical modelling of blood flow in abdominal aortic aneurysm disease. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2013; 29:165-178. [PMID: 23225751 DOI: 10.1002/cnm.2535] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Revised: 11/05/2012] [Accepted: 11/06/2012] [Indexed: 06/01/2023]
Abstract
Three inlet boundary condition datasets were derived from phase-contrast MRI: (i) centre line velocity data converted to two-dimensional (2D) velocity profile using Womersley equations (Womersley), (ii) 2D velocity profile with one axial component of velocity (1CV), (iii) 2D velocity profile with three components of velocity (3CV). Computational fluid dynamics was performed using a rigid wall approach with geometry data extracted from the computed tomography dataset. Helical flow was present in the 1CV and 3CV simulations, with more complex patterns for the 3CV case. The Womersley method produced simplified flow patterns with an absence of helical flow. Mean values of quantitative indices (helical flow index, mean wall shear stress, oscillatory index) were compared with the 3CV inlet data. These were lower for both the Womersley inlet data (28%, 71%, 56%) and the 1CV inlet data (9%, 24%, 69%). It was concluded that inlet methods based on centre line velocity, such as might be obtained from Doppler ultrasound, lead to significantly simplified abdominal aortic aneurysm haemodynamics and thus are not recommended. Single velocity component (axial) data from MRI might suffice when general flow characteristics and spatial wall shear stress are required. Ideally 2D MRI velocity profiles with 3-velocity component data are preferred to fully account for helical flow.
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Affiliation(s)
- David Hardman
- Centre for Cardiovascular Science, University of Edinburgh, UK
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44
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Computational modeling of thrombosis as a tool in the design and optimization of vascular implants. J Biomech 2013; 46:248-52. [DOI: 10.1016/j.jbiomech.2012.11.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 11/01/2012] [Indexed: 01/23/2023]
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45
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O'Rourke MJ, McCullough JP, Kelly S. An investigation of the relationship between hemodynamics and thrombus deposition within patient-specific models of abdominal aortic aneurysm. Proc Inst Mech Eng H 2012; 226:548-64. [PMID: 22913102 DOI: 10.1177/0954411912444080] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The relationship between hemodynamics and thrombus deposition in abdominal aortic aneurysm is investigated for three patients (A, B and C), each with mature fusiform aneurysms. Our methodology utilises initial and follow-up computerised tomography scans for each patient to identify regions of mural thrombus growth and to provide patient-specific models for hemodynamic analysis using computational fluid dynamics. The intervals between scans for patients A, B and C were 17, 15 and 3 months, respectively. The simulations were performed using physiologically realistic boundary conditions. The hemodynamic features of the flow considered include the velocity field, the shear strain rate field, the time averaged wall shear stress and the oscillatory shear index. The parameter that showed best correlation with the location of thrombus growth was the oscillatory shear index. In particular, in the case of patient C where the interval between scans was the shortest, thrombus growth was observed at regions of low oscillatory shear index (OSI < 0.1).
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Affiliation(s)
- Malachy J O'Rourke
- School of Mechanical and Materials Engineering, University College Dublin Engineering and Materials Science Centre, Dublin, Ireland.
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46
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Deplano V, Meyer C, Guivier-Curien C, Bertrand E. New insights into the understanding of flow dynamics in an in vitro model for abdominal aortic aneurysms. Med Eng Phys 2012; 35:800-9. [PMID: 22981221 DOI: 10.1016/j.medengphy.2012.08.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 06/05/2012] [Accepted: 08/17/2012] [Indexed: 10/27/2022]
Abstract
An in vitro dynamics set-up of the flow in a compliant abdominal aortic aneurysm (AAA) model with an anterior posterior asymmetry, aorto-iliac bifurcation, and physiological inlet flow rate and outlet pressure waveforms was developed. The aims were first to show that the structural mechanical behavior of the used material to mimic the AAA wall was similar to this of patients with AAA and then to study the influence of the aorto-iliac bifurcation presence and to study the influence of the imbalanced flow rate in the iliac branches on the AAA flow field. 3D visualizations, never performed in the literature, have clearly put into evidence the development of a vortex ring generated at the AAA proximal neck during the decelerating phase of flow rate, which detaches and progresses downstream during the cardiac cycle, impinges on the anterior wall in the distal AAA region, breaks up, and separates into two vortices of which one rolls on upstream along the anterior wall. 2D particle image velocimetry measurements, swirling strength and enstrophy calculations allowed quantification of the vorticity, vortex trajectory and energy for the different geometrical and hydrodynamical conditions. The main results show that the instant and the intensity of the vortex ring impingement depend on the presence of the aorto-iliac bifurcation, with higher intensity, by about 90%, for an AAA without bifurcation. The imbalance of the flow rates into the iliac branches induces different propagation velocities of the vortex ring and lowers the intensity of the vortex impact by about 60%. The potential influence of the AAA dynamics is discussed in terms of AAA remodeling and rupture.
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Arzani A, Shadden SC. Characterization of the transport topology in patient-specific abdominal aortic aneurysm models. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2012; 24:81901. [PMID: 22952409 PMCID: PMC3427345 DOI: 10.1063/1.4744984] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 07/19/2012] [Indexed: 05/24/2023]
Abstract
Abdominal aortic aneurysm (AAA) is characterized by disturbed blood flow patterns that are hypothesized to contribute to disease progression. The transport topology in six patient-specific abdominal aortic aneurysms was studied. Velocity data were obtained by image-based computational fluid dynamics modeling, with magnetic resonance imaging providing the necessary simulation parameters. Finite-time Lyapunov exponent (FTLE) fields were computed from the velocity data, and used to identify Lagrangian coherent structures (LCS). The combination of FTLE fields and LCS was used to characterize topological flow features such as separation zones, vortex transport, mixing regions, and flow impingement. These measures offer a novel perspective into AAA flow. It was observed that all aneurysms exhibited coherent vortex formation at the proximal segment of the aneurysm. The evolution of the systolic vortex strongly influences the flow topology in the aneurysm. It was difficult to predict the vortex dynamics from the aneurysm morphology, motivating the application of image-based flow modeling.
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Affiliation(s)
- Amirhossein Arzani
- Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, 10 W 32nd St., Chicago, Illinois 60616, USA
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Scull SA, Dow MB, Athreya BH. Physical and occupational therapy for children with rheumatic diseases. J Biomech Eng 1986; 133:121004. [PMID: 3489919 DOI: 10.1115/1.4005478] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Total management of rheumatic disorders of children includes antiinflammatory drugs, active therapy, maintenance of ADLs, and attention to the psychosocial development of the child. This article focuses on the role that physical and occupational therapists play in the management of children with arthritis. The complexity of the problems of these children necessitates a multidisciplinary team approach, with professionals who are committed to helping the child lead as normal a life as possible. This objective can be accomplished only by teaching families and school personnel how to manage the child's daily therapeutic needs.
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