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Wong ZY, Azimi M, Khamooshi M, Wickramarachchi A, Burrell A, Gregory SD. The impact of small movements with dual lumen cannulae during venovenous extracorporeal membrane oxygenation: A computational fluid dynamics analysis. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2024; 250:108186. [PMID: 38692252 DOI: 10.1016/j.cmpb.2024.108186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/15/2024] [Accepted: 04/17/2024] [Indexed: 05/03/2024]
Abstract
BACKGROUND AND OBJECTIVES Venovenous Extracorporeal Membrane Oxygenation (VV ECMO) provides respiratory support to patients with severe lung disease failing conventional medical therapy. An essential component of the ECMO circuit are the cannulas, which drain and return blood into the body. Despite being anchored to the patient to prevent accidental removal, minor cannula movements are common during ECMO. The clinical and haemodynamic consequences of these small movements are currently unclear. This study investigated the risk of thrombosis and recirculation caused by small movements of a dual lumen cannula (DLC) in an adult using computational fluid dynamics. METHODS The 3D model of an AVALON Elite DLC (27 Fr) and a patient-specific vena cava and right atrium were generated for an adult patient on ECMO. The baseline cannula position was generated where the return jet enters the tricuspid valve. Alternative cannula positions were obtained by shifting the cannula 5 and 15 mm towards inferior (IVC) and superior (SVC) vena cava, respectively. ECMO settings of 4 L/min blood flow and pulsatile flow at SVC and IVC were applied. Recirculation was defined as a scalar value indicating the infused oxygenated blood inside the drainage lumen, while thrombosis risk was evaluated by shear stress, stagnation volume, washout, and turbulent kinetic energy. RESULTS Recirculation for all models was less than 3.1 %. DLC movements between -5 to 15 mm increased shear stress and turbulence kinetic energy up to 24.7 % and 11.8 %, respectively, compared to the baseline cannula position leading to a higher predicted thrombosis risk. All models obtained a complete washout after nine seconds except for when the cannula migrated 15 mm into the SVC, indicating persisting stasis and circulating zones. CONCLUSION In conclusion, small DLC movements were not associated with an increased risk of recirculation. However, they may increase the risk of thrombosis due to increased shear rate, turbulence, and slower washout of blood. Developing effective cannula securement devices may reduce this risk.
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Affiliation(s)
- Zhun Yung Wong
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia
| | - Marjan Azimi
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia.
| | - Mehrdad Khamooshi
- School of Mechanical, Medical and Process Engineering and the Centre for Biomedical Technologies, Queensland University of Technology, Brisbane, Australia
| | - Avishka Wickramarachchi
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia
| | - Aidan Burrell
- Department of Intensive Care and Hyperbaric Medicine, Alfred Hospital, Melbourne, Australia; ANZ Intensive Care Research Centre (ANZIC-RC), Dept. of Epidemiology and Preventive Medicine, Monash University, Australia
| | - Shaun D Gregory
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia; School of Mechanical, Medical and Process Engineering and the Centre for Biomedical Technologies, Queensland University of Technology, Brisbane, Australia
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Straccia A, Chassagne F, Barbour MC, Beckman J, Li S, Mahr C, Aliseda A. A Computational Investigation of the Effects of Temporal Synchronization of Left Ventricular Assist Device Speed Modulation with the Cardiac Cycle on Intraventricular Hemodynamics. Ann Biomed Eng 2024; 52:1763-1778. [PMID: 38517620 DOI: 10.1007/s10439-024-03489-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 03/07/2024] [Indexed: 03/24/2024]
Abstract
Patients with advanced heart failure are implanted with a left ventricular assist device (LVAD) as a bridge-to-transplantation or destination therapy. Despite advances in pump design, the risk of stroke remains high. LVAD implantation significantly alters intraventricular hemodynamics, where regions of stagnation or elevated shear stresses promote thrombus formation. Third generation pumps incorporate a pulsatility mode that modulates rotational speed of the pump to enhance in-pump washout. We investigated how the timing of the pulsatility mode with the cardiac cycle affects intraventricular hemodynamic factors linked to thrombus formation. Computational fluid dynamics simulations with Lagrangian particle tracking to model platelet behavior in a patient-specific left ventricle captured altered intraventricular hemodynamics due to LVAD implantation. HeartMate 3 incorporates a pulsatility mode that modulates the speed of the pump every two seconds. Four different timings of this pulsatility mode with respect to the cardiac cycle were investigated. A strong jet formed between the mitral valve and inflow cannula. Blood stagnated in the left ventricular outflow tract beneath a closed aortic valve, in the near-wall regions off-axis of the jet, and in a large counterrotating vortex near the anterior wall. Computational results showed good agreement with particle image velocimetry results. Synchronization of the pulsatility mode with peak systole decreased stasis, reflected in the intraventricular washout of virtual contrast and Lagrangian particles over time. Temporal synchronization of HeartMate 3 pulsatility with the cardiac cycle reduces intraventricular stasis and could be beneficial for decreasing thrombogenicity.
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Affiliation(s)
- Angela Straccia
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA.
| | | | - Michael C Barbour
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Jennifer Beckman
- Division of Cardiology, University of Washington, Seattle, WA, USA
| | - Song Li
- Institute for Advanced Cardiac Care, Medical City Healthcare, Dallas, TX, USA
| | - Claudius Mahr
- Institute for Advanced Cardiac Care, Medical City Healthcare, Dallas, TX, USA
| | - Alberto Aliseda
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
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Lopez-Santana G, De Rosis A, Grant S, Venkateswaran R, Keshmiri A. Enhancing the implantation of mechanical circulatory support devices using computational simulations. Front Bioeng Biotechnol 2024; 12:1279268. [PMID: 38737533 PMCID: PMC11084291 DOI: 10.3389/fbioe.2024.1279268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 04/08/2024] [Indexed: 05/14/2024] Open
Abstract
Introduction: Patients with end-stage heart failure (HF) may need mechanical circulatory support such as a left ventricular assist device (LVAD). However, there are a range of complications associated with LVAD including aortic regurgitation (AR) and thrombus formation. This study assesses whether the risk of developing aortic conditions can be minimised by optimising LVAD implantation technique. Methods: In this work, we evaluate the aortic flow patterns produced under different geometrical parameters for the anastomosis of the outflow graft (OG) to the aorta using computational fluid dynamics (CFD). A three-dimensional aortic model is created and the HeartMate III OG positioning is simulated by modifying (i) the distance from the anatomic ventriculo-arterial junction (AVJ) to the OG, (ii) the cardinal position around the aorta, and (iii) the angle between the aorta and the OG. The continuous LVAD flow and the remnant native cardiac cycle are used as inlet boundaries and the three-element Windkessel model is applied at the pressure outlets. Results: The analysis quantifies the impact of OG positioning on different haemodynamic parameters, including velocity, wall shear stress (WSS), pressure, vorticity and turbulent kinetic energy (TKE). We find that WSS on the aortic root (AoR) is around two times lower when the OG is attached to the coronal side of the aorta using an angle of 45° ± 10° at a distance of 55 mm. Discussion: The results show that the OG placement may significantly influence the haemodynamic patterns, demonstrating the potential application of CFD for optimising OG positioning to minimise the risk of cardiovascular complications after LVAD implantation.
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Affiliation(s)
- Gabriela Lopez-Santana
- School of Engineering, The University of Manchester, Manchester, United Kingdom
- Department of Cardiothoracic Transplantation and Mechanical Circulatory Support, Wythenshawe Hospital, Manchester, United Kingdom
| | - Alessandro De Rosis
- School of Engineering, The University of Manchester, Manchester, United Kingdom
| | - Stuart Grant
- Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom
- Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
| | - Rajamiyer Venkateswaran
- Department of Cardiothoracic Transplantation and Mechanical Circulatory Support, Wythenshawe Hospital, Manchester, United Kingdom
- Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
| | - Amir Keshmiri
- School of Engineering, The University of Manchester, Manchester, United Kingdom
- Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom
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Khamooshi M, Azimi M, Gregory SD. Computational analysis of thrombosis risk with variations in left ventricular assist device inflow cannula design in a multi-patient model. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2023; 240:107730. [PMID: 37531687 DOI: 10.1016/j.cmpb.2023.107730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 07/03/2023] [Accepted: 07/21/2023] [Indexed: 08/04/2023]
Abstract
BACKGROUND AND OBJECTIVES Left ventricular assist devices (LVADs) are mechanical pumps used to support patients with end-stage heart failure. The inflow cannula is a critical component of the LVAD as it connects the pump to the left ventricle, allowing blood to be drawn from the heart. However, the design of the cannula can significantly impact LV hemodynamics and cause complications, including thrombosis. Therefore, this study aimed to analyze the numerical effects of left ventricle (LV) size on cannula design in order to enhance hemodynamic performance using post-operative left ventricular assist device (LVAD) models. METHODS A parametric design evaluation of two different inflow cannulas were carried out on left ventricles (LV) of varying sizes (ranging from 154 to 430 ml) constructed from computerized tomography (CT) data from VAD patients using computational fluid dynamics (CFD) simulations. The study analyzed three key factors contributing to thrombosis formation: blood residence time, blood stagnation ratio, and wall shear stress. RESULTS Results showed higher blood residence time and stagnation ratio for larger left ventricular sizes. In addition, increasing the insertion length of the cannula reduced the average wall shear stress. CONCLUSION Overall, the study's findings suggest that the optimal cannula shape for LVADs varies with left ventricular size.
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Affiliation(s)
- Mehrdad Khamooshi
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia.
| | - Marjan Azimi
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia
| | - Shaun D Gregory
- Cardio-Respiratory Engineering and Technology Laboratory (CREATElab), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC, Australia
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5
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Wilson SI, Ingram KE, Oh A, Moreno MR, Kassi M. The role of innovative modeling and imaging techniques in improving outcomes in patients with LVAD. Front Cardiovasc Med 2023; 10:1248300. [PMID: 37692033 PMCID: PMC10484111 DOI: 10.3389/fcvm.2023.1248300] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 08/10/2023] [Indexed: 09/12/2023] Open
Abstract
Heart failure remains a significant cause of mortality in the United States and around the world. While organ transplantation is acknowledged as the gold standard treatment for end stage heart failure, supply is limited, and many patients are treated with left ventricular assist devices (LVADs). LVADs extend and improve patients' lives, but they are not without their own complications, particularly the hemocompatibility related adverse events (HRAE) including stroke, bleeding and pump thrombosis. Mainstream imaging techniques currently in use to assess appropriate device function and troubleshoot complications, such as echocardiography and cardiac computed tomography, provide some insight but do not provide a holistic understanding of pump induced flow alterations that leads to HRAEs. In contrast, there are technologies restricted to the benchtop-such as computational fluid dynamics and mock circulatory loops paired with methods like particle image velocimetry-that can assess flow metrics but have not been optimized for clinical care. In this review, we outline the potential role and current limitations of converging available technologies to produce novel imaging techniques, and the potential utility in evaluating hemodynamic flow to determine whether LVAD patients may be at higher risk of HRAEs. This addition to diagnostic and monitoring capabilities could improve prevention and treatment of LVAD-induced complications in heart failure patients.
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Affiliation(s)
- Shannon I. Wilson
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, United States
| | - Katelyn E. Ingram
- DeBakey Heart and Vascular- Heart Center Research, Houston Methodist Research Institute, Houston, TX, United States
| | - Albert Oh
- School of Engineering Medicine, Texas A&M University, Houston, TX, United States
| | - Michael R. Moreno
- J. Mike Walker ‘66 Department of Mechanical Engineering, Texas A&M University, College Station, TX, United States
| | - Mahwash Kassi
- Cardiology, DeBakey Heart and Vascular, Houston Methodist Hospital, Houston, TX, United States
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Rocchi M, Ingram M, Claus P, D'hooge J, Meyns B, Fresiello L. Use of 3D anatomical models in mock circulatory loops for cardiac medical device testing. Artif Organs 2023; 47:260-272. [PMID: 36370033 DOI: 10.1111/aor.14433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 08/16/2022] [Accepted: 10/11/2022] [Indexed: 11/13/2022]
Abstract
INTRODUCTION Mock circulatory loops (MCLs) are mechanical representations of the cardiovascular system largely used to test the hemodynamic performance of cardiovascular medical devices (MD). Thanks to 3 dimensional (3D) printing technologies, MCLs can nowadays also incorporate anatomical models so to offer enhanced testing capabilities. The aim of this review is to provide an overview on MCLs and to discuss the recent developments of 3D anatomical models for cardiovascular MD testing. METHODS The review first analyses the different techniques to develop 3D anatomical models, in both rigid and compliant materials. In the second section, the state of the art of MCLs with 3D models is discussed, along with the testing of different MDs: implantable blood pumps, heart valves, and imaging techniques. For each class of MD, the MCL is analyzed in terms of: the cardiovascular model embedded, the 3D model implemented (the anatomy represented, the material used, and the activation method), and the testing applications. DISCUSSIONS AND CONCLUSIONS MCLs serve the purpose of testing cardiovascular MDs in different (patho-)physiological scenarios. The addition of 3D anatomical models enables more realistic connections of the MD with the implantation site and enhances the testing capabilities of the MCL. Current attempts focus on the development of personalized MCLs to test MDs in patient-specific hemodynamic and anatomical scenarios. The main limitation of MCLs is the impossibility to assess the impact of a MD in the long-term and at a biological level, for which animal experiments are still needed.
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Affiliation(s)
- Maria Rocchi
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Marcus Ingram
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Piet Claus
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Jan D'hooge
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Bart Meyns
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.,Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Libera Fresiello
- Cardiovasuclar and Respiratory Physiology, University of Twente, Enschede, The Netherlands
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Ghodrati-Misek M, Schlöglhofer T, Gross C, Maurer A, Zimpfer D, Beitzke D, Zonta F, Moscato F, Schima H, Aigner P. Left atrial appendage occlusion in ventricular assist device patients to decrease thromboembolic events: A computer simulation study. Front Physiol 2022; 13:1010862. [PMID: 36246102 PMCID: PMC9557157 DOI: 10.3389/fphys.2022.1010862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 09/01/2022] [Indexed: 11/17/2022] Open
Abstract
Atrial fibrillation (AF) is a common comorbidity in left ventricular assist device (LVAD) patients and has been identified as a risk factor for thromboembolic stroke. Blood stagnation within the left atrial appendage (LAA) is considered a possible major source of thrombosis and clinical studies have shown reduced thromboembolic risk after LAA occlusion (LAAO). Therefore, this study aims to investigate the effect of LAAO on thrombosis-related parameters using patient-specific simulations. Left ventricular and left atrial geometries of an LVAD patient were obtained from computed tomography and combined with hemodynamic data with either sinus rhythm (SR) or AF generated by a lumped parameter model. In four simulations applying contractile walls, stagnation volume and blood residence times were evaluated with or without AF and with or without LAAO. Reduced atrial contraction in AF resulted in unfavorable flow dynamics within the left atrium. The average atrial velocity was lower for the AF simulation when compared to SR, resulting in a 55% increase in the atrial stagnation volume (from 4.2 to 6.5 cm3). Moreover, blood remained in the LAA for more than 8 cardiac cycles. After LAAO the atrial stagnation decreased from 4.2 to 1.4 cm3 for SR and from 6.5 to 2.3 cm3 for the AF simulation. A significant stagnation volume was found in the LAA for both SR and AF, with larger values occurring with AF. These regions are known as potential sources for thrombus formation and can be diminished by LAAO. This significantly improved the thrombus-related flow parameters and may also lower the risk of thromboembolic events from the appendage.
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Affiliation(s)
- Mojgan Ghodrati-Misek
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- *Correspondence: Mojgan Ghodrati-Misek,
| | - Thomas Schlöglhofer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Christoph Gross
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Alexander Maurer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Daniel Zimpfer
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Dietrich Beitzke
- Department of Biomedical Imaging and Image Guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Francesco Zonta
- Institute of Fluid Dynamics and Heat Transfer, Technical University of Vienna, Vienna, Austria
| | - Francesco Moscato
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Heinrich Schima
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Philipp Aigner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
- Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
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Zuo X, Xu Z, Jia H, Mu Y, Zhang M, Yuan M, Wu C. Co-simulation of hypertensive left ventricle based on computational fluid dynamics and a closed-loop network model. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 216:106649. [PMID: 35124478 DOI: 10.1016/j.cmpb.2022.106649] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 12/03/2021] [Accepted: 01/18/2022] [Indexed: 06/14/2023]
Abstract
OBJECTIVE Hypertension is one of the most common chronic and cardiovascular diseases, with the largest number of deaths. According to clinical experience, long-term hypertension will cause cardiac hypertrophy and other complications, and heart structure remodeling will significantly change the energy characteristics of the heart chambers, and impair heart function. Research shows that, early hypertension can be diagnosed by the blood flow and energy loss in the left ventricle. Therefore, it is important to choose an appropriate method to simulate and predict the flow domain of this ventricle. METHODS This study took the left ventricular flow field of patients with hypertensive myocardial hypertrophy as the research object, used MATLAB-SIMULINK to establish a closed-loop network cardiovascular model, provided flow boundary conditions for the computational fluid dynamics (CFD) numerical simulation method, and, finally, completed a co-simulation. RESULTS This article compared the degree of agreement between the energy loss in different phases of the heart cavity and clinical experimental data and summarized the characteristics of the flow field in patients with hypertensive myocardial hypertrophy. The analysis of three simulation groups (control group, non-left ventricular hypertrophy group, and left ventricular hypertrophy [LVH] group) showed that the vortices in the LVH group were irregular and not fully developed, accompanied by significant energy loss. CONCLUSION The simulation method used in this study is basically consistent with the clinical data. Myocardial hypertrophy has a significant influence on the blood flow of the left ventricle. Changes in the blood flow make the left ventricular vortex distribution abnormal during the rapid systole and rapid ejection periods, leading to a series of dangerous factors, including increased energy loss and a low cardiac ejection fraction.
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Affiliation(s)
- Xiaowen Zuo
- Department of Ultrasound Medicine, Chinese PLA Strategic Support Force Characteristic Medical Center, Beijing 100020, China.
| | - Zhike Xu
- Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Huaping Jia
- Department of Ultrasound Medicine, Chinese PLA Strategic Support Force Characteristic Medical Center, Beijing 100020, China.
| | - Yang Mu
- Department of Cardiology, the First Medical Center of Chinese PLA General Hospital, Beijing 100089, China
| | - Mingming Zhang
- Department of Ultrasound Medicine, Chinese PLA Strategic Support Force Characteristic Medical Center, Beijing 100020, China
| | - Manli Yuan
- Department of Ultrasound Medicine, Chinese PLA Strategic Support Force Characteristic Medical Center, Beijing 100020, China
| | - Chengwei Wu
- Department of Engineering Mechanics, Dalian University of Technology, Dalian 106024, China
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9
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Ghodrati M, Schlöglhofer T, Maurer A, Khienwad T, Zimpfer D, Beitzke D, Zonta F, Moscato F, Schima H, Aigner P. Effects of the atrium on intraventricular flow patterns during mechanical circulatory support. Int J Artif Organs 2021; 45:421-430. [PMID: 34715752 PMCID: PMC8922056 DOI: 10.1177/03913988211056018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Simulations of the ventricular flow patterns during left ventricular assist device (LVAD) support are mainly performed with idealized cylindrical inflow, neglecting the influence of the atrial vortex. In this study, the influence of the left atrium (LA) on the intra-ventricular flow was investigated via Computational Fluid Dynamics (CFD) simulations. Ventricular flow was simulated by a combined Eulerian (carrier flow)/Lagrangian (particles) approach taking into account either the LA or a cylindrical inflow section to mimic a fully support condition. The flow deviation at the mitral valve, the blood low-velocity volume as well as the residence time and shear stress history of the particles were calculated. Inclusion of the LA deflects the flow at the mitral valve by 25°, resulting in an asymmetric flow jet entering the left ventricle. This reduced the ventricular low-velocity volume by 40% (from 6.4 to 3.9 cm3), increased (40%) the shear stress experienced by particles and correspondingly increased (27%) their residence time. Under the studied conditions, the atrial geometry plays a major role in the development of intraventricular flow patterns. A reliable prediction of blood flow dynamics and consequently thrombosis risk analysis within the ventricle requires the consideration of the LA in computational simulations.
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Affiliation(s)
- Mojgan Ghodrati
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Thomas Schlöglhofer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria.,Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Alexander Maurer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Thananya Khienwad
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Daniel Zimpfer
- Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Dietrich Beitzke
- Department of Biomedical Imaging and Image guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Francesco Zonta
- Institute of Fluid Dynamics and Heat Transfer, Technical University of Vienna, Vienna, Austria
| | - Francesco Moscato
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Heinrich Schima
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria.,Department of Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Philipp Aigner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
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10
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Méndez Rojano R, Zhussupbekov M, Antaki JF. Multi-constituent simulation of thrombus formation at LVAD inlet cannula connection: Importance of Virchow's triad. Artif Organs 2021; 45:1014-1023. [PMID: 33683718 PMCID: PMC9987618 DOI: 10.1111/aor.13949] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 02/24/2021] [Accepted: 02/28/2021] [Indexed: 12/12/2022]
Abstract
As pump thrombosis is reduced in current-generation ventricular assist devices (VAD), adverse events such as bleeding or stroke remain at unacceptable rates. Thrombosis around the VAD inlet cannula (IC) has been highlighted as a possible source of stroke events. Recent computational fluid dynamics (CFD) studies have attempted to characterize the thrombosis risk of different IC-ventricle configurations. However, purely CFD simulations relate thrombosis risk to ad hoc criteria based on flow characteristics, with little consideration of biochemical factors. This study investigates the genesis of IC thrombosis including two elements of the Virchow's triad: endothelial injury and hypercoagulability. To this end a multi-scale thrombosis simulation that includes platelet activity and coagulation reactions was performed. Our results show significant thrombin formation in stagnation regions (|u| < 0.005 m/s) close to the IC wall. In addition, high shear-mediated platelet activation was observed over the leading-edge tip of the cannula. The current study reveals the importance of biochemical factors to the genesis of thrombosis at the ventricular-cannula junction in a perioperative state. This study is a first step toward the long-term objective of including clinically relevant pharmacological kinetics such as heparin or aspirin in simulations of inflow cannula thrombosis.
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Affiliation(s)
| | - Mansur Zhussupbekov
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - James F Antaki
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
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11
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Ghodrati M, Maurer A, Schlöglhofer T, Khienwad T, Zimpfer D, Beitzke D, Zonta F, Moscato F, Schima H, Aigner P. The influence of left ventricular assist device inflow cannula position on thrombosis risk. Artif Organs 2020; 44:939-946. [PMID: 32302423 PMCID: PMC7496759 DOI: 10.1111/aor.13705] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 03/09/2020] [Accepted: 04/08/2020] [Indexed: 12/25/2022]
Abstract
The use of left ventricular assist devices (LVADs) as a treatment method for heart failure patients has been steadily increasing; however, pathological studies showed presence of thrombi around the HeartWare ventricular assist device inflow cannula (IC) in more than 95% of patients after device explantation. Flow fields around the IC might trigger thrombus formation and require further investigation. In this study flow dynamics parameters were evaluated for different patient geometries using computational fluid dynamics (CFD) simulations. Left ventricular (LV) models of two LVAD patients were obtained from CT scans. The LV volumes of Patient 1 (P1) and Patient 2 (P2) were 264 and 114 cm3 with an IC angle of 20° and 9° from the mitral‐IC tip axis at the coronal plane. The IC insertion site at the apex was central for P1, whereas it was lateral for P2. Transient CFD simulations were performed over 9 cardiac cycles. The wedge area was defined from the cannula tip to the wall of the LV apex. Mean velocity magnitude and blood stagnation region (volume with mean velocity <5 mm/s) as well as the wall shear stress (WSS) at the IC surface were calculated. Cardiac support resulted in a flow mainly crossing the ventricle from the mitral valve to the LVAD cannula for P2, while the main inflow jet deviated toward the septal wall in P1. Lower WSS at the IC surface and consequently larger stagnation volumes were observed for P2 (P1: 0.17, P2: 0.77 cm3). Flow fields around an LVAD cannula can be influenced by many parameters such as LV size, IC angle, and implantation site. Careful consideration of influencing parameters is essential to get reliable evaluations of the apical flow field and its connection to apical thrombus formation. Higher blood washout and lower stagnation were observed for a central implantation of the IC at the apex.
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Affiliation(s)
- Mojgan Ghodrati
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Alexander Maurer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Thomas Schlöglhofer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria.,Department for Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Thananya Khienwad
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
| | - Daniel Zimpfer
- Department for Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Dietrich Beitzke
- Department of Biomedical Imaging and Image Guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Francesco Zonta
- Institute of Fluid Dynamics and Heat Transfer, Technical University of Vienna, Vienna, Austria
| | - Francesco Moscato
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
| | - Heinrich Schima
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria.,Department for Cardiac Surgery, Medical University of Vienna, Vienna, Austria
| | - Philipp Aigner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.,Ludwig Boltzmann Institute for Cardiovascular Research, Vienna, Austria
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