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Suriany S, Liu H, Cheng AL, Wenby R, Patel N, Badran S, Meiselman HJ, Denton C, Coates TD, Wood JC, Detterich JA. Decreased erythrocyte aggregation in Glenn and Fontan: univentricular circulation as a rheologic disease model. Pediatr Res 2024; 95:1335-1345. [PMID: 38177250 DOI: 10.1038/s41390-023-02969-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/19/2023] [Accepted: 12/04/2023] [Indexed: 01/06/2024]
Abstract
BACKGROUND In the Fontan palliation for single ventricle heart disease (SVHD), pulmonary blood flow is non-pulsatile/passive, low velocity, and low shear, making viscous power loss a critical determinant of cardiac output. The rheologic properties of blood in SVHD patients are essential for understanding and modulating their limited cardiac output and they have not been systematically studied. We hypothesize that viscosity is decreased in single ventricle circulation. METHODS We evaluated whole blood viscosity, red blood cell (RBC) aggregation, and RBC deformability to evaluate changes in healthy children and SVHD patients. We altered suspending media to understand cellular and plasma differences contributing to rheologic differences. RESULTS Whole blood viscosity was similar between SVHD and healthy at their native hematocrits, while viscosity was lower at equivalent hematocrits for SVHD patients. RBC deformability is increased, and RBC aggregation is decreased in SVHD patients. Suspending SVHD RBCs in healthy plasma resulted in increased RBC aggregation and suspending healthy RBCs in SVHD plasma resulted in lower RBC aggregation. CONCLUSIONS Hematocrit corrected blood viscosity is lower in SVHD vs. healthy due to decreased RBC aggregation and higher RBC deformability, a viscous adaptation of blood in patients whose cardiac output is dependent on minimizing viscous power loss. IMPACT Patients with single ventricle circulation have decreased red blood cell aggregation and increased red blood cell deformability, both of which result in a decrease in blood viscosity across a large shear rate range. Since the unique Fontan circulation has very low-shear and low velocity flow in the pulmonary arteries, blood viscosity plays an increased role in vascular resistance, therefore this work is the first to describe a novel mechanism to target pulmonary vascular resistance as a modifiable risk factor. This is a novel, modifiable risk factor in this patient population.
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Affiliation(s)
- Silvie Suriany
- Division of Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - Honglei Liu
- Division of Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - Andrew L Cheng
- Division of Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - Rosalinda Wenby
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Neil Patel
- Division of Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - Sarah Badran
- Division of Pediatric and Congenital Cardiology, Helen Devos Children's Hospital at Spectrum Health, Grand Rapids, MI, USA
- Division of Cardiology, Department of Medicine, Michigan State University, East Lansing, MI, USA
| | - Herbert J Meiselman
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Christopher Denton
- Division of Hematology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - Thomas D Coates
- Division of Hematology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - John C Wood
- Division of Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, USA
| | - Jon A Detterich
- Division of Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, USA.
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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Rasooli R, Holmstrom H, Giljarhus KET, Jolma IW, Vinningland JL, de Lange C, Brun H, Hiorth A. In vitro hemodynamic performance of a blood pump for self-powered venous assist in univentricular hearts. Sci Rep 2024; 14:6941. [PMID: 38521832 PMCID: PMC10960831 DOI: 10.1038/s41598-024-57269-7] [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: 09/05/2023] [Accepted: 03/15/2024] [Indexed: 03/25/2024] Open
Abstract
Univentricular heart anomalies represent a group of severe congenital heart defects necessitating early surgical intervention in infancy. The Fontan procedure, the final stage of single-ventricle palliation, establishes a serial connection between systemic and pulmonary circulation by channeling venous return to the lungs. The absence of the subpulmonary ventricle in this peculiar circulation progressively eventuates in failure, primarily due to chronic elevation in inferior vena cava (IVC) pressure. This study experimentally validates the effectiveness of an intracorporeally-powered venous ejector pump (VEP) in reducing IVC pressure in Fontan patients. The VEP exploits a fraction of aortic flow to create a jet-venturi effect for the IVC, negating the external power requirement and driveline infections. An invitro Fontan mock-up circulation loop is developed and the impact of VEP design parameters and physiological conditions is assessed using both idealized and patient-specific total cavopulmonary connection (TCPC) phantoms. The VEP performance in reducing IVC pressure exhibited an inverse relationship with the cardiac output and extra-cardiac conduit (ECC) size and a proportional relationship with the transpulmonary pressure gradient (TPG) and mean arterial pressure (MAP). The ideal VEP with fail-safe features provided an IVC pressure drop of 1.82 ± 0.49, 2.45 ± 0.54, and 3.12 ± 0.43 mm Hg for TPG values of 6, 8, and 10 mm Hg, respectively, averaged over all ECC sizes and cardiac outputs. Furthermore, the arterial oxygen saturation was consistently maintained above 85% during full-assist mode. These results emphasize the potential utility of the VEP to mitigate elevated venous pressure in Fontan patients.
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Affiliation(s)
- Reza Rasooli
- Department of Energy Resources, Faculty of Science and Technology, University of Stavanger, 4036, Stavanger, Norway.
| | - Henrik Holmstrom
- Department of Pediatric Cardiology, Division of Pediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Knut Erik Teigen Giljarhus
- Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, 4036, Stavanger, Norway
| | - Ingunn Westvik Jolma
- Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | | | - Charlotte de Lange
- Department of Pediatric Radiology, Sahlgrenska University Hospital, Gothenburg, Sweden
- Institute of Clinical Science, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Henrik Brun
- Department of Pediatric Cardiology, Division of Pediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
- Section for Medical Cybernetics and Image Processing, The Intervention Centre, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Aksel Hiorth
- Department of Energy Resources, Faculty of Science and Technology, University of Stavanger, 4036, Stavanger, Norway
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Rasooli R, Giljarhus KET, Hiorth A, Jolma IW, Vinningland JL, de Lange C, Brun H, Holmstrom H. In Silico Evaluation of a Self-powered Venous Ejector Pump for Fontan Patients. Cardiovasc Eng Technol 2023; 14:428-446. [PMID: 36877450 PMCID: PMC10412470 DOI: 10.1007/s13239-023-00663-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 02/06/2023] [Indexed: 03/07/2023]
Abstract
PURPOSE The Fontan circulation carries a dismal prognosis in the long term due to its peculiar physiology and lack of a subpulmonic ventricle. Although it is multifactorial, elevated IVC pressure is accepted to be the primary cause of Fontan's high mortality and morbidity. This study presents a self-powered venous ejector pump (VEP) that can be used to lower the high IVC venous pressure in single-ventricle patients. METHODS A self-powered venous assist device that exploits the high-energy aortic flow to lower IVC pressure is designed. The proposed design is clinically feasible, simple in structure, and is powered intracorporeally. The device's performance in reducing IVC pressure is assessed by conducting comprehensive computational fluid dynamics simulations in idealized total cavopulmonary connections with different offsets. The device was finally applied to complex 3D reconstructed patient-specific TCPC models to validate its performance. RESULTS The assist device provided a significant IVC pressure drop of more than 3.2 mm Hg in both idealized and patient-specific geometries, while maintaining a high systemic oxygen saturation of more than 90%. The simulations revealed no significant caval pressure rise (< 0.1 mm Hg) and sufficient systemic oxygen saturation (> 84%) in the event of device failure, demonstrating its fail-safe feature. CONCLUSIONS A self-powered venous assist with promising in silico performance in improving Fontan hemodynamics is proposed. Due to its passive nature, the device has the potential to provide palliation for the growing population of patients with failing Fontan.
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Affiliation(s)
- Reza Rasooli
- Department of Energy Resources, Faculty of Science and Technology, University of Stavanger, 4036, Stavanger, Norway.
| | - Knut Erik Teigen Giljarhus
- Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, 4036, Stavanger, Norway
| | - Aksel Hiorth
- Department of Energy Resources, Faculty of Science and Technology, University of Stavanger, 4036, Stavanger, Norway
| | - Ingunn Westvik Jolma
- Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | | | - Charlotte de Lange
- Department of Paediatric Radiology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Henrik Brun
- Section for Medical Cybernetics and Image Processing, The Intervention Centre, Oslo University Hospital Rikshospitalet, Oslo, Norway
- Department of Paediatric Cardiology, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
| | - Henrik Holmstrom
- Department of Paediatric Cardiology, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
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Yi H, Yang Z, Johnson M, Bramlage L, Ludwig B. Hemodynamic characteristics in a cerebral aneurysm model using non-Newtonian blood analogues. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2022; 34:103101. [PMID: 36212224 PMCID: PMC9533395 DOI: 10.1063/5.0118097] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 09/05/2022] [Indexed: 06/16/2023]
Abstract
This study aims to develop an experimentally validated computational fluid dynamics (CFD) model to estimate hemodynamic characteristics in cerebral aneurysms (CAs) using non-Newtonian blood analogues. Blood viscosities varying with shear rates were measured under four temperatures first, which serves as the reference for the generation of blood analogues. Using the blood analogue, particle image velocimetry (PIV) measurements were conducted to quantify flow characteristics in a CA model. Then, using the identical blood properties in the experiment, CFD simulations were executed to quantify the flow patterns, which were used to compare with the PIV counterpart. Additionally, hemodynamic characteristics in the simplified Newtonian and non-Newtonian models were quantified and compared using the experimentally validated CFD model. Results showed the proposed non-Newtonian viscosity model can predict blood shear-thinning properties accurately under varying temperatures and shear rates. Another developed viscosity model based on the blood analogue can well represent blood rheological properties. The comparisons in flow characteristics show good agreements between PIV and CFD, demonstrating the developed CFD model is qualified to investigate hemodynamic factors within CAs. Furthermore, results show the differences of absolute values were insignificant between Newtonian and non-Newtonian fluids in the distributions of wall shear stress (WSS) and oscillatory shear index (OSI) on arterial walls. However, not only does the simplified Newtonian model underestimate WSS and OSI in most regions of the aneurysmal sac, but it also makes mistakes in identifying the high OSI regions on the sac surface, which may mislead the hemodynamic assessment on the pathophysiology of CAs.
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Affiliation(s)
- Hang Yi
- Department of Mechanical and Material Engineering, Wright State University, 3640 Colonel Glenn Hwy., Dayton, Ohio 45435, USA
| | - Zifeng Yang
- Department of Mechanical and Material Engineering, Wright State University, 3640 Colonel Glenn Hwy., Dayton, Ohio 45435, USA
| | - Mark Johnson
- Department of Mechanical and Material Engineering, Wright State University, 3640 Colonel Glenn Hwy., Dayton, Ohio 45435, USA
| | - Luke Bramlage
- Boonshoft School of Medicine, Wright State University, Dayton, Ohio 45435, USA
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Fallon ME, Mathews R, Hinds MT. In Vitro Flow Chamber Design for the Study of Endothelial Cell (Patho)Physiology. J Biomech Eng 2022; 144:020801. [PMID: 34254640 PMCID: PMC8628846 DOI: 10.1115/1.4051765] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 07/06/2021] [Indexed: 02/03/2023]
Abstract
In the native vasculature, flowing blood produces a frictional force on vessel walls that affects endothelial cell function and phenotype. In the arterial system, the vasculature's local geometry directly influences variations in flow profiles and shear stress magnitudes. Straight arterial sections with pulsatile shear stress have been shown to promote an athero-protective endothelial phenotype. Conversely, areas with more complex geometry, such as arterial bifurcations and branch points with disturbed flow patterns and lower, oscillatory shear stress, typically lead to endothelial dysfunction and the pathogenesis of cardiovascular diseases. Many studies have investigated the regulation of endothelial responses to various shear stress environments. Importantly, the accurate in vitro simulation of in vivo hemodynamics is critical to the deeper understanding of mechanotransduction through the proper design and use of flow chamber devices. In this review, we describe several flow chamber apparatuses and their fluid mechanics design parameters, including parallel-plate flow chambers, cone-and-plate devices, and microfluidic devices. In addition, chamber-specific design criteria and relevant equations are defined in detail for the accurate simulation of shear stress environments to study endothelial cell responses.
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Affiliation(s)
- Meghan E. Fallon
- Department of Biomedical Engineering, Oregon Health & Science University, 3303 S Bond Ave CH13B, Portland, OR 97239
| | - Rick Mathews
- Department of Biomedical Engineering, Oregon Health & Science University, 3303 S Bond Ave CH13B, Portland, OR 97239
| | - Monica T. Hinds
- Department of Biomedical Engineering, Oregon Health & Science University, 3303 S Bond Ave CH13B, Portland, OR 97239
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Engineering Perspective on Cardiovascular Simulations of Fontan Hemodynamics: Where Do We Stand with a Look Towards Clinical Application. Cardiovasc Eng Technol 2021; 12:618-630. [PMID: 34114202 DOI: 10.1007/s13239-021-00541-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Accepted: 04/30/2021] [Indexed: 01/02/2023]
Abstract
BACKGROUND Cardiovascular simulations for patients with single ventricles undergoing the Fontan procedure can assess patient-specific hemodynamics, explore surgical advances, and develop personalized strategies for surgery and patient care. These simulations have not yet been broadly accepted as a routine clinical tool owing to a number of limitations. Numerous approaches have been explored to seek innovative solutions for improving methodologies and eliminating these limitations. PURPOSE This article first reviews the current state of cardiovascular simulations of Fontan hemodynamics. Then, it will discuss the technical progress of Fontan simulations with the emphasis of its clinical impact, noting that substantial improvements have been made in the considerations of patient-specific anatomy, flow, and blood rheology. The article concludes with insights into potential future directions involving clinical validation, uncertainty quantification, and computational efficiency. The advancements in these aspects could promote the clinical usage of Fontan simulations, facilitating its integration into routine clinical practice.
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7
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Iskander A, Bilgi C, Naftalovich R, Hacihaliloglu I, Berkman T, Naftalovich D, Pahlevan N. The Rheology of the Carotid Sinus: A Path Toward Bioinspired Intervention. Front Bioeng Biotechnol 2021; 9:678048. [PMID: 34178967 PMCID: PMC8222608 DOI: 10.3389/fbioe.2021.678048] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/05/2021] [Indexed: 11/30/2022] Open
Abstract
The association between blood viscosity and pathological conditions involving a number of organ systems is well known. However, how the body measures and maintains appropriate blood viscosity is not well-described. The literature endorsing the function of the carotid sinus as a site of baroreception can be traced back to some of the earliest descriptions of digital pressure on the neck producing a drop in blood delivery to the brain. For the last 30 years, improved computational fluid dynamic (CFD) simulations of blood flow within the carotid sinus have demonstrated a more nuanced understanding of the changes in the region as it relates to changes in conventional metrics of cardiovascular function, including blood pressure. We suggest that the unique flow patterns within the carotid sinus may make it an ideal site to transduce flow data that can, in turn, enable real-time measurement of blood viscosity. The recent characterization of the PIEZO receptor family in the sinus vessel wall may provide a biological basis for this characterization. When coupled with other biomarkers of cardiovascular performance and descriptions of the blood rheology unique to the sinus region, this represents a novel venue for bioinspired design that may enable end-users to manipulate and optimize blood flow.
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Affiliation(s)
- Andrew Iskander
- Department of Anesthesiology, Westchester Medical Center, New York Medical College, Valhalla, NY, United States
| | - Coskun Bilgi
- Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA, United States
| | - Rotem Naftalovich
- Department of Anesthesiology, New Jersey Medical School, University Hospital, Rutgers University, Newark, NJ, United States.,Medical Corps of the U.S. Army, U.S. Army Medical Department, Fort Sam Houston, San Antonio, TX, United States
| | - Ilker Hacihaliloglu
- Department of Biomedical Engineering, Rutgers School of Engineering, Rutgers University, Piscataway, NJ, United States
| | - Tolga Berkman
- Department of Anesthesiology, New Jersey Medical School, University Hospital, Rutgers University, Newark, NJ, United States
| | - Daniel Naftalovich
- Department of Computational and Mathematical Sciences, California Institute of Technology, Pasadena, CA, United States.,Keck School of Medicine, University of Southern California, Los Angeles, CA, United States
| | - Niema Pahlevan
- Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA, United States.,Keck School of Medicine, University of Southern California, Los Angeles, CA, United States
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8
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Gerrah R, Haller SJ. Computational fluid dynamics: a primer for congenital heart disease clinicians. Asian Cardiovasc Thorac Ann 2020; 28:520-532. [PMID: 32878458 DOI: 10.1177/0218492320957163] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Computational fluid dynamics has become an important tool for studying blood flow dynamics. As an in-silico collection of methods, computational fluid dynamics is noninvasive and provides numerical values for the most important parameters of blood flow, such as velocity and pressure that are crucial in hemodynamic studies. In this primer, we briefly explain the basic theory and workflow of the two most commonly applied computational fluid dynamics techniques used in the congenital heart disease literature: the finite element method and the finite volume method. We define important terminology and include specific examples of how using these methods can answer important clinical questions in congenital cardiac surgery planning and perioperative patient management.
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Affiliation(s)
- Rabin Gerrah
- Stanford University, Samaritan Cardiovascular Surgery, Corvallis, OR, USA
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9
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López JM, Fortuny G, Puigjaner D, Herrero J, Marimon F. Hemodynamic effects of blood clots trapped by an inferior vena cava filter. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2020; 36:e3343. [PMID: 32323487 DOI: 10.1002/cnm.3343] [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: 11/04/2019] [Revised: 04/13/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
The alteration of blood flow around an OPTEASE inferior vena cava filter with one or two blood clots attached was investigated by means of computational fluid dynamics. We used a patient-specific vein wall geometry, and we generated different clot models with shapes adapted to the filter and vein wall geometries. A total of eight geometries, with one or two clots and a total clot volume of 0.5 or 1 cm3 , were considered. A non-Newtonian model for blood viscosity was adopted and the possible development of turbulence was accounted for by means of a three-equation model. Two blood flow rates were considered for each case, representative for rest and exercise conditions. In exercise conditions, flow unsteadiness and even turbulence was detected in some cases. Pressure and wall shear stress (WSS) distributions were modified in all cases. Clots attached to the filter downstream basket considerably increased averaged WSS values by up to almost 50%. In all the cases a flow recirculation region appeared downstream of the clot. The degree of flow stagnation in these regions, an indicator of propensity to thrombogenesis, was estimated in terms of mean residence times and mean blood viscosity. High levels of flow stagnation were detected in rest conditions in the wake of those clots that were placed upstream from the filter. Our results suggest that one downstream placed big clot, showing a higher tendency to induce flow instabilities and turbulence, might be more harmful than two small clots placed in tandem.
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Affiliation(s)
- Josep M López
- Departament d'Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Tarragona, Catalunya, Spain
| | - Gerard Fortuny
- Departament d'Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Tarragona, Catalunya, Spain
| | - Dolors Puigjaner
- Departament d'Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Tarragona, Catalunya, Spain
| | - Joan Herrero
- Departament d'Enginyeria Química, Universitat Rovira i Virgili, Tarragona, Catalunya, Spain
| | - Francesc Marimon
- Departament de Medicina i Cirurgia, Universitat Rovira i Virgili, Reus, Catalunya, Spain
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10
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Non-Newtonian Effects on Patient-Specific Modeling of Fontan Hemodynamics. Ann Biomed Eng 2020; 48:2204-2217. [PMID: 32372365 DOI: 10.1007/s10439-020-02527-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 04/29/2020] [Indexed: 12/15/2022]
Abstract
The Fontan procedure is a common palliative surgery for congenital single ventricle patients. In silico and in vitro patient-specific modeling approaches are widely utilized to investigate potential improvements of Fontan hemodynamics that are related to long-term complications. However, there is a lack of consensus regarding the use of non-Newtonian rheology, warranting a systematic investigation. This study conducted in silico patient-specific modeling for twelve Fontan patients, using a Newtonian and a non-Newtonian model for each patient. Differences were quantified by examining clinically relevant metrics: indexed power loss (iPL), indexed viscous dissipation rate (iVDR), hepatic flow distribution (HFD), and regions of low wall shear stress (AWSS). Four sets of "non-Newtonian importance factors" were calculated to explore their effectiveness in identifying the non-Newtonian effect. No statistical differences were observed in iPL, iVDR, and HFD between the two models at the population-level, but large inter-patient variations exist. Significant differences were detected regarding AWSS, and its correlations with non-Newtonian importance factors were discussed. Additionally, simulations using the non-Newtonian model were computationally faster than those using the Newtonian model. These findings distinguish good importance factors for identifying non-Newtonian rheology and encourage the use of a non-Newtonian model to assess Fontan hemodynamics.
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11
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Cheng AL, Wee CP, Pahlevan NM, Wood JC. A 4D flow MRI evaluation of the impact of shear-dependent fluid viscosity on in vitro Fontan circulation flow. Am J Physiol Heart Circ Physiol 2019; 317:H1243-H1253. [PMID: 31585044 DOI: 10.1152/ajpheart.00296.2019] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Fontan procedure for univentricular heart defects creates a nonphysiologic circulation where systemic venous blood drains directly into the pulmonary arteries, leading to multiorgan dysfunction secondary to chronic low-shear nonpulsatile pulmonary blood flow and central venous hypertension. Although blood viscosity increases exponentially in this low-shear environment, the role of shear-dependent ("non-Newtonian") blood viscosity in this pathophysiology is unclear. We studied three-dimensional (3D)-printed Fontan models in an in vitro flow loop with a Philips 3-T magnetic resonance imaging (MRI) scanner. A 4D flow phase-contrast sequence was used to acquire a time-varying 3D velocity field for each experimental condition. On the basis of blood viscosity of a cohort of patients who had undergone the Fontan procedure, it was decided to use 0.04% xanthan gum as a non-Newtonian blood analog; 45% glycerol was used as a Newtonian control fluid. MRI data were analyzed using GTFlow and MATLAB software. The primary outcome, power loss, was significantly higher with the Newtonian fluid [14.8 (13.3, 16.4) vs. 8.1 (6.4, 9.8)%, medians with 95% confidence interval, P < 0.0001]. The Newtonian fluid also demonstrated marginally higher right pulmonary artery flow, marginally lower shear stress, and a trend toward higher caval flow mixing. Outcomes were modulated by Fontan model complexity, cardiac output, and caval flow ratio. Vortexes, helical flow, and stagnant flow were more prevalent with the non-Newtonian fluid. Our data demonstrate that shear-dependent viscosity significantly alters qualitative flow patterns, power loss, pulmonary flow distribution, shear stress, and caval flow mixing in synthetic models of the Fontan circulation. Potential clinical implications include effects on exercise capacity, ventilation-perfusion matching, risk of pulmonary arteriovenous malformations, and risk of thromboembolism.NEW & NOTEWORTHY Although blood viscosity increases exponentially in low-shear environments, the role of shear-dependent ("non-Newtonian") blood viscosity in the pathophysiology of the low-shear Fontan circulation is unclear. We demonstrate that shear-dependent viscosity significantly alters qualitative flow patterns, power loss, pulmonary flow distribution, shear stress, and caval flow mixing in synthetic models of the Fontan circulation. Potential clinical implications include effects on exercise capacity, ventilation-perfusion matching, risk of pulmonary arteriovenous malformations, and risk of thromboembolism.
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Affiliation(s)
- Andrew L Cheng
- Division of Pediatric Cardiology, Children's Hospital Los Angeles, Los Angeles, California.,Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Choo Phei Wee
- Biostatistics Core, Children's Hospital Los Angeles, Los Angeles, California
| | - Niema M Pahlevan
- Keck School of Medicine, University of Southern California, Los Angeles, California.,Department of Aerospace and Mechanical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California
| | - John C Wood
- Division of Pediatric Cardiology, Children's Hospital Los Angeles, Los Angeles, California.,Keck School of Medicine, University of Southern California, Los Angeles, California
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