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https://www.readbyqxmd.com/read/28512434/evaluation-of-a-rapid-anisotropic-model-for-ecg-simulation
#1
Simone Pezzuto, Peter Kal'avský, Mark Potse, Frits W Prinzen, Angelo Auricchio, Rolf Krause
State-of-the-art cardiac electrophysiology models that are able to deliver physiologically motivated activation maps and electrocardiograms (ECGs) can only be solved on high-performance computing architectures. This makes it nearly impossible to adopt such models in clinical practice. ECG imaging tools typically rely on simplified models, but these neglect the anisotropic electric conductivity of the tissue in the forward problem. Moreover, their results are often confined to the heart-torso interface. We propose a forward model that fully accounts for the anisotropic tissue conductivity and produces the standard 12-lead ECG in a few seconds...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28507234/modelling-far-field-pacing-for-terminating-spiral-waves-pinned-to-ischaemic-heterogeneities-in-cardiac-tissue
#2
E Boccia, S Luther, U Parlitz
In cardiac tissue, electrical spiral waves pinned to a heterogeneity can be unpinned (and eventually terminated) using electric far field pulses and recruiting the heterogeneity as a virtual electrode. While for isotropic media the process of unpinning is much better understood, the case of an anisotropic substrate with different conductivities in different directions still needs intensive investigation. To study the impact of anisotropy on the unpinning process, we present numerical simulations based on the bidomain formulation of the phase I of the Luo and Rudy action potential model modified due to the occurrence of acute myocardial ischaemia...
June 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28502873/synchronization-as-a-mechanism-for-low-energy-anti-fibrillation-pacing-leap
#3
Yanyan Claire Ji, Ilija Uzelac, Niels Otani, Stefan Luther, Robert F Gilmour, Elizabeth M Cherry, Flavio H Fenton
BACKGROUND: Low-energy anti-fibrillation pacing (LEAP) has been suggested as an alternative treatment to symptomatic fibrillation patients. It significantly lowers the energy required compared with standard one-shock defibrillation. OBJECTIVE: In this study, we investigated the mechanism of arrhythmia termination by LEAP and systematically analyzed the influence of shock period and timing on the success rate of LEAP. METHODS: We induced atrial and ventricular fibrillation in isolated canine hearts and applied LEAP and standard one-shock defibrillation to terminate the arrhythmia...
May 11, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28451591/the-role-of-reduced-left-ventricular-systolic-blood-volumes-in-st-segment-potentials-overlying-diseased-tissue-of-the-ischemic-heart
#4
Brett M Burton, Jess D Tate, Wilson Good, Rob S Macleod
Myocardial ischemia is the response of the heart to reduced coronary blood flow, leading to changes in ST segment potentials. ST segment depression is regarded as an indicator of nontransmural myocardial ischemia; however, not all nontransmural ischemia results in ST depression. This apparent discrepancy may be the result of many complex factors in cardiac response mechanisms to reduced blood flow. As a result, sophisticated computer models have emerged that have provided key insights into this complex phenomenon and the circumstances surrounding ST depression...
September 2016: Computing in Cardiology
https://www.readbyqxmd.com/read/28396856/bidomain-predictions-of-virtual-electrode-induced-make-and-break-excitations-around-blood-vessels
#5
Adam J Connolly, Edward Vigmond, Martin J Bishop
INTRODUCTION AND BACKGROUND: Virtual electrodes formed by field stimulation during defibrillation of cardiac tissue play an important role in eliciting activations. It has been suggested that the coronary vasculature is an important source of virtual electrodes, especially during low-energy defibrillation. This work aims to further the understanding of how virtual electrodes from the coronary vasculature influence defibrillation outcomes. METHODS: Using the bidomain model, we investigated how field stimulation elicited activations from virtual electrodes around idealized intramural blood vessels...
2017: Frontiers in Bioengineering and Biotechnology
https://www.readbyqxmd.com/read/28321943/development-of-3-d-intramural-and-surface-potentials-in-the-lv-microstructural-basis-of-preferential-transmural-conduction
#6
Bryan J Caldwell, Mark L Trew, Ian J Legrice, Bruce H Smaill
INTRODUCTION: Extracellular potentials measured on the heart surfaces are used to infer events that originate deep within the heart wall. We have reconstructed intramural potentials in three dimensions for the first time, and compare these with epicardial and endocardial surface potentials and cardiac microstructure. METHODS AND RESULTS: Extracellular potentials from intramural point stimulation were measured from a high density 3-D electrode array in the in vivo pig LV...
March 21, 2017: Journal of Cardiovascular Electrophysiology
https://www.readbyqxmd.com/read/28269630/simulating-the-activation-contraction-and-movement-of-skeletal-muscles-using-the-bidomain-model
#7
A Lopez Rincon, C Cantu, R Soto, S Shimoda
A simulation of the muscle activation, contraction and movement is here presented. This system was developed based on the Bidomain mathematical model of the electrical propagation in muscles. This study shows an electrical stimuli input to a muscle and how this behave. The comparison between healthy subject and patient with muscle activation impairment is depicted, depending on whether the signal reaches a threshold. A 3D model of a bicep muscle and a forearm bone connected was constructed using OpenGL. This platform could be used for development of controllers for biomechatronic systems in future works...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28253365/virtual-electrodes-around-anatomical-structures-and-their-roles-in-defibrillation
#8
Adam Connolly, Edward Vigmond, Martin Bishop
BACKGROUND: Virtual electrodes from structural/conductivity heterogeneities are known to elicit wavefront propagation, upon field-stimulation, and are thought to be important for defibrillation. In this work we investigate how the constitutive and geometrical parameters associated with such anatomical heterogeneities, represented by endo/epicardial surfaces and intramural surfaces in the form of blood-vessels, affect the virtual electrode patterns produced. METHODS AND RESULTS: The steady-state bidomain model is used to obtain, using analytical and numerical methods, the virtual electrode patterns created around idealized endocardial trabeculations and blood-vessels...
2017: PloS One
https://www.readbyqxmd.com/read/28227888/simulating-the-activation-contraction-and-movement-of-skeletal-muscles-using-the-bidomain-model
#9
A Lopez Rincon, C Cantu, R Soto, S Shimoda, A Lopez Rincon, C Cantu, R Soto, S Shimoda, A Lopez Rincon, R Soto, C Cantu, S Shimoda
A simulation of the muscle activation, contraction and movement is here presented. This system was developed based on the Bidomain mathematical model of the electrical propagation in muscles. This study shows an electrical stimuli input to a muscle and how this behave. The comparison between healthy subject and patient with muscle activation impairment is depicted, depending on whether the signal reaches a threshold. A 3D model of a bicep muscle and a forearm bone connected was constructed using OpenGL. This platform could be used for development of controllers for biomechatronic systems in future works...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28222136/cardiac-strength-interval-curves-calculated-using-a-bidomain-tissue-with-a-parsimonious-ionic-current
#10
Suran K Galappaththige, Richard A Gray, Bradley J Roth
The strength-interval curve plays a major role in understanding how cardiac tissue responds to an electrical stimulus. This complex behavior has been studied previously using the bidomain formulation incorporating the Beeler-Reuter and Luo-Rudy dynamic ionic current models. The complexity of these models renders the interpretation and extrapolation of simulation results problematic. Here we utilize a recently developed parsimonious ionic current model with only two currents-a sodium current that activates rapidly upon depolarization INa and a time-independent inwardly rectifying repolarization current IK-which reproduces many experimentally measured action potential waveforms...
2017: PloS One
https://www.readbyqxmd.com/read/28179138/the-interdigitating-loop-of-the-enolase-superfamily-as-a-specificity-binding-determinant-or-flying-buttress
#11
REVIEW
Stephen L Bearne
BACKGROUND: Enzymes of the enolase superfamily (ENS) are mechanistically diverse, yet share a common partial reaction (abstraction of the α-proton from a carboxylate substrate). While the catalytic machinery responsible for the deprotonation reaction has been conserved, divergent evolution has led to numerous ENS members that catalyze different overall reactions. This rich functional diversity has made the ENS an excellent model system for developing the approaches necessary to validate enzyme function...
February 4, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28011826/human-ventricular-activation-sequence-and-the-simulation-of-the-electrocardiographic-qrs-complex-and-its-variability-in-healthy-and-intraventricular-block-conditions
#12
Louie Cardone-Noott, Alfonso Bueno-Orovio, Ana Mincholé, Nejib Zemzemi, Blanca Rodriguez
AIMS: To investigate how variability in activation sequence and passive conduction properties translates into clinical variability in QRS biomarkers, and gain novel physiological knowledge on the information contained in the human QRS complex. METHODS AND RESULTS: Multiscale bidomain simulations using a detailed heart-torso human anatomical model are performed to investigate the impact of activation sequence characteristics on clinical QRS biomarkers. Activation sequences are built and validated against experimentally-derived ex vivo and in vivo human activation data...
December 2016: Europace: European Pacing, Arrhythmias, and Cardiac Electrophysiology
https://www.readbyqxmd.com/read/27824910/3d-finite-element-electrical-model-of-larval-zebrafish-ecg-signals
#13
James Crowcombe, Sundeep Singh Dhillon, Rhiannon Mary Hurst, Stuart Egginton, Ferenc Müller, Attila Sík, Edward Tarte
Assessment of heart function in zebrafish larvae using electrocardiography (ECG) is a potentially useful tool in developing cardiac treatments and the assessment of drug therapies. In order to better understand how a measured ECG waveform is related to the structure of the heart, its position within the larva and the position of the electrodes, a 3D model of a 3 days post fertilisation (dpf) larval zebrafish was developed to simulate cardiac electrical activity and investigate the voltage distribution throughout the body...
2016: PloS One
https://www.readbyqxmd.com/read/27737776/the-inverse-problem-in-electroencephalography-using-the-bidomain-model-of-electrical-activity
#14
Alejandro Lopez Rincon, Shingo Shimoda
BACKGROUND: Acquiring information about the distribution of electrical sources in the brain from electroencephalography (EEG) data remains a significant challenge. An accurate solution would provide an understanding of the inner mechanisms of the electrical activity in the brain and information about damaged tissue. NEW METHOD: In this paper, we present a methodology for reconstructing brain electrical activity from EEG data by using the bidomain formulation. The bidomain model considers continuous active neural tissue coupled with a nonlinear cell model...
December 1, 2016: Journal of Neuroscience Methods
https://www.readbyqxmd.com/read/27613652/analytic-modeling-of-neural-tissue-i-a-spherical-bidomain
#15
Benjamin L Schwartz, Munish Chauhan, Rosalind J Sadleir
Presented here is a model of neural tissue in a conductive medium stimulated by externally injected currents. The tissue is described as a conductively isotropic bidomain, i.e. comprised of intra and extracellular regions that occupy the same space, as well as the membrane that divides them, and the injection currents are described as a pair of source and sink points. The problem is solved in three spatial dimensions and defined in spherical coordinates [Formula: see text]. The system of coupled partial differential equations is solved by recasting the problem to be in terms of the membrane and a monodomain, interpreted as a weighted average of the intra and extracellular domains...
December 2016: Journal of Mathematical Neuroscience
https://www.readbyqxmd.com/read/27545966/joint-influence-of-transmural-heterogeneities-and-wall-deformation-on-cardiac-bioelectrical-activity-a-simulation-study
#16
P Colli Franzone, L F Pavarino, S Scacchi
The aim of this work is to investigate, by means of numerical simulations, the influence of myocardial deformation due to muscle contraction and relaxation on the cardiac repolarization process in presence of transmural intrinsic action potential duration (APD) heterogeneities. The three-dimensional electromechanical model considered consists of the following four coupled components: the quasi-static transversely isotropic finite elasticity equations for the deformation of the cardiac tissue; the active tension model for the intracellular calcium dynamics and cross-bridge binding; the anisotropic Bidomain model for the electrical current flow through the deforming cardiac tissue; the membrane model of ventricular myocytes, including stretch-activated channels...
October 2016: Mathematical Biosciences
https://www.readbyqxmd.com/read/27168382/positive-to-negative-zero-field-cooled-exchange-bias-in-la0-5sr0-5mn0-8co0-2o3-ceramics
#17
Cui Shang, Shaopu Guo, Ruilong Wang, Zhigang Sun, Haibo Xiao, Lingfang Xu, Changping Yang, Zhengcai Xia
Exchange bias effect obtained after zero-field cooling from unmagnetized state usually exhibits a shift of hysteresis loop negative to the direction of the initial magnetic field, known as negative zero-field cooled exchange bias. Here, positive zero-field cooled exchange bias is reported in La0.5Sr0.5Mn0.8Co0.2O3 ceramics. In addition, a transition from positive to negative exchange bias has been observed with increasing initial magnetization field and measurement temperature. Based on a simple spin bidomain model with variable interface, two type of interfacial spin configuration formed during the initial magnetization process are proposed to interpret the observed phenomenon...
2016: Scientific Reports
https://www.readbyqxmd.com/read/26737583/low-energy-defibrillation-with-multi-electrodes-stimulation-a-simulation-study
#18
Lian Jin, Jianfei Wang, Biao Song, Xiaomei Wu, Zuxiang Fang
The objective of this study is to explore the possible ways to reduce defibrillation energy and further reveal the mechanism of electric defibrillation. A bidomain simulation study was performed on a rabbit whole-ventricle electrophysiological model and the feasibility of the defibrillation strategy with multi-electrodes stimulation was verified. Simulation results indicate that the new approach is effective in low-energy defibrillation.
August 2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26736753/external-current-application-in-a-bidomain-model-of-active-neural-tissue
#19
Steven F Keim, Fanrui Fu, Rosalind J Sadleir
The formal treatment of tissue as two coupled continua is referred to as a bidomain model. Bidomain models have recently been used to describe the properties of neural tissue and nerve fiber bundles [1, 2]. By adapting the Hodgkin Huxley equations in COMSOL Multiphysics, we have investigated the propagation of an action potential through neural tissue by external current stimulation.
2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/26736752/analysis-of-bipolar-external-excitation-of-spherical-tissue-by-spatially-opposed-current-source-and-sink-points
#20
Benjamin L Schwartz, Rosalind J Sadleir
The recently increasing role in medical imaging that electrophysiology plays has spurned the need for its quantitative analysis at all scales-ions, cells, tissues, organs, etc.; so, here is presented a model of nerve tissue in a spherical volume excited by a point current source at one pole and a point current sink at the opposite pole. The sphere of tissue is described as an isotropic bidomain, consisting of the intra- and extra-cellular regions and the membrane that separates them, and is immersed in an infinite isotropic conductive bath...
2015: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
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