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  1. Article: A comparative study of altered hemodynamics in iliac vein compression syndrome.

    Assi, Ismael Z / Lynch, Sabrina R / Ricker, Brian D / Ranjane, Siddhant V / Williams, David M / Wakefield, Thomas W / Obi, Andrea T / Figueroa, C Alberto

    Frontiers in bioengineering and biotechnology

    2024  Volume 12, Page(s) 1302063

    Abstract: Introduction: ...

    Abstract Introduction:
    Language English
    Publishing date 2024-01-18
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2719493-0
    ISSN 2296-4185
    ISSN 2296-4185
    DOI 10.3389/fbioe.2024.1302063
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: An ultrasound imaging and computational fluid dynamics protocol to assess hemodynamics in iliac vein compression syndrome.

    Assi, Ismael Z / Lynch, Sabrina R / Samulak, Krystal / Williams, David M / Wakefield, Thomas W / Obi, Andrea T / Figueroa, C Alberto

    Journal of vascular surgery. Venous and lymphatic disorders

    2023  Volume 11, Issue 5, Page(s) 1023–1033.e5

    Abstract: Objective: Elevated shear rates are known to play a role in arterial thrombosis; however, shear rates have not been thoroughly investigated in patients with iliac vein compression syndrome (IVCS) owing to imaging limitations and assumptions on the low ... ...

    Abstract Objective: Elevated shear rates are known to play a role in arterial thrombosis; however, shear rates have not been thoroughly investigated in patients with iliac vein compression syndrome (IVCS) owing to imaging limitations and assumptions on the low shear nature of venous flows. This study was undertaken to develop a standardized protocol that quantifies IVCS shear rates and can aid in the diagnosis and treatment of patients with moderate yet symptomatic compression.
    Methods: Study patients with and without IVCS had their iliac vein hemodynamics measured via duplex ultrasound (US) at two of the following three vessel locations: infrarenal inferior vena cava (IVC), right common iliac vein, and left common iliac vein, in addition to acquiring data at the right and left external iliac veins. US velocity spectra were multiplied by a weighted cross-sectional area calculated from US and computed tomography (CT) data to create flow waveforms. Flow waveforms were then scaled to enforce conservation of flow across the IVC and common iliac veins. A three-dimensional (3D), patient-specific model of the iliac vein anatomy was constructed from CT and US examination. Flow waveforms and the 3D model were used as a basis to run a computational fluid dynamics (CFD) simulation. Owing to collateral vessel flow and discrepancies between CT and US area measurements, flows in internal iliac veins and cross-sectional areas of the common iliac veins were calibrated iteratively against target common iliac flow. Simulation results on mean velocity were validated against US data at measurement locations. Simulation results were postprocessed to derive spatial and temporal values of quantities such as velocity and shear rate.
    Results: Using our modeling protocol, we were able to build CFD models of the iliac veins that matched common iliac flow splits within 2% and measured US velocities within 10%. Proof-of-concept analyses (1 subject, 1 control) have revealed that patients with IVCS may experience elevated shear rates in the compressed left common iliac vein, more typical of the arterial rather than the venous circulation. These results encourage us to extend this protocol to a larger group of patients with IVCS and controls.
    Conclusions: We developed a protocol that obtains hemodynamic measurements of the IVC and iliac veins from US, creates patient-specific 3D reconstructions of the venous anatomy using CT and US examinations, and computes shear rates using calibrated CFD methods. Proof-of-concept results have indicated that patients with IVCS may experience elevated shear rates in the compressed left common iliac vein. Larger cohorts are needed to assess the relationship between venous compression and shear rates in patients with IVCS as compared with controls with noncompressed iliac veins. Further studies using this protocol may also give promising insights into whether or not to treat patients with moderate, yet symptomatic compression.
    MeSH term(s) Humans ; May-Thurner Syndrome/diagnostic imaging ; May-Thurner Syndrome/therapy ; Hydrodynamics ; Thrombosis ; Hemodynamics ; Iliac Vein/diagnostic imaging ; Ultrasonography, Doppler, Duplex
    Language English
    Publishing date 2023-06-22
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ISSN 2213-3348
    ISSN (online) 2213-3348
    DOI 10.1016/j.jvsv.2023.05.017
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  3. Article ; Online: Numerical considerations for advection-diffusion problems in cardiovascular hemodynamics.

    Lynch, Sabrina R / Nama, Nitesh / Xu, Zelu / Arthurs, Christopher J / Sahni, Onkar / Figueroa, C Alberto

    International journal for numerical methods in biomedical engineering

    2020  Volume 36, Issue 9, Page(s) e3378

    Abstract: Numerical simulations of cardiovascular mass transport pose significant challenges due to the wide range of Péclet numbers and backflow at Neumann boundaries. In this paper we present and discuss several numerical tools to address these challenges in the ...

    Abstract Numerical simulations of cardiovascular mass transport pose significant challenges due to the wide range of Péclet numbers and backflow at Neumann boundaries. In this paper we present and discuss several numerical tools to address these challenges in the context of a stabilized finite element computational framework. To overcome numerical instabilities when backflow occurs at Neumann boundaries, we propose an approach based on the prescription of the total flux. In addition, we introduce a "consistent flux" outflow boundary condition and demonstrate its superior performance over the traditional zero diffusive flux boundary condition. Lastly, we discuss discontinuity capturing (DC) stabilization techniques to address the well-known oscillatory behavior of the solution near the concentration front in advection-dominated flows. We present numerical examples in both idealized and patient-specific geometries to demonstrate the efficacy of the proposed procedures. The three contributions discussed in this paper successfully address commonly found challenges when simulating mass transport processes in cardiovascular flows.
    MeSH term(s) Biological Transport ; Cardiovascular System ; Diffusion ; Hemodynamics ; Humans
    Language English
    Publishing date 2020-08-03
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 2540968-2
    ISSN 2040-7947 ; 2040-7939
    ISSN (online) 2040-7947
    ISSN 2040-7939
    DOI 10.1002/cnm.3378
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  4. Article ; Online: Patient-Specific Computational Modeling of Different Cannulation Strategies for Extracorporeal Membrane Oxygenation.

    Ahmed, Yunus / Lynch, Sabrina R / Haft, Jonathan W / Moll, Frans L / van Herwaarden, Joost A / Burris, Nicholas S / Patel, Himanshu J / Figueroa, C Alberto

    ASAIO journal (American Society for Artificial Internal Organs : 1992)

    2022  Volume 68, Issue 11, Page(s) e179–e187

    Abstract: Institution of extracorporeal membrane oxygenation (ECMO) results in unique blood flow characteristics to the end-organ vascular beds. We studied the interplay between cardiac-driven and extracorporeal membrane oxygenation (ECMO)-driven flow to vascular ... ...

    Abstract Institution of extracorporeal membrane oxygenation (ECMO) results in unique blood flow characteristics to the end-organ vascular beds. We studied the interplay between cardiac-driven and extracorporeal membrane oxygenation (ECMO)-driven flow to vascular beds in different ECMO configurations using a patient-specific computational fluid dynamics (CFD) analysis. A computational ECMO model (femoral artery cannulation [FAC]) was constructed using patient-specific imaging and hemodynamic data. Following model calibration, we augmented the 3D geometrical model to represent alternative ECMO configurations (ascending aorta cannulation [AAC] and subclavian artery cannulation [SAC]). We performed CFD analyses, including a novel virtual color-dye analysis to compare global and regional blood flow and pressure characteristics as well as contributions of cardiac and ECMO-derived flow to the various vascular beds. Flow waveforms at all the aortic branch vessels were pulsatile, despite low cardiac output and predominant nonpulsatile ECMO-driven hemodynamics. Virtual color-dye analysis revealed differential contribution of cardiac and ECMO-derived flow to the end-organ vascular beds in the FAC model, while this was more evenly distributed in the AAC and SAC models. While global hemodynamics were relatively similar between various ECMO configurations, several distinct hemodynamic indices, in particular wall shear stress and oscillatory shear patterns, as well as differential contribution of ECMO-derived flow to various vascular beds, showed remarkable differences. The clinical impact of this study highlighting the relevance of CFD modeling in assessment of complex hemodynamics in ECMO warrants further evaluation.
    MeSH term(s) Humans ; Extracorporeal Membrane Oxygenation/methods ; Patient-Specific Modeling ; Hemodynamics/physiology ; Catheterization ; Aorta
    Language English
    Publishing date 2022-11-03
    Publishing country United States
    Document type Journal Article
    ZDB-ID 759982-1
    ISSN 1538-943X ; 0162-1432 ; 1058-2916
    ISSN (online) 1538-943X
    ISSN 0162-1432 ; 1058-2916
    DOI 10.1097/MAT.0000000000001819
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  5. Article ; Online: CRIMSON: An open-source software framework for cardiovascular integrated modelling and simulation.

    Arthurs, Christopher J / Khlebnikov, Rostislav / Melville, Alex / Marčan, Marija / Gomez, Alberto / Dillon-Murphy, Desmond / Cuomo, Federica / Silva Vieira, Miguel / Schollenberger, Jonas / Lynch, Sabrina R / Tossas-Betancourt, Christopher / Iyer, Kritika / Hopper, Sara / Livingston, Elizabeth / Youssefi, Pouya / Noorani, Alia / Ben Ahmed, Sabrina / Nauta, Foeke J H / van Bakel, Theodorus M J /
    Ahmed, Yunus / van Bakel, Petrus A J / Mynard, Jonathan / Di Achille, Paolo / Gharahi, Hamid / Lau, Kevin D / Filonova, Vasilina / Aguirre, Miquel / Nama, Nitesh / Xiao, Nan / Baek, Seungik / Garikipati, Krishna / Sahni, Onkar / Nordsletten, David / Figueroa, C Alberto

    PLoS computational biology

    2021  Volume 17, Issue 5, Page(s) e1008881

    Abstract: In this work, we describe the CRIMSON (CardiovasculaR Integrated Modelling and SimulatiON) software environment. CRIMSON provides a powerful, customizable and user-friendly system for performing three-dimensional and reduced-order computational ... ...

    Abstract In this work, we describe the CRIMSON (CardiovasculaR Integrated Modelling and SimulatiON) software environment. CRIMSON provides a powerful, customizable and user-friendly system for performing three-dimensional and reduced-order computational haemodynamics studies via a pipeline which involves: 1) segmenting vascular structures from medical images; 2) constructing analytic arterial and venous geometric models; 3) performing finite element mesh generation; 4) designing, and 5) applying boundary conditions; 6) running incompressible Navier-Stokes simulations of blood flow with fluid-structure interaction capabilities; and 7) post-processing and visualizing the results, including velocity, pressure and wall shear stress fields. A key aim of CRIMSON is to create a software environment that makes powerful computational haemodynamics tools accessible to a wide audience, including clinicians and students, both within our research laboratories and throughout the community. The overall philosophy is to leverage best-in-class open source standards for medical image processing, parallel flow computation, geometric solid modelling, data assimilation, and mesh generation. It is actively used by researchers in Europe, North and South America, Asia, and Australia. It has been applied to numerous clinical problems; we illustrate applications of CRIMSON to real-world problems using examples ranging from pre-operative surgical planning to medical device design optimization.
    MeSH term(s) Alagille Syndrome/physiopathology ; Alagille Syndrome/surgery ; Blood Vessels/anatomy & histology ; Blood Vessels/diagnostic imaging ; Blood Vessels/physiology ; Computational Biology ; Computer Simulation ; Finite Element Analysis ; Heart Disease Risk Factors ; Hemodynamics/physiology ; Humans ; Imaging, Three-Dimensional ; Liver Transplantation/adverse effects ; Magnetic Resonance Imaging/statistics & numerical data ; Models, Anatomic ; Models, Cardiovascular ; Patient-Specific Modeling ; Postoperative Complications/etiology ; Software ; User-Computer Interface
    Language English
    Publishing date 2021-05-10
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 2193340-6
    ISSN 1553-7358 ; 1553-734X
    ISSN (online) 1553-7358
    ISSN 1553-734X
    DOI 10.1371/journal.pcbi.1008881
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