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Fan L, Wang H, Kassab GS, Lee LC. Review of cardiac-coronary interaction and insights from mathematical modeling. WIREs Mech Dis 2024; 16:e1642. [PMID: 38316634 PMCID: PMC11081852 DOI: 10.1002/wsbm.1642] [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: 09/13/2023] [Revised: 12/10/2023] [Accepted: 01/08/2024] [Indexed: 02/07/2024]
Abstract
Cardiac-coronary interaction is fundamental to the function of the heart. As one of the highest metabolic organs in the body, the cardiac oxygen demand is met by blood perfusion through the coronary vasculature. The coronary vasculature is largely embedded within the myocardial tissue which is continually contracting and hence squeezing the blood vessels. The myocardium-coronary vessel interaction is two-ways and complex. Here, we review the different types of cardiac-coronary interactions with a focus on insights gained from mathematical models. Specifically, we will consider the following: (1) myocardial-vessel mechanical interaction; (2) metabolic-flow interaction and regulation; (3) perfusion-contraction matching, and (4) chronic interactions between the myocardium and coronary vasculature. We also provide a discussion of the relevant experimental and clinical studies of different types of cardiac-coronary interactions. Finally, we highlight knowledge gaps, key challenges, and limitations of existing mathematical models along with future research directions to understand the unique myocardium-coronary coupling in the heart. This article is categorized under: Cardiovascular Diseases > Computational Models Cardiovascular Diseases > Biomedical Engineering Cardiovascular Diseases > Molecular and Cellular Physiology.
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Affiliation(s)
- Lei Fan
- Joint Department of Biomedical Engineering, Marquette University and Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Haifeng Wang
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan, USA
| | - Ghassan S Kassab
- California Medical Innovations Institute, San Diego, California, USA
| | - Lik Chuan Lee
- Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan, USA
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2
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Baluk P, Shirakura K, Vestweber D, McDonald DM. Heterogeneity of endothelial VE-PTP downstream polarization, Tie2 activation, junctional claudin-5, and permeability in the aorta and vena cava. Cell Tissue Res 2024; 395:81-103. [PMID: 38032480 PMCID: PMC10774230 DOI: 10.1007/s00441-023-03844-9] [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: 06/16/2023] [Accepted: 11/10/2023] [Indexed: 12/01/2023]
Abstract
Endothelial cells of mammalian blood vessels have multiple levels of heterogeneity along the vascular tree and among different organs. Further heterogeneity results from blood flow turbulence and variations in shear stress. In the aorta, vascular endothelial protein tyrosine phosphatase (VE-PTP), which dephosphorylates tyrosine kinase receptor Tie2 in the plasma membrane, undergoes downstream polarization and endocytosis in endothelial cells exposed to laminar flow and high shear stress. VE-PTP sequestration promotes Tie2 phosphorylation at tyrosine992 and endothelial barrier tightening. The present study characterized the heterogeneity of VE-PTP polarization, Tie2-pY992 and total Tie2, and claudin-5 in anatomically defined regions of endothelial cells in the mouse descending thoracic aorta, where laminar flow is variable and IgG extravasation is patchy. We discovered that VE-PTP and Tie2-pY992 had mosaic patterns, unlike the uniform distribution of total Tie2. Claudin-5 at tight junctions also had a mosaic pattern, whereas VE-cadherin at adherens junctions bordered all endothelial cells. Importantly, the amounts of Tie2-pY992 and claudin-5 in aortic endothelial cells correlated with downstream polarization of VE-PTP. VE-PTP and Tie2-pY992 also had mosaic patterns in the vena cava, but claudin-5 was nearly absent and extravasated IgG was ubiquitous. Correlation of Tie2-pY992 and claudin-5 with VE-PTP polarization supports their collective interaction in the regulation of endothelial barrier function in the aorta, yet differences between the aorta and vena cava indicate additional flow-related determinants of permeability. Together, the results highlight new levels of endothelial cell functional mosaicism in the aorta and vena cava, where blood flow dynamics are well known to be heterogeneous.
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Affiliation(s)
- Peter Baluk
- Department of Anatomy, Cardiovascular Research Institute, and UCSF Helen Diller Family Comprehensive Cancer Center, University of California, 513 Parnassus Avenue, Room S1349, San Francisco, CA, 94143-0452, USA
| | - Keisuke Shirakura
- Max Planck Institute for Molecular Biomedicine, Röntgenstrasse 20, Münster, 48149, Germany
| | - Dietmar Vestweber
- Max Planck Institute for Molecular Biomedicine, Röntgenstrasse 20, Münster, 48149, Germany
| | - Donald M McDonald
- Department of Anatomy, Cardiovascular Research Institute, and UCSF Helen Diller Family Comprehensive Cancer Center, University of California, 513 Parnassus Avenue, Room S1349, San Francisco, CA, 94143-0452, USA.
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3
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Celant M, Toro EF, Bertaglia G, Cozzio S, Caleffi V, Valiani A, Blanco PJ, Müller LO. Modeling essential hypertension with a closed-loop mathematical model for the entire human circulation. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2023; 39:e3748. [PMID: 37408358 DOI: 10.1002/cnm.3748] [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: 08/01/2022] [Revised: 06/06/2023] [Accepted: 06/11/2023] [Indexed: 07/07/2023]
Abstract
Arterial hypertension, defined as an increase in systemic arterial pressure, is a major risk factor for the development of diseases affecting the cardiovascular system. Every year, 9.4 million deaths worldwide are caused by complications arising from hypertension. Despite well-established approaches to diagnosis and treatment, fewer than half of all hypertensive patients have adequately controlled blood pressure. In this scenario, computational models of hypertension can be a practical approach for better quantifying the role played by different components of the cardiovascular system in the determination of this condition. In the present work we adopt a global closed-loop multi-scale mathematical model for the entire human circulation to reproduce a hypertensive scenario. In particular, we modify the model to reproduce alterations in the cardiovascular system that are cause and/or consequence of the hypertensive state. The adaptation does not only affect large systemic arteries and the heart but also the microcirculation, the pulmonary circulation and the venous system. Model outputs for the hypertensive scenario are validated through assessment of computational results against current knowledge on the impact of hypertension on the cardiovascular system.
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Affiliation(s)
- Morena Celant
- Department of Mathematics, University of Trento, Trento, Italy
| | - Eleuterio F Toro
- Laboratory of Applied Mathematics, DICAM, University of Trento, Trento, Italy
| | - Giulia Bertaglia
- Department of Environmental and Prevention Sciences, University of Ferrara, Ferrara, Italy
| | - Susanna Cozzio
- U.O. di Medicina Interna, Ospedale di Rovereto, Azienda Sanitaria per i Servizi Provinciali di Trento, Trento, Italy
| | - Valerio Caleffi
- Department of Engineering, University of Ferrara, Ferrara, Italy
| | | | - Pablo J Blanco
- National Laboratory for Scientific Computing, Petròpolis, Brazil
| | - Lucas O Müller
- Department of Mathematics, University of Trento, Trento, Italy
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4
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Müller LO, Watanabe SM, Toro EF, Feijóo RA, Blanco PJ. An anatomically detailed arterial-venous network model. Cerebral and coronary circulation. Front Physiol 2023; 14:1162391. [PMID: 37435309 PMCID: PMC10332167 DOI: 10.3389/fphys.2023.1162391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 05/22/2023] [Indexed: 07/13/2023] Open
Abstract
In recent years, several works have addressed the problem of modeling blood flow phenomena in veins, as a response to increasing interest in modeling pathological conditions occurring in the venous network and their connection with the rest of the circulatory system. In this context, one-dimensional models have proven to be extremely efficient in delivering predictions in agreement with in-vivo observations. Pursuing the increase of anatomical accuracy and its connection to physiological principles in haemodynamics simulations, the main aim of this work is to describe a novel closed-loop Anatomically-Detailed Arterial-Venous Network (ADAVN) model. An extremely refined description of the arterial network consisting of 2,185 arterial vessels is coupled to a novel venous network featuring high level of anatomical detail in cerebral and coronary vascular territories. The entire venous network comprises 189 venous vessels, 79 of which drain the brain and 14 are coronary veins. Fundamental physiological mechanisms accounting for the interaction of brain blood flow with the cerebro-spinal fluid and of the coronary circulation with the cardiac mechanics are considered. Several issues related to the coupling of arterial and venous vessels at the microcirculation level are discussed in detail. Numerical simulations are compared to patient records published in the literature to show the descriptive capabilities of the model. Furthermore, a local sensitivity analysis is performed, evidencing the high impact of the venous circulation on main cardiovascular variables.
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Affiliation(s)
- Lucas O. Müller
- Department of Mathematics, University of Trento, Trento, Italy
| | - Sansuke M. Watanabe
- Federal University of Agreste de Pernambuco, UFAPE, Garanhuns, Brazil
- National Institute of Science and Technology in Medicine Assisted by Scientific Computing, INCT-MACC, Petrópolis, Brazil
| | - Eleuterio F. Toro
- Laboratory of Applied Mathematics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy
| | - Raúl A. Feijóo
- National Institute of Science and Technology in Medicine Assisted by Scientific Computing, INCT-MACC, Petrópolis, Brazil
- National Laboratory for Scientific Computing, LNCC/MCTI, Petrópolis, Brazil
| | - Pablo J. Blanco
- National Institute of Science and Technology in Medicine Assisted by Scientific Computing, INCT-MACC, Petrópolis, Brazil
- National Laboratory for Scientific Computing, LNCC/MCTI, Petrópolis, Brazil
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5
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Cho S, Lee J, Park SC, Park HS, Lee DH, Lee J. Development of in-vitro pulsatile flow generator for evaluating the performance of hemodialysis catheters. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:044102. [PMID: 38081258 DOI: 10.1063/5.0087584] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 03/21/2023] [Indexed: 12/18/2023]
Abstract
Hemodialysis (HD) using an HD catheter is performed widely on renal failure patients. The catheter was evaluated using the recirculation ratio in pre-clinical status, which is a crucial index indicating its performance. However, pre-clinical in-vivo experiments have limitations: high cost, and ethical issues. Hence, computational and in-vitro methods have been developed as alternatives. However, computational methods require fluid dynamic knowledge, whereas in-vitro experiments are complicated and expensive. In this study, we developed a pulsatile flow generator to mimic blood flow achieving cost effectiveness and user convenience. The device used iterative learning control, achieving blood flow in the superior and inferior vena cava within a 3.3% error. Furthermore, the recirculation ratios were measured based on two insertion directions and two different external pipe materials to evaluate the catheter regarding patients' posture and blood vessel stiffness. The results provide a better understanding of cardiovascular device performance without complicated and costly pre-clinical tests.
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Affiliation(s)
- Seongsu Cho
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jihyeong Lee
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Sun Cheol Park
- Division of Vascular and Transplant Surgery, Department of Surgery, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
| | - Hoon Suk Park
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea
| | - Dae Hee Lee
- Sungwon Medical Co., Ltd., Cheongju 28174, Republic of Korea
| | - Jinkee Lee
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Institute of Quantum Biophysics (IQB), Sungkyunkwan University, Suwon 16419, Republic of Korea
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6
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Li M, Wang J, Huang W, Zhou Y, Song X. Evaluation of hemodynamic effects of different inferior vena cava filter heads using computational fluid dynamics. Front Bioeng Biotechnol 2022; 10:1034120. [PMID: 36299290 PMCID: PMC9589238 DOI: 10.3389/fbioe.2022.1034120] [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: 09/01/2022] [Accepted: 09/26/2022] [Indexed: 11/29/2022] Open
Abstract
Inferior vena cava (IVC) filters are used to prevent pulmonary embolism in patients with deep vein thrombosis for whom anticoagulation is unresponsive. The head is a necessary structure for an Inferior vena cava filter (IVCF) in clinic use. At present, there are various head configurations for IVCFs. However, the effect of head pattern on the hemodynamics of IVCF is still a matter of unclear. In this study, computational fluid dynamics is used to simulate non-Newtonian blood flows around four IVCFs with different heads inside an IVC model, in which the Denali filter with a solid and hooked head is employed as a prototype, and three virtual variants are reconstructed either with a no-hook head or with a through-hole head for comparison. The simulation results show that the through-hole head can effectively avoid the recirculation region and weaken the blood flow stasis closely downstream the IVCF head. The shape change of the filter head has no significant effect on the blood flow acceleration inside the IVCF cone as well as little influence on the wall shear stress (WSS) distribution on the filter wire surface and IVC wall. The structure pattern of filter head greatly affects the flow resistance of its own. However, the flow drag of filter head only occupies a small proportion of the total resistance of IVCF. Therefore, to reduce the flow resistance of an IVCF should optimize its whole structure.
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Affiliation(s)
- Mingrui Li
- School of Energy and Power Engineering, Shandong University, Jinan, China
| | - Jingying Wang
- School of Energy and Power Engineering, Shandong University, Jinan, China
- *Correspondence: Jingying Wang, ; Wen Huang,
| | - Wen Huang
- The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
- *Correspondence: Jingying Wang, ; Wen Huang,
| | - Yue Zhou
- School of Aeronautical Science and Engineering, Beihang University, Beijing, China
| | - Xue Song
- School of Energy and Power Engineering, Shandong University, Jinan, China
- Jinan Central Hospital, Jinan, China
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7
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Hong SG, Shin J, Aldokhayyil M, Brown MD, Park JY. Mitochondrial and Metabolic Adaptations to Exercise-Induced Fluid Shear Stress in Endothelial Cells. Exerc Sport Sci Rev 2022; 50:145-155. [PMID: 35152237 PMCID: PMC9203873 DOI: 10.1249/jes.0000000000000289] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent studies have greatly advanced our understanding of the central role of mitochondria on endothelial function. Here, we propose a hypothesis that unidirectional laminar (pulsatile) flow and disturbed laminar (oscillatory) flow may differentially modulate mitochondrial phenotypes in the context of their bioenergetic, signaling, and biosynthetic functions, providing novel insights into subcellular mechanisms underlying how exercise benefits the improvement of vascular health.
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Affiliation(s)
- Soon-Gook Hong
- Department of Kinesiology & Cardiovascular Research Center, Temple University, Philadelphia, PA
| | - Junchul Shin
- Department of Kinesiology & Cardiovascular Research Center, Temple University, Philadelphia, PA
| | | | | | - Joon-Young Park
- Department of Kinesiology & Cardiovascular Research Center, Temple University, Philadelphia, PA
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8
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Johnson A, Cupp G, Armour N, Warren K, Stone C, Lee D, Gilbert N, Hammond C, Moore J, Kang YA. An Inexpensive Cardiovascular Flow Simulator for Cardiac Catheterization Procedure Using a Pulmonary Artery Catheter. FRONTIERS IN MEDICAL TECHNOLOGY 2022; 3:764007. [PMID: 35047963 PMCID: PMC8757711 DOI: 10.3389/fmedt.2021.764007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/06/2021] [Indexed: 11/20/2022] Open
Abstract
Cardiac catheterization associated with central vein cannulation can involve potential thrombotic and infectious complications due to multiple cannulation trials or improper placement. To minimize the risks, medical simulators are used for training. Simulators are also employed to test medical devices such as catheters before performing animal tests because they are more cost-effective and still reveal necessary improvements. However, commercial simulators are expensive, simplified for their purpose, and provide limited access sites. Inexpensive and anatomical cardiovascular simulators with central venous access for cannulation are sparse. Here, we developed an anatomically and physiologically accurate cardiovascular flow simulator to help train medical professionals and test medical devices. Our simulator includes an anatomical right atrium/ventricle, femoral and radial access sites, and considers the variability of arm position. It simulates physiological pulsatile blood flow with a setting for constant flow from 3 to 6 L/min and mimics physiological temperature (37°C). We demonstrated simulation by inserting a catheter into the system at radial/femoral access sites, passing it through the vasculature, and advancing it into the heart. We expect that our simulator can be used as an educational tool for cardiac catheterization as well as a testing tool that will allow for design iteration before moving to animal trials.
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Affiliation(s)
- Annika Johnson
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | - Grace Cupp
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | - Nicholas Armour
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | - Kyle Warren
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | - Christopher Stone
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | - Davin Lee
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | - Nicholas Gilbert
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
| | | | - John Moore
- TZ Medical Inc, Portland, OR, United States
| | - Youngbok Abraham Kang
- Department of Mechanical, Civil, and Biomedical Engineering, George Fox University, Newberg, OR, United States
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9
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Toro EF, Celant M, Zhang Q, Contarino C, Agarwal N, Linninger A, Müller LO. Cerebrospinal fluid dynamics coupled to the global circulation in holistic setting: Mathematical models, numerical methods and applications. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2022; 38:e3532. [PMID: 34569188 PMCID: PMC9285081 DOI: 10.1002/cnm.3532] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 09/13/2021] [Indexed: 06/13/2023]
Abstract
This paper presents a mathematical model of the global, arterio-venous circulation in the entire human body, coupled to a refined description of the cerebrospinal fluid (CSF) dynamics in the craniospinal cavity. The present model represents a substantially revised version of the original Müller-Toro mathematical model. It includes one-dimensional (1D), non-linear systems of partial differential equations for 323 major blood vessels and 85 zero-dimensional, differential-algebraic systems for the remaining components. Highlights include the myogenic mechanism of cerebral blood regulation; refined vasculature for the inner ear, the brainstem and the cerebellum; and viscoelastic, rather than purely elastic, models for all blood vessels, arterial and venous. The derived 1D parabolic systems of partial differential equations for all major vessels are approximated by hyperbolic systems with stiff source terms following a relaxation approach. A major novelty of this paper is the coupling of the circulation, as described, to a refined description of the CSF dynamics in the craniospinal cavity, following Linninger et al. The numerical solution methodology employed to approximate the hyperbolic non-linear systems of partial differential equations with stiff source terms is based on the Arbitrary DERivative Riemann problem finite volume framework, supplemented with a well-balanced formulation, and a local time stepping procedure. The full model is validated through comparison of computational results against published data and bespoke MRI measurements. Then we present two medical applications: (i) transverse sinus stenoses and their relation to Idiopathic Intracranial Hypertension; and (ii) extra-cranial venous strictures and their impact in the inner ear circulation, and its implications for Ménière's disease.
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Affiliation(s)
| | - Morena Celant
- Department of MathematicsUniversity of TrentoTrentoItaly
| | - Qinghui Zhang
- Laboratory of Applied Mathematics, DICAMUniversity of TrentoTrentoItaly
| | | | | | - Andreas Linninger
- Department of BioengineeringUniversity of Illinois at ChicagoChicagoIllinoisUSA
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10
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Chies AB, Spadella MA, de Oliveira PR, Domeniconi RF, de Mello Santos T, Moreira RP, Rosales CB, Casarini DE, Navar LG. Exercise-Induced Modulation of Angiotensin II Responses in Femoral Veins From 2-Kidney-1-Clip Hypertensive Rats. Front Physiol 2021; 12:620438. [PMID: 33897446 PMCID: PMC8058411 DOI: 10.3389/fphys.2021.620438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 03/15/2021] [Indexed: 11/17/2022] Open
Abstract
The present study investigated the angiotensin II (Ang II) responses in rat femoral veins taken from 2-kidney-1clip (2K1C) hypertensive rats at 4 weeks after clipping, as well as the effects of exercise on these responses. In this manner, femoral veins taken from 2K1C rats kept at rest or exposed to acute exercise or to exercise training were challenged with Ang II or endothelin-1 (ET-1) in organ bath. Simultaneously, the presence of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were determined in these preparations by western blotting. In these experiments, femoral veins exhibited subdued Ang II responses. However, after nitric oxide (NO) synthesis blockade, the responses were higher in the femoral veins taken from animals kept at rest [0.137(0.049–0.245); n = 10] than those obtained in trained animals kept at rest [0.008(0.001–0.041); n = 10] or studied after a single bout of exercise [0.001(0.001–0.054); n = 11]. In preparations in which, in addition to NO synthesis, both the local production of prostanoids and the action of ET-1 on type A (ETA) or B (ETB) receptors were inhibited, the differences induced by exercise were no longer observed. In addition, neither ET-1 responses nor the presence of COX-1 and COX-2 in these preparations were modified by the employed exercise protocols. In conclusion, NO maintains Ang II responses reduced in femoral veins of 2K1C animals at rest. However, vasodilator prostanoids as well as other relaxing mechanisms, activated by ETB stimulation, are mobilized by exercise to cooperate with NO in order to maintain controlled Ang II responses in femoral veins.
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Affiliation(s)
| | | | | | | | | | - Roseli Peres Moreira
- Department of Medicine, Nephrology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Carla B Rosales
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States
| | - Dulce Elena Casarini
- Department of Medicine, Nephrology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Luis Gabriel Navar
- Department of Physiology and Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States
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11
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Riley JM, Price NS, Saaid HM, Good BC, Aycock KI, Craven BA, Manning KB. In Vitro Clot Trapping Efficiency of the FDA Generic Inferior Vena Cava Filter in an Anatomical Model: An Experimental Fluid-Structure Interaction Benchmark. Cardiovasc Eng Technol 2021; 12:339-352. [PMID: 33683671 DOI: 10.1007/s13239-021-00524-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 02/08/2021] [Indexed: 11/24/2022]
Abstract
PURPOSE Robust experimental data for performing validation of fluid-structure interaction (FSI) simulations of the transport of deformable solid bodies in internal flow are currently lacking. This in vitro experimental study characterizes the clot trapping efficiency of a new generic conical-type inferior vena cava (IVC) filter in a rigid anatomical model of the IVC with carefully characterized test conditions, fluid rheological properties, and clot mechanical properties. METHODS Various sizes of spherical and cylindrical clots made of synthetic materials (nylon and polyacrylamide gel) and bovine blood are serially injected into the anatomical IVC model under worst-case exercise flow conditions. Clot trapping efficiencies and their uncertainties are then quantified for each combination of clot shape, size, and material. RESULTS Experiments reveal the clot trapping efficiency increases with increasing clot diameter and length, with trapping efficiencies ranging from as low as approximately 42% for small 3.2 mm diameter spherical clots up to 100% for larger clot sizes. Because of the asymmetry of the anatomical IVC model, the data also reveal the iliac vein of clot origin influences the clot trapping efficiency, with the trapping efficiency for clots injected into the left iliac vein up to a factor of 7.5 times greater than that for clots injected into the right iliac (trapping efficiencies of approximately 10% versus 75%, respectively). CONCLUSION Overall, this data set provides a benchmark for validating simulations predicting IVC filter clot trapping efficiency and, more generally, low-Reynolds number FSI modeling.
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Affiliation(s)
- J M Riley
- Department of Biomedical Engineering, The Pennsylvania State University, 122 Chemical and Biomedical Engineering Building, University Park, PA, 16802, USA
| | - N S Price
- Department of Biomedical Engineering, The Pennsylvania State University, 122 Chemical and Biomedical Engineering Building, University Park, PA, 16802, USA
| | - H M Saaid
- Department of Biomedical Engineering, The Pennsylvania State University, 122 Chemical and Biomedical Engineering Building, University Park, PA, 16802, USA
| | - B C Good
- Department of Biomedical Engineering, The Pennsylvania State University, 122 Chemical and Biomedical Engineering Building, University Park, PA, 16802, USA
| | - K I Aycock
- Division of Applied Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD, USA
| | - B A Craven
- Division of Applied Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD, USA
| | - K B Manning
- Department of Biomedical Engineering, The Pennsylvania State University, 122 Chemical and Biomedical Engineering Building, University Park, PA, 16802, USA. .,Department of Surgery, Penn State Hershey Medical Center, Hershey, PA, USA.
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12
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Roux E, Bougaran P, Dufourcq P, Couffinhal T. Fluid Shear Stress Sensing by the Endothelial Layer. Front Physiol 2020; 11:861. [PMID: 32848833 PMCID: PMC7396610 DOI: 10.3389/fphys.2020.00861] [Citation(s) in RCA: 137] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 06/26/2020] [Indexed: 12/21/2022] Open
Abstract
Blood flow produces mechanical frictional forces, parallel to the blood flow exerted on the endothelial wall of the vessel, the so-called wall shear stress (WSS). WSS sensing is associated with several vascular pathologies, but it is first a physiological phenomenon. Endothelial cell sensitivity to WSS is involved in several developmental and physiological vascular processes such as angiogenesis and vascular morphogenesis, vascular remodeling, and vascular tone. Local conditions of blood flow determine the characteristics of WSS, i.e., intensity, direction, pulsatility, sensed by the endothelial cells that, through their effect of the vascular network, impact WSS. All these processes generate a local-global retroactive loop that determines the ability of the vascular system to ensure the perfusion of the tissues. In order to account for the physiological role of WSS, the so-called shear stress set point theory has been proposed, according to which WSS sensing acts locally on vessel remodeling so that WSS is maintained close to a set point value, with local and distant effects of vascular blood flow. The aim of this article is (1) to review the existing literature on WSS sensing involvement on the behavior of endothelial cells and its short-term (vasoreactivity) and long-term (vascular morphogenesis and remodeling) effects on vascular functioning in physiological condition; (2) to present the various hypotheses about WSS sensors and analyze the conceptual background of these representations, in particular the concept of tensional prestress or biotensegrity; and (3) to analyze the relevance, explanatory value, and limitations of the WSS set point theory, that should be viewed as dynamical, and not algorithmic, processes, acting in a self-organized way. We conclude that this dynamic set point theory and the biotensegrity concept provide a relevant explanatory framework to analyze the physiological mechanisms of WSS sensing and their possible shift toward pathological situations.
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Affiliation(s)
- Etienne Roux
- Inserm, UMR 1034, Biology of Cardiovascular Diseases, University of Bordeaux, Bordeaux, France.,UMR 8560 IHPST - Institut d'Histoire et de Philosophie des Sciences et des Techniques, CNRS, Université Paris 1 Panthéon-Sorbonne, Paris, France
| | - Pauline Bougaran
- Inserm, UMR 1034, Biology of Cardiovascular Diseases, University of Bordeaux, Bordeaux, France
| | - Pascale Dufourcq
- Inserm, UMR 1034, Biology of Cardiovascular Diseases, University of Bordeaux, Bordeaux, France
| | - Thierry Couffinhal
- Inserm, UMR 1034, Biology of Cardiovascular Diseases, University of Bordeaux, Bordeaux, France
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13
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Macdonald JA, Beshish AG, Corrado PA, Barton GP, Goss KN, Eldridge MW, François CJ, Wieben O. Feasibility of Cardiovascular Four-dimensional Flow MRI during Exercise in Healthy Participants. Radiol Cardiothorac Imaging 2020; 2:e190033. [PMID: 32734274 DOI: 10.1148/ryct.2020190033] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 11/04/2019] [Accepted: 12/23/2019] [Indexed: 11/11/2022]
Abstract
Purpose To explore the feasibility of using four-dimensional (4D) flow MRI to quantify blood flow and kinetic energy (KE) in the heart during strenuous exercise. Materials and Methods For this prospective study, cardiac 4D flow MRI was performed in 11 healthy young adult participants (eight men, three women; mean age, 26 years ± 1 [standard deviation]) at rest and during exercise with an MRI-compatible exercise stepper between March 2016 and July 2017. Flow was measured in the ascending aorta (AAo) and main pulmonary artery (MPA). KE was quantified in the left and right ventricle. Significant changes in flow and KE during exercise were identified by using t tests. Repeatability was assessed with inter- and intraobserver comparisons and an analysis of internal flow consistency. Results Nine participants successfully completed both rest and exercise imaging. Internal flow consistency analysis in systemic and pulmonary circulation showed average relative differences of 10% at rest and 16% during exercise. For flow measurements in the AAo and MPA, relative differences between observers never exceeded 6% in any vessel and showed excellent correlation, even during exercise. Relative differences were increased for KE, typically on the order of 30%, with poor interobserver correlation between measurements. Conclusion Four-dimensional flow MRI can quantify increases in flow in the AAo and MPA during strenuous exercise and is highly repeatable. KE had reduced repeatability because of suboptimal segmentation methods and requires further development before clinical implementation. Supplemental material is available for this article. © RSNA, 2020See also the commentary by Markl and Lee in this issue.
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Affiliation(s)
- Jacob A Macdonald
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Arij G Beshish
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Philip A Corrado
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Gregory P Barton
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Kara N Goss
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Marlowe W Eldridge
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Christopher J François
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
| | - Oliver Wieben
- Departments of Medical Physics (J.A.M., P.A.C., O.W.), Pediatrics (A.G.B., G.P.B., K.N.G., M.W.E.), Medicine (K.N.G.), Biomedical Engineering (M.W.E., O.W.), and Radiology (C.J.F., O.W.), University of Wisconsin, 1111 Highland Ave, Room 1005, Madison, WI 53705
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14
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Joseph AA, Voit D, Frahm J. Inferior vena cava revisited - Real-time flow MRI of respiratory maneuvers. NMR IN BIOMEDICINE 2020; 33:e4232. [PMID: 31913551 DOI: 10.1002/nbm.4232] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 11/05/2019] [Accepted: 11/07/2019] [Indexed: 06/10/2023]
Abstract
Recent MRI studies of blood flow in the inferior vena cava (IVC) resulted in findings which are inconsistent with earlier observations by invasive procedures - most likely because ECG-gated MRI techniques are unable to resolve dynamic adjustments due to respiration. The purpose of this work was to apply real-time phase-contrast MRI at 50 ms resolution to re-evaluate IVC flow in response to normal and deep breathing as well as breath holding and Valsalva maneuver (11 young healthy subjects). Real-time flow MRI relied on highly undersampled radial gradient-echo sequences and a model-based nonlinear inverse reconstruction. A frequency analysis of the predominant pulsatility classified IVC flow in individual subjects as "cardiac", "respiratory" or "mixed" type. Peak flow velocities during free breathing ranged from 30 to 58 cm s-1 , while flow rates varied from 15 to 37 ml s-1 . The subject-specific IVC flow pattern persists during deep breathing although the enhanced respiratory influence may shift subjects form "cardiac" to "mixed" or from "mixed" to "respiratory" type. Peak velocities increased relative to normal breathing but led to similar flow rates of 16 to 34 ml s-1 . Inspiration during deep breathing elicited brief periods of flow reversal in all subjects with mean peak velocities of -21 cm s-1 . The observation of only mildly flattened parabolic velocity distributions within the IVC indicated mostly laminar flow. Breath holding reduced blood flow velocities and rates by more than 40% on average, while Valsalva maneuvers completely abolished venous return. In conclusion, IVC blood flow is dominated by the acquired respiratory behavior of individual subjects and its pressure-induced alterations relative to cardiac pulsation. The responses to breath holding and Valsalva maneuver are in full agreement with previous invasive observations of reduced or even ceased flow, respectively.
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Affiliation(s)
- Arun A Joseph
- Biomedizinische NMR, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
| | - Dirk Voit
- Biomedizinische NMR, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
| | - Jens Frahm
- Biomedizinische NMR, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Germany
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15
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Gallagher MB, Aycock KI, Craven BA, Manning KB. Steady Flow in a Patient-Averaged Inferior Vena Cava-Part I: Particle Image Velocimetry Measurements at Rest and Exercise Conditions. Cardiovasc Eng Technol 2018; 9:641-653. [PMID: 30411228 PMCID: PMC10508872 DOI: 10.1007/s13239-018-00390-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 10/19/2018] [Indexed: 12/23/2022]
Abstract
PURPOSE Although many previous computational fluid dynamics (CFD) studies have investigated the hemodynamics in the inferior vena cava (IVC), few studies have compared computational predictions to experimental data, and only qualitative comparisons have been made. Herein, we provide particle image velocimetry (PIV) measurements of flow in a patient-averaged IVC geometry under idealized conditions typical of those used in the preclinical evaluation of IVC filters. METHODS Measurements are acquired under rest and exercise flow rate conditions in an optically transparent model fabricated using 3D printing. To ensure that boundary conditions are well-defined and to make follow-on CFD validation studies more convenient, fully-developed flow is provided at the inlets (i.e., the iliac veins) by extending them with straight rigid tubing longer than the estimated entrance lengths. Velocity measurements are then obtained at the downstream end of the tubing to confirm Poiseuille inflow boundary conditions. RESULTS Measurements in the infrarenal IVC reveal that flow profiles are blunter in the sagittal plane (minor axis) than in the coronal plane (major axis). Peak in-plane velocity magnitudes are 4.9 cm/s and 27 cm/s under the rest and exercise conditions, respectively. Flow profiles are less parabolic and exhibit more inflection points at the higher flow rate. Bimodal velocity peaks are also observed in the sagittal plane at the elevated flow condition. CONCLUSIONS The IVC geometry, boundary conditions, and infrarenal velocity measurements are provided for download on a free and publicly accessible repository at https://doi.org/10.6084/m9.figshare.7198703 . These data will facilitate future CFD validation studies of idealized, in vitro IVC hemodynamics and of similar laminar flows in vascular geometries.
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Affiliation(s)
- Maureen B Gallagher
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, USA
| | - Kenneth I Aycock
- Division of Applied Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD, USA
| | - Brent A Craven
- Division of Applied Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD, USA
| | - Keefe B Manning
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA, USA.
- Department of Surgery, Penn State Hershey Medical Center, Hershey, PA, USA.
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16
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López JM, Fortuny G, Puigjaner D, Herrero J, Marimon F. A comparative CFD study of four inferior vena cava filters. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018; 34:e2990. [PMID: 29603681 DOI: 10.1002/cnm.2990] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 03/20/2018] [Accepted: 03/20/2018] [Indexed: 06/08/2023]
Abstract
Computational fluid dynamics was used to simulate the flow of blood within an inferior vena cava (IVC) geometry model that was reconstructed from computed tomography images obtained from a real patient. The main novelty of the present work is that we simulated the implantation of 4 different filter models in this realistic IVC geometry. We considered different blood flow rates in the range between Vin =20 and Vin =80 cm3 /s, and all simulations were performed with both the Newtonian and a non-Newtonian model for the blood viscosity. We compared the hemodynamics performance of the different filter models, and we paid a special attention to the total drag force, Fd , exerted by the blood flow on the filter surface. This force is the sum of 2 contributions: the viscous skin friction force, which was found to be roughly proportional to the filter surface area, and the pressure force, which depended on the particular filter geometry design. The Fd force is relevant because it must be balanced by the total force exerted by the filter hooks/struts on the IVC wall at the attachment locations. For the highest Vin value investigated, the variation in Fd among filters was from 116 to 308 dyne. We also showed how the present results can be extrapolated to obtain good estimates of the drag forces if the blood viscosity levels change, ie, if the patient with a filter implanted is treated with anticoagulant therapy.
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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, Tarragona, Catalunya, Spain
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17
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An experimental and computational study of the inferior vena cava hemodynamics under respiratory-induced collapse of the infrarenal IVC. Med Eng Phys 2018; 54:44-55. [DOI: 10.1016/j.medengphy.2018.02.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 12/30/2017] [Accepted: 02/11/2018] [Indexed: 12/27/2022]
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18
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Computational predictions of the embolus-trapping performance of an IVC filter in patient-specific and idealized IVC geometries. Biomech Model Mechanobiol 2017; 16:1957-1969. [DOI: 10.1007/s10237-017-0931-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 06/13/2017] [Indexed: 12/15/2022]
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19
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Nicolás M, Lucea B, Laborda A, Peña E, De Gregorio MA, Martínez MA, Malvè M. Influence of a Commercial Antithrombotic Filter on the Caval Blood Flow During Neutra and Valsalva Maneuver. J Med Device 2017. [DOI: 10.1115/1.4035983] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Anticoagulants are the treatment of choice for pulmonary embolism. When these fail or are contraindicated, vena cava filters are effective devices for preventing clots from the legs from migrating to the lung. Many uncertainties exist when a filter is inserted, especially during physiological activity such as normal breathing and the Valsalva maneuver. These activities are often connected with filter migration and vena cava damage due to the various related vein geometrical configurations. In this work, we analyzed the response of the vena cava during normal breathing and Valsalva maneuver, for a healthy vena cava and after insertion of a commercial Günther-Tulip® filter. Validated computational fluid dynamics (CFD) and patient specific data are used for analyzing blood flow inside the vena cava during these maneuvers. While during normal breathing, the vena cava flow can be considered almost stationary with a very low pressure gradient, during Valsalva the extravascular pressure compresses the vena cava resulting in a drastic reduction of the vein section, a global flow decrease through the cava but increasing the velocity magnitude. This change in the section is altered by the presence of the filter which forces the section of the vena cava before the renal veins to keep open. The effect of the presence of the filter is investigated during these maneuvers showing changes in wall shear stress and velocity patterns.
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Affiliation(s)
- M. Nicolás
- Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna s/n, Zaragoza E-50018, Spain
| | - B. Lucea
- Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna s/n, Zaragoza E-50018, Spain
| | - A. Laborda
- Grupo de Investigación Técnicas de Mínima Invasión (GITMI), Faculty of Veterinary, Universidad de Zaragoza, C/Miguel Servet 177, Zaragoza E-50013, Spain
| | - E. Peña
- Centro de Investigación Biomédica en Red en Bioingeniería Biomateriales y Nanomedicina (CIBER-BBN), Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna s/n, Zaragoza E-50018, Spain
| | - M. A. De Gregorio
- Grupo de Investigación Técnicas de Mínima Invasión (GITMI), Faculty of Veterinary, Universidad de Zaragoza, C/Miguel Servet 177, Zaragoza E-50013, Spain
| | - M. A. Martínez
- Centro de Investigación Biomédica en Red en Bioingeniería Biomateriales y Nanomedicina (CIBER-BBN), Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna s/n, Zaragoza E-50018, Spain
| | - M. Malvè
- Department of Mechanical Engineering, Energetics and Materials, Public University of Navarra, Campus Arrosadía, Pamplona E-36001, Spain; Centro de Investigación Biomédica en Red en Bioingeniería Biomateriales y Nanomedicina (CIBER-BBN), Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna s/n, Zaragoza E-50018, Spain e-mail:
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20
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Yeon JH, Mazinani N, Schlappi TS, Chan KYT, Baylis JR, Smith SA, Donovan AJ, Kudela D, Stucky GD, Liu Y, Morrissey JH, Kastrup CJ. Localization of Short-Chain Polyphosphate Enhances its Ability to Clot Flowing Blood Plasma. Sci Rep 2017; 7:42119. [PMID: 28186112 PMCID: PMC5301195 DOI: 10.1038/srep42119] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/04/2017] [Indexed: 11/09/2022] Open
Abstract
Short-chain polyphosphate (polyP) is released from platelets upon platelet activation, but it is not clear if it contributes to thrombosis. PolyP has increased propensity to clot blood with increased polymer length and when localized onto particles, but it is unknown whether spatial localization of short-chain polyP can accelerate clotting of flowing blood. Here, numerical simulations predicted the effect of localization of polyP on clotting under flow, and this was tested in vitro using microfluidics. Synthetic polyP was more effective at triggering clotting of flowing blood plasma when localized on a surface than when solubilized in solution or when localized as nanoparticles, accelerating clotting at 10-200 fold lower concentrations, particularly at low to sub-physiological shear rates typical of where thrombosis occurs in large veins or valves. Thus, sub-micromolar concentrations of short-chain polyP can accelerate clotting of flowing blood plasma under flow at low to sub-physiological shear rates. However, a physiological mechanism for the localization of polyP to platelet or vascular surfaces remains unknown.
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Affiliation(s)
- Ju Hun Yeon
- Michael Smith Laboratories and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Nima Mazinani
- Michael Smith Laboratories and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Travis S Schlappi
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Karen Y T Chan
- Michael Smith Laboratories and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - James R Baylis
- Michael Smith Laboratories and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Stephanie A Smith
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Alexander J Donovan
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Damien Kudela
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Galen D Stucky
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Ying Liu
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - James H Morrissey
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Christian J Kastrup
- Michael Smith Laboratories and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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21
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Chies AB, de Oliveira PB, Rossignoli PDS, Baptista RDFF, de Lábio RW, Payão SLM. Prostanoids counterbalance the synergism between endothelin-1 and angiotensin II in mesenteric veins of trained rats. Peptides 2017; 88:67-73. [PMID: 28012855 DOI: 10.1016/j.peptides.2016.12.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 12/15/2016] [Accepted: 12/20/2016] [Indexed: 11/30/2022]
Abstract
Exercise-induced adaptations of the modulating mechanisms that influence the angiotensin (Ang II) responses assume different features depending on the venous bed. In femoral veins, exercise mobilizes vasodilator prostanoids to cooperate with NO in order to maintain reduced Ang II responses. On the other hand, exercise's influence on the Ang II responses in veins that drain blood from the mesenteric region has been poorly described. Therefore, the present study aimed to identify the effects of a single bout of exercise, as well as exercise training, on the Ang II responses in mesenteric veins. The present study also aimed to investigate the involvement of prostanoids, NO and ET-1 in eventual exercise-induced modifications in these veins. To this end, mesenteric veins taken from resting-sedentary, exercised-sedentary, resting-trained and exercised-trained animals were studied in organ baths. In addition, the mRNA expression of prepro-endothelin-1 (ppET-1), as well as that of the ETA and ETB receptors, were quantified by real-time PCR in these veins. The results show that, either in absence or in presence of L-NAME, the Ang II responses were not different between groups. In the presence of indomethacin, higher Ang II responses were observed in the resting-trained animals than in the resting-sedentary animals. This difference, however, disappeared when L-NAME, BQ-123 or BQ-788 were added during incubation. In addition, no differences in ppET-1, ETA or ETB mRNA expression were observed between groups. Furthermore, in the presence of PD123,319, the Ang II responses in the exercised-sedentary animals were higher than those in the resting-sedentary animals. In conclusion, exercise training mobilizes endothelin-1 (ET-1) to reinforce the Ang II-induced responses mainly through ETA activation. On the other hand, vasodilator prostanoids are mobilized to act in parallel with NO in order to counterbalance the Ang II responses that have been potentiated by ET-1 in these trained animals.
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22
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Badiei N, Sowedan AM, Curtis DJ, Brown MR, Lawrence MJ, Campbell AI, Sabra A, Evans PA, Weisel JW, Chernysh IN, Nagaswami C, Williams PR, Hawkins K. Effects of unidirectional flow shear stresses on the formation, fractal microstructure and rigidity of incipient whole blood clots and fibrin gels. Clin Hemorheol Microcirc 2016; 60:451-64. [PMID: 25624413 PMCID: PMC4923731 DOI: 10.3233/ch-151924] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Incipient clot formation in whole blood and fibrin gels was studied by the rheometric techniques of controlled stress parallel superposition (CSPS) and small amplitude oscillatory shear (SAOS). The effects of unidirectional shear stress on incipient clot microstructure, formation kinetics and elasticity are reported in terms of the fractal dimension (df) of the fibrin network, the gel network formation time (TGP) and the shear elastic modulus, respectively. The results of this first haemorheological application of CSPS reveal the marked sensitivity of incipient clot microstructure to physiologically relevant levels of shear stress, these being an order of magnitude lower than have previously been studied by SAOS. CSPS tests revealed that exposure of forming clots to increasing levels of shear stress produces a corresponding elevation in df, consistent with the formation of tighter, more compact clot microstructures under unidirectional flow. A corresponding increase in shear elasticity was recorded. The scaling relationship established between shear elasticity and df for fibrin clots and whole blood confirms the fibrin network as the dominant microstructural component of the incipient clot in terms of its response to imposed stress. Supplementary studies of fibrin clot formation by rheometry and microscopy revealed the substantial additional network mass required to increase df and provide evidence to support the hypothesis that microstructural changes in blood clotted under unidirectional shear may be attributed to flow enhanced thrombin generation and activation. CSPS also identified a threshold value of unidirectional shear stress above which no incipient clot formation could be detected. CSPS was shown to be a valuable haemorheological tool for the study of the effects of physiological and pathological levels of shear on clot properties.
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Affiliation(s)
- N Badiei
- College of Engineering, Swansea University, Swansea, UK
| | - A M Sowedan
- College of Engineering, Swansea University, Swansea, UK.,College of Medicine, Swansea University, Swansea, UK
| | - D J Curtis
- College of Engineering, Swansea University, Swansea, UK
| | - M R Brown
- College of Engineering, Swansea University, Swansea, UK
| | - M J Lawrence
- College of Medicine, Swansea University, Swansea, UK.,NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK
| | - A I Campbell
- College of Engineering, Swansea University, Swansea, UK
| | - A Sabra
- College of Medicine, Swansea University, Swansea, UK.,NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK
| | - P A Evans
- College of Medicine, Swansea University, Swansea, UK.,NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK
| | - J W Weisel
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - I N Chernysh
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - C Nagaswami
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - P R Williams
- College of Engineering, Swansea University, Swansea, UK
| | - K Hawkins
- College of Medicine, Swansea University, Swansea, UK.,NISCHR Clinical Haemostasis and Biomarker Research Unit, ABMU NHS Trust Hospital, Morriston, Swansea, UK
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23
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Aycock KI, Campbell RL, Manning KB, Craven BA. A resolved two-way coupled CFD/6-DOF approach for predicting embolus transport and the embolus-trapping efficiency of IVC filters. Biomech Model Mechanobiol 2016; 16:851-869. [DOI: 10.1007/s10237-016-0857-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 11/15/2016] [Indexed: 12/27/2022]
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24
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The Importance of Hemorheology and Patient Anatomy on the Hemodynamics in the Inferior Vena Cava. Ann Biomed Eng 2016; 44:3568-3582. [DOI: 10.1007/s10439-016-1663-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/27/2016] [Indexed: 12/26/2022]
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25
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Yu H, Huang GP, Yang Z, Liang F, Ludwig B. The Influence of Normal and Early Vascular Aging on Hemodynamic Characteristics in Cardio- and Cerebrovascular Systems. J Biomech Eng 2016; 138:061002. [DOI: 10.1115/1.4033179] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Indexed: 11/08/2022]
Abstract
Age-associated alterations in cardiovascular structure and function induce cardiovascular disease in elderly subjects. To investigate the effects of normal vascular aging (NVA) and early vascular aging (EVA) on hemodynamic characteristics in the circle of Willis (CoW), a closed-loop one-dimensional computational model was developed based on fluid mechanics in the vascular system. The numerical simulations revealed that higher central pulse pressure and augmentation index (AIx) appear in the EVA subjects due to early arrival of reflected waves, resulted in the increase of cardiac afterload compared with the NVA subjects. Moreover, the hemodynamic characteristics in the CoW show that the EVA subjects in an older age display a higher blood pressure than that of the NVA with a complete CoW. Herein, the increased blood pressure and flow rate coexist in the subjects with an incomplete CoW. In conclusion, the hemodynamic characteristics in the aortic tree and CoW related to aging appear to play an important role in causing cardiovascular and intravascular disease.
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Affiliation(s)
- Hongtao Yu
- Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435 e-mail:
| | - George P. Huang
- Fellow ASME Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435 e-mail:
| | - Zifeng Yang
- Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435 e-mail:
| | - Fuyou Liang
- School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China e-mail:
| | - Bryan Ludwig
- Boonshoft School of Medicine, Wright State University, Dayton, OH 45435
- Department of Neurology—Division of NeuroInterventional Surgery, Wright State University/Premier Health-Clinical Neuroscience Institute, 30 East Apple Street, Dayton, OH 45409 e-mail:
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Roujol S, Basha TA, Weingärtner S, Akçakaya M, Berg S, Manning WJ, Nezafat R. Impact of motion correction on reproducibility and spatial variability of quantitative myocardial T2 mapping. J Cardiovasc Magn Reson 2015; 17:46. [PMID: 26067275 PMCID: PMC4465156 DOI: 10.1186/s12968-015-0141-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 05/01/2015] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND To evaluate and quantify the impact of a novel image-based motion correction technique in myocardial T2 mapping in terms of measurement reproducibility and spatial variability. METHODS Twelve healthy adult subjects were imaged using breath-hold (BH), free breathing (FB), and free breathing with respiratory navigator gating (FB + NAV) myocardial T2 mapping sequences. Fifty patients referred for clinical CMR were imaged using the FB + NAV sequence. All sequences used a T2 prepared (T2prep) steady-state free precession acquisition. In-plane myocardial motion was corrected using an adaptive registration of varying contrast-weighted images for improved tissue characterization (ARCTIC). DICE similarity coefficient (DSC) and myocardial boundary errors (MBE) were measured to quantify the motion estimation accuracy in healthy subjects. T2 mapping reproducibility and spatial variability were evaluated in healthy subjects using 5 repetitions of the FB + NAV sequence with either 4 or 20 T2prep echo times (TE). Subjective T2 map quality was assessed in patients by an experienced reader using a 4-point scale (1-non diagnostic, 4-excellent). RESULTS ARCTIC led to increased DSC in BH data (0.85 ± 0.08 vs. 0.90 ± 0.02, p = 0.007), FB data (0.78 ± 0.13 vs. 0.90 ± 0.21, p < 0.001), and FB + NAV data (0.86 ± 0.05 vs. 0.90 ± 0.02, p = 0.002), and reduced MBE in BH data (0.90 ± 0.40 vs. 0.64 ± 0.19 mm, p = 0.005), FB data (1.21 ± 0.65 vs. 0.63 ± 0.10 mm, p < 0.001), and FB + NAV data (0.81 ± 0.21 vs. 0.63 ± 0.08 mm, p < 0.001). Improved reproducibility (4TE: 5.3 ± 2.5 ms vs. 4.0 ± 1.5 ms, p = 0.016; 20TE: 3.9 ± 2.3 ms vs. 2.2 ± 0.5 ms, p = 0.002), reduced spatial variability (4TE: 12.8 ± 3.5 ms vs. 10.3 ± 2.5 ms, p < 0.001; 20TE: 9.7 ± 3.5 ms vs. 7.5 ± 1.4 ms) and improved subjective score of T2 map quality (3.43 ± 0.79 vs. 3.69 ± 0.55, p < 0.001) were obtained using ARCTIC. CONCLUSIONS The ARCTIC technique substantially reduces spatial mis-alignment among T2-weighted images and improves the reproducibility and spatial variability of in-vivo T2 mapping.
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Affiliation(s)
- Sébastien Roujol
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
| | - Tamer A Basha
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
- Biomedical Engineering Department, Cairo University, Giza, Egypt.
| | - Sebastian Weingärtner
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
- Computer Assisted Clinical Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany.
| | - Mehmet Akçakaya
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
| | - Sophie Berg
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
| | - Warren J Manning
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
- Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
| | - Reza Nezafat
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA, 02215, USA.
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Pflugi S, Roujol S, Akçakaya M, Kawaji K, Foppa M, Heydari B, Goddu B, Kissinger K, Berg S, Manning WJ, Kozerke S, Nezafat R. Accelerated cardiac MR stress perfusion with radial sampling after physical exercise with an MR-compatible supine bicycle ergometer. Magn Reson Med 2014; 74:384-95. [PMID: 25105469 DOI: 10.1002/mrm.25405] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 06/30/2014] [Accepted: 07/22/2014] [Indexed: 12/30/2022]
Abstract
PURPOSE To evaluate the feasibility of accelerated cardiac MR (CMR) perfusion with radial sampling using nonlinear image reconstruction after exercise on an MR-compatible supine bike ergometer. METHODS Eight healthy subjects were scanned on two separate days using radial and Cartesian CMR perfusion sequences in rest and exercise stress perfusion. Four different methods (standard gridding, conjugate gradient SENSE [CG-SENSE], nonlinear inversion with joint estimation of coil-sensitivity profiles [NLINV] and compressed sensing with a total variation constraint [TV]) were compared for the reconstruction of radial data. Cartesian data were reconstructed using SENSE. All images were assessed by two blinded readers in terms of image quality and diagnostic value. RESULTS CG-SENSE and NLINV were scored more favorably than TV (in both rest and stress perfusion cases, P < 0.05) and gridding (for rest perfusion cases, P < 0.05). TV images showed patchy artifacts, which negatively influenced image quality especially in the stress perfusion images acquired with a low number of radial spokes. Although CG-SENSE and NLINV received better scores than Cartesian sampling in both rest and exercise stress perfusion cases, these differences were not statistically significant (P > 0.05). CONCLUSION We have demonstrated the feasibility of accelerated CMR perfusion using radial sampling after physical exercise using a supine bicycle ergometer in healthy subjects. For reconstruction of undersampled radial perfusion, CG-SENSE and NLINV resulted in better image quality than standard gridding or TV reconstruction. Further technical improvements and clinical assessment are needed before using this approach in patients with suspected coronary artery disease.
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Affiliation(s)
- Silvio Pflugi
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.,Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Sébastien Roujol
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Mehmet Akçakaya
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Keigo Kawaji
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Murilo Foppa
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Bobby Heydari
- Department of Medicine, Brigham and Women Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Beth Goddu
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Kraig Kissinger
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Sophie Berg
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Warren J Manning
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.,Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Reza Nezafat
- Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
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Kuo WT, Deso SE, Robertson SW. Vena Tech LGM filter retrieval 16 years after implantation: piecemeal removal by intentional mechanical fracture. J Vasc Interv Radiol 2014; 24:1731-7. [PMID: 24160825 DOI: 10.1016/j.jvir.2013.07.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 07/30/2013] [Accepted: 07/30/2013] [Indexed: 10/26/2022] Open
Abstract
A 48-year-old man presented with symptomatic inferior vena cava (IVC) occlusion from a chronically thrombosed and embedded Vena Tech LGM filter resulting in exercise intolerance from diminished cardiac preload and postthrombotic syndrome from chronic venous insufficiency. The patient was treated using a new PRIME technique--Piecemeal Removal by Intentional MEchanical fracture--to achieve successful filter retrieval 16 years after implantation. Removal of the obstructing filter permitted endovascular IVC recanalization with restoration of venous outflow and alleviation of venous obstructive symptoms. Cardiac preload was restored, allowing the patient to resume long-distance running, and he successfully completed a half-marathon 3 months after treatment.
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Affiliation(s)
- William T Kuo
- Division of Vascular and Interventional Radiology, Department of Radiology, Stanford University Medical Center, 300 Pasteur Dr., H-3651, Stanford, CA 94305-5642.
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Aycock KI, Campbell RL, Manning KB, Sastry SP, Shontz SM, Lynch FC, Craven BA. A Computational Method for Predicting Inferior Vena Cava Filter Performance on a Patient-Specific Basis. J Biomech Eng 2014; 136:1870705. [DOI: 10.1115/1.4027612] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Accepted: 05/08/2014] [Indexed: 12/19/2022]
Abstract
A computational methodology for simulating virtual inferior vena cava (IVC) filter placement and IVC hemodynamics was developed and demonstrated in two patient-specific IVC geometries: a left-sided IVC and an IVC with a retroaortic left renal vein. An inverse analysis was performed to obtain the approximate in vivo stress state for each patient vein using nonlinear finite element analysis (FEA). Contact modeling was then used to simulate IVC filter placement. Contact area, contact normal force, and maximum vein displacements were higher in the retroaortic IVC than in the left-sided IVC (144 mm2, 0.47 N, and 1.49 mm versus 68 mm2, 0.22 N, and 1.01 mm, respectively). Hemodynamics were simulated using computational fluid dynamics (CFD), with four cases for each patient-specific vein: (1) IVC only, (2) IVC with a placed filter, (3) IVC with a placed filter and model embolus, all at resting flow conditions, and (4) IVC with a placed filter and model embolus at exercise flow conditions. Significant hemodynamic differences were observed between the two patient IVCs, with the development of a right-sided jet, larger flow recirculation regions, and lower maximum flow velocities in the left-sided IVC. These results support further investigation of IVC filter placement and hemodynamics on a patient-specific basis.
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Affiliation(s)
- Kenneth I. Aycock
- Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802 e-mail:
| | - Robert L. Campbell
- Department of Mechanical and Nuclear Engineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802
| | - Keefe B. Manning
- Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802
- Department of Surgery, Penn State Hershey Medical Center, Hershey, PA 17033
| | - Shankar P. Sastry
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112
| | - Suzanne M. Shontz
- Department of Mathematics and Statistics, Department of Computer Science and Engineering, Center for Computational Sciences, Graduate Program in Computational Engineering, Mississippi State University, Mississippi State, MS 39762
| | - Frank C. Lynch
- Department of Surgery, Penn State Hershey Medical Center, Hershey, PA 17033
| | - Brent A. Craven
- Department of Mechanical and Nuclear Engineering, Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802 e-mail:
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Willumeit R, Feyerabend F, Huber N. Magnesium degradation as determined by artificial neural networks. Acta Biomater 2013; 9:8722-9. [PMID: 23470548 DOI: 10.1016/j.actbio.2013.02.042] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 01/29/2013] [Accepted: 02/20/2013] [Indexed: 12/16/2022]
Abstract
Magnesium degradation under physiological conditions is a highly complex process in which temperature, the use of cell culture growth medium and the presence of CO2, O2 and proteins can influence the corrosion rate and the composition of the resulting corrosion layer. Due to the complexity of this process it is almost impossible to predict the parameters that are most important and whether some parameters have a synergistic effect on the corrosion rate. Artificial neural networks are a mathematical tool that can be used to approximate and analyse non-linear problems with multiple inputs. In this work we present the first analysis of corrosion data obtained using this method, which reveals that CO2 and the composition of the buffer system play a crucial role in the corrosion of magnesium, whereas O2, proteins and temperature play a less prominent role.
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Robinson RA, Herbertson LH, Sarkar Das S, Malinauskas RA, Pritchard WF, Grossman LW. Limitations of using synthetic blood clots for measuring in vitro clot capture efficiency of inferior vena cava filters. MEDICAL DEVICES-EVIDENCE AND RESEARCH 2013; 6:49-57. [PMID: 23690701 PMCID: PMC3656916 DOI: 10.2147/mder.s42555] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The purpose of this study was first to evaluate the clot capture efficiency and capture location of six currently-marketed vena cava filters in a physiological venous flow loop, using synthetic polyacrylamide hydrogel clots, which were intended to simulate actual blood clots. After observing a measured anomaly for one of the test filters, we redirected the focus of the study to identify the cause of poor clot capture performance for large synthetic hydrogel clots. We hypothesized that the uncharacteristic low clot capture efficiency observed when testing the outlying filter can be attributed to the inadvertent use of dense, stiff synthetic hydrogel clots, and not as a result of the filter design or filter orientation. To study this issue, sheep blood clots and polyacrylamide (PA) synthetic clots were injected into a mock venous flow loop containing a clinical inferior vena cava (IVC) filter, and their captures were observed. Testing was performed with clots of various diameters (3.2, 4.8, and 6.4 mm), length-to-diameter ratios (1:1, 3:1, 10:1), and stiffness. By adjusting the chemical formulation, PA clots were fabricated to be soft, moderately stiff, or stiff with elastic moduli of 805 ± 2, 1696 ± 10 and 3295 ± 37 Pa, respectively. In comparison, the elastic moduli for freshly prepared sheep blood clots were 1690 ± 360 Pa. The outlying filter had a design that was characterized by peripheral gaps (up to 14 mm) between its wire struts. While a low clot capture rate was observed using large, stiff synthetic clots, the filter effectively captured similarly sized sheep blood clots and soft PA clots. Because the stiffer synthetic clots remained straight when approaching the filter in the IVC model flow loop, they were more likely to pass between the peripheral filter struts, while the softer, physiological clots tended to fold and were captured by the filter. These experiments demonstrated that if synthetic clots are used as a surrogate for animal or human blood clots for in vitro evaluation of vena cava filters, the material properties (eg, elastic modulus) and dynamic behavior of the surrogate should first be assessed to ensure that they accurately mimic an actual blood clot within the body.
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Affiliation(s)
- Ronald A Robinson
- Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, USA
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Simmons CS, Petzold BC, Pruitt BL. Microsystems for biomimetic stimulation of cardiac cells. LAB ON A CHIP 2012; 12:3235-48. [PMID: 22782590 DOI: 10.1039/c2lc40308k] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The heart is a complex integrated system that leverages mechanoelectrical signals to synchronize cardiomyocyte contraction and push blood throughout the body. The correct magnitude, timing, and distribution of these signals is critical for proper functioning of the heart; aberrant signals can lead to acute incidents, long-term pathologies, and even death. Due to the heart's limited regenerative capacity and the wide variety of pathologies, heart disease is often studied in vitro. However, it is difficult to accurately replicate the cardiac environment outside of the body. Studying the biophysiology of the heart in vitro typically consists of studying single cells in a tightly controlled static environment or whole tissues in a complex dynamic environment. Micro-electromechanical systems (MEMS) allow us to bridge these two extremes by providing increasing complexity for cell culture without having to use a whole tissue. Here, we carefully describe the electromechanical environment of the heart and discuss MEMS specifically designed to replicate these stimulation modes. Strengths, limitations and future directions of various designs are discussed for a variety of applications.
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Affiliation(s)
- Chelsey S Simmons
- Department of Mechanical Engineering, Stanford University, Stanford, California, USA
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Modeling hemodynamics in an unoccluded and partially occluded inferior vena cava under rest and exercise conditions. Med Biol Eng Comput 2012; 50:277-87. [DOI: 10.1007/s11517-012-0867-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Accepted: 02/06/2012] [Indexed: 01/26/2023]
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Kam KYR, Mari JM, Wigmore TJ. Adjacent central venous catheters can result in immediate aspiration of infused drugs during renal replacement therapy*. Anaesthesia 2011; 67:115-21. [DOI: 10.1111/j.1365-2044.2011.06955.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Weber TF, von Tengg-Kobligk H, Kopp-Schneider A, Ley-Zaporozhan J, Kauczor HU, Ley S. High-resolution phase-contrast MRI of aortic and pulmonary blood flow during rest and physical exercise using a MRI compatible bicycle ergometer. Eur J Radiol 2011; 80:103-8. [DOI: 10.1016/j.ejrad.2010.06.045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 06/22/2010] [Accepted: 06/25/2010] [Indexed: 10/19/2022]
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Pierce IT, Gatehouse PD, Xu XY, Firmin DN. MR phase-contrast velocity mapping methods for measuring venous blood velocity in the deep veins of the calf. J Magn Reson Imaging 2011; 34:634-44. [PMID: 21761470 DOI: 10.1002/jmri.22655] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 04/28/2011] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To evaluate the feasibility of using un-gated, real-time MRI for venous blood velocity mapping in the calf, comparing an interleaved spiral k-space sequence (ISP) against a standard segmented gradient echo sequence (GRE). MATERIALS AND METHODS A flow phantom with a variable flow-rate was scanned using both GRE and ISP sequences for an in vitro comparison. Seven subjects were scanned prone, performing metronome guided breathing, using the (externally triggered) segmented GRE and real-time ISP sequences. The segmented GRE acquisition duration was 2.5 mins (22 guided respiratory cycles) and the ISP sequence ran continuously for 35 s, 4 full guided respiratory cycles. Mean velocity from each of the deep veins was measured and peak mean velocity, peak flow rate and cumulative volume flow over a respiratory cycle compared between sequences. RESULTS The two sequences compared well both in vitro and in vivo. The real-time ISP sequence showed short-term variations in mean velocity superimposed on the respiratory induced flow, which were averaged out using the segmented GRE sequence. CONCLUSION Real-time ISP provides comparable time-averaged flow results to the standard sequence with additional information on real-time flow variations and so could be used for further investigation into venous blood flow in the lower leg.
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Affiliation(s)
- Iain T Pierce
- CMR Unit, National Heart and Lung Institute, Imperial College London, United Kingdom.
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Rahbar E, Mori D, Moore JE. Three-dimensional Analysis of Flow Disturbances Caused by Clots in Inferior Vena Cava Filters. J Vasc Interv Radiol 2011; 22:835-42. [DOI: 10.1016/j.jvir.2010.12.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 04/07/2010] [Accepted: 12/17/2010] [Indexed: 10/18/2022] Open
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Singer MA, Wang SL. Modeling Blood Flow in a Tilted Inferior Vena Cava Filter: Does Tilt Adversely Affect Hemodynamics? J Vasc Interv Radiol 2011; 22:229-35. [DOI: 10.1016/j.jvir.2010.09.032] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 09/12/2010] [Accepted: 09/23/2010] [Indexed: 10/18/2022] Open
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Waters SL, Alastruey J, Beard DA, Bovendeerd PHM, Davies PF, Jayaraman G, Jensen OE, Lee J, Parker KH, Popel AS, Secomb TW, Siebes M, Sherwin SJ, Shipley RJ, Smith NP, van de Vosse FN. Theoretical models for coronary vascular biomechanics: progress & challenges. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 104:49-76. [PMID: 21040741 PMCID: PMC3817728 DOI: 10.1016/j.pbiomolbio.2010.10.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 09/17/2010] [Accepted: 10/06/2010] [Indexed: 01/09/2023]
Abstract
A key aim of the cardiac Physiome Project is to develop theoretical models to simulate the functional behaviour of the heart under physiological and pathophysiological conditions. Heart function is critically dependent on the delivery of an adequate blood supply to the myocardium via the coronary vasculature. Key to this critical function of the coronary vasculature is system dynamics that emerge via the interactions of the numerous constituent components at a range of spatial and temporal scales. Here, we focus on several components for which theoretical approaches can be applied, including vascular structure and mechanics, blood flow and mass transport, flow regulation, angiogenesis and vascular remodelling, and vascular cellular mechanics. For each component, we summarise the current state of the art in model development, and discuss areas requiring further research. We highlight the major challenges associated with integrating the component models to develop a computational tool that can ultimately be used to simulate the responses of the coronary vascular system to changing demands and to diseases and therapies.
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Affiliation(s)
- Sarah L Waters
- Oxford Centre for Industrial and Applied mathematics, Mathematical Institute, 24-29 St Giles', Oxford, OX1 3LB, UK.
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Singer MA, Wang SL, Diachin DP. Design Optimization of Vena Cava Filters: An Application to Dual Filtration Devices. J Biomech Eng 2010; 132:101006. [DOI: 10.1115/1.4002488] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Pulmonary embolism (PE) is a significant medical problem that results in over 300,000 fatalities per year. A common preventative treatment for PE is the insertion of a metallic filter into the inferior vena cava that traps thrombi before they reach the lungs. The goal of this work is to use methods of mathematical modeling and design optimization to determine the configuration of trapped thrombi that minimizes the hemodynamic disruption. The resulting configuration has implications for constructing an optimally designed vena cava filter. Computational fluid dynamics is coupled with a nonlinear optimization algorithm to determine the optimal configuration of a trapped model thrombus in the inferior vena cava. The location and shape of the thrombus are parametrized, and an objective function, based on wall shear stresses, determines the worthiness of a given configuration. The methods are fully automated and demonstrate the capabilities of a design optimization framework that is broadly applicable. Changes to thrombus location and shape alter the velocity contours and wall shear stress profiles significantly. For vena cava filters that trap two thrombi simultaneously, the undesirable flow dynamics past one thrombus can be mitigated by leveraging the flow past the other thrombus. Streamlining the shape of the thrombus trapped along the cava wall reduces the disruption to the flow but increases the area exposed to low wall shear stress. Computer-based design optimization is a useful tool for developing vena cava filters. Characterizing and parametrizing the design requirements and constraints is essential for constructing devices that address clinical complications. In addition, formulating a well-defined objective function that quantifies clinical risks and benefits is needed for designing devices that are clinically viable.
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Affiliation(s)
- Michael A. Singer
- Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, Livermore, CA 94551
| | - Stephen L. Wang
- Division of Vascular and Interventional Radiology, Kaiser Permanente Santa Clara Medical Center, Santa Clara, CA 95051
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Lewis GD, Farrell L, Wood MJ, Martinovic M, Arany Z, Rowe GC, Souza A, Cheng S, McCabe EL, Yang E, Shi X, Deo R, Roth FP, Asnani A, Rhee EP, Systrom DM, Semigran MJ, Vasan RS, Carr SA, Wang TJ, Sabatine MS, Clish CB, Gerszten RE. Metabolic signatures of exercise in human plasma. Sci Transl Med 2010; 2:33ra37. [PMID: 20505214 DOI: 10.1126/scitranslmed.3001006] [Citation(s) in RCA: 301] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Exercise provides numerous salutary effects, but our understanding of how these occur is limited. To gain a clearer picture of exercise-induced metabolic responses, we have developed comprehensive plasma metabolite signatures by using mass spectrometry to measure >200 metabolites before and after exercise. We identified plasma indicators of glycogenolysis (glucose-6-phosphate), tricarboxylic acid cycle span 2 expansion (succinate, malate, and fumarate), and lipolysis (glycerol), as well as modulators of insulin sensitivity (niacinamide) and fatty acid oxidation (pantothenic acid). Metabolites that were highly correlated with fitness parameters were found in subjects undergoing acute exercise testing and marathon running and in 302 subjects from a longitudinal cohort study. Exercise-induced increases in glycerol were strongly related to fitness levels in normal individuals and were attenuated in subjects with myocardial ischemia. A combination of metabolites that increased in plasma in response to exercise (glycerol, niacinamide, glucose-6-phosphate, pantothenate, and succinate) up-regulated the expression of nur77, a transcriptional regulator of glucose utilization and lipid metabolism genes in skeletal muscle in vitro. Plasma metabolic profiles obtained during exercise provide signatures of exercise performance and cardiovascular disease susceptibility, in addition to highlighting molecular pathways that may modulate the salutary effects of exercise.
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Affiliation(s)
- Gregory D Lewis
- Cardiology Division and Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA 02114, USA.
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Chies AB, de Souza Rossignoli P, Daniel EF. Exercise increases the angiotensin II effects in isolated portal vein of trained rats. Peptides 2010; 31:883-8. [PMID: 20172009 DOI: 10.1016/j.peptides.2010.02.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 02/11/2010] [Accepted: 02/12/2010] [Indexed: 12/17/2022]
Abstract
Training in rats adapts the portal vein to respond vigorously to sympathetic stimuli even when the animal is re-exposed to exercise. Moreover, changes in the exercise-induced effects of angiotensin II, a potent venoconstrictor agonist, in venous beds remain to be investigated. Therefore, the present study aimed to assess the effects of angiotensin II in the portal vein and vena cava from sedentary and trained rats at rest or submitted to an exercise session immediately before organ bath experiments. We found that training or exposure of sedentary animals to a single bout of running exercise does not significantly change the responses of the rat portal vein to angiotensin II. However, the exposure of trained animals to a single bout of running exercise enhanced the response of the rat portal vein to angiotensin II. This enhancement appeared to be territory-specific because it was not observed in the vena cava. Moreover, it was not observed in endothelium-disrupted preparations and in preparations treated with N(omega)-nitro-l-arginine methyl ester hydrochloride, indomethacin, BQ-123 or BQ-788. These data indicate that training causes adaptations in the rat portal vein that respond vigorously to angiotensin II even upon re-exposure to exercise. This increased response to angiotensin II requires an enhancement of the vasocontractile influence of endothelin beyond the influence of nitric oxide and vasodilator prostanoids.
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Affiliation(s)
- Agnaldo Bruno Chies
- Laboratory of Pharmacology, Faculty of Medicine of Marília, Av. Monte Carmelo, 800, Fragata, 17 519-030, Marília, SP, Brazil.
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Wang SL, Singer MA. Toward an Optimal Position for Inferior Vena Cava Filters: Computational Modeling of the Impact of Renal Vein Inflow with Celect and TrapEase Filters. J Vasc Interv Radiol 2010; 21:367-74; quiz 374. [DOI: 10.1016/j.jvir.2009.11.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 10/28/2009] [Accepted: 11/11/2009] [Indexed: 10/19/2022] Open
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Wen CY, Yang AS, Tseng LY, Chai JW. Investigation of pulsatile flowfield in healthy thoracic aorta models. Ann Biomed Eng 2009; 38:391-402. [PMID: 19890715 DOI: 10.1007/s10439-009-9835-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Accepted: 10/27/2009] [Indexed: 10/20/2022]
Abstract
Cardiovascular disease is the primary cause of morbidity and mortality in the western world. Complex hemodynamics plays a critical role in the development of aortic dissection and atherosclerosis, as well as many other diseases. Since fundamental fluid mechanics are important for the understanding of the blood flow in the cardiovascular circulatory system of the human body aspects, a joint experimental and numerical study was conducted in this study to determine the distributions of wall shear stress and pressure and oscillatory WSS index, and to examine their correlation with the aortic disorders, especially dissection. Experimentally, the Phase-Contrast Magnetic Resonance Imaging (PC-MRI) method was used to acquire the true geometry of a normal human thoracic aorta, which was readily converted into a transparent thoracic aorta model by the rapid prototyping (RP) technique. The thoracic aorta model was then used in the in vitro experiments and computations. Simulations were performed using the computational fluid dynamic (CFD) code ACE+((R)) to determine flow characteristics of the three-dimensional, pulsatile, incompressible, and Newtonian fluid in the thoracic aorta model. The unsteady boundary conditions at the inlet and the outlet of the aortic flow were specified from the measured flowrate and pressure results during in vitro experiments. For the code validation, the predicted axial velocity reasonably agrees with the PC-MRI experimental data in the oblique sagittal plane of the thoracic aorta model. The thorough analyses of the thoracic aorta flow, WSSs, WSS index (OSI), and wall pressures are presented. The predicted locations of the maxima of WSS and the wall pressure can be then correlated with that of the thoracic aorta dissection, and thereby may lead to a useful biological significance. The numerical results also suggest that the effects of low WSS and high OSI tend to cause wall thickening occurred along the inferior wall of the aortic arch and the anterior wall of the brachiocephalic artery, similar implication reported in a number of previous studies.
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Affiliation(s)
- Chih-Yung Wen
- Department of Aeronautics and Astronautics, National Cheng-Kung University, No. 1 University Road, Tainan City 701, Taiwan, R.O.C.
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Chies AB, de Souza Rossignoli P. Exercise increases the phenylephrine effects in isolated portal vein of trained rats. Vascul Pharmacol 2009; 51:125-32. [DOI: 10.1016/j.vph.2009.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 03/20/2009] [Accepted: 05/28/2009] [Indexed: 10/20/2022]
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Singer MA, Henshaw WD, Wang SL. Computational Modeling of Blood Flow in the TrapEase Inferior Vena Cava Filter. J Vasc Interv Radiol 2009; 20:799-805. [DOI: 10.1016/j.jvir.2009.02.015] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2008] [Revised: 01/31/2009] [Accepted: 02/04/2009] [Indexed: 11/24/2022] Open
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Effects of breath-hold and cardiac cycle on the MRI appearance of the aorta and inferior vena cava in t2 abdominal imaging. AJR Am J Roentgenol 2009; 192:1348-58. [PMID: 19380560 DOI: 10.2214/ajr.08.1646] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The purpose of this article is to review the MR principles of blood signal and normal flow-related phenomena seen in the aorta and inferior vena cava (IVC) on T2-weighted images of the abdomen and to discuss the physiologic and physical basis of signal alterations with breath-hold imaging. We define time-of-flight (TOF) loss and list the factors that affect it; explain the physiologic effects of breath-hold imaging on both aortic and IVC waveforms and velocity; state which abdominal T2 imaging techniques are most susceptible to variable TOF effects and explain why based on physiologic effects and MR principles; and describe three trouble-shooting techniques to confirm that unexpected signal does not reflect pathology. CONCLUSION T2 images customarily result in TOF loss and dark blood signal. Abdominal MRI relies extensively on breath-hold imaging techniques that may alter markedly the flow velocity in normal vessels. This marked flow change results in signal heterogeneity and variable TOF loss especially with faster sequences filling k-space in shorter time frames. Breath-hold imaging decreases k-space fill time, and of the breath-hold T2 techniques, single-shot fast spin-echo decreases k-space fill time the most. Atypical blood signal during breath-hold imaging may mimic pathology, but abnormal findings can be verified by review of other sequences and planes of imaging.
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