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Pretorius D, Kahn-Krell AM, Lou X, Fast VG, Berry JL, Kamp TJ, Zhang J. Layer-By-Layer Fabrication of Large and Thick Human Cardiac Muscle Patch Constructs With Superior Electrophysiological Properties. Front Cell Dev Biol 2021; 9:670504. [PMID: 33937272 PMCID: PMC8086556 DOI: 10.3389/fcell.2021.670504] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 03/29/2021] [Indexed: 02/02/2023] Open
Abstract
Engineered cardiac tissues fabricated from human induced pluripotent stem cells (hiPSCs) show promise for ameliorating damage from myocardial infarction, while also restoring function to the damaged left ventricular (LV) myocardium. For these constructs to reach their clinical potential, they need to be of a clinically relevant volume and thickness, and capable of generating synchronous and forceful contraction to assist the pumping action of the recipient heart. Design prerequisites include a structure thickness sufficient to produce a beneficial contractile force, prevascularization to overcome diffusion limitations and sufficient structural development to allow for maximal cell communication. Previous attempts to meet these prerequisites have been hindered by lack of oxygen and nutrient transport due to diffusion limits (100–200 μm) resulting in necrosis. This study employs a layer-by-layer (LbL) fabrication method to produce cardiac tissue constructs that meet these design prerequisites and mimic normal myocardium in form and function. Thick (>2 mm) cardiac tissues created from hiPSC-derived cardiomyocytes, -endothelial cells (ECs) and -fibroblasts (FBs) were assessed, in vitro, over a 4-week period for viability (<6% necrotic cells), cell morphology and functionality. Functional performance assessment showed enhanced t-tubule network development, gap junction communication as well as previously unseen, physiologically relevant conduction velocities (CVs) (>30 cm/s). These results demonstrate that LbL fabrication can be utilized successfully to create prevascularized, functional cardiac tissue constructs from hiPSCs for potential therapeutic applications.
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Affiliation(s)
- Danielle Pretorius
- Department of Biomedical Engineering, School of Medicine and School of Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Asher M Kahn-Krell
- Department of Biomedical Engineering, School of Medicine and School of Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Xi Lou
- Department of Biomedical Engineering, School of Medicine and School of Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Vladimir G Fast
- Department of Biomedical Engineering, School of Medicine and School of Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Joel L Berry
- Department of Biomedical Engineering, School of Medicine and School of Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Timothy J Kamp
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, United States
| | - Jianyi Zhang
- Department of Biomedical Engineering, School of Medicine and School of Engineering, University of Alabama at Birmingham, Birmingham, AL, United States
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Liu W, Wang Z. Current Understanding of the Biomechanics of Ventricular Tissues in Heart Failure. Bioengineering (Basel) 2019; 7:bioengineering7010002. [PMID: 31861916 PMCID: PMC7175293 DOI: 10.3390/bioengineering7010002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/17/2019] [Accepted: 12/18/2019] [Indexed: 12/17/2022] Open
Abstract
Heart failure is the leading cause of death worldwide, and the most common cause of heart failure is ventricular dysfunction. It is well known that the ventricles are anisotropic and viscoelastic tissues and their mechanical properties change in diseased states. The tissue mechanical behavior is an important determinant of the function of ventricles. The aim of this paper is to review the current understanding of the biomechanics of ventricular tissues as well as the clinical significance. We present the common methods of the mechanical measurement of ventricles, the known ventricular mechanical properties including the viscoelasticity of the tissue, the existing computational models, and the clinical relevance of the ventricular mechanical properties. Lastly, we suggest some future research directions to elucidate the roles of the ventricular biomechanics in the ventricular dysfunction to inspire new therapies for heart failure patients.
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Affiliation(s)
- Wenqiang Liu
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA;
| | - Zhijie Wang
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA;
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA
- Correspondence:
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Paun B, Bijnens B, Butakoff C. Relationship between the left ventricular size and the amount of trabeculations. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018; 34:e2939. [PMID: 29124903 DOI: 10.1002/cnm.2939] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 10/25/2017] [Accepted: 10/26/2017] [Indexed: 06/07/2023]
Abstract
Contemporary imaging modalities offer noninvasive quantification of myocardial deformation; however, they make gross assumptions about internal structure of the cardiac walls. Our aim is to study the possible impact of the trabeculations on the stroke volume, strain, and capacity of differently sized ventricles. The cardiac left ventricle is represented by an ellipsoid and the trabeculations by a tissue occupying a fixed volume. The ventricular contraction is modeled by scaling the ellipsoid whereupon the measurements of longitudinal strain, end-diastolic, end-systolic, and stroke volumes are derived and compared. When the trabeculated and nontrabeculated ventricles, having the same geometry and deformation pattern, contain the same amount of blood and contract with the same strain, we observed an increased stroke volume in our model of the trabeculated ventricle. When these ventricles contain and eject the same amount of blood, we observed a reduced strain in the trabeculated case. We identified that a trade-off between the strain and the amount of trabeculations could be reached with a 0.35- to 0.41-cm dense trabeculated layer, without blood filled recesses (for a ventricle with end-diastolic volume of about 150 mL). A trabeculated ventricle can work at lower strains compared to a nontrabeculated ventricle to produce the same stroke volume, which could be a possible explanation why athletes and pregnant women develop reversible signs of left ventricular noncompaction, since the trabeculations could help generating extra cardiac output. This knowledge might help to assess heart failure patients with dilated cardiomyopathies who often show signs of noncompaction.
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Affiliation(s)
- Bruno Paun
- PhySense, Universitat Pompeu Fabra, Barcelona, Spain
| | - Bart Bijnens
- PhySense, Universitat Pompeu Fabra, Barcelona, Spain
- ICREA, Barcelona, Spain
- KU Leuven, Leuven, Belgium
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Yao J, Varner VD, Brilli LL, Young JM, Taber LA, Perucchio R. Viscoelastic material properties of the myocardium and cardiac jelly in the looping chick heart. J Biomech Eng 2012; 134:024502. [PMID: 22482677 DOI: 10.1115/1.4005693] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Accurate material properties of developing embryonic tissues are a crucial factor in studies of the mechanics of morphogenesis. In the present work, we characterize the viscoelastic material properties of the looping heart tube in the chick embryo through nonlinear finite element modeling and microindentation experiments. Both hysteresis and ramp-hold experiments were performed on the intact heart and isolated cardiac jelly (extracellular matrix). An inverse computational method was used to determine the constitutive relations for the myocardium and cardiac jelly. With both layers assumed to be quasilinear viscoelastic, material coefficients for an Ogden type strain-energy density function combined with Prony series of two terms or less were determined by fitting numerical results from a simplified model of a heart segment to experimental data. The experimental and modeling techniques can be applied generally for determining viscoelastic material properties of embryonic tissues.
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Affiliation(s)
- Jiang Yao
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA.
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Liao D, Lu X, Kirkup AJ, Jiang W, Grundy D, Gregersen H. Interdependency of stress relaxation and afferent nerve discharge in rat small intestine. J Biomech 2012; 45:1574-9. [DOI: 10.1016/j.jbiomech.2012.04.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 01/27/2012] [Accepted: 04/12/2012] [Indexed: 01/13/2023]
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Creep behavior of passive bovine extraocular muscle. J Biomed Biotechnol 2011; 2011:526705. [PMID: 22131809 PMCID: PMC3216464 DOI: 10.1155/2011/526705] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 08/16/2011] [Indexed: 12/01/2022] Open
Abstract
This paper characterized bovine extraocular muscles (EOMs) using creep, which represents long-term stretching induced by a constant force. After preliminary optimization of testing conditions, 20 fresh EOM samples were subjected to four different loading rates of 1.67, 3.33, 8.33, and 16.67%/s, after which creep was observed for 1,500 s. A published quasilinear viscoelastic (QLV) relaxation function was transformed to a creep function that was compared with data. Repeatable creep was observed for each loading rate and was similar among all six anatomical EOMs. The mean creep coefficient after 1,500 seconds for a wide range of initial loading rates was at 1.37 ± 0.03 (standard deviation, SD). The creep function derived from the relaxation-based QLV model agreed with observed creep to within 2.7% following 16.67%/s ramp loading. Measured creep agrees closely with a derived QLV model of EOM relaxation, validating a previous QLV model for characterization of EOM biomechanics.
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Fernández-Golfín C, Pachón M, Corros C, Bustos A, Cabeza B, Ferreirós J, de Isla LP, Macaya C, Zamorano J. Left ventricular trabeculae: quantification in different cardiac diseases and impact on left ventricular morphological and functional parameters assessed with cardiac magnetic resonance. J Cardiovasc Med (Hagerstown) 2010; 10:827-33. [PMID: 19543106 DOI: 10.2459/jcm.0b013e32832e1c60] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVES Left ventricle trabeculae (LVT) are frequently seen in different cardiac diseases. Normal reference values of LVT in different cardiac conditions are not known. The aim of the study was to quantify with cardiac magnetic resonance (CMR), LVT mass (LVTM) and LVTM percentage (LVTM%) in different heart diseases and to evaluate their influence on left ventricular morphological and functional parameters. METHODS Fifty-nine patients (14 controls, 17 ischemic cardiomyopathy, 15 nonischemic dilated cardiomyopathy, 7 valvular heart disease and 6 with left ventricle hypertrophy) were enrolled. Cine-MR images were acquired with steady-state free-precession sequence in a short-axis view. LVTM was calculated as the difference between LVM excluding/including trabecuale from the blood cavity. LVTM% was calculated as the percentage of the whole left ventricle mass excluding trabeculae from the blood cavity. RESULTS Mean age was 47.60 +/- 22.03 years; male 62.7%. Mean LVTM was of 33.38 +/- 16.1 g with mean LVTM% of 19.22 +/- 6.5%. Significant differences between groups for both parameters with P values of 0.02 were obtained. Nonischemic dilated cardiomyopathy showed the highest degree of LVTM (44.73 +/- 16.0 g) and LVTM% (23.26 +/- 6%). Significant differences were noted in left ventricular morphological and functional parameters with inclusion/exclusion of LVT in the myocardial mass. CONCLUSIONS Reference values and differences of LVTM and LVTM% in various cardiac conditions are given for the first time. Quantification of these parameters with CMR may be clinically useful in the differential diagnosis between left ventricular noncompaction and other cardiac diseases. Exclusion of LVT from myocardium alters left ventricular morphological and functional parameters, which have significant clinical importance.
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Yoo L, Kim H, Gupta V, Demer JL. Quasilinear viscoelastic behavior of bovine extraocular muscle tissue. Invest Ophthalmol Vis Sci 2009; 50:3721-8. [PMID: 19357357 DOI: 10.1167/iovs.08-3245] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Until now, there has been no comprehensive mathematical model of the nonlinear viscoelastic stress-strain behavior of extraocular muscles (EOMs). The present study describes, with the use of a quasilinear viscoelastic (QLV) model, the nonlinear, history-dependent viscoelastic properties and elastic stress-strain relationship of EOMs. METHODS Six oculorotary EOMs were obtained fresh from a local abattoir. Longitudinally oriented specimens were taken from different regions of the EOMs and subjected to uniaxial tensile, relaxation, and cyclic loading testing with the use of an automated load cell under temperature and humidity control. Twelve samples were subjected to uniaxial tensile loading with 1.7%/s strain rate until failure. Sixteen specimens were subjected to relaxation studies over 1500 seconds. Cyclic loading was performed to validate predictions of the QLV model characterized from uniaxial tensile loading and relaxation data. RESULTS Uniform and highly repeatable stress-strain behavior was observed for 12 specimens extracted from various regions of all EOMs. Results from 16 different relaxation trials illustrated that most stress relaxation occurred during the first 30 to 60 seconds for 30% extension. Elastic and reduced relaxation functions were fit to the data, from which a QLV model was assembled and compared with cyclic loading data. Predictions of the QLV model agreed with observed peak cyclic loading stress values to within 8% for all specimens and conditions. CONCLUSIONS Close agreement between the QLV model and the relaxation and cyclic loading data validates model quantification of EOM mechanical properties and will permit the development of accurate overall models of mechanics of ocular motility and strabismus.
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Affiliation(s)
- Lawrence Yoo
- Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, CA 90095-7002, USA
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Ramasubramanian A, Nerurkar NL, Achtien KH, Filas BA, Voronov DA, Taber LA. On modeling morphogenesis of the looping heart following mechanical perturbations. J Biomech Eng 2009; 130:061018. [PMID: 19045547 DOI: 10.1115/1.2978990] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Looping is a crucial early phase during heart development, as the initially straight heart tube (HT) deforms into a curved tube to lay out the basic plan of the mature heart. This paper focuses on the first phase of looping, called c-looping, when the HT bends ventrally and twists dextrally (rightward) to create a c-shaped tube. Previous research has shown that bending is an intrinsic process, while dextral torsion is likely caused by external forces acting on the heart. However, the specific mechanisms that drive and regulate looping are not yet completely understood. Here, we present new experimental data and finite element models to help define these mechanisms for the torsional component of c-looping. First, with regions of growth and contraction specified according to experiments on chick embryos, a three-dimensional model exhibits morphogenetic deformation consistent with observations for normal looping. Next, the model is tested further using experiments in which looping is perturbed by removing structures that exert forces on the heart--a membrane (splanchnopleure (SPL)) that presses against the ventral surface of the heart and the left and right primitive atria. In all cases, the model predicts the correct qualitative behavior. Finally, a two-dimensional model of the HT cross section is used to study a feedback mechanism for stress-based regulation of looping. The model is tested using experiments in which the SPL is removed before, during, and after c-looping. In each simulation, the model predicts the correct response. Hence, these models provide new insight into the mechanical mechanisms that drive and regulate cardiac looping.
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Affiliation(s)
- Ashok Ramasubramanian
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA
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A combination of right ventricular hypertrabeculation/noncompaction and arrhythmogenic right ventricular cardiomyopathy: a syndrome? Cardiovasc Ultrasound 2008; 6:63. [PMID: 19105817 PMCID: PMC2631473 DOI: 10.1186/1476-7120-6-63] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Accepted: 12/23/2008] [Indexed: 11/15/2022] Open
Abstract
A combination of ARVC and RV NVM/HVM, which is extremely rare, to our knowledge, is never reported. RV NVM/HVM could be the cause and consequence of ARVC, or RV NVM/HVM and ARVC could be a consequence of a certain undetermined cause. It must be kept in mind, however, that the interaction of NVM/HVM and ARVC could be in part of pathophysiology mechanism of the combination even if as a consequence of an underlying genetic factor.
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Abstract
This article concerns the development of myocardial architecture--crucial for contractile performance of the heart and its conduction system, essential for generation and coordinated spread of electrical activity. Topics discussed include molecular determination of cardiac phenotype (contractile and conducting), remodeling of ventricular wall architecture and its blood supply, and relation of trabecular compaction to noncompaction cardiomyopathy. Illustrated are the structure and function of the tubular heart, time course of trabecular compaction, and development of multilayered spiral systems of the compact layer.
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Affiliation(s)
- David Sedmera
- Institute of Animal Physiology and Genetics, Prague, Czech Republic.
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Tahkola J, Räsänen J, Sund M, Mäkikallio K, Autio-Harmainen H, Pihlajaniemi T. Cardiac dysfunction in transgenic mouse fetuses overexpressing shortened type XIII collagen. Cell Tissue Res 2008; 333:61-9. [PMID: 18481090 DOI: 10.1007/s00441-008-0617-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Accepted: 03/31/2008] [Indexed: 10/22/2022]
Abstract
Overexpression of type XIII collagen molecules with an 83-amino-acid residue in-frame deletion of part of the ectodomain leads to fetal lethality in Col13a1COL2del transgenic mice. We characterize here the functional disturbances in the cardiovascular system of mouse fetuses overexpressing mutant type XIII collagen. Doppler ultrasonography was performed at 12.5 days of gestation on 33 fetuses resulting from heterozygous matings of seven female mice and on 16 fetuses from two matings between heterozygous and wild-type mice. Nine fetuses had atrioventricular valve regurgitation (AVVR), and all of them were transgene-positive. The fetuses with AVVR had a lower outflow mean velocity (Vmean; P<0.005) and a greater proportion of isovolumetric relaxation time (IRT%) in the cardiac cycle (P<0.0001) than those without AVVR, and their ductus venosus pulsatility indices for veins (DV PIV) and the umbilical artery pulsatility indices were increased. A positive correlation was found between IRT% and DV PIV, and a negative correlation was seen between outflow V(mean) and DV PIV. Morphological analysis of the heart revealed no differences between the two groups of fetuses, but histological analysis showed the trabeculation of the ventricles to be reduced and the myocardium to be thinner in the fetuses with AVVR. Based on in situ hybridization, type XIII collagen mRNAs were normal constituents of these structures. Moreover, a positive correlation was found between outflow Vmean and myocardial thickness. IRT% and DV PIV correlated negatively with myocardial thickness. Thus, overexpression of mutant type XIII collagen results in mid-gestation cardiac dysfunction in mouse fetuses, and these disturbances in cardiac function may lead to death in utero.
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Affiliation(s)
- Jenni Tahkola
- Oulu Center to Cell-Matrix Research, Biocenter Oulu, Department of Medical Biochemistry and Molecular Biology, University of Oulu, P. O. Box 5000, 90014, Oulu, Finland
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Schmid H, O'Callaghan P, Nash MP, Lin W, LeGrice IJ, Smaill BH, Young AA, Hunter PJ. Myocardial material parameter estimation: a non-homogeneous finite element study from simple shear tests. Biomech Model Mechanobiol 2007; 7:161-73. [PMID: 17487519 DOI: 10.1007/s10237-007-0083-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Accepted: 03/07/2007] [Indexed: 11/28/2022]
Abstract
The passive material properties of myocardium play a major role in diastolic performance of the heart. In particular, the shear behaviour is thought to play an important mechanical role due to the laminar architecture of myocardium. We have previously compared a number of myocardial constitutive relations with the aim to extract their suitability for inverse material parameter estimation. The previous study assumed a homogeneous deformation. In the present study we relaxed the homogeneous assumption by implementing these laws into a finite element environment in order to obtain more realistic measures for the suitability of these laws in both their ability to fit a given set of experimental data, as well as their stability in the finite element environment. In particular, we examined five constitutive laws and compare them on the basis of (i) "goodness of fit": how well they fit a set of six shear deformation tests, (ii) "determinability": how well determined the objective function is at the optimal parameter fit, and (iii) "variability": how well determined the material parameters are over the range of experiments. Furthermore, we compared the FE results with those from the previous study.It was found that the same material law as in the previous study, the orthotropic Fung-type "Costa-Law", was the most suitable for inverse material parameter estimation for myocardium in simple shear.
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Affiliation(s)
- H Schmid
- Bioengineering Institute, University of Auckland, Auckland, New Zealand.
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Nikolić A, Jovović L. Left ventricular noncompaction: A rarity or something else. VOJNOSANIT PREGL 2007; 64:211-7. [PMID: 17438968 DOI: 10.2298/vsp0703211n] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
<zakljucak> Nedovoljno formiran miokard je atipicna forma kardiomiopatije koju treba poznavati i na koju treba misliti pri rutinskim ehokardiografskim pregledima. Novija istrazivanja ukazuju da LVNC ima vecu prevalenciju zahvaljujuci poboljsanju imaging tehnika. Kako su kriterijumi za dijagnozu LVNC prvenstveno ehokardiografski, potrebno je upoznati lekare koji se bave ultrazvucnim pregledima srca sa osnovnim karkteristikama ovog oboljenja, kako bi ga u buducnosti lakse prepoznali. Nedovoljno formiran miokard je udruzen sa drugim nesrcanim oboljenjima, kao sto su neuromuskularna oboljenja. Predlaze se skrining bolesnika, narocito u porodicama sa neuromuskularnim oboljenjima da bi se pronasli bolesnici sa LVNC, kao i skrining bolesnika sa LVNC kako bi se otkrila neuromuskularna oboljenja. Kod familijarnog javljanja bolesti utvrdjena je genetska osnova nasledjivanja. Zbog pretpostavke da postoji dug preklinicki period, potrebno je da se otkriju bolesnici u asimptomatskoj ili oligosimptomatskoj fazi, kako bi se pratili i pravilno tretirali. Iako postoje kontroverze koje se odnose na etiologiju, patogenezu, dijagnosticke kriterijume i prognozu, vecina istrazivaca izrazava stav da i ovu kardiomiopatiju SZO treba da svrsta u poseban entitet.
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Abstract
OBJECTIVE To investigate first trimester human fetal cardiac function in relation to cardiac volume blood flow, and peripheral arterial and venous blood flow patterns. METHODS Transvaginal Doppler ultrasonography was performed in 16 uncomplicated pregnancies at 6+, 7+, 8+, 9+, and 10+ gestational weeks. The shape of the inflow waveform and the presence of atrioventricular valve regurgitation (AVVR) were noted. The outflow mean velocity (Vmean) was calculated. The proportions of the isovolumetric relaxation (IRT%) and contraction times (ICT%) of the cardiac cycle were defined. Ductus venosus and umbilical artery pulsatility indices (PI) were obtained. RESULTS Every inflow waveform was monophasic before 9+ weeks. At 9+ weeks 11 of 16 and at 10+ weeks all waveforms were biphasic. At 7+ and 8+ weeks AVVR was documented in one case. At 9+ and 10+ weeks AVVR was present in four and seven fetuses, respectively. Mean (SD) outflow Vmean increased between 6+ and 8+ weeks from 3.6 (1.5) to 8.4 (3.0) cm/s (p < 0.05). IRT% decreased significantly from 6+ to 7+ weeks (39.8 (2.6) to 19.2 (6.2), p < 0.001). ICT% decreased between 8+ and 9+ weeks from 13.2 (4.0) to 8.5 (2.5) (p < 0.05). Ductus venosus PIs were unchanged. Umbilical artery Vmean increased between 7+ and 10+ weeks from 1.59 (0.51) to 5.06 (1.06) cm/s (p < 0.001) and PIs remained unchanged. CONCLUSIONS The first trimester of pregnancy is characterised by significant improvements in cardiac diastolic and systolic function with a concomitant increase in cardiac volume blood flow. At 10+ weeks AVVR is a common finding. Placental volume blood flow increases significantly with no change in the placental vascular impedance.
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Affiliation(s)
- K Mäkikallio
- Department of Obstetrics and Gynaecology, University of Oulu, Oulu, Finland
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Abstract
In normal human hearts the left ventricle (LV) has up to 3 prominent trabeculations and is, thus, less trabeculated than the right ventricle. Rarely, more than 3 prominent trabeculations can be found at autopsy and by various imaging techniques in the LV. For this abnormality, different synonyms are used such as spongy myocardium, LV noncompaction, and LV hypertrabeculation (LVHT). In this review it is stated that: (1) LVHT has a higher prevalence than previously thought and the prevalence of LVHT seems to increase with the improvement of cardiac imaging; (2) because LVHT is most frequently diagnosed primarily by echocardiography, echocardiographers should be aware and trained to recognize this abnormality; (3) LVHT is frequently associated with other cardiac and extracardiac, particularly neuromuscular, disorders; (4) there are indications that the cause of LVHT is usually a genetic one and quite heterogeneous; and (5) controversies exist about diagnostic criteria, nomenclature, prognosis, origin, pathogenesis, and the necessity to classify LVHT as a distinct entity and cardiomyopathy by the World Health Organization.
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Miller CE, Wong CL, Sedmera D. Pressure overload alters stress-strain properties of the developing chick heart. Am J Physiol Heart Circ Physiol 2003; 285:H1849-56. [PMID: 12855423 DOI: 10.1152/ajpheart.00384.2002] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
As a first step in investigating a control mechanism regulating stress and/or strain in the embryonic heart, this study tests the hypothesis that passive mechanical properties of left ventricular (LV) embryonic myocardium change with chronically increased pressure during the chamber septation period. Conotruncal banding (CTB) created ventricular pressure overload in chicks from Hamburger-Hamilton (HH) stage 21 (HH21) to HH27, HH29, or HH31. LV sections were cyclically stretched while biaxial strains and force were measured. Wall architecture was assessed with scanning electron microscopy. In controls, porosity-adjusted stress-strain relations decreased significantly from HH27 to HH31. CTB at HH21 resulted in significantly stiffer stress-strain relations by HH27, with larger increases at HH29 and HH31, and nearly constant wall thickness. Strain patterns, hysteresis, and loading-curve convergence showed few differences after CTB. Trabecular extent decreased with age, but neither extent nor porosity changed significantly after CTB. The stiffened stress-strain relations and constant wall thickness suggest that mechanical load may play a regulatory role in this response.
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Affiliation(s)
- Christine E Miller
- Division of Pediatric Cardiology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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Alford PW, Taber LA. Regional epicardial strain in the embryonic chick heart during the early looping stages. J Biomech 2003; 36:1135-41. [PMID: 12831739 DOI: 10.1016/s0021-9290(03)00089-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Epicardial strains were measured in Hamburger-Hamilton stage 11 and 12 embryonic chick hearts (1.6-2.0 days of incubation). These stages include part of the early phase of cardiac looping, as the initially straight heart tube bends and twists to form a curved c-shaped tube. By analyzing the motion of microbeads placed on the myocardial surface, we measured strains near the outer curvature, in the central region, and near the inner curvature of the primitive ventricle. No significant differences in strain were found between stages. Relative to end diastole, all three regions shortened by about 10% during systole in the circumferential direction, and the outer curvature shortened longitudinally by about 5%. In contrast, and unlike strains in older hearts, the inner curvature and central regions elongated by approximately 5-10% in the longitudinal direction during systole. These results are consistent with microstructural data and suggest that the material properties of the outer curvature are relatively isotropic, whereas the properties of the central and inner curvature regions are orthotropic, with contractile stress exerted primarily in the circumferential direction.
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Affiliation(s)
- Patrick W Alford
- Department of Biomedical Engineering, Washington University, Campus Box 1097, St Louis, MO 63130, USA
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Tamura A, Omori K, Miki K, Lee JB, Yang KH, King AI. Mechanical characterization of porcine abdominal organs. STAPP CAR CRASH JOURNAL 2002; 46:55-69. [PMID: 17096218 DOI: 10.4271/2002-22-0003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Typical automotive related abdominal injuries occur due to contact with the rim of the steering wheel, seatbelt and armrest, however, the rate is less than in other body regions. When solid abdominal organs, such as the liver, kidneys and spleen are involved, the injury severity tends to be higher. Although sled and pendulum impact tests have been conducted using cadavers and animals, the mechanical properties and the tissue level injury tolerance of abdominal solid organs are not well characterized. These data are needed in the development of computer models, the improvement of current anthropometric test devices and the enhancement of our understanding of abdominal injury mechanisms. In this study, a series of experimental tests on solid abdominal organs was conducted using porcine liver, kidney and spleen specimens. Additionally, the injury tolerance of the solid organs was deduced from the experimental data.
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Abstract
It long has been known that mechanical forces play a role in the development of the cardiovascular system, but only recently have biomechanical engineers begun to explore this field. This paper reviews some of this work. First, an overview of the relevant biology is discussed. Next, a mechanical theory is presented that can be used to model developmental processes. The theory includes the effects of finite volumetric growth and active contractile forces. Finally, applications of this and other theories to problems of cardiovascular development are discussed, and some future directions are suggested. The intent is to stimulate further interest among engineers in this important area of research.
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Affiliation(s)
- L A Taber
- Department of Biomedical Engineering, Campus Box 1097, Washington University, St. Louis, Missouri 63130, USA.
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Abstract
During the morphogenetic process of myocardial trabeculation, most of the cardiac jelly of the initially smooth-walled heart is replaced by sponge-like muscle. The mechanisms that drive and regulate this important process are poorly understood. Using a theoretical model, we examined the possible role that cytoskeletal contraction plays during the initial stages of trabeculation. The myocardium is modeled as a thin viscoelastic membrane consisting of contractile (stress) fibers embedded in an isotropic incompressible matrix, with the interaction of myocardial cells and cardiac jelly fibers providing long-range mechanical effects. The stress fibers are assumed to behave like smooth muscle and to normally operate on the descending limb of their stress-stretch curve. Mechanical instability due to the effectively negative stiffness then leads to the creation of pattern. As a first approximation, computations were carried out for a flat rectangular membrane with stress fibers aligned along a single direction. The computed deformation patterns depend strongly on the magnitude and anisotropy of the long-range effects. Given plausible assumptions about the mechanical properties of the embryonic heart, the model predicts trabecular patterns similar to those observed in the embryo, including the development of circumferential ridges and relatively thin regions ("holes") in the trabecular sheets.
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Affiliation(s)
- L A Taber
- Department of Biomedical Engineering, Washington University, St. Louis, Missouri 63130, USA
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