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Al-Owais MM, Hettiarachchi NT, Dallas ML, Scragg JL, Lippiat JD, Holden AV, Steele DS, Peers C. Inhibition of the voltage-gated potassium channel Kv1.5 by hydrogen sulfide attenuates remodeling through S-nitrosylation-mediated signaling. Commun Biol 2023; 6:651. [PMID: 37336943 PMCID: PMC10279668 DOI: 10.1038/s42003-023-05016-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 06/05/2023] [Indexed: 06/21/2023] Open
Abstract
The voltage-gated K+ channel plays a key role in atrial excitability, conducting the ultra-rapid rectifier K+ current (IKur) and contributing to the repolarization of the atrial action potential. In this study, we examine its regulation by hydrogen sulfide (H2S) in HL-1 cardiomyocytes and in HEK293 cells expressing human Kv1.5. Pacing induced remodeling resulted in shorting action potential duration, enhanced both Kv1.5 channel and H2S producing enzymes protein expression in HL-1 cardiomyocytes. H2S supplementation reduced these remodeling changes and restored action potential duration through inhibition of Kv1.5 channel. H2S also inhibited recombinant hKv1.5, lead to nitric oxide (NO) mediated S-nitrosylation and activated endothelial nitric oxide synthase (eNOS) by increased phosphorylation of Ser1177, prevention of NO formation precluded these effects. Regulation of Ikur by H2S has important cardiovascular implications and represents a novel and potential therapeutic target.
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Affiliation(s)
- Moza M Al-Owais
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
| | - Nishani T Hettiarachchi
- Division of Cardiovascular and Diabetes Research, LICAMM, Faculty of Medicine and Health, University of Leeds, Leeds, LS2 9JT, UK
| | - Mark L Dallas
- Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK
| | - Jason L Scragg
- Division of Cardiovascular and Diabetes Research, LICAMM, Faculty of Medicine and Health, University of Leeds, Leeds, LS2 9JT, UK
| | - Jonathan D Lippiat
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Arun V Holden
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Derek S Steele
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Chris Peers
- Division of Cardiovascular and Diabetes Research, LICAMM, Faculty of Medicine and Health, University of Leeds, Leeds, LS2 9JT, UK
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2
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Abstract
The global burden caused by cardiovascular disease is substantial, with heart disease representing the most common cause of death around the world. There remains a need to develop better mechanistic models of cardiac function in order to combat this health concern. Heart rhythm disorders, or arrhythmias, are one particular type of disease which has been amenable to quantitative investigation. Here we review the application of quantitative methodologies to explore dynamical questions pertaining to arrhythmias. We begin by describing single-cell models of cardiac myocytes, from which two and three dimensional models can be constructed. Special focus is placed on results relating to pattern formation across these spatially-distributed systems, especially the formation of spiral waves of activation. Next, we discuss mechanisms which can lead to the initiation of arrhythmias, focusing on the dynamical state of spatially discordant alternans, and outline proposed mechanisms perpetuating arrhythmias such as fibrillation. We then review experimental and clinical results related to the spatio-temporal mapping of heart rhythm disorders. Finally, we describe treatment options for heart rhythm disorders and demonstrate how statistical physics tools can provide insights into the dynamics of heart rhythm disorders.
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Affiliation(s)
- Wouter-Jan Rappel
- Department of Physics, University of California San Diego, La Jolla, CA 92037
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3
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Das TS, Wilson D. Optimal entrainment for removal of pinned spiral waves. Phys Rev E 2022; 105:064213. [PMID: 35854563 DOI: 10.1103/physreve.105.064213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Cardiac fibrillation is caused by self-sustaining spiral waves that occur in the myocardium, some of which can be pinned to anatomical obstacles, making them more difficult to eliminate. A small electrical stimulation is often sufficient to unpin these spirals but only if it is applied during the vulnerable unpinning window. Even if these unpinning windows can be inferred from data, when multiple pinned spirals exist, their unpinning windows will not generally overlap. Using phase-based reduction techniques, we formulate and solve an optimal control problem to yield a time-varying external voltage gradient that can synchronize a collection of spiral waves that are pinned to a collection of heterogeneous obstacles. Upon synchronization, the unpinning windows overlap so that they can be simultaneously unpinned by applying an external voltage gradient pulse at an appropriate moment. Numerical validation is presented in bidomain model simulations. Results represent a proof-of-concept illustration of the proposed unpinning strategy which explicitly incorporates heterogeneity in the problem formulation and requires no real-time feedback about the system state.
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Affiliation(s)
- Tuhin Subhra Das
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Dan Wilson
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee 37996, USA
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4
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Salvador-Montañés Ó, Ramirez RJ, Takemoto Y, Ennis SR, Garcia-Iglesias D, Wang S, Wolfer PJ, Jiang J, Mironov SV, Pandit SV, Jalife J, Berenfeld O. Panoramic Endocardial Optical Mapping Demonstrates Serial Rotors Acceleration and Increasing Complexity of Activity During Onset of Cholinergic Atrial Fibrillation. J Am Heart Assoc 2021; 10:e022300. [PMID: 34726079 PMCID: PMC8751940 DOI: 10.1161/jaha.121.022300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background Activation during onset of atrial fibrillation is poorly understood. We aimed at developing a panoramic optical mapping system for the atria and test the hypothesis that sequential rotors underlie acceleration of atrial fibrillation during onset. Methods and Results Five sheep hearts were Langendorff perfused in the presence of 0.25 µmol/L carbachol. Novel optical system recorded activations simultaneously from the entire left and right atrial endocardial surfaces. Twenty sustained (>40 s) atrial fibrillation episodes were induced by a train and premature stimuli protocol. Movies obtained immediately (Initiation stage) and 30 s (Early Stabilization stage) after premature stimulus were analyzed. Serial rotor formation was observed in all sustained inductions and none in nonsustained inductions. In sustained episodes maximal dominant frequency increased from (mean±SD) 11.5±1.74 Hz during Initiation to 14.79±1.30 Hz at Early Stabilization (P<0.0001) and stabilized thereafter. At rotor sites, mean cycle length (CL) during 10 prerotor activations increased every cycle by 0.53% (P=0.0303) during Initiation and 0.34% (P=0.0003) during Early Stabilization. In contrast, CLs at rotor sites showed abrupt decreases after the rotors appearances by a mean of 9.65% (P<0.0001) during both stages. At Initiation, atria‐wide accelerations and decelerations during rotors showed a net acceleration result whereby post‐rotors atria‐wide minimal CL (CLmin) were 95.5±6.8% of the prerotor CLmin (P=0.0042). In contrast, during Early Stabilization, there was no net acceleration in CLmin during accelerating rotors (prerotor=84.9±11.0% versus postrotor=85.8±10.8% of Initiation, P=0.4029). Levels of rotor drift distance and velocity correlated with atria‐wide acceleration. Nonrotor phase singularity points did not accelerate atria‐wide activation but multiplied during Initiation until Early Stabilization. Increasing number of singularity points, indicating increased complexity, correlated with atria‐wide CLmin reduction (P<0.0001). Conclusions Novel panoramic optical mapping of the atria demonstrates shortening CL at rotor sites during cholinergic atrial fibrillation onset. Atrial fibrillation acceleration toward Early Stabilization correlates with the net result of atria‐wide accelerations during drifting rotors activity.
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Affiliation(s)
- Óscar Salvador-Montañés
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,Facultad de Medicina Universidad Francisco de Vitoria, Pozuelo de Alarcon Mardid Spain.,Hospital Universitario de Torrejón Mardid Spain
| | - Rafael J Ramirez
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,The Department of Physiology and Biophysics Virginia Commonwealth University Richmond VA
| | - Yoshio Takemoto
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,Cardiovascular Medicine Gifu Prefectural Tajimi Hospital Tajimi Japan
| | - Steven R Ennis
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI
| | - Daniel Garcia-Iglesias
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,Hospital Universitario Central de Asturias Oviedo Spain
| | - Sicong Wang
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,Institute for Stem Cell Biology and Regenerative Medicine Stanford University Palo Alto CA
| | - Patrick J Wolfer
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,Michigan Technological University Houghton MI
| | - Jiang Jiang
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI
| | - Sergey V Mironov
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI
| | - Sandeep V Pandit
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI
| | - José Jalife
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI.,Centro Nacional de Investigaciones Cardiovasculares Carlos III Madrid Spain
| | - Omer Berenfeld
- Center for Arrhythmia Research Department of Internal Medicine - Cardiology University of Michigan Ann Arbor MI
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5
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Coveney S, Corrado C, Oakley JE, Wilkinson RD, Niederer SA, Clayton RH. Bayesian Calibration of Electrophysiology Models Using Restitution Curve Emulators. Front Physiol 2021; 12:693015. [PMID: 34366883 PMCID: PMC8339909 DOI: 10.3389/fphys.2021.693015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/28/2021] [Indexed: 11/13/2022] Open
Abstract
Calibration of cardiac electrophysiology models is a fundamental aspect of model personalization for predicting the outcomes of cardiac therapies, simulation testing of device performance for a range of phenotypes, and for fundamental research into cardiac function. Restitution curves provide information on tissue function and can be measured using clinically feasible measurement protocols. We introduce novel "restitution curve emulators" as probabilistic models for performing model exploration, sensitivity analysis, and Bayesian calibration to noisy data. These emulators are built by decomposing restitution curves using principal component analysis and modeling the resulting coordinates with respect to model parameters using Gaussian processes. Restitution curve emulators can be used to study parameter identifiability via sensitivity analysis of restitution curve components and rapid inference of the posterior distribution of model parameters given noisy measurements. Posterior uncertainty about parameters is critical for making predictions from calibrated models, since many parameter settings can be consistent with measured data and yet produce very different model behaviors under conditions not effectively probed by the measurement protocols. Restitution curve emulators are therefore promising probabilistic tools for calibrating electrophysiology models.
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Affiliation(s)
- Sam Coveney
- Insigneo Institute for In-Silico Medicine and Department of Computer Science, University of Sheffield, Sheffield, United Kingdom
| | - Cesare Corrado
- Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom
| | - Jeremy E Oakley
- School of Mathematics and Statistics, University of Sheffield, Sheffield, United Kingdom
| | - Richard D Wilkinson
- School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Steven A Niederer
- Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom
| | - Richard H Clayton
- Insigneo Institute for In-Silico Medicine and Department of Computer Science, University of Sheffield, Sheffield, United Kingdom
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6
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Augustin CM, Fastl TE, Neic A, Bellini C, Whitaker J, Rajani R, O'Neill MD, Bishop MJ, Plank G, Niederer SA. The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium. Biomech Model Mechanobiol 2020; 19:1015-1034. [PMID: 31802292 PMCID: PMC7203597 DOI: 10.1007/s10237-019-01268-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 11/21/2019] [Indexed: 12/31/2022]
Abstract
The left atrium (LA) has a complex anatomy with heterogeneous wall thickness and curvature. The anatomy plays an important role in determining local wall stress; however, the relative contribution of wall thickness and curvature in determining wall stress in the LA is unknown. We have developed electromechanical finite element (FE) models of the LA using patient-specific anatomical FE meshes with rule-based myofiber directions. The models of the LA were passively inflated to 10mmHg followed by simulation of the contraction phase of the atrial cardiac cycle. The FE models predicted maximum LA volumes of 156.5 mL, 99.3 mL and 83.4 mL and ejection fractions of 36.9%, 32.0% and 25.2%. The median wall thickness in the 3 cases was calculated as [Formula: see text] mm, [Formula: see text] mm, and [Formula: see text] mm. The median curvature was determined as [Formula: see text] [Formula: see text], [Formula: see text], and [Formula: see text]. Following passive inflation, the correlation of wall stress with the inverse of wall thickness and curvature was 0.55-0.62 and 0.20-0.25, respectively. At peak contraction, the correlation of wall stress with the inverse of wall thickness and curvature was 0.38-0.44 and 0.16-0.34, respectively. In the LA, the 1st principal Cauchy stress is more dependent on wall thickness than curvature during passive inflation and both correlations decrease during active contraction. This emphasizes the importance of including the heterogeneous wall thickness in electromechanical FE simulations of the LA. Overall, simulation results and sensitivity analyses show that in complex atrial anatomy it is unlikely that a simple anatomical-based law can be used to estimate local wall stress, demonstrating the importance of FE analyses.
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Affiliation(s)
- Christoph M Augustin
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, USA
- Gottfried Schatz Research Center: Division of Biophysics, Medical University of Graz, Graz, Austria
| | - Thomas E Fastl
- Department of Biomedical Engineering, King's College London, London, UK
| | - Aurel Neic
- Gottfried Schatz Research Center: Division of Biophysics, Medical University of Graz, Graz, Austria
| | - Chiara Bellini
- Department of Bioengineering, Northeastern University, Boston, USA
| | - John Whitaker
- Department of Cardiology, Guy's and St Thomas' Hospitals, London, UK
| | - Ronak Rajani
- Department of Cardiology, Guy's and St Thomas' Hospitals, London, UK
| | - Mark D O'Neill
- Department of Cardiology, Guy's and St Thomas' Hospitals, London, UK
| | - Martin J Bishop
- Department of Biomedical Engineering, King's College London, London, UK
| | - Gernot Plank
- Gottfried Schatz Research Center: Division of Biophysics, Medical University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Steven A Niederer
- Department of Biomedical Engineering, King's College London, London, UK.
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7
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Ganesan P, Cherry EM, Huang DT, Pertsov AM, Ghoraani B. Atrial fibrillation source area probability mapping using electrogram patterns of multipole catheters. Biomed Eng Online 2020; 19:27. [PMID: 32370754 PMCID: PMC7201756 DOI: 10.1186/s12938-020-00769-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 04/15/2020] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Catheter ablation therapy involving isolation of pulmonary veins (PVs) from the left atrium is performed to terminate atrial fibrillation (AF). Unfortunately, standalone PV isolation procedure has shown to be a suboptimal success with AF continuation or recurrence. One reason, especially in patients with persistent or high-burden paroxysmal AF, is known to be due to the formation of repeating-pattern AF sources with a meandering core inside the atria. However, there is a need for accurate mapping and localization of these sources during catheter ablation. METHODS A novel AF source area probability (ASAP) mapping algorithm was developed and evaluated in 2D and 3D atrial simulated tissues with various arrhythmia scenarios and a retrospective study with three cases of clinical human AF. The ASAP mapping analyzes the electrograms collected from a multipole diagnostic catheter that is commonly used during catheter ablation procedure to intelligently sample the atria and delineate the trajectory path of a meandering repeating-pattern AF source. ASAP starts by placing the diagnostic catheter at an arbitrary location in the atria. It analyzes the recorded bipolar electrograms to build an ASAP map over the atrium anatomy and suggests an optimal location for the subsequent catheter location. ASAP then determines from the constructed ASAP map if an AF source has been delineated. If so, the catheter navigation is stopped and the algorithm provides the area of the AF source. Otherwise, the catheter is navigated to the suggested location, and the process is continued until an AF-source area is delineated. RESULTS ASAP delineated the AF source in over 95% of the simulated human AF cases within less than eight catheter placements regardless of the initial catheter placement. The success of ASAP in the clinical AF was confirmed by the ablation outcomes and the electrogram patterns at the delineated area. CONCLUSION Our analysis indicates the potential of the ASAP mapping to provide accurate information about the area of the meandering repeating-pattern AF sources as AF ablation targets for effective AF termination. Our algorithm could improve the success of AF catheter ablation therapy by locating and subsequently targeting patient-specific and repeating-pattern AF sources inside the atria.
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Affiliation(s)
- Prasanth Ganesan
- Department of Computer and Electrical Engineering, Florida Atlantic University, Boca Raton, FL, USA
| | - Elizabeth M Cherry
- School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - David T Huang
- Department of Cardiology, University of Rochester Medical Center, Rochester, NY, USA
| | - Arkady M Pertsov
- Department of Pharmacology, SUNY Upstate Medical Center, Syracuse, NY, USA
| | - Behnaz Ghoraani
- Department of Computer and Electrical Engineering, Florida Atlantic University, Boca Raton, FL, USA.
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8
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Coveney S, Clayton RH. Sensitivity and Uncertainty Analysis of Two Human Atrial Cardiac Cell Models Using Gaussian Process Emulators. Front Physiol 2020; 11:364. [PMID: 32390867 PMCID: PMC7191317 DOI: 10.3389/fphys.2020.00364] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 03/30/2020] [Indexed: 12/20/2022] Open
Abstract
Biophysically detailed cardiac cell models reconstruct the action potential and calcium dynamics of cardiac myocytes. They aim to capture the biophysics of current flow through ion channels, pumps, and exchangers in the cell membrane, and are highly detailed. However, the relationship between model parameters and model outputs is difficult to establish because the models are both complex and non-linear. The consequences of uncertainty and variability in model parameters are therefore difficult to determine without undertaking large numbers of model evaluations. The aim of the present study was to demonstrate how sensitivity and uncertainty analysis using Gaussian process emulators can be used for a systematic and quantitive analysis of biophysically detailed cardiac cell models. We selected the Courtemanche and Maleckar models of the human atrial action potential for analysis because these models describe a similar set of currents, with different formulations. In our approach Gaussian processes emulate the main features of the action potential and calcium transient. The emulators were trained with a set of design data comprising samples from parameter space and corresponding model outputs, initially obtained from 300 model evaluations. Variance based sensitivity indices were calculated using the emulators, and first order and total effect indices were calculated for each combination of parameter and output. The differences between the first order and total effect indices indicated that the effect of interactions between parameters was small. A second set of emulators were then trained using a new set of design data with a subset of the model parameters with a sensitivity index of more than 0.1 (10%). This second stage analysis enabled comparison of mechanisms in the two models. The second stage sensitivity indices enabled the relationship between the L-type Ca 2+ current and the action potential plateau to be quantified in each model. Our quantitative analysis predicted that changes in maximum conductance of the ultra-rapid K + channel I Kur would have opposite effects on action potential duration in the two models, and this prediction was confirmed by additional simulations. This study has demonstrated that Gaussian process emulators are an effective tool for sensitivity and uncertainty analysis of biophysically detailed cardiac cell models.
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Affiliation(s)
| | - Richard H. Clayton
- Insigneo Institute for in-silico Medicine and Department of Computer Science, University of Sheffield, Sheffield, United Kingdom
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9
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Wilson D. Phase-amplitude reduction far beyond the weakly perturbed paradigm. Phys Rev E 2020; 101:022220. [PMID: 32168672 DOI: 10.1103/physreve.101.022220] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 01/27/2020] [Indexed: 06/10/2023]
Abstract
While phase reduction is a well-established technique for the analysis of perturbed limit cycle oscillators, practical application requires perturbations to be sufficiently weak thereby limiting its utility in many situations. Here, a general strategy is developed for constructing a set of phase-amplitude reduced equations that is valid to arbitrary orders of accuracy in the amplitude coordinates. This reduction framework can be used to investigate the behavior of oscillatory dynamical systems far beyond the weakly perturbed paradigm. Additionally, a patchwork phase-amplitude reduction method is suggested that is useful when exceedingly large magnitude perturbations are considered. This patchwork method incorporates the high-accuracy phase-amplitude reductions of multiple nearby periodic orbits that result from modifications to nominal parameters. The proposed method of high-accuracy phase-amplitude reduction can be readily implemented numerically and examples are provided where reductions are computed up to fourteenth order accuracy.
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Affiliation(s)
- Dan Wilson
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee 37996, USA
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10
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Filos D, Tachmatzidis D, Maglaveras N, Vassilikos V, Chouvarda I. Understanding the Beat-to-Beat Variations of P-Waves Morphologies in AF Patients During Sinus Rhythm: A Scoping Review of the Atrial Simulation Studies. Front Physiol 2019; 10:742. [PMID: 31275161 PMCID: PMC6591370 DOI: 10.3389/fphys.2019.00742] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 05/28/2019] [Indexed: 11/13/2022] Open
Abstract
The remarkable advances in high-performance computing and the resulting increase of the computational power have the potential to leverage computational cardiology toward improving our understanding of the pathophysiological mechanisms of arrhythmias, such as Atrial Fibrillation (AF). In AF, a complex interaction between various triggers and the atrial substrate is considered to be the leading cause of AF initiation and perpetuation. In electrocardiography (ECG), P-wave is supposed to reflect atrial depolarization. It has been found that even during sinus rhythm (SR), multiple P-wave morphologies are present in AF patients with a history of AF, suggesting a higher dispersion of the conduction route in this population. In this scoping review, we focused on the mechanisms which modify the electrical substrate of the atria in AF patients, while investigating the existence of computational models that simulate the propagation of the electrical signal through different routes. The adopted review methodology is based on a structured analytical framework which includes the extraction of the keywords based on an initial limited bibliographic search, the extensive literature search and finally the identification of relevant articles based on the reference list of the studies. The leading mechanisms identified were classified according to their scale, spanning from mechanisms in the cell, tissue or organ level, and the produced outputs. The computational modeling approaches for each of the factors that influence the initiation and the perpetuation of AF are presented here to provide a clear overview of the existing literature. Several levels of categorization were adopted while the studies which aim to translate their findings to ECG phenotyping are highlighted. The results denote the availability of multiple models, which are appropriate under specific conditions. However, the consideration of complex scenarios taking into account multiple spatiotemporal scales, personalization of electrophysiological and anatomical models and the reproducibility in terms of ECG phenotyping has only partially been tackled so far.
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Affiliation(s)
- Dimitrios Filos
- Lab of Computing, Medical Informatics and Biomedical Imaging Technologies, School of Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | | | - Nicos Maglaveras
- Lab of Computing, Medical Informatics and Biomedical Imaging Technologies, School of Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
- Department of Industrial Engineering and Management Sciences, Northwestern University, Evanston, IL, United States
| | - Vassilios Vassilikos
- 3rd Cardiology Department, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Ioanna Chouvarda
- Lab of Computing, Medical Informatics and Biomedical Imaging Technologies, School of Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
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11
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Ganesan P, Cherry EM, Huang DT, Pertsov AM, Ghoraani B. Locating Atrial Fibrillation Rotor and Focal Sources Using Iterative Navigation of Multipole Diagnostic Catheters. Cardiovasc Eng Technol 2019; 10:354-366. [PMID: 30989616 PMCID: PMC6527788 DOI: 10.1007/s13239-019-00414-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 04/08/2019] [Indexed: 01/14/2023]
Abstract
Purpose Multi-polar diagnostic catheters are used to construct the 3D electro-anatomic mapping of the atrium during atrial fibrillation (AF) ablation procedures; however, it remains unclear how to use the electrograms recorded by these catheters to locate AF-driving sites known as focal and rotor source types. The purpose of this study is to present the first algorithm to iteratively navigate a circular multi-polar catheter to locate AF focal and rotor sources without the need to map the entire atria. Methods Starting from an initial location, the algorithm, which was blinded to the location and type of the AF source, iteratively advanced a Lasso catheter based on its electrogram characteristics. The algorithm stopped the catheter when it located of an AF source and identified the type. The efficiency of the algorithm is validated using a set of simulated focal and rotor-driven arrhythmias in fibrotic human 2D and 3D atrial tissue. Results Our study shows the feasibility of locating AF sources with a success rate of greater than 95.25% within average 7.56 ± 2.28 placements independently of the initial position of the catheter and the source type. Conclusions The algorithm could play a critical role in clinical electrophysiology laboratories for mapping patient-specific ablation of AF sources located outside the pulmonary veins and improving the procedure success. Electronic supplementary material The online version of this article (10.1007/s13239-019-00414-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Prasanth Ganesan
- Department of Computer and Electrical Engineering, Florida Atlantic University, Boca Raton, FL, USA
| | - Elizabeth M Cherry
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, NY, USA
| | - David T Huang
- Department of Cardiology, University of Rochester Medical Center, Rochester, NY, USA
| | - Arkady M Pertsov
- Department of Pharmacology, SUNY Upstate Medical Center, Syracuse, NY, USA
| | - Behnaz Ghoraani
- Department of Computer and Electrical Engineering, Florida Atlantic University, Boca Raton, FL, USA. .,, 777 Glades Road, EE (Bldg. 96) Room 319, Boca Raton, FL, 33431, USA.
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12
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Monga B, Wilson D, Matchen T, Moehlis J. Phase reduction and phase-based optimal control for biological systems: a tutorial. BIOLOGICAL CYBERNETICS 2019; 113:11-46. [PMID: 30203130 DOI: 10.1007/s00422-018-0780-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 08/25/2018] [Indexed: 05/20/2023]
Abstract
A powerful technique for the analysis of nonlinear oscillators is the rigorous reduction to phase models, with a single variable describing the phase of the oscillation with respect to some reference state. An analog to phase reduction has recently been proposed for systems with a stable fixed point, and phase reduction for periodic orbits has recently been extended to take into account transverse directions and higher-order terms. This tutorial gives a unified treatment of such phase reduction techniques and illustrates their use through mathematical and biological examples. It also covers the use of phase reduction for designing control algorithms which optimally change properties of the system, such as the phase of the oscillation. The control techniques are illustrated for example neural and cardiac systems.
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Affiliation(s)
- Bharat Monga
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, 93106, USA
| | - Dan Wilson
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, 37996, USA
| | - Tim Matchen
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, 93106, USA
| | - Jeff Moehlis
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, 93106, USA.
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13
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Ganesan P, Salmin A, Cherry EM, Huang DT, Pertsov AM, Ghoraani B. Iterative navigation of multipole diagnostic catheters to locate repeating-pattern atrial fibrillation drivers. J Cardiovasc Electrophysiol 2019; 30:758-768. [PMID: 30725499 PMCID: PMC6554033 DOI: 10.1111/jce.13872] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 01/16/2019] [Accepted: 01/31/2019] [Indexed: 01/01/2023]
Abstract
Introduction Targeting repeating‐pattern atrial fibrillation (AF) sources (reentry or focal drivers) can help in patient‐specific ablation therapy for AF; however, the development of reliable and accurate tools for locating such sources remains a major challenge. We describe iterative catheter navigation (ICAN) algorithm to locate AF drivers using a conventional circular Lasso catheter. Methods and Results At each step, the algorithm analyzes 10 bipolar electrograms recoded at a given catheter location and the history of previous catheter movements to determine if the source is inside the catheter loop. If not, it calculates new coordinates and selects a new position for the catheter. The process continues until a source is located. The algorithm was evaluated in a computer model of atrial tissue with various degrees of fibrosis under a broad range of arrhythmia scenarios. The latter included slow and fast reentry, macroreentry, figure‐of‐eight reentry, and fibrillatory conduction. Depending on the initial distance of the catheter from the source and scenario, it took about 3 to 16 steps to localize an AF source. In 94% of cases, the identified location was within 4 mm from the source, independently of the initial position of the catheter. The algorithm worked equally well in the presence of patchy fibrosis, low‐voltage areas, fragmented electrograms, and dominant‐frequency gradients. Conclusions AF repeating‐pattern sources can be localized using circular catheters without the need to map the entire tissue. The proposed algorithm has the potential to become a useful tool for patient‐specific ablation of AF sources located outside the pulmonary veins.
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Affiliation(s)
- Prasanth Ganesan
- Computer and Electrical Engineering and Computer Science, Florida Atlantic University, Boca Raton, Florida
| | - Anthony Salmin
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York
| | - Elizabeth M Cherry
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York
| | - David T Huang
- Department of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Arkady M Pertsov
- Department of Pharmacology, SUNY Upstate Medical Center, Syracuse, New York
| | - Behnaz Ghoraani
- Computer and Electrical Engineering and Computer Science, Florida Atlantic University, Boca Raton, Florida
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14
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Williams SE, Harrison JL, Chubb H, Whitaker J, Kiedrowicz R, Rinaldi CA, Cooklin M, Wright M, Niederer S, O'Neill MD. Local activation time sampling density for atrial tachycardia contact mapping: how much is enough? Europace 2018; 20:e11-e20. [PMID: 28379525 PMCID: PMC5834039 DOI: 10.1093/europace/eux037] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 02/12/2017] [Indexed: 11/25/2022] Open
Abstract
Aims Local activation time (LAT) mapping forms the cornerstone of atrial tachycardia diagnosis. Although anatomic and positional accuracy of electroanatomic mapping (EAM) systems have been validated, the effect of electrode sampling density on LAT map reconstruction is not known. Here, we study the effect of chamber geometry and activation complexity on optimal LAT sampling density using a combined in silico and in vivo approach. Methods and results In vivo 21 atrial tachycardia maps were studied in three groups: (1) focal activation, (2) macro-re-entry, and (3) localized re-entry. In silico activation was simulated on a 4×4cm atrial monolayer, sampled randomly at 0.25–10 points/cm2 and used to re-interpolate LAT maps. Activation patterns were studied in the geometrically simple porcine right atrium (RA) and complex human left atrium (LA). Activation complexity was introduced into the porcine RA by incomplete inter-caval linear ablation. In all cases, optimal sampling density was defined as the highest density resulting in minimal further error reduction in the re-interpolated maps. Optimal sampling densities for LA tachycardias were 0.67 ± 0.17 points/cm2 (focal activation), 1.05 ± 0.32 points/cm2 (macro-re-entry) and 1.23 ± 0.26 points/cm2 (localized re-entry), P = 0.0031. Increasing activation complexity was associated with increased optimal sampling density both in silico (focal activation 1.09 ± 0.14 points/cm2; re-entry 1.44 ± 0.49 points/cm2; spiral-wave 1.50 ± 0.34 points/cm2, P < 0.0001) and in vivo (porcine RA pre-ablation 0.45 ± 0.13 vs. post-ablation 0.78 ± 0.17 points/cm2, P = 0.0008). Increasing chamber geometry was also associated with increased optimal sampling density (0.61 ± 0.22 points/cm2 vs. 1.0 ± 0.34 points/cm2, P = 0.0015). Conclusion Optimal sampling densities can be identified to maximize diagnostic yield of LAT maps. Greater sampling density is required to correctly reveal complex activation and represent activation across complex geometries. Overall, the optimal sampling density for LAT map interpolation defined in this study was ∼1.0–1.5 points/cm2.
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Affiliation(s)
- Steven E Williams
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
| | - James L Harrison
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
| | - Henry Chubb
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
| | - John Whitaker
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
| | - Radek Kiedrowicz
- Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London, UK
| | - Christopher A Rinaldi
- Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London, UK
| | - Michael Cooklin
- Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London, UK
| | - Matthew Wright
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
| | - Steven Niederer
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
| | - Mark D O'Neill
- Division of Imaging Sciences and Biomedical Engineering, King's College London, 4th Floor North Wing, St Thomas' Hospital, 249 Westminster Bridge Road, SE1 7EH London
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15
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Saha M, Roney CH, Bayer JD, Meo M, Cochet H, Dubois R, Vigmond EJ. Wavelength and Fibrosis Affect Phase Singularity Locations During Atrial Fibrillation. Front Physiol 2018; 9:1207. [PMID: 30246796 PMCID: PMC6139329 DOI: 10.3389/fphys.2018.01207] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/10/2018] [Indexed: 01/06/2023] Open
Abstract
The mechanisms underlying atrial fibrillation (AF), the most common sustained cardiac rhythm disturbance, remain elusive. Atrial fibrosis plays an important role in the development of AF and rotor dynamics. Both electrical wavelength (WL) and the degree of atrial fibrosis change as AF progresses. However, their combined effect on rotor core location remains unknown. The aim of this study was to analyze the effects of WL change on rotor core location in both fibrotic and non-fibrotic atria. Three patient specific fibrosis distributions (total fibrosis content: 16.6, 22.8, and 19.2%) obtained from clinical imaging data of persistent AF patients were incorporated in a bilayer atrial computational model. Fibrotic effects were modeled as myocyte-fibroblast coupling + conductivity remodeling; structural remodeling; ionic current changes + conductivity remodeling; and combinations of these methods. To change WL, action potential duration (APD) was varied from 120 to 240ms, representing the range of clinically observed AF cycle length, by modifying the inward rectifier potassium current (IK1) conductance between 80 and 140% of the original value. Phase singularities (PSs) were computed to identify rotor core locations. Our results show that IK1 conductance variation resulted in a decrease of APD and WL across the atria. For large WL in the absence of fibrosis, PSs anchored to regions with high APD gradient at the center of the left atrium (LA) anterior wall and near the junctions of the inferior pulmonary veins (PVs) with the LA. Decreasing the WL induced more PSs, whose distribution became less clustered. With fibrosis, PS locations depended on the fibrosis distribution and the fibrosis implementation method. The proportion of PSs in fibrotic areas and along the borders varied with both WL and fibrosis modeling method: for patient one, this was 4.2-14.9% as IK1 varied for the structural remodeling representation, but 12.3-88.4% using the combination of structural remodeling with myocyte-fibroblast coupling. The degree and distribution of fibrosis and the choice of implementation technique had a larger effect on PS locations than the WL variation. Thus, distinguishing the fibrotic mechanisms present in a patient is important for interpreting clinical fibrosis maps to create personalized models.
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Affiliation(s)
- Mirabeau Saha
- IMB, UMR 5251, University of Bordeaux, Pessac, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux University, Pessac, France
| | - Caroline H. Roney
- Department of Biomedical Engineering, King's College London, London, United Kingdom
| | - Jason D. Bayer
- IMB, UMR 5251, University of Bordeaux, Pessac, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux University, Pessac, France
| | - Marianna Meo
- IMB, UMR 5251, University of Bordeaux, Pessac, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux University, Pessac, France
| | - Hubert Cochet
- IMB, UMR 5251, University of Bordeaux, Pessac, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux University, Pessac, France
| | - Remi Dubois
- IMB, UMR 5251, University of Bordeaux, Pessac, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux University, Pessac, France
| | - Edward J. Vigmond
- IMB, UMR 5251, University of Bordeaux, Pessac, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux University, Pessac, France
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16
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Clayton RH. Dispersion of Recovery and Vulnerability to Re-entry in a Model of Human Atrial Tissue With Simulated Diffuse and Focal Patterns of Fibrosis. Front Physiol 2018; 9:1052. [PMID: 30131713 PMCID: PMC6090998 DOI: 10.3389/fphys.2018.01052] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 07/16/2018] [Indexed: 12/03/2022] Open
Abstract
Fibrosis in atrial tissue can act as a substrate for persistent atrial fibrillation, and can be focal or diffuse. Regions of fibrosis are associated with slowed or blocked conduction, and several approaches have been used to model these effects. In this study a computational model of 2D atrial tissue was used to investigate how the spatial scale of regions of simulated fibrosis influenced the dispersion of action potential duration (APD) and vulnerability to re-entry in simulated normal human atrial tissue, and human tissue that has undergone remodeling as a result of persistent atrial fibrillation. Electrical activity was simulated in a 10 × 10 cm square 2D domain, with a spatially varying diffusion coefficient as described below. Cellular electrophysiology was represented by the Courtemanche model for human atrial cells, with the model parameters set for normal and remodeled cells. The effect of fibrosis was modeled with a smoothly varying diffusion coefficient, obtained from sampling a Gaussian random field (GRF) with length scales of between 1.25 and 10.0 mm. Twenty samples were drawn from each field, and used to allocate a value of diffusion coefficient between 0.05 and 0.2 mm2/ms. Dispersion of APD was assessed in each sample by pacing at a cycle length of 1,000 ms, followed by a premature beat with a coupling interval of 400 ms. Vulnerability to re-entry was assessed with an aggressive pacing protocol with pacing cycle lengths decreasing from 450 to 250 ms in 25 ms intervals for normal tissue and 300–150 ms for remodeled tissue. Simulated fibrosis at smaller spatial scales tended to lengthen APD, increase APD dispersion, and increase vulnerability to sustained re-entry relative to fibrosis at larger spatial scales. This study shows that when fibrosis is represented by smoothly varying tissue diffusion, the spatial scale of fibrosis has important effects on both dispersion of recovery and vulnerability to re-entry.
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Affiliation(s)
- Richard H Clayton
- Department of Computer Science, Insigneo Institute for in-silico Medicine, University of Sheffield, Sheffield, United Kingdom
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17
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Ugarte JP, Tobón C, Lopes AM, Machado JAT. Atrial Rotor Dynamics Under Complex Fractional Order Diffusion. Front Physiol 2018; 9:975. [PMID: 30087620 PMCID: PMC6066719 DOI: 10.3389/fphys.2018.00975] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 07/03/2018] [Indexed: 12/27/2022] Open
Abstract
The mechanisms of atrial fibrillation (AF) are a challenging research topic. The rotor hypothesis states that the AF is sustained by a reentrant wave that propagates around an unexcited core. Cardiac tissue heterogeneities, both structural and cellular, play an important role during fibrillatory dynamics, so that the ionic characteristics of the currents, their spatial distribution and their structural heterogeneity determine the meandering of the rotor. Several studies about rotor dynamics implement the standard diffusion equation. However, this mathematical scheme carries some limitations. It assumes the myocardium as a continuous medium, ignoring, therefore, its discrete and heterogeneous aspects. A computational model integrating both, electrical and structural properties could complement experimental and clinical results. A new mathematical model of the action potential propagation, based on complex fractional order derivatives is presented. The complex derivative order appears of considering the myocardium as discrete-scale invariant fractal. The main aim is to study the role of a myocardial, with fractal characteristics, on atrial fibrillatory dynamics. For this purpose, the degree of structural heterogeneity is described through derivatives of complex order γ = α + jβ. A set of variations for γ is tested. The real part α takes values ranging from 1.1 to 2 and the imaginary part β from 0 to 0.28. Under this scheme, the standard diffusion is recovered when α = 2 and β = 0. The effect of γ on the action potential propagation over an atrial strand is investigated. Rotors are generated in a 2D model of atrial tissue under electrical remodeling due to chronic AF. The results show that the degree of structural heterogeneity, given by γ, modulates the electrophysiological properties and the dynamics of rotor-type reentrant mechanisms. The spatial stability of the rotor and the area of its unexcited core are modulated. As the real part decreases and the imaginary part increases, simulating a higher structural heterogeneity, the vulnerable window to reentrant is increased, as the total meandering of the rotor tip. This in silico study suggests that structural heterogeneity, described by means of complex order derivatives, modulates the stability of rotors and that a wide range of rotor dynamics can be generated.
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Affiliation(s)
- Juan P. Ugarte
- Grupo de Investigación en Modelamiento y Simulación Computacional, Facultad de Ingenierías, Universidad de San Buenaventura, Medellín, Colombia
| | | | - António M. Lopes
- UISPA-LAETA/INEGI, Faculty of Engineering, University of Porto, Porto, Portugal
| | - J. A. Tenreiro Machado
- Department of Electrical Engineering, Institute of Engineering, Polytechnic of Porto, Porto, Portugal
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18
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Ganesan P, Shillieto KE, Ghoraani B. Simulation of Spiral Waves and Point Sources in Atrial Fibrillation with Application to Rotor Localization. PROCEEDINGS. IEEE INTERNATIONAL SYMPOSIUM ON COMPUTER-BASED MEDICAL SYSTEMS 2018; 2017:379-384. [PMID: 29629398 DOI: 10.1109/cbms.2017.161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cardiac simulations play an important role in studies involving understanding and investigating the mechanisms of cardiac arrhythmias. Today, studies of arrhythmogenesis and maintenance are largely being performed by creating simulations of a particular arrhythmia with high accuracy comparable to the results of clinical experiments. Atrial fibrillation (AF), the most common arrhythmia in the United States and many other parts of the world, is one of the major field where simulation and modeling is largely used. AF simulations not only assist in understanding its mechanisms but also help to develop, evaluate and improve the computer algorithms used in electrophysiology (EP) systems for ablation therapies. In this paper, we begin with a brief overeview of some common techniques used in simulations to simulate two major AF mechanisms - spiral waves (or rotors) and point (or focal) sources. We particularly focus on 2D simulations using Nygren et al.'s mathematical model of human atrial cell. Then, we elucidate an application of the developed AF simulation to an algorithm designed for localizing AF rotors for improving current AF ablation therapies. Our simulation methods and results, along with the other discussions presented in this paper is aimed to provide engineers and professionals with a working-knowledge of application-specific simulations of spirals and foci.
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Affiliation(s)
- Prasanth Ganesan
- Department of Electrical Engineering, Florida Atlantic University, Boca Raton, Florida
| | | | - Behnaz Ghoraani
- Department of Electrical Engineering, Florida Atlantic University, Boca Raton, Florida
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19
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McGillivray MF, Cheng W, Peters NS, Christensen K. Machine learning methods for locating re-entrant drivers from electrograms in a model of atrial fibrillation. ROYAL SOCIETY OPEN SCIENCE 2018; 5:172434. [PMID: 29765687 PMCID: PMC5936952 DOI: 10.1098/rsos.172434] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 03/13/2018] [Indexed: 05/14/2023]
Abstract
Mapping resolution has recently been identified as a key limitation in successfully locating the drivers of atrial fibrillation (AF). Using a simple cellular automata model of AF, we demonstrate a method by which re-entrant drivers can be located quickly and accurately using a collection of indirect electrogram measurements. The method proposed employs simple, out-of-the-box machine learning algorithms to correlate characteristic electrogram gradients with the displacement of an electrogram recording from a re-entrant driver. Such a method is less sensitive to local fluctuations in electrical activity. As a result, the method successfully locates 95.4% of drivers in tissues containing a single driver, and 95.1% (92.6%) for the first (second) driver in tissues containing two drivers of AF. Additionally, we demonstrate how the technique can be applied to tissues with an arbitrary number of drivers. In its current form, the techniques presented are not refined enough for a clinical setting. However, the methods proposed offer a promising path for future investigations aimed at improving targeted ablation for AF.
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Affiliation(s)
- Max Falkenberg McGillivray
- The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK
- Centre for Complexity Science, Imperial College London, London SW7 2AZ, UK
| | - William Cheng
- The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK
- Centre for Complexity Science, Imperial College London, London SW7 2AZ, UK
| | - Nicholas S Peters
- ElectroCardioMaths Programme, Imperial Centre for Cardiac Engineering, Imperial College London, London W12 0NN, UK
| | - Kim Christensen
- The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK
- Centre for Complexity Science, Imperial College London, London SW7 2AZ, UK
- ElectroCardioMaths Programme, Imperial Centre for Cardiac Engineering, Imperial College London, London W12 0NN, UK
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20
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Wilson D, Ermentrout B. Stochastic Pacing Inhibits Spatially Discordant Cardiac Alternans. Biophys J 2017; 113:2552-2572. [PMID: 29212008 DOI: 10.1016/j.bpj.2017.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 09/28/2017] [Accepted: 10/02/2017] [Indexed: 12/19/2022] Open
Abstract
Depressed heart rate variability is a well-established risk factor for sudden cardiac death in survivors of acute myocardial infarction and for those with congestive heart failure. Although measurements of heart rate variability provide a valuable prognostic tool, it is unclear whether reduced heart rate variability itself is proarrhythmic or if it simply correlates with the severity of autonomic nervous system dysfunction. In this work, we investigate a possible mechanism by which heart rate variability could protect against cardiac arrhythmia. Specifically, in numerical simulations, we observe an inverse relationship between the variance of stochastic pacing and the occurrence of spatially discordant alternans, an arrhythmia that is widely believed to facilitate the development of cardiac fibrillation. By analyzing the effects of conduction velocity restitution, cellular dynamics, electrotonic coupling, and stochastic pacing on the nodal dynamics of spatially discordant alternans, we provide intuition for this observed behavior and propose control strategies to inhibit discordant alternans.
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Affiliation(s)
- Dan Wilson
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania.
| | - Bard Ermentrout
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania
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21
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Campana C, Akar FG. Commentary: Atrial Fibrillation Dynamics and Ionic Block Effects in Six Heterogeneous Human 3D Virtual Atria with Distinct Repolarization Dynamics. Front Bioeng Biotechnol 2017; 5:59. [PMID: 29057224 PMCID: PMC5635327 DOI: 10.3389/fbioe.2017.00059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 09/20/2017] [Indexed: 11/26/2022] Open
Affiliation(s)
- Chiara Campana
- Icahn School of Medicine at Mount Sinai, The Cardiovascular Institute, New York, NY, United States
| | - Fadi G Akar
- Icahn School of Medicine at Mount Sinai, The Cardiovascular Institute, New York, NY, United States
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22
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Krogh-Madsen T, Christini DJ. Slow [Na +] i dynamics impacts arrhythmogenesis and spiral wave reentry in cardiac myocyte ionic model. CHAOS (WOODBURY, N.Y.) 2017; 27:093907. [PMID: 28964146 DOI: 10.1063/1.4999475] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Accumulation of intracellular Na+ is gaining recognition as an important regulator of cardiac myocyte electrophysiology. The intracellular Na+ concentration can be an important determinant of the cardiac action potential duration, can modulate the tissue-level conduction of excitation waves, and can alter vulnerability to arrhythmias. Mathematical models of cardiac electrophysiology often incorporate a dynamic intracellular Na+ concentration, which changes much more slowly than the remaining variables. We investigated the dependence of several arrhythmogenesis-related factors on [Na+]i in a mathematical model of the human atrial action potential. In cell simulations, we found that [Na+]i accumulation stabilizes the action potential duration to variations in several conductances and that the slow dynamics of [Na+]i impacts bifurcations to pro-arrhythmic afterdepolarizations, causing intermittency between different rhythms. In long-lasting tissue simulations of spiral wave reentry, [Na+]i becomes spatially heterogeneous with a decreased area around the spiral wave rotation center. This heterogeneous region forms a functional anchor, resulting in diminished meandering of the spiral wave. Our findings suggest that slow, physiological, rate-dependent variations in [Na+]i may play complex roles in cellular and tissue-level cardiac dynamics.
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Affiliation(s)
- Trine Krogh-Madsen
- Greenberg Division of Cardiology, Weill Cornell Medicine, New York, New York 10065, USA; Institute for Computational Biomedicine, Weill Cornell Medicine, New York, New York 10065, USA; and Cardiovascular Research Institute, Weill Cornell Medicine, New York, New York 10065, USA
| | - David J Christini
- Greenberg Division of Cardiology, Weill Cornell Medicine, New York, New York 10065, USA; Institute for Computational Biomedicine, Weill Cornell Medicine, New York, New York 10065, USA; and Cardiovascular Research Institute, Weill Cornell Medicine, New York, New York 10065, USA
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23
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Bittihn P, Berg S, Parlitz U, Luther S. Emergent dynamics of spatio-temporal chaos in a heterogeneous excitable medium. CHAOS (WOODBURY, N.Y.) 2017; 27:093931. [PMID: 28964139 DOI: 10.1063/1.4999604] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Self-organized activation patterns in excitable media such as spiral waves and spatio-temporal chaos underlie dangerous cardiac arrhythmias. While the interaction of single spiral waves with different types of heterogeneity has been studied extensively, the effect of heterogeneity on fully developed spatio-temporal chaos remains poorly understood. We investigate how the complexity and stability properties of spatio-temporal chaos in the Bär-Eiswirth model of excitable media depend on the heterogeneity of the underlying medium. We employ different measures characterizing the chaoticity of the system and find that the spatial arrangement of multiple discrete lower excitability regions has a strong impact on the complexity of the dynamics. Varying the number, shape, and spatial arrangement of the heterogeneities, we observe strong emergent effects ranging from increases in chaoticity to the complete cessation of chaos, contrasting the expectation from the homogeneous behavior. The implications of our findings for the development and treatment of arrhythmias in the heterogeneous cardiac muscle are discussed.
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Affiliation(s)
- Philip Bittihn
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Sebastian Berg
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Ulrich Parlitz
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Stefan Luther
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
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24
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Lombardo DM, Fenton FH, Narayan SM, Rappel WJ. Comparison of Detailed and Simplified Models of Human Atrial Myocytes to Recapitulate Patient Specific Properties. PLoS Comput Biol 2016; 12:e1005060. [PMID: 27494252 PMCID: PMC4975409 DOI: 10.1371/journal.pcbi.1005060] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 07/12/2016] [Indexed: 11/19/2022] Open
Abstract
Computer studies are often used to study mechanisms of cardiac arrhythmias, including atrial fibrillation (AF). A crucial component in these studies is the electrophysiological model that describes the membrane potential of myocytes. The models vary from detailed, describing numerous ion channels, to simplified, grouping ionic channels into a minimal set of variables. The parameters of these models, however, are determined across different experiments in varied species. Furthermore, a single set of parameters may not describe variations across patients, and models have rarely been shown to recapitulate critical features of AF in a given patient. In this study we develop physiologically accurate computational human atrial models by fitting parameters of a detailed and of a simplified model to clinical data for five patients undergoing ablation therapy. Parameters were simultaneously fitted to action potential (AP) morphology, action potential duration (APD) restitution and conduction velocity (CV) restitution curves in these patients. For both models, our fitting procedure generated parameter sets that accurately reproduced clinical data, but differed markedly from published sets and between patients, emphasizing the need for patient-specific adjustment. Both models produced two-dimensional spiral wave dynamics for that were similar for each patient. These results show that simplified, computationally efficient models are an attractive choice for simulations of human atrial electrophysiology in spatially extended domains. This study motivates the development and validation of patient-specific model-based mechanistic studies to target therapy.
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Affiliation(s)
- Daniel M. Lombardo
- Department of Physics, University of California, San Diego, La Jolla, California, United States of America
| | - Flavio H. Fenton
- School of Physics, Georgia Tech University, Atlanta, Georgia, United States of America
| | - Sanjiv M. Narayan
- Department of Medicine, Stanford University, Palo Alto, California, United States of America
| | - Wouter-Jan Rappel
- Department of Physics, University of California, San Diego, La Jolla, California, United States of America
- * E-mail:
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25
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Shillieto KE, Ganesan P, Salmin AJ, Cherry EM, Pertsov AM, Ghoraani B. Catheter simulator software tool to generate electrograms of any multi-polar diagnostic catheter from 3D atrial tissue. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2016:2741-2744. [PMID: 28268886 PMCID: PMC5884094 DOI: 10.1109/embc.2016.7591297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Simulations are excellent tools for assessing new therapeutic strategies and are often conducted before implementing new therapy options in a clinical practice. For patients suffering from a heart arrhythmia, the main source of information comes from an intracardiac catheter. One of the common catheters is a Lasso multi-pole diagnostic catheter, which is a catheter that has 20 electrodes in a circular pattern. In this paper, we developed algorithm and simulation software that allows the users to place a multi-pole catheter on the atrial endocardial surface and record electrograms. In 3D atrial tissue, the plane of principal curvature is determined using eigenvectors of catheter vertices, from where the normals are projected and registered to the surface using 3D geodesic distance. This tool provides a platform for performing customized virtual cardiac experiments.
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Affiliation(s)
- Kristina E. Shillieto
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY
| | - Prasanth Ganesan
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY
| | - Anthony J. Salmin
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY
| | - Elizabeth M. Cherry
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY
| | - Arkady M. Pertsov
- Department of Pharmacology SUNY Upstate Medical Center, Syracuse, NY
| | - Behnaz Ghoraani
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY
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26
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Wilson D, Moehlis J. Toward a More Efficient Implementation of Antifibrillation Pacing. PLoS One 2016; 11:e0158239. [PMID: 27391010 PMCID: PMC4938213 DOI: 10.1371/journal.pone.0158239] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 06/12/2016] [Indexed: 11/18/2022] Open
Abstract
We devise a methodology to determine an optimal pattern of inputs to synchronize firing patterns of cardiac cells which only requires the ability to measure action potential durations in individual cells. In numerical bidomain simulations, the resulting synchronizing inputs are shown to terminate spiral waves with a higher probability than comparable inputs that do not synchronize the cells as strongly. These results suggest that designing stimuli which promote synchronization in cardiac tissue could improve the success rate of defibrillation, and point towards novel strategies for optimizing antifibrillation pacing.
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Affiliation(s)
- Dan Wilson
- Department of Mechanical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, United States of America
- * E-mail:
| | - Jeff Moehlis
- Department of Mechanical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, United States of America
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27
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Greisas A, Zlochiver S. The Multi-Domain Fibroblast/Myocyte Coupling in the Cardiac Tissue: A Theoretical Study. Cardiovasc Eng Technol 2016; 7:290-304. [PMID: 27150222 DOI: 10.1007/s13239-016-0266-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 04/29/2016] [Indexed: 02/02/2023]
Abstract
Cardiac fibroblast proliferation and concomitant collagenous matrix accumulation (fibrosis) develop during multiple cardiac pathologies. Recent studies have demonstrated direct electrical coupling between myocytes and fibroblasts in vitro, and assessed the electrophysiological implications of such coupling. However, in the living tissues, such coupling has not been demonstrated, and only indirect coupling via the extracellular space is likely to exist. In this study we employed a multi-domain model to assess the modulation of the cardiac electrophysiological properties by neighboring fibroblasts assuming only indirect coupling. Numerical simulations in 1D and 2D human atrial models showed that extracellular coupling sustains a significant impact on conduction velocity (CV) and a less significant effect on the action potential duration. Both CV and the slope of the CV restitution increased with increasing fibroblast density. This effect was more substantial for lower extracellular conductance. In 2D, spiral waves exhibited reduced frequency with increasing fibroblast density, and the propensity of wavebreaks and complex dynamics at high pacing rates significantly increased.
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Affiliation(s)
- Ariel Greisas
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel
| | - Sharon Zlochiver
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel.
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28
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Heijman J, Erfanian Abdoust P, Voigt N, Nattel S, Dobrev D. Computational models of atrial cellular electrophysiology and calcium handling, and their role in atrial fibrillation. J Physiol 2015; 594:537-53. [PMID: 26582329 DOI: 10.1113/jp271404] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 10/08/2015] [Indexed: 11/08/2022] Open
Abstract
The complexity of the heart makes an intuitive understanding of the relative contribution of ion channels, transporters and signalling pathways to cardiac electrophysiology challenging. Computational modelling of cardiac cellular electrophysiology has proven useful to integrate experimental findings, extrapolate results obtained in expression systems or animal models to other systems, test quantitatively ideas based on experimental data and provide novel hypotheses that are experimentally testable. While the bulk of computational modelling has traditionally been directed towards ventricular bioelectricity, increasing recognition of the clinical importance of atrial arrhythmias, particularly atrial fibrillation, has led to widespread efforts to apply computational approaches to understanding atrial electrical function. The increasing availability of detailed, atrial-specific experimental data has stimulated the development of novel computational models of atrial-cellular electrophysiology and Ca(2+) handling. To date, more than 300 studies have employed mathematical simulations to enhance our understanding of atrial electrophysiology, arrhythmogenesis and therapeutic responses. Future modelling studies are likely to move beyond current whole-cell models by incorporating new data on subcellular architecture, macromolecular protein complexes, and localized ion-channel regulation by signalling pathways. At the same time, more integrative multicellular models that take into account regional electrophysiological and Ca(2+) handling properties, mechano-electrical feedback and/or autonomic regulation will be needed to investigate the mechanisms governing atrial arrhythmias. A combined experimental and computational approach is expected to provide the more comprehensive understanding of atrial arrhythmogenesis that is required to develop improved diagnostic and therapeutic options. Here, we review this rapidly expanding area, with a particular focus on Ca(2+) handling, and provide ideas about potential future directions.
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Affiliation(s)
- Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands.,Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Pegah Erfanian Abdoust
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Niels Voigt
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Stanley Nattel
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany.,Department of Medicine, Montreal Heart Institute and Université de Montréal, Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
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29
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Ganesan P, Cherry EM, Pertsov AM, Ghoraani B. Characterization of Electrograms from Multipolar Diagnostic Catheters during Atrial Fibrillation. BIOMED RESEARCH INTERNATIONAL 2015; 2015:272954. [PMID: 26581316 PMCID: PMC4637153 DOI: 10.1155/2015/272954] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Revised: 02/13/2015] [Accepted: 02/19/2015] [Indexed: 11/17/2022]
Abstract
Atrial fibrillation (AF) is the most common arrhythmia in USA with more than 2.3 million people affected annually. Catheter ablation procedure is a method for treatment of AF, which involves 3D electroanatomic mapping of the patient's left atrium (LA) by maneuvering a conventional multipolar diagnostic catheter (MPDC) along the LA endocardial surface after which pulmonary vein (PV) isolation is performed, thus eliminating the AF triggers originating from the PVs. However, it remains unclear how to effectively utilize the information provided by the MPDC to locate the AF-sustaining sites, known as sustained rotor-like activities (RotAs). In this study, we use computer modeling to investigate the variations in the characteristics of the MPDC electrograms, namely, total conduction delay (TCD) and average cycle length (CL), as the MPDC moves towards a RotA source. Subsequently, a study with a human subject was performed in order to verify the predictions of the simulation study. The conclusions from this study may be used to iteratively direct an MPDC towards RotA sources thus allowing the RotAs to be localized for customized and improved AF ablation.
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Affiliation(s)
- Prasanth Ganesan
- Biomedical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Elizabeth M. Cherry
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Arkady M. Pertsov
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Behnaz Ghoraani
- Biomedical Engineering Department, Rochester Institute of Technology, Rochester, NY 14623, USA
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30
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Human atrial cell models to analyse haemodialysis-related effects on cardiac electrophysiology: work in progress. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2014; 2014:291598. [PMID: 25587348 PMCID: PMC4284940 DOI: 10.1155/2014/291598] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/05/2014] [Accepted: 11/12/2014] [Indexed: 11/25/2022]
Abstract
During haemodialysis (HD) sessions, patients undergo alterations in the extracellular environment, mostly concerning plasma electrolyte concentrations, pH, and volume, together with a modification of sympathovagal balance. All these changes affect cardiac electrophysiology, possibly leading to an increased arrhythmic risk. Computational modeling may help to investigate the impact of HD-related changes on atrial electrophysiology. However, many different human atrial action potential (AP) models are currently available, all validated only with the standard electrolyte concentrations used in experiments. Therefore, they may respond in different ways to the same environmental changes. After an overview on how the computational approach has been used in the past to investigate the effect of HD therapy on cardiac electrophysiology, the aim of this work has been to assess the current state of the art in human atrial AP models, with respect to the HD context. All the published human atrial AP models have been considered and tested for electrolytes, volume changes, and different acetylcholine concentrations. Most of them proved to be reliable for single modifications, but all of them showed some drawbacks. Therefore, there is room for a new human atrial AP model, hopefully able to physiologically reproduce all the HD-related effects. At the moment, work is still in progress in this specific field.
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31
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Sánchez C, Bueno-Orovio A, Wettwer E, Loose S, Simon J, Ravens U, Pueyo E, Rodriguez B. Inter-subject variability in human atrial action potential in sinus rhythm versus chronic atrial fibrillation. PLoS One 2014; 9:e105897. [PMID: 25157495 PMCID: PMC4144914 DOI: 10.1371/journal.pone.0105897] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 07/26/2014] [Indexed: 02/07/2023] Open
Abstract
AIMS Human atrial electrophysiology exhibits high inter-subject variability in both sinus rhythm (SR) and chronic atrial fibrillation (cAF) patients. Variability is however rarely investigated in experimental and theoretical electrophysiological studies, thus hampering the understanding of its underlying causes but also its implications in explaining differences in the response to disease and treatment. In our study, we aim at investigating the ability of populations of human atrial cell models to capture the inter-subject variability in action potential (AP) recorded in 363 patients both under SR and cAF conditions. METHODS AND RESULTS Human AP recordings in atrial trabeculae (n = 469) from SR and cAF patients were used to calibrate populations of computational SR and cAF atrial AP models. Three populations of over 2000 sampled models were generated, based on three different human atrial AP models. Experimental calibration selected populations of AP models yielding AP with morphology and duration in range with experimental recordings. Populations using the three original models can mimic variability in experimental AP in both SR and cAF, with median conductance values in SR for most ionic currents deviating less than 30% from their original peak values. All cAF populations show similar variations in G(K1), G(Kur) and G(to), consistent with AF-related remodeling as reported in experiments. In all SR and cAF model populations, inter-subject variability in I(K1) and I(NaK) underlies variability in APD90, variability in I(Kur), I(CaL) and I(NaK) modulates variability in APD50 and combined variability in Ito and I(Kur) determines variability in APD20. The large variability in human atrial AP triangulation is mostly determined by I(K1) and either I(NaK) or I(NaCa) depending on the model. CONCLUSION Experimentally-calibrated human atrial AP models populations mimic AP variability in SR and cAF patient recordings, and identify potential ionic determinants of inter-subject variability in human atrial AP duration and morphology in SR versus cAF.
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Affiliation(s)
- Carlos Sánchez
- Biosignal Interpretation and Computational Simulation (BSICoS), Aragón Institute of Engineering Research (I3A) and Aragón Health Research Institute (IIS), University of Zaragoza, Zaragoza, Spain
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Zaragoza, Spain
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | | | - Erich Wettwer
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany
| | - Simone Loose
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany
| | - Jana Simon
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany
| | - Ursula Ravens
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany
| | - Esther Pueyo
- Biosignal Interpretation and Computational Simulation (BSICoS), Aragón Institute of Engineering Research (I3A) and Aragón Health Research Institute (IIS), University of Zaragoza, Zaragoza, Spain
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Zaragoza, Spain
| | - Blanca Rodriguez
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
- * E-mail:
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32
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Dvir H, Zlochiver S. The interrelations among stochastic pacing, stability, and memory in the heart. Biophys J 2014; 107:1023-34. [PMID: 25140438 DOI: 10.1016/j.bpj.2014.07.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 06/25/2014] [Accepted: 07/02/2014] [Indexed: 11/18/2022] Open
Abstract
Low pacing variability in the heart has been clinically reported as a risk factor for lethal cardiac arrhythmias and arrhythmic death. In ia previous simulation study, we demonstrated that stochastic pacing sustains an antiarrhythmic effect by moderating the slope of the action potential duration (APD) restitution curve, by reducing the propensity of APD alternans, converting discordant to concordant alternans, and ultimately preventing wavebreaks. However, the dynamic mechanisms relating pacing stochasticity to tissue stability are not yet known. In this work, we develop a mathematical framework to describe the APD signal using an autoregressive stochastic model, and we establish the interrelations between stochastic pacing, cardiac memory, and cardiac stability, as manifested by the degree of APD alternans. Employing stability analysis tools, we show that increased stochasticity in the ventricular tissue activation sequence works to lower the maximal absolute eigenvalues of the stochastic model, thereby contributing to increased stability. We also show that the memory coefficients of the autoregressive model are modulated by pacing stochasticity in a nonlinear, biphasic way, so that for exceedingly high levels of pacing stochasticity, the antiarrhythmic effect is hampered by increasing APD variance. This work may contribute to establishment of an optimal antiarrhythmic pacing protocol in a future study.
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Affiliation(s)
- Hila Dvir
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv, Israel
| | - Sharon Zlochiver
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv, Israel.
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33
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Trayanova NA. Mathematical approaches to understanding and imaging atrial fibrillation: significance for mechanisms and management. Circ Res 2014; 114:1516-31. [PMID: 24763468 DOI: 10.1161/circresaha.114.302240] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Atrial fibrillation (AF) is the most common sustained arrhythmia in humans. The mechanisms that govern AF initiation and persistence are highly complex, of dynamic nature, and involve interactions across multiple temporal and spatial scales in the atria. This article aims to review the mathematical modeling and computer simulation approaches to understanding AF mechanisms and aiding in its management. Various atrial modeling approaches are presented, with descriptions of the methodological basis and advancements in both lower-dimensional and realistic geometry models. A review of the most significant mechanistic insights made by atrial simulations is provided. The article showcases the contributions that atrial modeling and simulation have made not only to our understanding of the pathophysiology of atrial arrhythmias, but also to the development of AF management approaches. A summary of the future developments envisioned for the field of atrial simulation and modeling is also presented. The review contends that computational models of the atria assembled with data from clinical imaging modalities that incorporate electrophysiological and structural remodeling could become a first line of screening for new AF therapies and approaches, new diagnostic developments, and new methods for arrhythmia prevention.
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Affiliation(s)
- Natalia A Trayanova
- From the Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD
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34
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Dvir H, Zlochiver S. Stochastic cardiac pacing increases ventricular electrical stability--a computational study. Biophys J 2014; 105:533-42. [PMID: 23870274 DOI: 10.1016/j.bpj.2013.06.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 06/04/2013] [Accepted: 06/10/2013] [Indexed: 11/17/2022] Open
Abstract
The ventricular tissue is activated in a stochastic rather than in a deterministic rhythm due to the inherent heart rate variability (HRV). Low HRV is a known predictor for arrhythmia events and traditionally is attributed to autonomic nervous system tone damage. Yet, there is no model that directly assesses the antiarrhythmic effect of pacing stochasticity per se. One-dimensional (1D) and two-dimensional (2D) human ventricular tissues were modeled, and both deterministic and stochastic pacing protocols were applied. Action potential duration restitution (APDR) and conduction velocity restitution (CVR) curves were generated and analyzed, and the propensity and characteristics of action potential duration (APD) alternans were investigated. In the 1D model, pacing stochasticity was found to sustain a moderating effect on the APDR curve by reducing its slope, rendering the tissue less arrhythmogenic. Moreover, stochasticity was found to be a significant antagonist to the development of concordant APD alternans. These effects were generally amplified with increased variability in the pacing cycle intervals. In addition, in the 2D tissue configuration, stochastic pacing exerted a protective antiarrhythmic effect by reducing the spatial APD heterogeneity and converting discordant APD alternans to concordant ones. These results suggest that high cardiac pacing stochasticity is likely to reduce the risk of cardiac arrhythmias in patients.
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Affiliation(s)
- Hila Dvir
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv, Israel
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35
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Elshrif MM, Cherry EM. A quantitative comparison of the behavior of human ventricular cardiac electrophysiology models in tissue. PLoS One 2014; 9:e84401. [PMID: 24416228 PMCID: PMC3885549 DOI: 10.1371/journal.pone.0084401] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/19/2013] [Indexed: 11/19/2022] Open
Abstract
Numerical integration of mathematical models of heart cell electrophysiology provides an important computational tool for studying cardiac arrhythmias, but the abundance of available models complicates selecting an appropriate model. We study the behavior of two recently published models of human ventricular action potentials, the Grandi-Pasqualini-Bers (GPB) and the O'Hara-Virág-Varró-Rudy (OVVR) models, and compare the results with four previously published models and with available experimental and clinical data. We find the shapes and durations of action potentials and calcium transients differ between the GPB and OVVR models, as do the magnitudes and rate-dependent properties of transmembrane currents and the calcium transient. Differences also occur in the steady-state and S1–S2 action potential duration and conduction velocity restitution curves, including a maximum conduction velocity for the OVVR model roughly half that of the GPB model and well below clinical values. Between single cells and tissue, both models exhibit differences in properties, including maximum upstroke velocity, action potential amplitude, and minimum diastolic interval. Compared to experimental data, action potential durations for the GPB and OVVR models agree fairly well (although OVVR epicardial action potentials are shorter), but maximum slopes of steady-state restitution curves are smaller. Although studies show alternans in normal hearts, it occurs only in the OVVR model, and only for a narrow range of cycle lengths. We find initiated spiral waves do not progress to sustained breakup for either model. The dominant spiral wave period of the GPB model falls within clinically relevant values for ventricular tachycardia (VT), but for the OVVR model, the dominant period is longer than periods associated with VT. Our results should facilitate choosing a model to match properties of interest in human cardiac tissue and to replicate arrhythmia behavior more closely. Furthermore, by indicating areas where existing models disagree, our findings suggest avenues for further experimental work.
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Affiliation(s)
- Mohamed M. Elshrif
- B. Thomas Golisano College of Computing and Information Sciences, Rochester Institute of Technology, Rochester, New York, United States of America
| | - Elizabeth M. Cherry
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York, United States of America
- * E-mail:
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36
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Aslanidi OV, Colman MA, Zhao J, Smaill BH, Gilbert SH, Hancox JC, Boyett MR, Zhang H. Arrhythmogenic substrate for atrial fibrillation: insights from an integrative computational model of pulmonary veins. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:203-6. [PMID: 23365867 DOI: 10.1109/embc.2012.6345906] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Mechanisms underlying the genesis of re-entrant substrate for atrial fibrillation (AF) in the pulmonary veins (PVs) and left atrium (LA) are not well understood. We develop a biophysically detailed computational model for the PVs and surrounding LA tissue. The model integrates canine PV and LA single cell electrophysiology with the respective 3D tissue geometry and fiber orientation reconstructed from micro-CT data. The model simulations demonstrate that a combination of tissue anisotropy and electrical heterogeneity between the PVs and LA causes a break-down of normal electrical excitation wave-fronts. This leads to the generation of a high-frequency re-entrant source near the PV sleeves. Evidence of such sources have been seen clinically in AF patients. In summary, our modeling results provide new insights into the arrhythmogenic mechanisms of re-entrant excitation waves underlying AF.
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Affiliation(s)
- Oleg V Aslanidi
- Division of Imaging Sciences & Biomedical Engineering, King's College London, London SE1 7EH, United Kingdom.
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37
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Castaño AP, Ruiz CA, Castillo A, Heidenreich E. Propagación de onda en un tejido cardiaco 3D usando dos modelos auriculares. REVISTA COLOMBIANA DE CARDIOLOGÍA 2013. [DOI: 10.1016/s0120-5633(13)70056-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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38
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Hsueh CH, Chang PC, Hsieh YC, Reher T, Chen PS, Lin SF. Proarrhythmic effect of blocking the small conductance calcium activated potassium channel in isolated canine left atrium. Heart Rhythm 2013; 10:891-8. [PMID: 23376397 PMCID: PMC3663880 DOI: 10.1016/j.hrthm.2013.01.033] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Indexed: 11/30/2022]
Abstract
BACKGROUND Small conductance calcium activated potassium (SKCa) channels are voltage insensitive and are activated by intracellular calcium. Genome-wide association studies revealed that a variant of SKCa is associated with lone atrial fibrillation in humans. Roles of SKCa in atrial arrhythmias remain unclear. OBJECTIVE To determine roles of SKCa in atrial arrhythmias. METHODS Optical mapping using the isolated canine left atrium was performed. The optical action potential duration (APD) and induction of arrhythmia were evaluated before and after the addition of specific SKCa blockers-apamin or UCL-1684. RESULTS SKCa blockade significantly increased APD₈₀ (188 ± 19 ms vs 147 ± 11 ms; P<.001). The pacing cycle length thresholds to induce 2:2 alternans, and wave breaks were prolonged by SKCa blockade. Increased APD heterogeneity was observed after the SKCa blockade, as measured by the difference between the maximum and the minimum APD (39 ± 4 ms vs 26 ± 5 ms; P<.05), by standard deviation (12.43 ± 2.36 ms vs 7.49 ± 1.47 ms; P<.001), or by coefficient of variation (6.68% ± 0.97% vs 4.90% ± 0.84%; P<.05). No arrhythmia was induced at baseline by an S1-S2 protocol. After SKCa blockade, 4 of 6 atria developed arrhythmia. CONCLUSIONS SKCa blockade promotes arrhythmia and prolongs the pacing cycle length threshold of 2:2 alternans and wave breaks in the canine left atrium. The proarrhythmic effect could be attributed to increased APD heterogeneity in the canine left atrium. This study provides supportive evidence of genome-wide association studies showing association of KCNN3 and lone atrial fibrillation.
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Affiliation(s)
- Chia-Hsiang Hsueh
- Krannert Institute of Cardiology and Division of Cardiology, Indiana University, Indianapolis, Indiana 46202, USA
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39
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Deng DD, Gong YL, Shou GF, Jiao PF, Zhang HG, Ye XS, Xia L. Simulation of biatrial conduction via different pathways during sinus rhythm with a detailed human atrial model. J Zhejiang Univ Sci B 2013; 13:676-94. [PMID: 22949359 DOI: 10.1631/jzus.b1100339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In order to better understand biatrial conduction, investigate various conduction pathways, and compare the differences between isotropic and anisotropic conductions in human atria, we present a simulation study of biatrial conduction with known/assumed conduction pathways using a recently developed human atrial model. In addition to known pathways: (1) Bachmann's bundle (BB), (2) limbus of fossa ovalis (LFO), and (3) coronary sinus (CS), we also hypothesize that there exist two fast conduction bundles that connect the crista terminalis (CT), LFO, and CS. Our simulation demonstrates that use of these fast conduction bundles results in a conduction pattern consistent with experimental data. The comparison of isotropic and anisotropoic conductions in the BB case showed that the atrial working muscles had small effect on conduction time and conduction speed, although the conductivities assigned in anisotropic conduction were two to four times higher than the isotropic conduction. In conclusion, we suggest that the hypothesized intercaval bundles play a significant role in the biatrial conduction and that myofiber orientation has larger effects on the conduction system than the atrial working muscles. This study presents readers with new insights into human atrial conduction.
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Affiliation(s)
- Dong-dong Deng
- College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou 310027, China
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Wilhelms M, Hettmann H, Maleckar MM, Koivumäki JT, Dössel O, Seemann G. Benchmarking electrophysiological models of human atrial myocytes. Front Physiol 2013; 3:487. [PMID: 23316167 PMCID: PMC3539682 DOI: 10.3389/fphys.2012.00487] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 12/14/2012] [Indexed: 11/19/2022] Open
Abstract
Mathematical modeling of cardiac electrophysiology is an insightful method to investigate the underlying mechanisms responsible for arrhythmias such as atrial fibrillation (AF). In past years, five models of human atrial electrophysiology with different formulations of ionic currents, and consequently diverging properties, have been published. The aim of this work is to give an overview of strengths and weaknesses of these models depending on the purpose and the general requirements of simulations. Therefore, these models were systematically benchmarked with respect to general mathematical properties and their ability to reproduce certain electrophysiological phenomena, such as action potential (AP) alternans. To assess the models' ability to replicate modified properties of human myocytes and tissue in cardiac disease, electrical remodeling in chronic atrial fibrillation (cAF) was chosen as test case. The healthy and remodeled model variants were compared with experimental results in single-cell, 1D and 2D tissue simulations to investigate AP and restitution properties, as well as the initiation of reentrant circuits.
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Affiliation(s)
- Mathias Wilhelms
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology Karlsruhe, Germany
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41
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Aslanidi OV, Nikolaidou T, Zhao J, Smaill BH, Gilbert SH, Holden AV, Lowe T, Withers PJ, Stephenson RS, Jarvis JC, Hancox JC, Boyett MR, Zhang H. Application of micro-computed tomography with iodine staining to cardiac imaging, segmentation, and computational model development. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:8-17. [PMID: 22829390 PMCID: PMC3493467 DOI: 10.1109/tmi.2012.2209183] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Micro-computed tomography (micro-CT) has been widely used to generate high-resolution 3-D tissue images from small animals nondestructively, especially for mineralized skeletal tissues. However, its application to the analysis of soft cardiovascular tissues has been limited by poor inter-tissue contrast. Recent ex vivo studies have shown that contrast between muscular and connective tissue in micro-CT images can be enhanced by staining with iodine. In the present study, we apply this novel technique for imaging of cardiovascular structures in canine hearts. We optimize the method to obtain high-resolution X-ray micro-CT images of the canine atria and its distinctive regions-including the Bachmann's bundle, atrioventricular node, pulmonary arteries and veins-with clear inter-tissue contrast. The imaging results are used to reconstruct and segment the detailed 3-D geometry of the atria. Structure tensor analysis shows that the arrangement of atrial fibers can also be characterized using the enhanced micro-CT images, as iodine preferentially accumulates within the muscular fibers rather than in connective tissues. This novel technique can be particularly useful in nondestructive imaging of 3-D cardiac architectures from large animals and humans, due to the combination of relatively high speed ( ~ 1 h/per scan of the large canine heart) and high voxel resolution (36 μm) provided. In summary, contrast micro-CT facilitates fast and nondestructive imaging and segmenting of detailed 3-D cardiovascular geometries, as well as measuring fiber orientation, which are crucial in constructing biophysically detailed computational cardiac models.
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Affiliation(s)
- Oleg V Aslanidi
- Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
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42
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Roberts BN, Yang PC, Behrens SB, Moreno JD, Clancy CE. Computational approaches to understand cardiac electrophysiology and arrhythmias. Am J Physiol Heart Circ Physiol 2012; 303:H766-83. [PMID: 22886409 DOI: 10.1152/ajpheart.01081.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Cardiac rhythms arise from electrical activity generated by precisely timed opening and closing of ion channels in individual cardiac myocytes. These impulses spread throughout the cardiac muscle to manifest as electrical waves in the whole heart. Regularity of electrical waves is critically important since they signal the heart muscle to contract, driving the primary function of the heart to act as a pump and deliver blood to the brain and vital organs. When electrical activity goes awry during a cardiac arrhythmia, the pump does not function, the brain does not receive oxygenated blood, and death ensues. For more than 50 years, mathematically based models of cardiac electrical activity have been used to improve understanding of basic mechanisms of normal and abnormal cardiac electrical function. Computer-based modeling approaches to understand cardiac activity are uniquely helpful because they allow for distillation of complex emergent behaviors into the key contributing components underlying them. Here we review the latest advances and novel concepts in the field as they relate to understanding the complex interplay between electrical, mechanical, structural, and genetic mechanisms during arrhythmia development at the level of ion channels, cells, and tissues. We also discuss the latest computational approaches to guiding arrhythmia therapy.
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Affiliation(s)
- Byron N Roberts
- Tri-Institutional MD-PhD Program, Physiology, Biophysics and Systems Biology Graduate Program, Weill Cornell Medical College/The Rockefeller University/Sloan-Kettering Cancer Institute, Weill Medical College of Cornell University, New York, New York, USA
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43
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Cherry EM, Fenton FH, Gilmour RF. Mechanisms of ventricular arrhythmias: a dynamical systems-based perspective. Am J Physiol Heart Circ Physiol 2012; 302:H2451-63. [PMID: 22467299 PMCID: PMC3378269 DOI: 10.1152/ajpheart.00770.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 03/26/2012] [Indexed: 01/23/2023]
Abstract
Defining the cellular electrophysiological mechanisms for ventricular tachyarrhythmias is difficult, given the wide array of potential mechanisms, ranging from abnormal automaticity to various types of reentry and kk activity. The degree of difficulty is increased further by the fact that any particular mechanism may be influenced by the evolving ionic and anatomic environments associated with many forms of heart disease. Consequently, static measures of a single electrophysiological characteristic are unlikely to be useful in establishing mechanisms. Rather, the dynamics of the electrophysiological triggers and substrates that predispose to arrhythmia development need to be considered. Moreover, the dynamics need to be considered in the context of a system, one that displays certain predictable behaviors, but also one that may contain seemingly stochastic elements. It also is essential to recognize that even the predictable behaviors of this complex nonlinear system are subject to small changes in the state of the system at any given time. Here we briefly review some of the short-, medium-, and long-term alterations of the electrophysiological substrate that accompany myocardial disease and their potential impact on the initiation and maintenance of ventricular arrhythmias. We also provide examples of cases in which small changes in the electrophysiological substrate can result in rather large differences in arrhythmia outcome. These results suggest that an interrogation of cardiac electrical dynamics is required to provide a meaningful assessment of the immediate risk for arrhythmia development and for evaluating the effects of putative antiarrhythmic interventions.
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Affiliation(s)
- Elizabeth M Cherry
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA
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44
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Abstract
The dynamics of many cardiac arrhythmias, as well as the nature of transitions between different heart rhythms, have long been considered evidence of nonlinear phenomena playing a direct role in cardiac arrhythmogenesis. In most types of cardiac disease, the pathology develops slowly and gradually, often over many years. In contrast, arrhythmias often occur suddenly. In nonlinear systems, sudden changes in qualitative dynamics can, counterintuitively, result from a gradual change in a system parameter-this is known as a bifurcation. Here, we review how nonlinearities in cardiac electrophysiology influence normal and abnormal rhythms and how bifurcations change the dynamics. In particular, we focus on the many recent developments in computational modeling at the cellular level that are focused on intracellular calcium dynamics. We discuss two areas where recent experimental and modeling work has suggested the importance of nonlinearities in calcium dynamics: repolarization alternans and pacemaker cell automaticity.
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Affiliation(s)
- Trine Krogh-Madsen
- Greenberg Division of Cardiology, Department of Medicine, Weill Cornell Medical College, New York, New York 10065, USA.
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45
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Sarkar AX, Christini DJ, Sobie EA. Exploiting mathematical models to illuminate electrophysiological variability between individuals. J Physiol 2012; 590:2555-67. [PMID: 22495591 DOI: 10.1113/jphysiol.2011.223313] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Across individuals within a population, several levels of variability are observed, from the differential expression of ion channels at the molecular level, to the various action potential morphologies observed at the cellular level, to divergent responses to drugs at the organismal level. However, the limited ability of experiments to probe complex interactions between components has hitherto hindered our understanding of the factors that cause a range of behaviours within a population. Variability is a challenging issue that is encountered in all physiological disciplines, but recent work suggests that novel methods for analysing mathematical models can assist in illuminating its causes. In this review, we discuss mathematical modelling studies in cardiac electrophysiology and neuroscience that have enhanced our understanding of variability in a number of key areas. Specifically, we discuss parameter sensitivity analysis techniques that may be applied to generate quantitative predictions based on considering behaviours within a population of models, thereby providing novel insight into variability. Our discussion focuses on four issues that have benefited from the utilization of these methods: (1) the comparison of different electrophysiological models of cardiac myocytes, (2) the determination of the individual contributions of different molecular changes in complex disease phenotypes, (3) the identification of the factors responsible for the variable response to drugs, and (4) the constraining of free parameters in electrophysiological models of heart cells. Together, the studies that we discuss suggest that rigorous analyses of mathematical models can generate quantitative predictions regarding how molecular-level variations contribute to functional differences between experimental samples. These strategies may be applicable not just in cardiac electrophysiology, but in a wide range of disciplines.
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Affiliation(s)
- Amrita X Sarkar
- Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY 10029, USA
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46
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Sánchez C, Corrias A, Bueno-Orovio A, Davies M, Swinton J, Jacobson I, Laguna P, Pueyo E, Rodríguez B. The Na+/K+ pump is an important modulator of refractoriness and rotor dynamics in human atrial tissue. Am J Physiol Heart Circ Physiol 2012; 302:H1146-59. [PMID: 22198174 PMCID: PMC3311461 DOI: 10.1152/ajpheart.00668.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 12/04/2011] [Indexed: 11/22/2022]
Abstract
Pharmacological treatment of atrial fibrillation (AF) exhibits limited efficacy. Further developments require a comprehensive characterization of ionic modulators of electrophysiology in human atria. Our aim is to systematically investigate the relative importance of ionic properties in modulating excitability, refractoriness, and rotor dynamics in human atria before and after AF-related electrical remodeling (AFER). Computer simulations of single cell and tissue atrial electrophysiology were conducted using two human atrial action potential (AP) models. Changes in AP, refractory period (RP), conduction velocity (CV), and rotor dynamics caused by alterations in key properties of all atrial ionic currents were characterized before and after AFER. Results show that the investigated human atrial electrophysiological properties are primarily modulated by maximal value of Na(+)/K(+) pump current (G(NaK)) as well as conductances of inward rectifier potassium current (G(K1)) and fast inward sodium current (G(Na)). G(NaK) plays a fundamental role through both electrogenic and homeostatic modulation of AP duration (APD), APD restitution, RP, and reentrant dominant frequency (DF). G(K1) controls DF through modulation of AP, APD restitution, RP, and CV. G(Na) is key in determining DF through alteration of CV and RP, particularly in AFER. Changes in ionic currents have qualitatively similar effects in control and AFER, but effects are smaller in AFER. The systematic analysis conducted in this study unravels the important role of the Na(+)/K(+) pump current in determining human atrial electrophysiology.
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Affiliation(s)
- Carlos Sánchez
- Communications Technology Group, I3A and IIS, University of Zaragoza, Zaragoza
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47
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Krogh-Madsen T, Abbott GW, Christini DJ. Effects of electrical and structural remodeling on atrial fibrillation maintenance: a simulation study. PLoS Comput Biol 2012; 8:e1002390. [PMID: 22383869 PMCID: PMC3285569 DOI: 10.1371/journal.pcbi.1002390] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 01/03/2012] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation, a common cardiac arrhythmia, often progresses unfavourably: in patients with long-term atrial fibrillation, fibrillatory episodes are typically of increased duration and frequency of occurrence relative to healthy controls. This is due to electrical, structural, and contractile remodeling processes. We investigated mechanisms of how electrical and structural remodeling contribute to perpetuation of simulated atrial fibrillation, using a mathematical model of the human atrial action potential incorporated into an anatomically realistic three-dimensional structural model of the human atria. Electrical and structural remodeling both shortened the atrial wavelength--electrical remodeling primarily through a decrease in action potential duration, while structural remodeling primarily slowed conduction. The decrease in wavelength correlates with an increase in the average duration of atrial fibrillation/flutter episodes. The dependence of reentry duration on wavelength was the same for electrical vs. structural remodeling. However, the dynamics during atrial reentry varied between electrical, structural, and combined electrical and structural remodeling in several ways, including: (i) with structural remodeling there were more occurrences of fragmented wavefronts and hence more filaments than during electrical remodeling; (ii) dominant waves anchored around different anatomical obstacles in electrical vs. structural remodeling; (iii) dominant waves were often not anchored in combined electrical and structural remodeling. We conclude that, in simulated atrial fibrillation, the wavelength dependence of reentry duration is similar for electrical and structural remodeling, despite major differences in overall dynamics, including maximal number of filaments, wave fragmentation, restitution properties, and whether dominant waves are anchored to anatomical obstacles or spiralling freely.
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Affiliation(s)
- Trine Krogh-Madsen
- Greenberg Division of Cardiology, Department of Medicine, Weill Cornell Medical College, New York, New York, United States of America
- Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, United States of America
| | - Geoffrey W. Abbott
- Department of Pharmacology, Weill Cornell Medical College, New York, New York, United States of America
| | - David J. Christini
- Greenberg Division of Cardiology, Department of Medicine, Weill Cornell Medical College, New York, New York, United States of America
- Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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48
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Dvir H, Zlochiver S. Heart rate variability effect on the myocyte action potential duration restitution: insights from switched systems theory. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:685-8. [PMID: 22254402 DOI: 10.1109/iembs.2011.6090154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The physiological heart rate presents a stochastic behavior known as heart rate variability (HRV). In this framework the influence of HRV on the action potential duration (APD) of the atrial myocyte is analyzed in a computer model. We have found that introducing HRV into the myocyte action potential model decreases the APD of the extra beat S2 in an S1-S2 protocol compared to constant heart rate. A possible theoretical explanation for this is also presented and is derived from switched systems theory. It is suggested to consider the myocyte action potential phase 4 and phase 2 as two operation modes of a switching system and analyze the stability of switching between them. Since random switching is known to have a stabilization effect on a switching system, this might explain why HRV has a stabilization effect on the myocyte APD restitution. Implications of this finding include reduced system stability for conditions with low HRV. A possible application for this phenomenon regards artificial pacemakers, where a preset added HRV is predicted to reduce susceptibility to arrhythmias.
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Affiliation(s)
- Hila Dvir
- Department of Biomedical Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
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49
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Bartocci E, Singh R, von Stein FB, Amedome A, Caceres AJJ, Castillo J, Closser E, Deards G, Goltsev A, Ines RS, Isbilir C, Marc JK, Moore D, Pardi D, Sadhu S, Sanchez S, Sharma P, Singh A, Rogers J, Wolinetz A, Grosso-Applewhite T, Zhao K, Filipski AB, Gilmour RF, Grosu R, Glimm J, Smolka SA, Cherry EM, Clarke EM, Griffeth N, Fenton FH. Teaching cardiac electrophysiology modeling to undergraduate students: laboratory exercises and GPU programming for the study of arrhythmias and spiral wave dynamics. ADVANCES IN PHYSIOLOGY EDUCATION 2011; 35:427-37. [PMID: 22139782 DOI: 10.1152/advan.00034.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
As part of a 3-wk intersession workshop funded by a National Science Foundation Expeditions in Computing award, 15 undergraduate students from the City University of New York(1) collaborated on a study aimed at characterizing the voltage dynamics and arrhythmogenic behavior of cardiac cells for a broad range of physiologically relevant conditions using an in silico model. The primary goal of the workshop was to cultivate student interest in computational modeling and analysis of complex systems by introducing them through lectures and laboratory activities to current research in cardiac modeling and by engaging them in a hands-on research experience. The success of the workshop lay in the exposure of the students to active researchers and experts in their fields, the use of hands-on activities to communicate important concepts, active engagement of the students in research, and explanations of the significance of results as the students generated them. The workshop content addressed how spiral waves of electrical activity are initiated in the heart and how different parameter values affect the dynamics of these reentrant waves. Spiral waves are clinically associated with tachycardia, when the waves remain stable, and with fibrillation, when the waves exhibit breakup. All in silico experiments were conducted by simulating a mathematical model of cardiac cells on graphics processing units instead of the standard central processing units of desktop computers. This approach decreased the run time for each simulation to almost real time, thereby allowing the students to quickly analyze and characterize the simulated arrhythmias. Results from these simulations, as well as some of the background and methodology taught during the workshop, is presented in this article along with the programming code and the explanations of simulation results in an effort to allow other teachers and students to perform their own demonstrations, simulations, and studies.
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Affiliation(s)
- Ezio Bartocci
- Department of Applied Mathematics and Statistics, Stony Brook University, New York, USA
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50
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Niederer SA, Kerfoot E, Benson AP, Bernabeu MO, Bernus O, Bradley C, Cherry EM, Clayton R, Fenton FH, Garny A, Heidenreich E, Land S, Maleckar M, Pathmanathan P, Plank G, Rodríguez JF, Roy I, Sachse FB, Seemann G, Skavhaug O, Smith NP. Verification of cardiac tissue electrophysiology simulators using an N-version benchmark. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:4331-51. [PMID: 21969679 PMCID: PMC3263775 DOI: 10.1098/rsta.2011.0139] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Ongoing developments in cardiac modelling have resulted, in particular, in the development of advanced and increasingly complex computational frameworks for simulating cardiac tissue electrophysiology. The goal of these simulations is often to represent the detailed physiology and pathologies of the heart using codes that exploit the computational potential of high-performance computing architectures. These developments have rapidly progressed the simulation capacity of cardiac virtual physiological human style models; however, they have also made it increasingly challenging to verify that a given code provides a faithful representation of the purported governing equations and corresponding solution techniques. This study provides the first cardiac tissue electrophysiology simulation benchmark to allow these codes to be verified. The benchmark was successfully evaluated on 11 simulation platforms to generate a consensus gold-standard converged solution. The benchmark definition in combination with the gold-standard solution can now be used to verify new simulation codes and numerical methods in the future.
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Affiliation(s)
- Steven A Niederer
- Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, UK.
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