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Tsuji Y, Yamazaki M, Shimojo M, Yanagisawa S, Inden Y, Murohara T. Mechanisms of torsades de pointes: an update. Front Cardiovasc Med 2024; 11:1363848. [PMID: 38504714 PMCID: PMC10948600 DOI: 10.3389/fcvm.2024.1363848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Accepted: 02/19/2024] [Indexed: 03/21/2024] Open
Abstract
Torsades de Pointes (TdP) refers to a polymorphic ventricular tachycardia (VT) with undulating QRS axis that occurs in long QT syndrome (LQTS), although the term has been used to describe polymorphic ventricular tachyarrhythmias in which QT intervals are not prolonged, such as short-coupled variant of TdP currently known as short-coupled ventricular fibrillation (VF) and Brugada syndrome. Extensive works on LQTS-related TdP over more than 50 years since it was first recognized by Dessertennes who coined the French term meaning "twisting of the points", have led to current understanding of the electrophysiological mechanism that TdP is initiated by triggered activity due to early afterdepolarization (EAD) and maintained by reentry within a substrate of inhomogeneous repolarization. While a recently emerging notion that steep voltage gradients rather than EADs are crucial to generate premature ventricular contractions provides additions to the initiation mode, the research to elucidate the maintenance mechanism hasn't made much progress. The reentrant activity that produces the specific form of VT is not well characterized. We have conducted optical mapping in a rabbit model of electrical storm by electrical remodeling (QT prolongation) due to chronic complete atrioventricular block and demonstrated that a tissue-island with prolonged refractoriness due to enhanced late Na+ current (INa-L) contributes to the generation of drifting rotors in a unique manner, which may explain the ECG characteristic of TdP. Moreover, we have proposed that the neural Na+ channel NaV1.8-mediated INa-L may be a new player to form the substrate for TdP. Here we discuss TdP mechanisms by comparing the findings in electrical storm rabbits with recently published studies by others in simulation models and human and animal models of LQTS.
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Affiliation(s)
- Yukiomi Tsuji
- Departments of Cardiovascular Research and Innovation, Cardiology and Advanced Cardiovascular Therapeutics, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Masatoshi Yamazaki
- Department of Cardiology, Nagano Hospital, Soja and Medical Device Development and Regulation Research Center and Department of Precision Engineering, The University of Tokyo, Tokyo, Japan
| | - Masafumi Shimojo
- Departments of Cardiovascular Research and Innovation, Cardiology and Advanced Cardiovascular Therapeutics, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Satoshi Yanagisawa
- Departments of Cardiovascular Research and Innovation, Cardiology and Advanced Cardiovascular Therapeutics, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yasuya Inden
- Departments of Cardiovascular Research and Innovation, Cardiology and Advanced Cardiovascular Therapeutics, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Toyoaki Murohara
- Departments of Cardiovascular Research and Innovation, Cardiology and Advanced Cardiovascular Therapeutics, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Colman MA, Benson AP. A simple approach for image-based modelling of the heart that enables robust simulation of highly heterogeneous electrical excitation. Sci Rep 2023; 13:15119. [PMID: 37704647 PMCID: PMC10499818 DOI: 10.1038/s41598-023-39244-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/21/2023] [Indexed: 09/15/2023] Open
Abstract
Remodelling of cardiac tissue structure, including intercellular electrical coupling, is a major determinant of the complex and heterogeneous excitation patterns associated with cardiac arrhythmias. Evaluation of the precise mechanisms by which local tissue structure determines global arrhythmic excitation patterns is a major challenge that may be critically important for the development of effective treatment strategies. Computational modelling is a key tool in the study of cardiac arrhythmias, yet the established approaches for organ-scale modelling are unsuitable to capture the impact of local conduction heterogeneities; a novel approach is required to provide this multi-scale mechanistic insight. We present a fundamentally simple yet powerful approach to simulate electrical excitation in highly heterogeneous whole-heart models that exploits the underlying discreteness of the myocardium. Preliminary simulations demonstrate that this approach can capture lower conduction velocities and reproduce wave breakdown and the development of re-entry in a range of conditions.
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Affiliation(s)
- Michael A Colman
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK.
| | - Alan P Benson
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
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Van Den Abeele R, Hendrickx S, Van Nieuwenhuyse E, Dunnink A, Panfilov AV, Vos MA, Wülfers EM, Vandersickel N. Directed graph mapping shows rotors maintain non-terminating and focal sources maintain self-terminating Torsade de Pointes in canine model. Front Physiol 2023; 14:1201260. [PMID: 37565147 PMCID: PMC10411729 DOI: 10.3389/fphys.2023.1201260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 06/28/2023] [Indexed: 08/12/2023] Open
Abstract
Torsade de Pointes is a polymorphic ventricular tachycardia which is as yet incompletely understood. While the onset of a TdP episode is generally accepted to be caused by triggered activity, the mechanisms for the perpetuation is still under debate. In this study, we analysed data from 54 TdP episodes divided over 5 dogs (4 female, 1 male) with chronic atrioventricular block. Previous research on this dataset showed both reentry and triggered activity to perpetuate the arrhythmia. 13 of those TdP episodes showed reentry as part of the driving mechanism of perpetuating the episode. The remaining 41 episodes were purely ectopic. Reentry was the main mechanism in long-lasting episodes (>14 beats), while focal sources were responsible for maintaining shorter episodes. Building on these results, we re-analysed the data using directed graph mapping This program uses principles from network theory and a combination of positional data and local activation times to identify reentry loops and focal sources within the data. The results of this study are twofold. First, concerning reentry loops, we found that on average non-terminating (NT) episodes (≥10 s) show significantly more simultaneous reentry loops than self-terminating (ST) TdP (<10 s). Non-terminating episodes have on average 2.72 ± 1.48 simultaneous loops, compared to an average of 1.33 ± 0.66 for self-terminating episodes. In addition, each NT episode showed a presence of (bi-)ventricular loops between 10.10% and 69.62% of their total reentry duration. Compared to the ST episodes, only 1 in 4 episodes (25%) showed (bi-)ventricular reentry, lasting only 7.12% of its total reentry duration. This suggests that while focal beats trigger TdP, macro-reentry and multiple simultaneous localized reentries are the major drivers of long-lasting episodes. Second, using heatmaps, we found focal sources to occur in preferred locations, instead of being distributed randomly. This may have implications on treatment if such focal origins can be disabled reliably.
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Affiliation(s)
- Robin Van Den Abeele
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Sander Hendrickx
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Enid Van Nieuwenhuyse
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Albert Dunnink
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Alexander V. Panfilov
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Ghent, Belgium
- Laboratory of Computational Biology and Medicine, Ural Federal University, Yekaterinburg, Russia
- World-Class Research Center “Digital Biodesign and Personalized Healthcare”, Sechenov University, Moscow, Russia
| | - Marc A. Vos
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Eike M. Wülfers
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Nele Vandersickel
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Ghent, Belgium
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Alexander C, Bishop MJ, Gilchrist RJ, Burton FL, Smith GL, Myles RC. Initiation of ventricular arrhythmia in the acquired long QT syndrome. Cardiovasc Res 2023; 119:465-476. [PMID: 35727943 PMCID: PMC10064840 DOI: 10.1093/cvr/cvac103] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 04/25/2022] [Accepted: 06/02/2022] [Indexed: 11/15/2022] Open
Abstract
AIMS Long QT syndrome (LQTS) carries a risk of life-threatening polymorphic ventricular tachycardia (Torsades de Pointes, TdP) and is a major cause of premature sudden cardiac death. TdP is induced by R-on-T premature ventricular complexes (PVCs), thought to be generated by cellular early-afterdepolarisations (EADs). However, EADs in tissue require cellular synchronisation, and their role in TdP induction remains unclear. We aimed to determine the mechanism of TdP induction in rabbit hearts with acquired LQTS (aLQTS). METHODS AND RESULTS Optical mapping of action potentials (APs) and intracellular Ca2+ was performed in Langendorff-perfused rabbit hearts (n = 17). TdP induced by R-on-T PVCs was observed during aLQTS (50% K+/Mg++ & E4031) conditions in all hearts (P < 0.0001 vs. control). Islands of AP prolongation bounded by steep voltage gradients (VGs) were consistently observed before arrhythmia and peak VGs were more closely related to the PVC upstroke than EADs, both temporally (7 ± 5 ms vs. 44 ± 27 ms, P < 0.0001) and spatially (1.0 ± 0.7 vs. 3.6 ± 0.9 mm, P < 0.0001). PVCs were initiated at estimated voltages of ∼ -40 mV and had upstroke dF/dtmax and Vm-Ca2+ dynamics compatible with ICaL activation. Computational simulations demonstrated that PVCs could arise directly from VGs, through electrotonic triggering of ICaL. In experiments and the model, sub-maximal L-type Ca2+ channel (LTCC) block (200 nM nifedipine and 90% gCaL, respectively) abolished both PVCs and TdP in the continued presence of aLQTS. CONCLUSION These data demonstrate that ICaL activation at sites displaying steep VGs generates the PVCs which induce TdP, providing a mechanism and rationale for LTCC blockers as a novel therapeutic approach in LQTS.
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Affiliation(s)
- Cherry Alexander
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Martin J Bishop
- School of Biomedical Engineering and Imaging Sciences, King’s College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK
| | - Rebecca J Gilchrist
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Francis L Burton
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Godfrey L Smith
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Rachel C Myles
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
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DG-Mapping: a novel software package for the analysis of any type of reentry and focal activation of simulated, experimental or clinical data of cardiac arrhythmia. Med Biol Eng Comput 2022; 60:1929-1945. [DOI: 10.1007/s11517-022-02550-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 02/13/2022] [Indexed: 01/24/2023]
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Rotors anchored by refractory islands drive torsades de pointes in an experimental model of electrical storm. Heart Rhythm 2022; 19:318-329. [PMID: 34678525 PMCID: PMC8810573 DOI: 10.1016/j.hrthm.2021.10.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 02/03/2023]
Abstract
BACKGROUND Electrical storm (ES) is a life-threatening emergency in patients at high risk of ventricular tachycardia/ventricular fibrillation (VF), but the pathophysiology and molecular basis are poorly understood. OBJECTIVE The purpose of this study was to explore the electrophysiological substrate for experimental ES. METHODS A model was created by inducing chronic complete atrioventricular block in defibrillator-implanted rabbits, which recapitulates QT prolongation, torsades des pointes (TdP), and VF episodes. RESULTS Optical mapping revealed island-like regions with action potential duration (APD) prolongation in the left ventricle, leading to increased spatial APD dispersion, in rabbits with ES (defined as ≥3 VF episodes/24 h). The maximum APD and its dispersion correlated with the total number of VF episodes in vivo. TdP was initiated by an ectopic beat that failed to enter the island and formed a reentrant wave and perpetuated by rotors whose centers swirled in the periphery of the island. Epinephrine exacerbated the island by prolonging APD and enhancing APD dispersion, which was less evident after late Na+ current blockade with 10 μM ranolazine. Nonsustained ventricular tachycardia in a non-ES rabbit heart with homogeneous APD prolongation resulted from multiple foci with an electrocardiographic morphology different from TdP driven by drifting rotors in ES rabbit hearts. The neuronal Na+-channel subunit NaV1.8 was upregulated in ES rabbit left ventricular tissues and expressed within the myocardium corresponding to the island location in optically mapped ES rabbit hearts. The NaV1.8 blocker A-803467 (10 mg/kg, intravenously) attenuated QT prolongation and suppressed epinephrine-evoked TdP. CONCLUSION A tissue island with enhanced refractoriness contributes to the generation of drifting rotors that underlies ES in this model. NaV1.8-mediated late Na+ current merits further investigation as a contributor to the substrate for ES.
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Ellermann C, Wolfes J, Eckardt L, Frommeyer G. Role of the rabbit whole-heart model for electrophysiologic safety pharmacology of non-cardiovascular drugs. Europace 2021; 23:828-836. [PMID: 33200170 DOI: 10.1093/europace/euaa288] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 08/27/2020] [Indexed: 11/13/2022] Open
Abstract
Plenty of non-cardiovascular drugs alter cardiac electrophysiology and may ultimately lead to life-threatening arrhythmias. In clinical practice, measuring the QT interval as a marker for the repolarization period is the most common tool to assess the electrophysiologic safety of drugs. However, the sole measurement of the QT interval may be insufficient to determine the proarrhythmic risk of non-cardiovascular agents. Several other markers are considered in pre-clinical safety testing to determine potential harm on cardiac electrophysiology. Besides measuring typical electrophysiologic parameters such as repolarization duration, whole-heart models allow the determination of potential predictors for proarrhythmia. Spatial and temporal heterogeneity as well as changes of shape of the action potential can be easily assessed. In addition, provocation manoeuvers (either by electrolyte imbalances or programmed pacing protocols) may induce sustained arrhythmias and thereby determine ventricular vulnerability to arrhythmias. Compared with the human heart, the rabbit heart possesses a similar distribution of ion currents that govern cardiac repolarization, resulting in a rectangular action potential configuration in both species. In addition, similar biophysical properties of rabbit and human cardiac ion channels lead to a comparable pharmacologic response in human and rabbit hearts. Of note, arrhythmia patterns resemble in both species due to the similar effective size of human and rabbit hearts. Thus, the rabbit heart is particularly suitable for testing the electrophysiologic safety of drugs. Several experimental setups have been developed for studying cardiac electrophysiology in rabbits, ranging from single cell to tissue preparations, whole-heart setups, and in vivo models.
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Affiliation(s)
- Christian Ellermann
- Department of Cardiology II (Electrophysiology), University Hospital Münster, Albert-Schweitzer-Campus 1, Münster D-48149, Germany
| | - Julian Wolfes
- Department of Cardiology II (Electrophysiology), University Hospital Münster, Albert-Schweitzer-Campus 1, Münster D-48149, Germany
| | - Lars Eckardt
- Department of Cardiology II (Electrophysiology), University Hospital Münster, Albert-Schweitzer-Campus 1, Münster D-48149, Germany
| | - Gerrit Frommeyer
- Department of Cardiology II (Electrophysiology), University Hospital Münster, Albert-Schweitzer-Campus 1, Münster D-48149, Germany
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Smoczyńska A, Aarnink EW, Dunnink A, Bossu A, van Weperen VYH, Meijborg VMF, Beekman HDM, Coronel R, Vos MA. Interplay between temporal and spatial dispersion of repolarization in the initiation and perpetuation of torsades de pointes in the chronic atrioventricular block dog. Am J Physiol Heart Circ Physiol 2021; 321:H569-H576. [PMID: 34355987 DOI: 10.1152/ajpheart.00945.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ventricular arrhythmias, consisting of single ectopic beats (sEB), multiple EB (mEB), and torsades de pointes (TdP, defined as ≥5 beats with QRS vector twisting around isoelectric line) can be induced in the anesthetized chronic atrioventricular block (CAVB) dog by dofetilide (IKr blocker). The interplay between temporal dispersion of repolarization, quantified as short-term variability (STV), and spatial dispersion of repolarization (SDR) in the initiation and perpetuation of these arrhythmias remains unclear. Five inducible (≥3 TdPs/10 min) CAVB dogs underwent one mapping experiment and were observed for 10 min from the start of dofetilide infusion (0.025 mg/kg, 5 min). An intracardiac decapolar electrogram (EGM) catheter and 30 intramural cardiac needles in the left ventricle (LV) were introduced. STVARI was derived from 31 consecutive activation recovery intervals (ARIs) on the intracardiac EGM, using the formula: [Formula: see text]. The mean SDR3D in the LV was determined as the three-dimensional repolarization time differences between the intramural cardiac needles. Moments of measurement included baseline (BL) and after dofetilide infusion before first 1) sEB (occurrence at 100 ± 35 s), 2) mEB (224 ± 96 s), and 3) non-self-terminating TdP (454 ± 298 s). STVARI increased from 2.15 ± 0.32 ms at BL to 3.73 ± 0.99 ms* before the first sEB and remained increased without further significant progression to mEB (4.41 ± 0.45 ms*) and TdP (5.07 ± 0.84 ms*) (*P < 0.05 compared with BL). SDR3D did not change from 31 ± 11 ms at BL to 43 ± 13 ms before sEB but increased significantly before mEB (68 ± 7 ms*) and to TdP (86 ± 9 ms*+) (+P < 0.05 compared with sEB). An increase in STV contributes to the initiation of sEB, whereas an increase in SDR is important for the perpetuation of non-self-terminating TdPs.NEW & NOTEWORTHY This study compared two well-established electrophysiological parameters, being temporal and spatial dispersion of repolarization, and provided new insights into their interplay in the arrhythmogenesis of torsades de pointes arrhythmias. Although it confirmed that an increase in temporal dispersion of repolarization contributes to the initiation of single ectopic beats, it showed that an increase in spatial dispersion of repolarization is important for the perpetuation of non-self-terminating torsades de pointes arrhythmias.
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Affiliation(s)
- Agnieszka Smoczyńska
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Errol W Aarnink
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Albert Dunnink
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alexandre Bossu
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Valerie Y H van Weperen
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Veronique M F Meijborg
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands.,Netherlands Heart Institute, Holland Heart House, Utrecht, The Netherlands
| | - Henriëtte D M Beekman
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - R Coronel
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Marc A Vos
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
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Panchal AR, Bartos JA, Cabañas JG, Donnino MW, Drennan IR, Hirsch KG, Kudenchuk PJ, Kurz MC, Lavonas EJ, Morley PT, O’Neil BJ, Peberdy MA, Rittenberger JC, Rodriguez AJ, Sawyer KN, Berg KM, Arafeh J, Benoit JL, Chase M, Fernandez A, de Paiva EF, Fischberg BL, Flores GE, Fromm P, Gazmuri R, Gibson BC, Hoadley T, Hsu CH, Issa M, Kessler A, Link MS, Magid DJ, Marrill K, Nicholson T, Ornato JP, Pacheco G, Parr M, Pawar R, Jaxton J, Perman SM, Pribble J, Robinett D, Rolston D, Sasson C, Satyapriya SV, Sharkey T, Soar J, Torman D, Von Schweinitz B, Uzendu A, Zelop CM, Magid DJ. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2020; 142:S366-S468. [DOI: 10.1161/cir.0000000000000916] [Citation(s) in RCA: 371] [Impact Index Per Article: 92.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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10
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Smoczynska A, Beekman HD, Vos MA. The Increment of Short-term Variability of Repolarisation Determines the Severity of the Imminent Arrhythmic Outcome. Arrhythm Electrophysiol Rev 2019; 8:166-172. [PMID: 31576205 PMCID: PMC6766692 DOI: 10.15420/aer.2019.16.2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Ventricular remodelling can make the heart more susceptible to ventricular arrhythmias like torsades de pointes. Understanding the underlying mechanisms of initiation of ventricular arrhythmias and the determining factors for its severity has the potential to uncover new interventions. Beat-to-beat variation of repolarisation, quantified as short-term variability of repolarisation (STV), has been identified as an important factor contributing to arrhythmogenesis. This article provides an overview of experimental data about STV in relation to the initiation of torsades de pointes in a canine model of complete chronic atrioventricular block susceptible to torsades de pointes arrhythmias. Furthermore, it explores STV in relation to the severity of the arrhythmic outcome.
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Affiliation(s)
- Agnieszka Smoczynska
- Department of Medical Physiology, University Medical Center Utrecht Utrecht, the Netherlands
| | - Henriëtte Dm Beekman
- Department of Medical Physiology, University Medical Center Utrecht Utrecht, the Netherlands
| | - Marc A Vos
- Department of Medical Physiology, University Medical Center Utrecht Utrecht, the Netherlands
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Vo T, Bertram R. Why pacing frequency affects the production of early afterdepolarizations in cardiomyocytes: An explanation revealed by slow-fast analysis of a minimal model. Phys Rev E 2019; 99:052205. [PMID: 31212514 DOI: 10.1103/physreve.99.052205] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Indexed: 12/28/2022]
Abstract
Early afterdepolarizations (EADs) are pathological voltage oscillations in cardiomyocytes that have been observed in response to a number of pharmacological agents and disease conditions. Phase-2 EADs consist of small voltage fluctuations during the plateau of an action potential, typically under conditions in which the action potential is elongated. Although a single-cell behavior, EADs can lead to tissue-level arrhythmias. Much is currently known about the biophysical mechanisms (i.e., the roles of ion channels and intracellular Ca^{2+} stores) for the various forms of EADs, due partially to the development and analysis of mathematical models. This includes the application of slow-fast analysis, which takes advantage of timescale separation inherent in the system to simplify its analysis. We take this further, using a minimal three-dimensional model to demonstrate that phase-2 EADs are canards formed in the neighborhood of a folded node singularity. This allows us to predict the number of EADs that can be produced for a given parameter set, and provides guidance on parameter changes that facilitate or inhibit EAD production. With this approach, we demonstrate why periodic stimulation, as occurs in intact heart, preferentially facilitates EAD production when applied at low frequencies. We also explain the origin of complex alternan dynamics that can occur with intermediate-frequency stimulation, in which varying numbers of EADs are produced with each pulse. These revelations fall out naturally from an understanding of folded node singularities, but are difficult to glean from knowledge of the biophysical mechanism for EADs alone. Therefore, understanding the canard mechanism is a useful complement to understanding of the biophysical mechanism that has been developed over years of experimental and computational investigations.
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Affiliation(s)
- Theodore Vo
- Department of Mathematics, Florida State University, Tallahassee, Florida 32306, USA
| | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA
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Vandersickel N, Bossu A, De Neve J, Dunnink A, Meijborg VM, van der Heyden MA, Beekman JD, De Bakker JM, Vos MA, Panfilov AV. Short-Lasting Episodes of Torsade de Pointes in the Chronic Atrioventricular Block Dog Model Have a Focal Mechanism, While Longer-Lasting Episodes Are Maintained by Re-Entry. JACC Clin Electrophysiol 2017; 3:1565-1576. [DOI: 10.1016/j.jacep.2017.06.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/01/2017] [Indexed: 10/18/2022]
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Nayyar S, Porta-Sánchez A, Nanthakumar K. Twisting and Turning to Find an Explanation for Torsades de Pointes. JACC Clin Electrophysiol 2017; 3:1577-1579. [PMID: 29759840 DOI: 10.1016/j.jacep.2017.09.174] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 09/07/2017] [Indexed: 01/23/2023]
Affiliation(s)
- Sachin Nayyar
- Division of Cardiology, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Andreu Porta-Sánchez
- Division of Cardiology, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Kumaraswamy Nanthakumar
- Division of Cardiology, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada.
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Cho JH, Zhang R, Kilfoil PJ, Gallet R, de Couto G, Bresee C, Goldhaber JI, Marbán E, Cingolani E. Delayed Repolarization Underlies Ventricular Arrhythmias in Rats With Heart Failure and Preserved Ejection Fraction. Circulation 2017; 136:2037-2050. [PMID: 28974519 DOI: 10.1161/circulationaha.117.028202] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 09/07/2017] [Indexed: 12/20/2022]
Abstract
BACKGROUND Heart failure with preserved ejection fraction (HFpEF) represents approximately half of heart failure, and its incidence continues to increase. The leading cause of mortality in HFpEF is sudden death, but little is known about the underlying mechanisms. METHODS Dahl salt-sensitive rats were fed a high-salt diet (8% NaCl) from 7 weeks of age to induce HFpEF (n=38). Rats fed a normal-salt diet (0.3% NaCl) served as controls (n=13). Echocardiograms were performed to assess systolic and diastolic function from 14 weeks of age. HFpEF-verified and control rats underwent programmed electrical stimulation. Corrected QT interval was measured by surface ECG. The mechanisms of ventricular arrhythmias (VA) were probed by optical mapping, whole-cell patch clamp to measure action potential duration and ionic currents, and quantitative polymerase chain reaction and Western blotting to investigate changes in ion channel expression. RESULTS After 7 weeks of a high-salt diet, 31 of 38 rats showed diastolic dysfunction and preserved ejection fraction along with signs of heart failure and hence were diagnosed with HFpEF. Programmed electric stimulation demonstrated increased susceptibility to VA in HFpEF rats (P<0.001 versus controls). The arrhythmogenicity index was increased (P<0.001) and the corrected QT interval on ECG was prolonged (P<0.001) in HFpEF rats. Optical mapping of HFpEF hearts demonstrated prolonged action potentials (P<0.05) and multiple reentry circuits during induced VA. Single-cell recordings of cardiomyocytes isolated from HFpEF rats confirmed a delay of repolarization (P=0.001) and revealed downregulation of transient outward potassium current (Ito; P<0.05). The rapid components of the delayed rectifier potassium current (IKr) and the inward rectifier potassium current (IK1) were also downregulated (P<0.05), but the current densities were much lower than for Ito. In accordance with the reduction of Ito, both Kcnd3 transcript and Kv4.3 protein levels were decreased in HFpEF rat hearts. CONCLUSIONS Susceptibility to VA was markedly increased in rats with HFpEF. Underlying abnormalities include QT prolongation, delayed repolarization from downregulation of potassium currents, and multiple reentry circuits during VA. Our findings are consistent with the hypothesis that potassium current downregulation leads to abnormal repolarization in HFpEF, which in turn predisposes to VA and sudden cardiac death.
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Affiliation(s)
- Jae Hyung Cho
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
| | - Rui Zhang
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
| | - Peter J Kilfoil
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
| | - Romain Gallet
- Henri Mondor University Hospital, Créteil, France (R.G.)
| | - Geoffrey de Couto
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
| | - Catherine Bresee
- Biostatistics and Bioinformatics Research Center, Cedars-Sinai Medical Center, Los Angeles, CA (C.B.)
| | - Joshua I Goldhaber
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
| | - Eduardo Marbán
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
| | - Eugenio Cingolani
- Cedars-Sinai Heart Institute, Los Angeles, CA (J.H.C., R.Z., P.J.K., G.d.C., J.I.G., E.M., E.C.)
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Vandersickel N, Van Nieuwenhuyse E, Seemann G, Panfilov AV. Spatial Patterns of Excitation at Tissue and Whole Organ Level Due to Early Afterdepolarizations. Front Physiol 2017; 8:404. [PMID: 28690545 PMCID: PMC5479889 DOI: 10.3389/fphys.2017.00404] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 05/29/2017] [Indexed: 01/08/2023] Open
Abstract
Early after depolarizations (EAD) occur in many pathological conditions, such as congenital or acquired channelopathies, drug induced arrhythmias, and several other situations that are associated with increased arrhythmogenicity. In this paper we present an overview of the relevant computational studies on spatial EAD dynamics in 1D, 2D, and in 3D anatomical models and discuss the relation of EADs to cardiac arrhythmias. We also discuss unsolved problems and highlight new lines of research in this area.
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Affiliation(s)
| | | | - Gunnar Seemann
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg · Bad Krozingen, Medical Center, University of FreiburgFreiburg, Germany.,Faculty of Medicine, University of FreiburgFreiburg, Germany
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16
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Sridhar S, Vandersickel N, Panfilov AV. Effect of myocyte-fibroblast coupling on the onset of pathological dynamics in a model of ventricular tissue. Sci Rep 2017; 7:40985. [PMID: 28106124 PMCID: PMC5247688 DOI: 10.1038/srep40985] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 12/13/2016] [Indexed: 12/23/2022] Open
Abstract
Managing lethal cardiac arrhythmias is one of the biggest challenges in modern cardiology, and hence it is very important to understand the factors underlying such arrhythmias. While early afterdepolarizations (EAD) of cardiac cells is known to be one such arrhythmogenic factor, the mechanisms underlying the emergence of tissue level arrhythmias from cellular level EADs is not fully understood. Another known arrhythmogenic condition is fibrosis of cardiac tissue that occurs both due to aging and in many types of heart diseases. In this paper we describe the results of a systematic in-silico study, using the TNNP model of human cardiac cells and MacCannell model for (myo)fibroblasts, on the possible effects of diffuse fibrosis on arrhythmias occurring via EADs. We find that depending on the resting potential of fibroblasts (VFR), M-F coupling can either increase or decrease the region of parameters showing EADs. Fibrosis increases the probability of occurrence of arrhythmias after a single focal stimulation and this effect increases with the strength of the M-F coupling. While in our simulations, arrhythmias occur due to fibrosis induced ectopic activity, we do not observe any specific fibrotic pattern that promotes the occurrence of these ectopic sources.
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Affiliation(s)
- S. Sridhar
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Nele Vandersickel
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Alexander V. Panfilov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region, Russia
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17
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Antoniou CK, Dilaveris P, Manolakou P, Galanakos S, Magkas N, Gatzoulis K, Tousoulis D. QT Prolongation and Malignant Arrhythmia: How Serious a Problem? Eur Cardiol 2017; 12:112-120. [PMID: 30416582 DOI: 10.15420/ecr.2017:16:1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
QT prolongation constitutes one of the most frequently encountered electrical disorders of the myocardium. This is due not only to the presence of several associated congenital syndrome but also, and mainly, due to the QT-prolonging effects of several acquired conditions, such as ischaemia and heart failure, as well as multiple medications from widely different categories. Propensity of repolarization disturbances to arrhythmia appears to be inherent in the function of and electrophysiology of the myocardium. In the present review the issue of QT prolongation will be addressed in terms of pathophysiology, arrhythmogenesis, treatment and risk stratification approaches. Although already discussed in literature, it is hoped that the mechanistic approach of the present review will assist in improved understanding of the underlying changes in electrophysiology, as well as the rationale for current diagnostic and therapeutic approaches.
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Affiliation(s)
| | | | - Panagiota Manolakou
- First Department of Cardiology, Korgialenion-Benakion/Hellenic Red Cross Hospital Athens, Greece
| | - Spyridon Galanakos
- First University Department of Cardiology, Hippokration Hospital Athens, Greece
| | - Nikolaos Magkas
- First University Department of Cardiology, Hippokration Hospital Athens, Greece
| | | | - Dimitrios Tousoulis
- First University Department of Cardiology, Hippokration Hospital Athens, Greece
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18
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Vandersickel N, de Boer TP, Vos MA, Panfilov AV. Perpetuation of torsade de pointes in heterogeneous hearts: competing foci or re-entry? J Physiol 2016; 594:6865-6878. [PMID: 26830210 PMCID: PMC5134387 DOI: 10.1113/jp271728] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 01/28/2016] [Indexed: 01/29/2023] Open
Abstract
KEY POINTS The underlying mechanism of torsade de pointes (TdP) remains of debate: perpetuation may be due to (1) focal activity or (2) re-entrant activity. The onset of TdP correlates with action potential heterogeneities in different regions of the heart. We studied the mechanism of perpetuation of TdP in silico using a 2D model of human cardiac tissue and an anatomically accurate model of the ventricles of the human heart. We found that the mechanism of perpetuation TdP depends on the degree of heterogeneity. If the degree of heterogeneity is large, focal activity alone can sustain a TdP, otherwise re-entrant activity emerges. This result can help to understand the relationship between the mechanisms of TdP and tissue properties and may help in developing new drugs against it. ABSTRACT Torsade de pointes (TdP) can be the consequence of cardiac remodelling, drug effects or a combination of both. The mechanism underlying TdP is unclear, and may involve triggered focal activity or re-entry. Recent work by our group has indicated that both cases may exist, i.e. TdPs induced in the chronic atrioventricular block (CAVB) dog model may have a focal origin or are due to re-entry. Also it was found that heterogeneities might play an important role. In the current study we have used computational modelling to further investigate the mechanisms involved in TdP initiation and perpetuation, especially in the CAVB dog model, by the addition of heterogeneities with reduced repolarization reserve in comparison with the surrounding tissue. For this, the TNNP computer model was used for computations. We demonstrated in 2D and 3D simulations that ECGs with the typical TdP morphology can be caused by both multiple competing foci and re-entry circuits as a result of introduction of heterogeneities, depending on whether the heterogeneities have a large or a smaller reduced repolarization reserve in comparison with the surrounding tissue. Large heterogeneities can produce ectopic TdP, while smaller heterogeneities will produce re-entry-type TdP.
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Affiliation(s)
| | - Teun P. de Boer
- Department of Medical PhysiologyUniversity Medical Center UtrechtYalelaan 503584 CM UtrechtThe Netherlands
| | - Marc A. Vos
- Department of Medical PhysiologyUniversity Medical Center UtrechtYalelaan 503584 CM UtrechtThe Netherlands
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19
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Shah AJ, Hocini M, Denis A, Derval N, Sacher F, Jais P, Haissaguerre M. Polymorphic Ventricular Tachycardia/Ventricular Fibrillation and Sudden Cardiac Death in the Normal Heart. Card Electrophysiol Clin 2016; 8:581-591. [PMID: 27521091 DOI: 10.1016/j.ccep.2016.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Primary electrical diseases manifest with polymorphic ventricular tachycardia (PMVT) and ventricular fibrillation (VF) and along with idiopathic VF contribute to about 10% of sudden cardiac deaths (SCDs) overall. These disorders include long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, short QT syndrome, and early repolarization syndrome. This article reviews the clinical electrophysiological management of PMVT/VF in a structurally normal heart affected with these disorders.
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Affiliation(s)
- Ashok J Shah
- Cardio Vascular Services, South Consulting Suites, Peel Health Campus, 110 Lakes Road, Mandurah, Western Australia 6210, Australia.
| | - Meleze Hocini
- Department of Electrophysiology and Cardiac Pacing, Hôpital Cardiologique du Haut Lévêque, Avenue de Magellan, Pessac Cedex 33604, France
| | - Arnaud Denis
- Department of Electrophysiology and Cardiac Pacing, Hôpital Cardiologique du Haut Lévêque, Avenue de Magellan, Pessac Cedex 33604, France
| | - Nicolas Derval
- Department of Electrophysiology and Cardiac Pacing, Hôpital Cardiologique du Haut Lévêque, Avenue de Magellan, Pessac Cedex 33604, France
| | - Frederic Sacher
- Department of Electrophysiology and Cardiac Pacing, Hôpital Cardiologique du Haut Lévêque, Avenue de Magellan, Pessac Cedex 33604, France
| | - Pierre Jais
- Department of Electrophysiology and Cardiac Pacing, Hôpital Cardiologique du Haut Lévêque, Avenue de Magellan, Pessac Cedex 33604, France
| | - Michel Haissaguerre
- Department of Electrophysiology and Cardiac Pacing, Hôpital Cardiologique du Haut Lévêque, Avenue de Magellan, Pessac Cedex 33604, France.
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20
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Madhvani RV, Angelini M, Xie Y, Pantazis A, Suriany S, Borgstrom NP, Garfinkel A, Qu Z, Weiss JN, Olcese R. Targeting the late component of the cardiac L-type Ca2+ current to suppress early afterdepolarizations. ACTA ACUST UNITED AC 2016; 145:395-404. [PMID: 25918358 PMCID: PMC4411259 DOI: 10.1085/jgp.201411288] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Early afterdepolarizations (EADs) associated with prolongation of the cardiac action potential (AP) can create heterogeneity of repolarization and premature extrasystoles, triggering focal and reentrant arrhythmias. Because the L-type Ca(2+) current (ICa,L) plays a key role in both AP prolongation and EAD formation, L-type Ca(2+) channels (LTCCs) represent a promising therapeutic target to normalize AP duration (APD) and suppress EADs and their arrhythmogenic consequences. We used the dynamic-clamp technique to systematically explore how the biophysical properties of LTCCs could be modified to normalize APD and suppress EADs without impairing excitation-contraction coupling. Isolated rabbit ventricular myocytes were first exposed to H2O2 or moderate hypokalemia to induce EADs, after which their endogenous ICa,L was replaced by a virtual ICa,L with tunable parameters, in dynamic-clamp mode. We probed the sensitivity of EADs to changes in the (a) amplitude of the noninactivating pedestal current; (b) slope of voltage-dependent activation; (c) slope of voltage-dependent inactivation; (d) time constant of voltage-dependent activation; and (e) time constant of voltage-dependent inactivation. We found that reducing the amplitude of the noninactivating pedestal component of ICa,L effectively suppressed both H2O2- and hypokalemia-induced EADs and restored APD. These results, together with our previous work, demonstrate the potential of this hybrid experimental-computational approach to guide drug discovery or gene therapy strategies by identifying and targeting selective properties of LTCC.
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Affiliation(s)
- Roshni V Madhvani
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Marina Angelini
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Yuanfang Xie
- Department of Pharmacology, University of California, Davis, Davis, CA 95616
| | - Antonios Pantazis
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Silvie Suriany
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Nils P Borgstrom
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Alan Garfinkel
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Zhilin Qu
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - James N Weiss
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Riccardo Olcese
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
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22
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Winter J, Shattock MJ. Geometrical considerations in cardiac electrophysiology and arrhythmogenesis. Europace 2015; 18:320-31. [PMID: 26585597 DOI: 10.1093/europace/euv307] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 08/14/2015] [Indexed: 11/14/2022] Open
Abstract
The rate of repolarization (RRepol) and so the duration of the cardiac action potential are determined by the balance of inward and outward currents across the cardiac membrane (net ionic current). Plotting action potential duration (APD) as a function of the RRepol reveals an inverse non-linear relationship, arising from the geometric association between these two factors. From the RRepol-APD relationship, it can be observed that a longer action potential will exhibit a greater propensity to shorten, or prolong, for a given change in the RRepol (i.e. net ionic current), when compared with one that is initially shorter. This observation has recently been used to explain why so many interventions that prolong the action potential exert a greater effect at slow rates (reverse rate-dependence). In this article, we will discuss the broader implications of this simple principle and examine how common experimental observations on the electrical behaviour of the myocardium may be explained in terms of the RRepol-APD relationship. An argument is made, with supporting published evidence, that the non-linear relationship between the RRepol and APD is a fundamental, and largely overlooked, property of the myocardium. The RRepol-APD relationship appears to explain why interventions and disease with seemingly disparate mechanisms of action have similar electrophysiological consequences. Furthermore, the RRepol-APD relationship predicts that prolongation of the action potential, by slowing repolarization, will promote conditions of dynamic electrical instability, exacerbating several electrophysiological phenomena associated with arrhythmogenesis, namely, the rate dependence of dispersion of repolarization, APD restitution, and electrical alternans.
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Affiliation(s)
- James Winter
- Cardiovascular Division, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, King's College London, London SE1 7EH, UK
| | - Michael J Shattock
- Cardiovascular Division, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, King's College London, London SE1 7EH, UK
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23
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Chang PC, Wo HT, Lee HL, Lin SF, Wen MS, Chu Y, Yeh SJ, Chou CC. Role of sarcoplasmic reticulum calcium in development of secondary calcium rise and early afterdepolarizations in long QT syndrome rabbit model. PLoS One 2015; 10:e0123868. [PMID: 25875599 PMCID: PMC4395163 DOI: 10.1371/journal.pone.0123868] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 02/23/2015] [Indexed: 11/19/2022] Open
Abstract
Background L-type calcium current reactivation plays an important role in development of early afterdepolarizations (EADs) and torsades de pointes (TdP). Secondary intracellular calcium (Cai) rise is associated with initiation of EADs. Objective To test whether inhibition of sarcoplasmic reticulum (SR) Ca2+ cycling suppresses secondary Cai rise and genesis of EADs. Methods Langendorff perfusion and dual voltage and Cai optical mapping were conducted in 10 rabbit hearts. Atrioventricular block (AVB) was created by radiofrequency ablation. After baseline studies, E4031, SR Ca2+ cycling inhibitors (ryanodine plus thapsigargin) and nifedipine were then administrated subsequently, and the protocols were repeated. Results At baseline, there was no spontaneous or pacing-induced TdP. After E4031 administration, action potential duration (APD) was significantly prolonged and the amplitude of secondary Cai rise was enhanced, and 7 (70%) rabbits developed spontaneous or pacing-induced TdP. In the presence of ryanodine plus thapsigargin, TdP inducibility was significantly reduced (2 hearts, 20%, p = 0.03). Although APD was significantly prolonged (from 298 ± 30 ms to 457 ± 75 ms at pacing cycle length of 1000 m, p = 0.007) by ryanodine plus thapsigargin, the secondary Cai rise was suppressed (from 8.8 ± 2.6% to 1.2 ± 0.9%, p = 0.02). Nifedipine inhibited TdP inducibility in all rabbit hearts. Conclusion In this AVB and long QT rabbit model, inhibition of SR Ca2+ cycyling reduces the inducibility of TdP. The mechanism might be suppression of secondary Cai rise and genesis of EADs.
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Affiliation(s)
- Po-Cheng Chang
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linko, Taoyuan, Taiwan
- Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Hung-Ta Wo
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linko, Taoyuan, Taiwan
| | - Hui-Ling Lee
- Department of Anesthesia, Chang Gung Memorial Hospital, Taipei, Taiwan
| | - Shien-Fong Lin
- Institute of Biomedical Engineering, National Chiao Tung University, Hsin Chu, Taiwan
| | - Ming-Shien Wen
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linko, Taoyuan, Taiwan
- Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Yen Chu
- Chang Gung University College of Medicine, Taoyuan, Taiwan
- Division of Thoracic Surgery, Chang Gung Memorial Hospital, Linko, Taoyuan, Taiwan
- Institute of Biomedical Engineering, National Chiao Tung University, Hsin Chu, Taiwan
| | - San-Jou Yeh
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linko, Taoyuan, Taiwan
- Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Chung-Chuan Chou
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linko, Taoyuan, Taiwan
- Chang Gung University College of Medicine, Taoyuan, Taiwan
- * E-mail:
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Qu Z, Weiss JN. Mechanisms of ventricular arrhythmias: from molecular fluctuations to electrical turbulence. Annu Rev Physiol 2014; 77:29-55. [PMID: 25340965 DOI: 10.1146/annurev-physiol-021014-071622] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Ventricular arrhythmias have complex causes and mechanisms. Despite extensive investigation involving many clinical, experimental, and computational studies, effective biological therapeutics are still very limited. In this article, we review our current understanding of the mechanisms of ventricular arrhythmias by summarizing the state of knowledge spanning from the molecular scale to electrical wave behavior at the tissue and organ scales and how the complex nonlinear interactions integrate into the dynamics of arrhythmias in the heart. We discuss the challenges that we face in synthesizing these dynamics to develop safe and effective novel therapeutic approaches.
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Affiliation(s)
- Zhilin Qu
- Departments of 1Medicine (Cardiology) and
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25
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Abstract
In a normal human life span, the heart beats about 2 to 3 billion times. Under diseased conditions, a heart may lose its normal rhythm and degenerate suddenly into much faster and irregular rhythms, called arrhythmias, which may lead to sudden death. The transition from a normal rhythm to an arrhythmia is a transition from regular electrical wave conduction to irregular or turbulent wave conduction in the heart, and thus this medical problem is also a problem of physics and mathematics. In the last century, clinical, experimental, and theoretical studies have shown that dynamical theories play fundamental roles in understanding the mechanisms of the genesis of the normal heart rhythm as well as lethal arrhythmias. In this article, we summarize in detail the nonlinear and stochastic dynamics occurring in the heart and their links to normal cardiac functions and arrhythmias, providing a holistic view through integrating dynamics from the molecular (microscopic) scale, to the organelle (mesoscopic) scale, to the cellular, tissue, and organ (macroscopic) scales. We discuss what existing problems and challenges are waiting to be solved and how multi-scale mathematical modeling and nonlinear dynamics may be helpful for solving these problems.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Correspondence to: Zhilin Qu, PhD, Department of Medicine, Division of Cardiology, David Geffen School of Medicine at UCLA, A2-237 CHS, 650 Charles E. Young Drive South, Los Angeles, CA 90095, Tel: 310-794-6050, Fax: 310-206-9133,
| | - Gang Hu
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Alan Garfinkel
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California 90095, USA
| | - James N. Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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26
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Nakamura Y, Matsuo J, Miyamoto N, Ojima A, Ando K, Kanda Y, Sawada K, Sugiyama A, Sekino Y. Assessment of testing methods for drug-induced repolarization delay and arrhythmias in an iPS cell-derived cardiomyocyte sheet: multi-site validation study. J Pharmacol Sci 2014; 124:494-501. [PMID: 24694996 DOI: 10.1254/jphs.13248fp] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
A prospective comparison study across 3 independent research laboratories of a pure IKr blocker E-4031 was conducted by using the same batch of human iPS cell-derived cardiomyocytes in order to verify the utility and reliability of our original standard protocol. Field potential waveforms were recorded with a multi-electrode array system to measure the inter-spike interval and field potential duration. The effects of E-4031 at concentrations of 1 to 100 nM were sequentially examined every 10 min. In each facility, E-4031 significantly prolonged the field potential duration corrected by Fridericia's formula and caused early afterdepolarizations occasionally resulting in triggered activities, whereas it tended to decrease the rate of spontaneous contraction. These results were qualitatively and quantitatively consistent with previous non-clinical in vitro and in vivo studies as well as clinical reports. There were inter-facility differences in some absolute values of the results, which were not observed when the values were normalized as percentage change. Information described in this paper may serve as a guide when predicting the drug-induced repolarization delay and arrhythmias with this new technology of stem cells.
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Affiliation(s)
- Yuji Nakamura
- Department of Pharmacology, Faculty of Medicine, Toho University, Japan
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27
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Vandersickel N, Kazbanov IV, Nuitermans A, Weise LD, Pandit R, Panfilov AV. A study of early afterdepolarizations in a model for human ventricular tissue. PLoS One 2014; 9:e84595. [PMID: 24427289 PMCID: PMC3888406 DOI: 10.1371/journal.pone.0084595] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/15/2013] [Indexed: 12/13/2022] Open
Abstract
Sudden cardiac death is often caused by cardiac arrhythmias. Recently, special attention has been given to a certain arrhythmogenic condition, the long-QT syndrome, which occurs as a result of genetic mutations or drug toxicity. The underlying mechanisms of arrhythmias, caused by the long-QT syndrome, are not fully understood. However, arrhythmias are often connected to special excitations of cardiac cells, called early afterdepolarizations (EADs), which are depolarizations during the repolarizing phase of the action potential. So far, EADs have been studied mainly in isolated cardiac cells. However, the question on how EADs at the single-cell level can result in fibrillation at the tissue level, especially in human cell models, has not been widely studied yet. In this paper, we study wave patterns that result from single-cell EAD dynamics in a mathematical model for human ventricular cardiac tissue. We induce EADs by modeling experimental conditions which have been shown to evoke EADs at a single-cell level: by an increase of L-type Ca currents and a decrease of the delayed rectifier potassium currents. We show that, at the tissue level and depending on these parameters, three types of abnormal wave patterns emerge. We classify them into two types of spiral fibrillation and one type of oscillatory dynamics. Moreover, we find that the emergent wave patterns can be driven by calcium or sodium currents and we find phase waves in the oscillatory excitation regime. From our simulations we predict that arrhythmias caused by EADs can occur during normal wave propagation and do not require tissue heterogeneities. Experimental verification of our results is possible for experiments at the cell-culture level, where EADs can be induced by an increase of the L-type calcium conductance and by the application of I blockers, and the properties of the emergent patterns can be studied by optical mapping of the voltage and calcium.
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Affiliation(s)
- Nele Vandersickel
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- * E-mail:
| | - Ivan V. Kazbanov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Anita Nuitermans
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands
| | - Louis D. Weise
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands
| | - Rahul Pandit
- Center for Condensed Matter Theory - Department of Physics, Indian Institute of Science, Bangalore, India
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28
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Abstract
The objective of this article is to present a broad review of the role of cardiac electric rotors and their accompanying spiral waves in the mechanism of cardiac fibrillation. At the outset, we present a brief historical overview regarding reentry and then discuss the basic concepts and terminologies pertaining to rotors and their initiation. Thereafter, the intrinsic properties of rotors and spiral waves, including phase singularities, wavefront curvature, and dominant frequency maps, are discussed. The implications of rotor dynamics for the spatiotemporal organization of fibrillation, independent of the species being studied, are described next. The knowledge gained regarding the role of cardiac structure in the initiation or maintenance of rotors and the ionic bases of spiral waves in the past 2 decades, as well as the significance for drug therapy, is reviewed subsequently. We conclude by examining recent evidence suggesting that rotors are critical in sustaining both atrial and ventricular fibrillation in the human heart and its implications for treatment with radiofrequency ablation.
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Affiliation(s)
- Sandeep V Pandit
- Center for Arrhythmia Research, University of Michigan, NCRC, 2800 Plymouth Rd, Ann Arbor, MI 48109, USA
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29
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Han C, Pogwizd SM, Killingsworth CR, Zhou Z, He B. Noninvasive cardiac activation imaging of ventricular arrhythmias during drug-induced QT prolongation in the rabbit heart. Heart Rhythm 2013; 10:1509-15. [PMID: 23773986 DOI: 10.1016/j.hrthm.2013.06.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Indexed: 11/18/2022]
Abstract
BACKGROUND Imaging myocardial activation from noninvasive body surface potentials promises to aid in both cardiovascular research and clinical medicine. OBJECTIVE To investigate the ability of a noninvasive 3-dimensional cardiac electrical imaging technique for characterizing the activation patterns of dynamically changing ventricular arrhythmias during drug-induced QT prolongation in rabbits. METHODS Simultaneous body surface potential mapping and 3-dimensional intracardiac mapping were performed in a closed-chest condition in 8 rabbits. Data analysis was performed on premature ventricular complexes, couplets, and torsades de pointes (TdP) induced during intravenous administration of clofilium and phenylephrine with combinations of various infusion rates. RESULTS The drug infusion led to a significant increase in the QT interval (from 175 ± 7 to 274 ± 31 ms) and rate-corrected QT interval (from 183 ± 5 to 262 ± 21 ms) during the first dose cycle. All the ectopic beats initiated by a focal activation pattern. The initial beat of TdPs arose at the focal site, whereas the subsequent beats were due to focal activity from different sites or 2 competing focal sites. The imaged results captured the dynamic shift of activation patterns and were in good correlation with the simultaneous measurements, with a correlation coefficient of 0.65 ± 0.02 averaged over 111 ectopic beats. Sites of initial activation were localized to be ~5 mm from the directly measured initiation sites. CONCLUSIONS The 3-dimensional cardiac electrical imaging technique could localize the origin of activation and image activation sequence of TdP during QT prolongation induced by clofilium and phenylephrine in rabbits. It offers the potential to noninvasively investigate the proarrhythmic effects of drug infusion and assess the mechanisms of arrhythmias on a beat-to-beat basis.
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Affiliation(s)
- Chengzong Han
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota
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30
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Osadchii OE. Quinidine elicits proarrhythmic changes in ventricular repolarization and refractoriness in guinea-pig. Can J Physiol Pharmacol 2013; 91:306-15. [DOI: 10.1139/cjpp-2012-0379] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Quinidine is a class Ia Na+ channel blocker that prolongs cardiac repolarization owing to the inhibition of IKr, the rapid component of the delayed rectifier current. Although quinidine may induce proarrhythmia, the contributing mechanisms remain incompletely understood. This study examined whether quinidine may set proarrhythmic substrate by inducing spatiotemporal abnormalities in repolarization and refractoriness. The monophasic action potential duration (APD), effective refractory periods (ERPs), and volume-conducted electrocardiograms (ECGs) were assessed in perfused guinea-pig hearts. Quinidine was found to produce the reverse rate-dependent prolongation of ventricular repolarization, which contributed to increased steepness of APD restitution. Throughout the epicardium, quinidine elicited a greater APD increase in the left ventricular chamber compared with the right ventricle, thereby enhancing spatial repolarization heterogeneities. Quinidine prolonged APD to a greater extent than ERP, thus extending the vulnerable window for ventricular re-excitation. This change was attributed to increased triangulation of epicardial action potential because of greater APD lengthening at 90% repolarization than at 30% repolarization. Over the transmural plane, quinidine evoked a greater ERP prolongation at endocardium than epicardium and increased dispersion of refractoriness. Premature ectopic beats and monomorphic ventricular tachycardia were observed in 50% of quinidine-treated heart preparations. In summary, abnormal changes in repolarization and refractoriness contribute greatly to proarrhythmic substrate upon quinidine infusion.
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Affiliation(s)
- Oleg E. Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark
- Department of Health Science and Technology, University of Aalborg, Fredrik Bajers Vej 7E, 9220 Aalborg, Denmark
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31
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Chang MG, de Lange E, Calmettes G, Garfinkel A, Qu Z, Weiss JN. Pro- and antiarrhythmic effects of ATP-sensitive potassium current activation on reentry during early afterdepolarization-mediated arrhythmias. Heart Rhythm 2013; 10:575-82. [PMID: 23246594 PMCID: PMC4285341 DOI: 10.1016/j.hrthm.2012.12.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Indexed: 11/26/2022]
Abstract
BACKGROUND Under conditions promoting early afterdepolarizations (EADs), ventricular tissue can become bi-excitable, that is, capable of wave propagation mediated by either the Na current (INa) or the L-type calcium current (ICa,L), raising the possibility that ICa,L-mediated reentry may contribute to polymorphic ventricular tachycardia (PVT) and torsades de pointes. ATP-sensitive K current (IKATP) activation suppresses EADs, but the effects on ICa,L-mediated reentry are unknown. OBJECTIVE To investigate the effects of IKATP activation on ICa,L-mediated reentry. METHODS We performed optical voltage mapping in cultured neonatal rat ventricular myocyte monolayers exposed to BayK8644 and isoproterenol. The effects of pharmacologically activating IKATP with pinacidil were analyzed. RESULTS In 13 monolayers with anatomic ICa,L-mediated reentry around a central obstacle, pinacidil (50 μM) converted ICa,L-mediated reentry to INa-mediated reentry. In 33 monolayers with functional ICa,L-mediated reentry (spiral waves), pinacidil terminated reentry in 17, converted reentry into more complex INa-mediated reentry resembling fibrillation in 12, and had no effect in 4. In simulated 2-dimensional bi-excitable tissue in which ICa,L- and INa-mediated wave fronts coexisted, slow IKATP activation (over minutes) reliably terminated rotors but rapid IKATP activation (over seconds) often converted ICa,L-mediated reentry to INa-mediated reentry resembling fibrillation. CONCLUSIONS IKATP activation can have proarrhythmic effects on EAD-mediated arrhythmias if ICa,L-mediated reentry is present.
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Affiliation(s)
- Marvin G. Chang
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - Enno de Lange
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - Guillaume Calmettes
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - Alan Garfinkel
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
- Department of Integrative Biology and Physiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - James N. Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
- Department of Physiology, David Geffen School of Medicine at University of California, Los Angeles, California
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32
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Fenton FH, Gizzi A, Cherubini C, Pomella N, Filippi S. Role of temperature on nonlinear cardiac dynamics. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:042717. [PMID: 23679459 DOI: 10.1103/physreve.87.042717] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 12/19/2012] [Indexed: 06/02/2023]
Abstract
Thermal effects affecting spatiotemporal behavior of cardiac tissue are discussed by relating temperature variations to proarrhythmic dynamics in the heart. By introducing a thermoelectric coupling in a minimal model of cardiac tissue, we are able to reproduce experimentally measured dynamics obtained simultaneously from epicardial and endocardial canine right ventricles at different temperatures. A quantitative description of emergent proarrhythmic properties of restitution, conduction velocity, and alternans regimes as a function of temperature is presented. Complex discordant alternans patterns that enhance tissue dispersion consisting of one wave front and three wave backs are described in both simulations and experiments. Possible implications for model generalization are finally discussed.
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Affiliation(s)
- Flavio H Fenton
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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33
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Karagueuzian HS, Nguyen TP, Qu Z, Weiss JN. Oxidative stress, fibrosis, and early afterdepolarization-mediated cardiac arrhythmias. Front Physiol 2013; 4:19. [PMID: 23423152 PMCID: PMC3573324 DOI: 10.3389/fphys.2013.00019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 01/25/2013] [Indexed: 01/06/2023] Open
Abstract
Animal and clinical studies have demonstrated that oxidative stress, a common pathophysiological factor in cardiac disease, reduces repolarization reserve by enhancing the L-type calcium current, the late Na, and the Na-Ca exchanger, promoting early afterdepolarizations (EADs) that can initiate ventricular tachycardia and ventricular fibrillation (VT/VF) in structurally remodeled hearts. Increased ventricular fibrosis plays a key facilitatory role in allowing oxidative-stress induced EADs to manifest as triggered activity and VT/VF, since normal non-fibrotic hearts are resistant to arrhythmias when challenged with similar or higher levels of oxidative stress. The findings imply that antifibrotic therapy, in addition to therapies designed to suppress EAD formation at the cellular level, may be synergistic in reducing the risk of sudden cardiac death.
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Affiliation(s)
- Hrayr S Karagueuzian
- Cardiovascular Research Laboratory, Translational Arrhythmia Research Section, David Geffen School of Medicine at UCLA Los Angeles, CA, USA
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34
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Borek B, Shajahan TK, Gabriels J, Hodge A, Glass L, Shrier A. Pacemaker interactions induce reentrant wave dynamics in engineered cardiac culture. CHAOS (WOODBURY, N.Y.) 2012; 22:033132. [PMID: 23020471 DOI: 10.1063/1.4747709] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Pacemaker interactions can lead to complex wave dynamics seen in certain types of cardiac arrhythmias. We use experimental and mathematical models of pacemakers in heterogeneous excitable media to investigate how pacemaker interactions can be a mechanism for wave break and reentrant wave dynamics. Embryonic chick ventricular cells are cultured in vitro so as to create a dominant central pacemaker site that entrains other pacemakers in the medium. Exposure of those cultures to a potassium channel blocker, E-4031, leads to emergence of peripheral pacemakers that compete with each other and with the central pacemaker. Waves emitted by faster pacemakers break up over the slower pacemaker to form reentrant waves. Similar dynamics are observed in a modified FitzHugh-Nagumo model of heterogeneous excitable media with two distinct sites of pacemaking. These findings elucidate a mechanism of pacemaker-induced reentry in excitable media.
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Affiliation(s)
- Bartłomiej Borek
- Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada
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35
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Quail T, McVicar N, Aguilar M, Kim MY, Hodge A, Glass L, Shrier A. Chaotic dynamics in cardiac aggregates induced by potassium channel block. CHAOS (WOODBURY, N.Y.) 2012; 22:033140. [PMID: 23020479 DOI: 10.1063/1.4748854] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Chaotic rhythms in deterministic models can arise as a consequence of changes in model parameters. We carried out experimental studies in which we induced a variety of complex rhythms in aggregates of embryonic chick cardiac cells using E-4031 (1.0-2.5 μM), a drug that blocks the hERG potassium channel. Following the addition of the drug, the regular rhythm evolved to display a spectrum of complex dynamics: irregular rhythms, bursting oscillations, doublets, and accelerated rhythms. The interbeat intervals of the irregular rhythms can be described by one-dimensional return maps consistent with chaotic dynamics. A Hodgkin-Huxley-style cardiac ionic model captured the different types of complex dynamics following blockage of the hERG mediated potassium current.
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Affiliation(s)
- Thomas Quail
- Department of Physiology, McGill University, 3655 Promenade Sir William Osler Montreal, Quebec H3G 1Y6, Canada
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36
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de Lange E, Xie Y, Qu Z. Synchronization of early afterdepolarizations and arrhythmogenesis in heterogeneous cardiac tissue models. Biophys J 2012; 103:365-73. [PMID: 22853915 DOI: 10.1016/j.bpj.2012.06.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/05/2012] [Accepted: 06/07/2012] [Indexed: 02/05/2023] Open
Abstract
Early afterdepolarizations (EADs) are linked to both triggered arrhythmias and reentrant arrhythmias by causing premature ventricular complexes (PVCs), focal excitations, or heterogeneous tissue substrates for reentry formation. However, a critical number of cells that synchronously exhibit EADs are needed to result in arrhythmia triggers and substrates in tissue. In this study, we use mathematical modeling and computer simulations to investigate EAD synchronization and arrhythmia induction in tissue models with random cell-to-cell variations. Our major observations are as follows. Random cell-to-cell variations in action potential duration without EAD presence do not cause large dispersion of refractoriness in well-coupled tissue. In the presence of phase-2 EADs, the cells may synchronously exhibit the same number of EADs or no EADs with a very small dispersion of refractoriness, or synchronize regionally to result in large dispersion of refractoriness. In the presence of phase-3 EADs, regional synchronization leads to propagating EADs, forming PVCs in tissue. Interestingly, even though the uncoupled cells exhibit either no EAD or only a single EAD, when these cells are coupled to form a tissue, more than one PVC can occur. When the PVCs occur at different locations and time, multifocal arrhythmias are triggered, with the foci shifting in space and time in an irregular manner. The focal arrhythmias either spontaneously terminate or degenerate into reentrant arrhythmias due to heterogeneities and spatiotemporal chaotic dynamics of the foci.
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Affiliation(s)
- Enno de Lange
- Cardiovascular Research Laboratory, Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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37
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Leenhardt A, Messali A, Labbé JP, Denjoy I, Dejode P, Maison-Blanche P, Kedra A, Extramiana F. Les post-dépolarisations. ARCHIVES OF CARDIOVASCULAR DISEASES SUPPLEMENTS 2011. [DOI: 10.1016/s1878-6480(11)70389-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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38
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Atkinson A, Inada S, Li J, Tellez JO, Yanni J, Sleiman R, Allah EA, Anderson RH, Zhang H, Boyett MR, Dobrzynski H. Anatomical and molecular mapping of the left and right ventricular His–Purkinje conduction networks. J Mol Cell Cardiol 2011; 51:689-701. [DOI: 10.1016/j.yjmcc.2011.05.020] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Revised: 05/23/2011] [Accepted: 05/25/2011] [Indexed: 12/12/2022]
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39
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Boulaksil M, Jungschleger JG, Antoons G, Houtman MJ, de Boer TP, Wilders R, Beekman JD, Maessen JG, van der Hulst FF, van der Heyden MA, van Veen TA, van Rijen HV, de Bakker JM, Vos MA. Drug-Induced Torsade de Pointes Arrhythmias in the Chronic AV Block Dog Are Perpetuated by Focal Activity. Circ Arrhythm Electrophysiol 2011; 4:566-76. [DOI: 10.1161/circep.110.958991] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
The electrically remodeled canine heart after chronic AV block (CAVB) has a high susceptibility for drug-induced torsade de pointes (TdP) arrhythmias. Although focal mechanisms have been considered for initiation, there is still controversy about whether reentry is the dominant mechanism for perpetuation of TdP. In this animal model with known nonuniform prolongation of repolarization, the mechanism of perpetuation of TdP arrhythmia was explored.
Methods and Results—
Seventeen TdP-sensitive CAVB and 10 sinus rhythm (SR) dogs were studied. In 6 animals, 66 needle electrodes were evenly distributed transmurally to record 240 unipolar local electrograms simultaneously. Activation times and activation recovery intervals were determined before and during ibutilide-induced TdP. In 12 CAVB and 9 SR dogs, left ventricular (LV) and right ventricular (RV) epicardial electrograms were recorded with a 208-point multiterminal grid electrode allowing conduction velocity (CV) and ventricular effective refractory period (VERP) measurements. Biopsy specimens were processed for connexin43 (Cx43) expression and collagen content. Ventricular myocytes were isolated to determine sodium current (
I
Na
) density and cell dimensions. Computer simulations were used to assess the effects of changes therein. In CAVB, VERP and ARI were increased, whereas CV was unaltered in LV. Transversal but not longitudinal CV was increased in RV.
I
Na
was reduced by 37% in LV but unaltered in RV. LV and RV cell size were increased, but collagen and Cx43 content remained unchanged. Simulations showed increase in CV of RV as a consequence of increased cell size at normal
I
Na
. Ibutilide increased ARI, ERP, and maximal transmural dispersion of ERP (45±25 to 120±65 ms;
P
<0.05). Twenty-eight of 47 episodes of self-terminating TdP (43±72 beats) were analyzed. The majority (>90%) of beats were focal; reentry was observed only occasionally.
Conclusions—
Focal activity is the dominant mechanism involved in perpetuation of ibutilide-induced TdP in CAVB dogs based on detailed 3D mapping. This conclusion is in line with unaltered conduction and documented increase in VERP.
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Affiliation(s)
- Mohamed Boulaksil
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Jerome G. Jungschleger
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Gudrun Antoons
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Marien J.C. Houtman
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Teun P. de Boer
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Ronald Wilders
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Jet D. Beekman
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Jos G. Maessen
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Ferenc F. van der Hulst
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Marcel A.G. van der Heyden
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Toon A.B. van Veen
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Harold V.M. van Rijen
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Jacques M.T. de Bakker
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
| | - Marc A. Vos
- From the Department of Medical Physiology (M.B., G.A., M.J.C.H. T.P.d.B., J.D.B., M.A.G.v.d.H., T.A.B.v.V., H.V.M.v.R., J.M.T.d.B., M.A.V.) and Department of Cardio-Thoracic Surgery (F.F.v.d.H.), University Medical Center Utrecht, Utrecht, The Netherlands; Interuniversity Cardiology Institute of the Netherlands (M.B., J.M.T.d.B.), Department of Cardio-Thoracic Surgery (J.G.J., J.G.M.), and Department of Cardiology (F.F.v.d.H.), Cardiovascular Research Institute Maastricht, University Hospital
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Antzelevitch C, Dumaine R. Electrical Heterogeneity in the Heart: Physiological, Pharmacological and Clinical Implications. Compr Physiol 2011. [DOI: 10.1002/cphy.cp020117] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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So little source, so much sink: requirements for afterdepolarizations to propagate in tissue. Biophys J 2010; 99:1408-15. [PMID: 20816052 DOI: 10.1016/j.bpj.2010.06.042] [Citation(s) in RCA: 236] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 06/18/2010] [Accepted: 06/22/2010] [Indexed: 11/22/2022] Open
Abstract
How early (EADs) and delayed afterdepolarizations (DADs) overcome electrotonic source-sink mismatches in tissue to trigger premature ventricular complexes remains incompletely understood. To study this question, we used a rabbit ventricular action potential model to simulate tissues in which a central area of contiguous myocytes susceptible to EADs or DADs was surrounded by unsusceptible tissue. In 1D tissue with normal longitudinal conduction velocity (0.55 m/s), the numbers of contiguous susceptible myocytes required for an EAD and a barely suprathreshold DAD to trigger a propagating action potential were 70 and 80, respectively. In 2D tissue, these numbers increased to 6940 and 7854, and in 3D tissue to 696,910 and 817,280. These numbers were significantly decreased by reduced gap junction conductance, simulated fibrosis, reduced repolarization reserve and heart failure electrical remodeling. In conclusion, the source-sink mismatch in well-coupled cardiac tissue powerfully protects the heart from arrhythmias due to sporadic afterdepolarizations. Structural and electrophysiological remodeling decrease these numbers significantly but still require synchronization mechanisms for EADs and DADs to overcome the robust protective effects of source-sink mismatch.
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Abstract
T-wave alternans, a manifestation of repolarization alternans at the cellular level, is associated with lethal cardiac arrhythmias and sudden cardiac death. At the cellular level, several mechanisms can produce repolarization alternans, including: (1) electrical restitution resulting from collective ion channel recovery, which usually occurs at fast heart rates but can also occur at normal heart rates when action potential is prolonged resulting in a short diastolic interval; (2) the transient outward current, which tends to occur at normal or slow heart rates; (3) the dynamics of early after depolarizations, which tends to occur during bradycardia; and (4) intracellular calcium cycling alternans through its interaction with membrane voltage. In this review, we summarize the cellular mechanisms of alternans arising from these different mechanisms, and discuss their roles in arrhythmogenesis in the setting of cardiac disease.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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Qu Z. Chaos in the genesis and maintenance of cardiac arrhythmias. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 105:247-57. [PMID: 21078337 DOI: 10.1016/j.pbiomolbio.2010.11.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 07/04/2010] [Accepted: 11/05/2010] [Indexed: 11/18/2022]
Abstract
Dynamical chaos, an irregular behavior of deterministic systems, has been widely shown in nature. It also has been demonstrated in cardiac myocytes in many studies, including rapid pacing-induced irregular beat-to-beat action potential alterations and slow pacing-induced irregular early afterdepolarizations, etc. Here we review the roles of chaos in the genesis of cardiac arrhythmias, the transition to ventricular fibrillation, and the spontaneous termination of fibrillation, based on evidence from computer simulation of mathematical models and experiments of animal models.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, 650 Charles E. Young Drive South, Los Angeles, CA 90095, USA.
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Sato D, Xie LH, Nguyen TP, Weiss JN, Qu Z. Irregularly appearing early afterdepolarizations in cardiac myocytes: random fluctuations or dynamical chaos? Biophys J 2010; 99:765-73. [PMID: 20682253 DOI: 10.1016/j.bpj.2010.05.019] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 04/30/2010] [Accepted: 05/07/2010] [Indexed: 01/08/2023] Open
Abstract
Irregularly occurring early afterdepolarizations (EADs) in cardiac myocytes are traditionally hypothesized to be caused by random ion channel fluctuations. In this study, we combined 1), patch-clamp experiments in which action potentials were recorded at different pacing cycle lengths from isolated rabbit ventricular myocytes under several experimental conditions inducing EADs, including oxidative stress with hydrogen peroxide, calcium overload with BayK8644, and ionic stress with hypokalemia; 2), computer simulations using a physiologically detailed rabbit ventricular action potential model, in which repolarization reserve was reduced to generate EADs and random ion channel or path cycle length fluctuations were implemented; and 3), iterated maps with or without noise. By comparing experimental, modeling, and bifurcation analyses, we present evidence that noise-induced transitions between bistable states (i.e., between an action potential with and without an EAD) is not sufficient to account for the large variation in action potential duration fluctuations observed in experimental studies. We conclude that the irregular dynamics of EADs is intrinsically chaotic, with random fluctuations playing a nonessential, auxiliary role potentiating the complex dynamics.
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Affiliation(s)
- Daisuke Sato
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California, USA
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Link MS, Atkins DL, Passman RS, Halperin HR, Samson RA, White RD, Cudnik MT, Berg MD, Kudenchuk PJ, Kerber RE. Part 6: Electrical Therapies. Circulation 2010; 122:S706-19. [DOI: 10.1161/circulationaha.110.970954] [Citation(s) in RCA: 223] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
Early afterdepolarizations (EADs) are an important cause of lethal ventricular arrhythmias in long QT syndromes and heart failure, but the mechanisms by which EADs at the cellular scale cause arrhythmias such as polymorphic ventricular tachycardia (PVT) and torsades de pointes (TdP) at the tissue scale are not well understood. Here we summarize recent progress in this area, discussing (1) the ionic basis of EADs, (2) evidence that deterministic chaos underlies the irregular behavior of EADs, (3) mechanisms by which chaotic EADs synchronize in large numbers of coupled cells in tissue to overcome source-sink mismatches, (4) how this synchronization process allows EADs to initiate triggers and generate mixed focal reentrant ventricular arrhythmias underlying PVT and TdP, and (5) therapeutic implications.
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Guo L, Dong Z, Guthrie H. Validation of a guinea pig Langendorff heart model for assessing potential cardiovascular liability of drug candidates. J Pharmacol Toxicol Methods 2009; 60:130-51. [DOI: 10.1016/j.vascn.2009.07.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Accepted: 07/06/2009] [Indexed: 02/02/2023]
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Stewart P, Aslanidi OV, Noble D, Noble PJ, Boyett MR, Zhang H. Mathematical models of the electrical action potential of Purkinje fibre cells. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:2225-2255. [PMID: 19414454 DOI: 10.1098/rsta.2008.0283] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Early development of ionic models for cardiac myocytes, from the pioneering modification of the Hodgkin-Huxley giant squid axon model by Noble to the iconic DiFrancesco-Noble model integrating voltage-gated ionic currents, ion pumps and exchangers, Ca(2+) sequestration and Ca(2+)-induced Ca(2+) release, provided a general description for a mammalian Purkinje fibre (PF) and the framework for modern cardiac models. In the past two decades, development has focused on tissue-specific models with an emphasis on the sino-atrial (SA) node, atria and ventricles, while the PFs have largely been neglected. However, achieving the ultimate goal of creating a virtual human heart will require detailed models of all distinctive regions of the cardiac conduction system, including the PFs, which play an important role in conducting cardiac excitation and ensuring the synchronized timing and sequencing of ventricular contraction. In this paper, we present details of our newly developed model for the human PF cell including validation against experimental data. Ionic mechanisms underlying the heterogeneity between the PF and ventricular action potentials in humans and other species are analysed. The newly developed PF cell model adds a new member to the family of human cardiac cell models developed previously for the SA node, atrial and ventricular cells, which can be incorporated into an anatomical model of the human heart with details of its electrophysiological heterogeneity and anatomical complexity.
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Affiliation(s)
- Philip Stewart
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
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Farkas AS, Makra P, Csík N, Orosz S, Shattock MJ, Fülöp F, Forster T, Csanády M, Papp JG, Varró A, Farkas A. The role of the Na+/Ca2+ exchanger, I(Na) and I(CaL) in the genesis of dofetilide-induced torsades de pointes in isolated, AV-blocked rabbit hearts. Br J Pharmacol 2009; 156:920-32. [PMID: 19222480 DOI: 10.1111/j.1476-5381.2008.00096.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The Na+/Ca2+ exchanger (NCX) may contribute to triggered activity and transmural dispersion of repolarization, which are substrates of torsades de pointes (TdP) type arrhythmias. This study examined the effects of selective inhibition of the NCX by SEA0400 on the occurrence of dofetilide-induced TdP. EXPERIMENTAL APPROACH Effects of SEA0400 (1 micromol x L(-1)) on dofetilide-induced TdP was studied in isolated, Langendorff-perfused, atrioventricular (AV)-blocked rabbit hearts. To verify the relevance of the model, lidocaine (30 micromol x L(-1)) and verapamil (750 nmol x L(-1)) were also tested against dofetilide-induced TdP. KEY RESULTS Acute AV block caused a chaotic idioventricular rhythm and strikingly increased beat-to-beat variability of the RR and QT intervals. SEA0400 exaggerated the dofetilide-induced increase in the heart rate-corrected QT interval (QTc) and did not reduce the incidence of dofetilide-induced TdP [100% in the SEA0400 + dofetilide group vs. 75% in the dofetilide (100 nmol x L(-1)) control]. In the second set of experiments, verapamil further increased the dofetilide-induced QTc prolongation and neither verapamil nor lidocaine reduced the dofetilide-induced increase in the beat-to-beat variability of the QT interval. However, lidocaine decreased and verapamil prevented the development of dofetilide-induced TdP as compared with the dofetilide control (TdP incidence: 13%, 0% and 88% respectively). CONCLUSIONS AND IMPLICATIONS Na+/Ca2+ exchanger does not contribute to dofetilide-induced TdP, whereas Na+ and Ca2+ channel activity is involved in TdP genesis in isolated, AV-blocked rabbit hearts. Neither QTc prolongation nor an increase in the beat-to-beat variability of the QT interval is a sufficient prerequisite of TdP genesis in rabbit hearts.
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Affiliation(s)
- Attila S Farkas
- 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Szeged, Hungary.
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Synchronization of chaotic early afterdepolarizations in the genesis of cardiac arrhythmias. Proc Natl Acad Sci U S A 2009; 106:2983-8. [PMID: 19218447 DOI: 10.1073/pnas.0809148106] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The synchronization of coupled oscillators plays an important role in many biological systems, including the heart. In heart diseases, cardiac myocytes can exhibit abnormal electrical oscillations, such as early afterdepolarizations (EADs), which are associated with lethal arrhythmias. A key unanswered question is how cellular EADs partially synchronize in tissue, as is required for them to propagate. Here, we present evidence, from computational simulations and experiments in isolated myocytes, that irregular EAD behavior is dynamical chaos. We then show in electrically homogeneous tissue models that chaotic EADs synchronize globally when the tissue is smaller than a critical size. However, when the tissue exceeds the critical size, electrotonic coupling can no longer globally synchronize EADs, resulting in regions of partial synchronization that shift in time and space. These regional partially synchronized EADs then form premature ventricular complexes that propagate into recovered tissue without EADs. This process creates multiple premature ventricular complexes that propagate as [corrected] "shifting" foci resembling polymorphic ventricular tachycardia. Shifting foci encountering shifting repolarization gradients can also develop localized wave breaks leading to reentry and fibrillation. As predicted by the theory, rabbit hearts exposed to oxidative stress (H(2)O(2)) exhibited multiple shifting foci causing polymorphic tachycardia and fibrillation. This mechanism explains how collective cellular behavior integrates at the tissue scale to generate lethal cardiac arrhythmias over a wide range of heart rates.
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