Simulation of arrhythmia using adaptive spatio-temporal resolution (original) (raw)
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Simulation of cardiac arrhythmias using a 2D heterogeneous whole heart model
Cardiac arrhythmias are defined as disturbances in normal heart rhythm which vary from inconsequential to serious life threatening conditions. Simulation studies of cardiac arrhythmias at the whole heart level with electrocardiogram (ECG) gives an understanding how the underlying cell and tissue level changes manifest as rhythm disturbances in the ECG. We present a 2D whole heart model (WHM2D) which can accommodate variations at the cellular level and can generate an ECG waveform. It is shown that, by varying cellular-level parameters like the gap junction conductance (GJC), excitability, action potential duration(APD) and frequency of oscillations of the auto-rhythmic cells in WHM2D a large variety of cardiac arrhythmias can be generated. Sinus tachycardia, sinus bradycardia, sinus arrhythmia, sinus pause, junctional rhythm, Wolf Parkinson White syndrome and AV conduction blocks are thereby simulated. WHM2D includes key components of the electrical conduction system of the heart like the SA (Sino atrial) node cells, fast conducting inter-atrial pathways, slow conducting Atrivenctricular (AV) node, bundleof His cells, Purkinje network, atrial and ventricular myocardial cells. SA nodal cells, AV nodal cells, bundleof His cells and Purkinje cells are represented by the Fitzhugh-Nagumo (FN) model which is a reduced model of the Hodgkin-Huxley neuron model. The atrial and ventricular myocardial cells are modeled by the Aliev-Panfilov (AP) two-variable model proposed for cardiac excitation. WHM2D can prove to be a valuable clinical tool for understanding cardiac arrhythmias.
A 3D MRI-Based Cardiac Computer Model to Study Arrhythmia and Its In-vivo Experimental Validation
Lecture Notes in Computer Science, 2011
The aim of this work was to develop a simple and fast 3D MRI-based computer model of arrhythmia inducibility in porcine hearts with chronic infarct scar, and to further validate it using electrophysiology (EP) measures obtained in-vivo. The heart model was built from MRI scans (with voxel size smaller than 1mm 3 ) and had fiber directions extracted from diffusion tensor DT-MRI. We used a macroscopic model that calculates the propagation of action potential (AP) after application of a train of stimuli, with location and timing replicating precisely the stimulation protocol used in the in-vivo EP study. Simulation results were performed for two infarct hearts: one with noninducible and the other with inducible ventricular tachycardia (VT), successfully predicting the study outcome like in the in-vivo cases; for the inducible heart, the average predicted VT cycle length was 273ms, compared to a recorded VT of approximately 250ms. We also generated synthetic fibers for each heart and found the associated helix angle whose transmural variation (in healthy zones) from endo-to epicardium gave the smallest difference (i.e., approx. 41°) when compared to the helix angle corresponding to fibers from DW-MRI. Mean differences between activation times computed using DT-MRI fibers and using synthetic fibers for the two hearts were 6 ms and 11 ms, respectively.
Journal of Electrocardiology, 2011
Biophysically detailed and anatomically realistic atrial models are emerging as a valuable tool in the study of atrial arrhythmias, nevertheless clinical use of these models would be favored by a reduction of computational times. This paper introduces a novel adaptive mesh algorithm, based on multiresolution representation (MR), for the efficient integration of cardiac ordinary differential equation (ODE)-partial differential equation (PDE) systems on unstructured triangle meshes. The algorithm applies a dynamically adapted node-centered finite volume method (FVM) scheme for integration of diffusion. The method accuracy and efficiency were evaluated by simulating propagation scenarios of increasing complexity levels (pacing, stable spirals, atrial fibrillation) on tomography-derived three-dimensional monolayer atrial models, based on a monodomain reaction-diffusion formulation coupled with the Courtemanche atrial ionic model. All simulated propagation patterns were accurately reproduced with substantially reduced computational times (10%-30% of the full-resolution simulation time). The proposed algorithm, combining the MR computational efficiency with the geometrical flexibility of unstructured meshes, may favor the development of patient-specific multiscale models of atrial arrhythmias and their application in the clinical setting.
Journal of Electrocardiology, 1993
With the advent of catheter ablation procedures, it has become an important goal to predict noninvasively the site of origin of ventricular tachycardia. Site classifications based on the observed body surface potential maps (BSPMs) during ventricular endocardial pacing, as well as on the patterns of the QRS integrals of these maps, have been suggested. The goals of this study were to verify these maps and their QRS integral patterns via simulation using a computer heart model with realistic geometry and to determine whether the model could improve clinical understanding of these ectopic patterns. Simulation was achieved by initiating excitation of the heart model at different endocardial sites and their overlying epicardial counterparts. This excitation propagated in anisotropic fashion in the myocardium. Retrograde excitation of the model's His-Purkinje conduction system was necessary to obtain realistic activation durations. Simulated BSPMs, computed by placing the heart model inside a numerical torso model, and their QRS integrals were close to those observed clinically. Small differences in QRS integral map patterns and in the positions of the QRS integral map extrema were noted for endocardial sites in the left septal and anteroseptal regions. The simulated BSPMs during early QRS for an endocardial site and its epicardial counterpart tended to be mirror images about the zero isopotential contour, exchanging positive and negative map regions. The simulation results attest to the model's ability to reproduce accurately clinically recorded body surface potential distributions obtained following endocardial stimulation. The QRS integral maps from endocardial sites in the left septal and anteroseptal regions were the most labile, owing to considerable cancelation effects. Conventional BSPMs can be useful to help distinguish between endocardial and epicardial ectopic sites.
Simulating Normal and Arrhythmic Dynamics: From Sub-Cellular to Tissue and Organ Level
Frontiers Media SA eBooks, 2019
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Computer Simulations of Cardiac Electrophysiology
ACM/IEEE SC 2000 Conference (SC'00), 2000
CardioWave is a modular system for simulating wavefront conduction in the heart. These simulations may be used to investigate the factors that generate and sustain life-threatening arrhythmias such as ventricular fibrillation. The user selects a set of modules which most closely reflects the simulation they are interested in and the simulator is built automatically. Thus, we do not present one monolithic simulator, but rather a simulator-generator which allows the researcher to make the trade-offs of complexity versus performance. The results presented here are from simulations run on an IBM SP parallel computer and a cluster of workstations. The performance numbers show excellent scalability up through 128 processors. With the larger memory of the parallel machines, we have been able to perform highly realistic simulations of the human atria. These simulations include realistic, 3-D geometries with inhomogeneity and anisotropy as well as highly complex membrane dynamics.
Interactive Simulation of the ECG: Effects of Cell Types, Distributions, Shapes and Duration
2021
The shape of the ECG depends on the lead positions but also on the distribution and dispersion of different cell types their durations and shapes. We present an interactive program written in JavaScript that allows fast simulations of the ECG by solving and displaying the dynamics of cardiac cells in tissue using a web browser. We use physiologically accurate ODE models of cardiac cells of different types including SA node, right and left atria, AV node, Purkinje, and right and left ventricular cells with dispersion that accounts for apex-to-base and epi-to-endo variations. The software allows for real-time variations for each cell type and their spatial range so as to identify how the shape of the ECG varies as a function of the cell type, distribution, excitation duration and action potential shape. The propagation of the wave is visualized in real time through all the regions as parameters are kept fixed or varied, modifying the ECG morphology. This is a useful program to teach s...
IEEE Access, 2017
It has been suggested that the spatiotemporal characteristics of complex cardiac arrhythmias can be extracted from the spectrum of cardiac signals. However, the analysis of simple bioelectric models indicates that the spectrum of cardiac signals can be affected by the spatial resolution of the electrode system. In this study, we derive exact measurement transfer functions relating the spectrum of cardiac signals to the spatiotemporal dynamics of cardiac sources. The analysis of the measurement transfer bandwidths for dynamics with different degrees of spatiotemporal correlation shows that as the spatial resolution decreases, the bandwidth of the measurement transfer function decreases until it reaches a constant value. Moreover, this transition from decreasing to constant values is determined by the degree of spatiotemporal correlation of the underlying cardiac source. Motivated by our analytical results, we investigate in a realistic computer simulation environment the impact of additive noise on the accuracy of body-surface dominant frequency (DF) maps. Our simulation results show that meaningful DF values are obtained on those locations where the analytical measurement transfer bandwidth is wide. These findings suggest that the accuracy of body-surface DF maps can be limited by the low spatial resolution of body-surface electrode systems.
Simulation Methods and Validation Criteria for Modeling Cardiac Ventricular Electrophysiology
PLoS ONE, 2014
We describe a sequence of methods to produce a partial differential equation model of the electrical activation of the ventricles. In our framework, we incorporate the anatomy and cardiac microstructure obtained from magnetic resonance imaging and diffusion tensor imaging of a New Zealand White rabbit, the Purkinje structure and the Purkinje-muscle junctions, and an electrophysiologically accurate model of the ventricular myocytes and tissue, which includes transmural and apex-to-base gradients of action potential characteristics. We solve the electrophysiology governing equations using the finite element method and compute both a 6-lead precordial electrocardiogram (ECG) and the activation wavefronts over time. We are particularly concerned with the validation of the various methods used in our model and, in this regard, propose a series of validation criteria that we consider essential. These include producing a physiologically accurate ECG, a correct ventricular activation sequence, and the inducibility of ventricular fibrillation. Among other components, we conclude that a Purkinje geometry with a high density of Purkinje muscle junctions covering the right and left ventricular endocardial surfaces as well as transmural and apex-to-base gradients in action potential characteristics are necessary to produce ECGs and time activation plots that agree with physiological observations. Boundary conforming with seed 200mm 5 425 184
A Simple 2D Whole Heart Model for Simulating Electrocardiograms
A simplified 2D whole heart model (2DWHM) which simulates the Electrocardiogram (ECG) accurately is presented. Although extremely detailed whole heart 3D models are available, they are computationally expensive. On the other hand most of the 2D cardiac models are homogeneous models aiming at modeling activation propagation in a small patch of cardiac tissue; they are not meant to be whole heart models. A two-dimensional heterogeneous "whole heart" model consisting of an array of specialized cardiac cells, with appropriate anatomical distribution, interacting via gap junction conductance (GJC) is envisioned to be a midway solution to this problem. The proposed 2D whole heart model includes various key components of the electrical conduction system of the heart including the SA (Sino atrial) node, fast conducting inter-atrial pathways, slow conducting AV (atrio-ventricular) node, Bundle of His, Purkinje network, and atrial and ventricular myocardial cells. Atrial and ventric...