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Ezzeddine FM, Darlington AM, DeSimone CV, Asirvatham SJ. Catheter Ablation of Ventricular Fibrillation. Card Electrophysiol Clin 2022; 14:729-742. [PMID: 36396189 DOI: 10.1016/j.ccep.2022.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Ventricular fibrillation (VF) is a common cause of sudden cardiac death (SCD) and is unfortunately without a cure. Current therapies focus on prevention of SCD, such as implantable cardioverter-defibrillator (ICD) implantation and anti-arrhythmic agents. Significant progress has been made in improving our understanding and ability to target the triggers of VF, via advanced mapping and ablation techniques, as well as with autonomic modulation. However, the critical substrate for VF maintenance remains incompletely defined. In this review, we discuss the evidence behind the basic mechanisms of VF and review the current role of catheter ablation in patients with VF.
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Affiliation(s)
- Fatima M Ezzeddine
- Department of Cardiovascular Medicine, Mayo Clinic, 200 First Street Southwest, Rochester, MN, USA
| | - Ashley M Darlington
- Department of Cardiovascular Medicine, Mayo Clinic, 200 First Street Southwest, Rochester, MN, USA
| | - Christopher V DeSimone
- Department of Cardiovascular Medicine, Mayo Clinic, 200 First Street Southwest, Rochester, MN, USA
| | - Samuel J Asirvatham
- Department of Cardiovascular Medicine, Mayo Clinic, 200 First Street Southwest, Rochester, MN, USA.
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2
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Qu Z, Liu MB, Olcese R, Karagueuzian H, Garfinkel A, Chen PS, Weiss JN. R-on-T and the initiation of reentry revisited: Integrating old and new concepts. Heart Rhythm 2022; 19:1369-1383. [PMID: 35364332 PMCID: PMC11334931 DOI: 10.1016/j.hrthm.2022.03.1224] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/11/2022] [Accepted: 03/23/2022] [Indexed: 12/29/2022]
Abstract
Initiation of reentry requires 2 factors: (1) a triggering event, most commonly focal excitations such as premature ventricular complexes (PVCs); and (2) a vulnerable substrate with regional dispersion of refractoriness and/or excitability, such as occurs during the T wave of the electrocardiogram when some areas of the ventricle have repolarized and recovered excitability but others have not. When the R wave of a PVC coincides in time with the T wave of the previous beat, this timing can lead to unidirectional block and initiation of reentry, known as the R-on-T phenomenon. Classically, the PVC triggering reentry has been viewed as arising focally from 1 region and propagating into another region whose recovery is delayed, resulting in unidirectional conduction block and reentry initiation. However, more recent evidence indicates that PVCs also can arise from the T wave itself. In the latter case, the PVC initiating reentry is not a separate event from the T wave but rather is causally generated from the repolarization gradient that manifests as the T wave. We call the former an "R-to-T" mechanism and the latter an "R-from-T" mechanism, which are initiation mechanisms distinct from each other. Both are important components of the R-on-T phenomenon and need to be taken into account when designing antiarrhythmic strategies. Strategies targeting suppression of triggers alone or vulnerable substrate alone may be appropriate in some instances but not in others. Preventing R-from-T arrhythmias requires suppressing the underlying dynamic tissue instabilities responsible for producing both triggers and substrate vulnerability simultaneously. The same principles are likely to apply to supraventricular arrhythmias.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California.
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Hrayr Karagueuzian
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Alan Garfinkel
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Integrative Biology and Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
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3
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Das TS, Wilson D. Data-driven phase-isostable reduction for optimal nonfeedback stabilization of cardiac alternans. Phys Rev E 2021; 103:052203. [PMID: 34134261 DOI: 10.1103/physreve.103.052203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 04/07/2021] [Indexed: 11/07/2022]
Abstract
Phase-isostable reduction is an emerging model reduction strategy that can be used to accurately replicate nonlinear behaviors in systems for which standard phase reduction techniques fail. In this work, we derive relationships between the cycle-to-cycle variance of the reduced isostable coordinates for systems subject to both additive white noise and periodic stimulation. Using this information, we propose a data-driven technique for inferring nonlinear terms of the phase-isostable coordinate reduction framework. We apply the proposed model inference strategy to the biologically motivated problem of eliminating cardiac alternans, an arrhythmia that is widely considered to be a precursor to more deadly cardiac arrhythmias. Using this strategy, by simply measuring a series of action potential durations in response to periodic stimulation, we are able to identify energy-optimal, nonfeedback control inputs to stabilize a period-1, alternans-free solution.
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Affiliation(s)
- Tuhin Subhra Das
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Dan Wilson
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee 37996, USA
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4
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Xie D, Wu J, Wu Q, Zhang X, Zhou D, Dai W, Zhu M, Wang D. Integrating proteomic, lipidomic and metabolomic data to construct a global metabolic network of lethal ventricular tachyarrhythmias (LVTA) induced by aconitine. J Proteomics 2021; 232:104043. [PMID: 33161167 DOI: 10.1016/j.jprot.2020.104043] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/10/2020] [Accepted: 11/02/2020] [Indexed: 02/05/2023]
Abstract
Lethal ventricular tachyarrhythmias (LVTA)-related sudden cardiac death (SCD) is one of the major causes of death worldwide. However, the mechanisms underlying LVTA induced by myocardial ion channel diseases (MICDs) are not yet fully understood. Here, we produced an LVTA rat model induced by aconitine, to mimic MICDs-elicited LVTA, and constructed a global pathway network via integrating proteomic and lipidomic data, and our previously published metabolomic data. Results showed that both proteome and lipidome were disturbed during the LVTA process. Most of the differentially expressed proteins and lipid species were correlated. Proteomic data indicated disturbance of energy metabolism (e.g. fatty acid β-oxidation and the tricarboxylic acid cycle) and activation of the protein kinase C and nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase pathway; these alterations led to lowered ATP and elevated ROS, respectively. Altered levels of the Ca2+ handling proteins suggested aberrant intracellular Ca2+ homeostasis, which might also be secondary to the shortage of ATP and oxidative stress. Significantly, the disrupted pathways implied by proteomic data were largely confirmed by lipidomic and metabolomic data. Collectively, we have constructed a metabolic pathway network of aconitine-induced LVTA using a multi-omics strategy, which confers great promise for the deeper interpretation of the mechanisms underlying LVTA. SIGNIFICANCE: In this study, we integrated proteomics, lipidomics and metabolomics to explore the pathophysiological processes of LVTA induced by aconitine. It is innovative to try to integrate these three omics in a study exploring the relative mechanisms. Here, based on the DEPs and differentially abundant lipid species (DALPs) between the LVTA groups and the controls, and the different metabolites discovered previously from the same model, we have successfully constructed a global metabolic network. Taken together, the multi-omics integration strategies used in this study show the potential for a new interpretation of the pathophysiological processes of LVTA induced by different conditions and open the possibility to explore deeper and broader mechanisms of other diseases.
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Affiliation(s)
- Dezhi Xie
- Department of Forensic Medicine, Shantou University Medical College, Shantou 515041, China
| | - Jiayan Wu
- Department of Forensic Medicine, Shantou University Medical College, Shantou 515041, China
| | - Qian Wu
- Shanghai Center for Bioinformation Technology, Shanghai 201203, China
| | - Xiaojun Zhang
- Central laboratory, Shantou University Medical College, Shantou 515041, China
| | - Danya Zhou
- Department of Forensic Medicine, Shantou University Medical College, Shantou 515041, China
| | - Wentao Dai
- Shanghai Center for Bioinformation Technology, Shanghai 201203, China
| | - Mengting Zhu
- Department of Forensic Medicine, Shantou University Medical College, Shantou 515041, China
| | - Dian Wang
- Department of Forensic Medicine, Shantou University Medical College, Shantou 515041, China.
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5
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Pérez-Gutiérrez MF, Sánchez-Muñoz JJ, Erazo-Rodas M, Guerrero-Curieses A, Everss E, Quesada-Dorador A, Ruiz-Granell R, Ibáñez-Criado A, Bellver-Navarro A, Rojo-Álvarez JL, García-Alberola A. Spectral Analysis and Mutual Information Estimation of Left and Right Intracardiac Electrograms during Ventricular Fibrillation. SENSORS (BASEL, SWITZERLAND) 2020; 20:s20154162. [PMID: 32726931 PMCID: PMC7435921 DOI: 10.3390/s20154162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Revised: 07/19/2020] [Accepted: 07/22/2020] [Indexed: 06/11/2023]
Abstract
Ventricular fibrillation (VF) signals are characterized by highly volatile and erratic electrical impulses, the analysis of which is difficult given the complex behavior of the heart rhythms in the left (LV) and right ventricles (RV), as sometimes shown in intracardiac recorded Electrograms (EGM). However, there are few studies that analyze VF in humans according to the simultaneous behavior of heart signals in the two ventricles. The objective of this work was to perform a spectral and a non-linear analysis of the recordings of 22 patients with Congestive Heart Failure (CHF) and clinical indication for a cardiac resynchronization device, simultaneously obtained in LV and RV during induced VF in patients with a Biventricular Implantable Cardioverter Defibrillator (BICD) Contak Renewal IVTM (Boston Sci.). The Fourier Transform was used to identify the spectral content of the first six seconds of signals recorded in the RV and LV simultaneously. In addition, measurements that were based on Information Theory were scrutinized, including Entropy and Mutual Information. The results showed that in most patients the spectral envelopes of the EGM sources of RV and LV were complex, different, and with several frequency peaks. In addition, the Dominant Frequency (DF) in the LV was higher than in the RV, while the Organization Index (OI) had the opposite trend. The entropy measurements were more regular in the RV than in the LV, thus supporting the spectral findings. We can conclude that basic stochastic processing techniques should be scrutinized with caution and from basic to elaborated techniques, but they can provide us with useful information on the biosignals from both ventricles during VF.
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Affiliation(s)
- Milton Fabricio Pérez-Gutiérrez
- Departamento de Eléctrica y Electrónica, Universidad de las Fuerzas Armadas ESPE, Av. General Rumiñahui s/n, Sangolquí 171-5-231B, Ecuador;
| | - Juan José Sánchez-Muñoz
- Arrhythmia Unit and Electrophysiology, Department of Cardiology, Virgen de la Arrixaca University Hospital, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain; (J.J.S.-M.); (A.G.-A.)
| | - Mayra Erazo-Rodas
- Departamento de Eléctrica y Electrónica, Universidad de las Fuerzas Armadas ESPE, Av. General Rumiñahui s/n, Sangolquí 171-5-231B, Ecuador;
| | - Alicia Guerrero-Curieses
- Departamento de Teoría de la Señal y Comunicaciones, Sistemas Telemáticos y Computación, Universidad Rey Juan Carlos, 28943 Fuenlabrada, Spain; (A.G.-C.); (E.E.); (J.L.R.-Á.)
| | - Estrella Everss
- Departamento de Teoría de la Señal y Comunicaciones, Sistemas Telemáticos y Computación, Universidad Rey Juan Carlos, 28943 Fuenlabrada, Spain; (A.G.-C.); (E.E.); (J.L.R.-Á.)
| | - Aurelio Quesada-Dorador
- Arrhythmia Unit, Department of Cardiology, Hospital General de Valencia, 46014 Valencia, Spain;
| | - Ricardo Ruiz-Granell
- Arrhythmia Unit, Department of Cardiology, Hospital Clínico Universitario, Av. Blasco Ibañez, 17, 46010 Valencia, Spain;
| | - Alicia Ibáñez-Criado
- Arrhythmia Unit, Department of Cardiology, Hospital Clínico de Alicante, 03010 Alicante, Spain;
| | | | - José Luis Rojo-Álvarez
- Departamento de Teoría de la Señal y Comunicaciones, Sistemas Telemáticos y Computación, Universidad Rey Juan Carlos, 28943 Fuenlabrada, Spain; (A.G.-C.); (E.E.); (J.L.R.-Á.)
| | - Arcadi García-Alberola
- Arrhythmia Unit and Electrophysiology, Department of Cardiology, Virgen de la Arrixaca University Hospital, Instituto Murciano de Investigación Biosanitaria, 30120 Murcia, Spain; (J.J.S.-M.); (A.G.-A.)
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Restitution and Stability of Human Ventricular Action Potential at High and Variable Pacing Rate. Biophys J 2019; 117:2382-2395. [PMID: 31514969 DOI: 10.1016/j.bpj.2019.08.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 08/07/2019] [Accepted: 08/19/2019] [Indexed: 11/23/2022] Open
Abstract
Despite the key role of beat-to-beat action potential (AP) variability in the onset of ventricular arrhythmias at high pacing rate, the knowledge of the involved dynamics and of effective prognostic parameters is largely incomplete. Electrical restitution (ER), the way AP duration (APD) senses changes in preceding cycle length (CL), has been used to monitor transition to arrhythmias. The use of standard ER (sER), though, is controversial, not always suitable for in vivo and only rarely for clinical applications. By means of simulations on a human ventricular AP model, I investigate the dynamics of APD at high pacing rate under sinusoidally, saw-tooth, and randomly variable pacing CLs. AP sequences were compared in terms of beat-to-beat restitution (btb-ER) and of the collections of sER curves generated from each beat. A definition of APD stability is also proposed, based on successive APD changes introduced in an AP sequence by a premature beat. The explored CL range includes values leading to APD alternans under constant pacing. Three different types of response to CL variability were found, corresponding to progressively higher rate of beat-to-beat CL changes. Low rates (∼1 ms/beat) generate a btb-ER dominated by steady-state rate dependence of APD (type 1), intermediate rates (∼5 ms/beat) lead to a btb-ER similar to a single sER (type 2), and high rates (∼20 ms/beat) to hysteretic btb-ER under periodic pacing and to a vertically spread btb-ER in the case of random pacing (type 3). Stability of AP repolarization always increases with the rate of CL changes. Thus, rather than looking at sER slope, which requires additional interventions during the recording of cardiac electrical activity, this study provides rationale for the use of btb-ER representations as predictors of repolarization stability under extreme pacing conditions, known to be critical for the arrhythmia development.
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The effects of interleukin 17A on left stellate ganglion remodeling are mediated by neuroimmune communication in normal structural hearts. Int J Cardiol 2019; 279:64-71. [PMID: 30642646 DOI: 10.1016/j.ijcard.2019.01.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 12/06/2018] [Accepted: 01/02/2019] [Indexed: 12/28/2022]
Abstract
BACKGROUND It is reported interleukin (IL)-17A, a classical proinflammatory cytokine, is implicated in neuroimmune-associated remodeling in neural plasticity and pathological conditions. However, the effect of IL-17A on left stellate ganglion (LSG) remodeling remains unclear. OBJECTIVE This study was performed to determine whether exogenous IL-17A promotes LSG remodeling and destabilize ventricular electrophysiological properties (EPs) in normal canines. METHODS 24 beagles were randomly allocated into three groups. In the first group, animals were subjected to 0.1 ml phosphate buffer saline (PBS) microinjection of into LSG (n = 8), an equivalent IL-17A was administrated in the second group (n = 8), and an equivalent anti-IL-17A mAb plus IL-17A was administrated in the third group (n = 8). The ventricular EPs, neural function and activity of the LSG were determined at baseline and 30 min after administration. In the end, LSG tissues were collected. RESULTS Compared with the control group, the experimental group had a significantly shorter effective refractory period (ERP) and action potential duration (APD)90, an increased ERP, APD90, Smax dispersion, and APD alternans cycle length; and steepened APD restitution curves. In addition, IL-17A enhanced the neural function and activity of the LSG, upregulated the expressions of neuropeptides and proinflammatory cytokines and cells. And all these effects were attenuated by anti-IL-17A mAb. Importantly, IL-17 receptor A (IL-17R-A) was detected in sympathetic neurons in the LSG. CONCLUSION IL-17A promoted LSG remodeling by regulating the neural inflammation response. It did so by binding to IL-17R-A, resulting in unstable ventricular electrophysiology in normal structural hearts.
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Kanaporis G, Kalik ZM, Blatter LA. Action potential shortening rescues atrial calcium alternans. J Physiol 2018; 597:723-740. [PMID: 30412286 DOI: 10.1113/jp277188] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 11/08/2018] [Indexed: 01/08/2023] Open
Abstract
KEY POINTS Cardiac alternans refers to a beat-to-beat alternation in contraction, action potential (AP) morphology and Ca2+ transient (CaT) amplitude, and represents a risk factor for cardiac arrhythmia, including atrial fibrillation. We developed strategies to pharmacologically manipulate the AP waveform with the goal to reduce or eliminate the occurrence of CaT and contraction alternans in atrial tissue. With combined patch-clamp and intracellular Ca2+ measurements we investigated the effect of specific ion channel inhibitors and activators on alternans. In single rabbit atrial myocytes, suppression of Ca2+ -activated Cl- channels eliminated AP duration alternans, but prolonged the AP and failed to eliminate CaT alternans. In contrast, activation of K+ currents (IKs and IKr ) shortened the AP and eliminated both AP duration and CaT alternans. As demonstrated also at the whole heart level, activation of K+ conductances represents a promising strategy to suppress alternans, and thus reducing a risk factor for atrial fibrillation. ABSTRACT At the cellular level alternans is observed as beat-to-beat alternations in contraction, action potential (AP) morphology and magnitude of the Ca2+ transient (CaT). Alternans is a well-established risk factor for cardiac arrhythmia, including atrial fibrillation. This study investigates whether pharmacological manipulation of AP morphology is a viable strategy to reduce the risk of arrhythmogenic CaT alternans. Pacing-induced AP and CaT alternans were studied in rabbit atrial myocytes using combined Ca2+ imaging and electrophysiological measurements. Increased AP duration (APD) and beat-to-beat alternations in AP morphology lowered the pacing frequency threshold and increased the degree of CaT alternans. Inhibition of Ca2+ -activated Cl- channels reduced beat-to-beat AP alternations, but prolonged APD and failed to suppress CaT alternans. In contrast, AP shortening induced by activators of two K+ channels (ML277 for Kv7.1 and NS1643 for Kv11.1) abolished both APD and CaT alternans in field-stimulated and current-clamped myocytes. K+ channel activators had no effect on the degree of Ca2+ alternans in AP voltage-clamped cells, confirming that suppression of Ca2+ alternans was caused by the changes in AP morphology. Finally, activation of Kv11.1 channel significantly attenuated or even abolished atrial T-wave alternans in isolated Langendorff perfused hearts. In summary, AP shortening suppressed or completely eliminated both CaT and APD alternans in single atrial myocytes and atrial T-wave alternans at the whole heart level. Therefore, we suggest that AP shortening is a potential intervention to avert development of alternans with important ramifications for arrhythmia prevention and therapy.
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Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Zane M Kalik
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
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Muñoz LM, Gelzer ARM, Fenton FH, Qian W, Lin W, Gilmour RF, Otani NF. Discordant Alternans as a Mechanism for Initiation of Ventricular Fibrillation In Vitro. J Am Heart Assoc 2018; 7:e007898. [PMID: 30371176 PMCID: PMC6201417 DOI: 10.1161/jaha.117.007898] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 06/19/2018] [Indexed: 11/16/2022]
Abstract
Background Ventricular tachyarrhythmias are often preceded by short sequences of premature ventricular complexes. In a previous study, a restitution-based computational model predicted which sequences of stimulated premature complexes were most likely to induce ventricular fibrillation in canines in vivo. However, the underlying mechanism, based on discordant-alternans dynamics, could not be verified in that study. The current study seeks to elucidate the mechanism by determining whether the spatiotemporal evolution of action potentials and initiation of ventricular fibrillation in in vitro experiments are consistent with model predictions. Methods and Results Optical mapping voltage signals from canine right-ventricular tissue (n=9) were obtained simultaneously from the entire epicardium and endocardium during and after premature stimulus sequences. Model predictions of action potential propagation along a 1-dimensional cable were developed using action potential duration versus diastolic interval data. The model predicted sign-change patterns in action potential duration and diastolic interval spatial gradients with posterior probabilities of 91.1%, and 82.1%, respectively. The model predicted conduction block with 64% sensitivity and 100% specificity. A generalized estimating equation logistic-regression approach showed that model-prediction effects were significant for both conduction block ( P<1×10-15, coefficient 44.36) and sustained ventricular fibrillation ( P=0.0046, coefficient, 1.63) events. Conclusions The observed sign-change patterns favored discordant alternans, and the model successfully identified sequences of premature stimuli that induced conduction block. This suggests that the relatively simple discordant-alternans-based process that led to block in the model may often be responsible for ventricular fibrillation onset when preceded by premature beats. These observations may aid in developing improved methods for anticipating block and ventricular fibrillation.
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Affiliation(s)
- Laura M. Muñoz
- School of Mathematical SciencesRochester Institute of TechnologyRochesterNY
| | | | | | | | | | - Robert F. Gilmour
- University of Prince Edward IslandCharlottetownPrince Edward IslandCanada
| | - Niels F. Otani
- School of Mathematical SciencesRochester Institute of TechnologyRochesterNY
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10
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Zaniboni M. Short-term action potential memory and electrical restitution: A cellular computational study on the stability of cardiac repolarization under dynamic pacing. PLoS One 2018; 13:e0193416. [PMID: 29494628 PMCID: PMC5832261 DOI: 10.1371/journal.pone.0193416] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Accepted: 02/09/2018] [Indexed: 01/24/2023] Open
Abstract
Electrical restitution (ER) is a major determinant of repolarization stability and, under fast pacing rate, it reveals memory properties of the cardiac action potential (AP), whose dynamics have never been fully elucidated, nor their ionic mechanisms. Previous studies have looked at ER mainly in terms of changes in AP duration (APD) when the preceding diastolic interval (DI) changes and described dynamic conditions where this relationship shows hysteresis which, in turn, has been proposed as a marker of short-term AP memory and repolarization stability. By means of numerical simulations of a non-propagated human ventricular AP, we show here that measuring ER as APD versus the preceding cycle length (CL) provides additional information on repolarization dynamics which is not contained in the companion formulation. We focus particularly on fast pacing rate conditions with a beat-to-beat variable CL, where memory properties emerge from APD vs CL and not from APD vs DI and should thus be stored in APD and not in DI. We provide an ion-currents characterization of such conditions under periodic and random CL variability, and show that the memory stored in APD plays a stabilizing role on AP repolarization under pacing rate perturbations. The gating kinetics of L-type calcium current seems to be the main determinant of this safety mechanism. We also show that, at fast pacing rate and under otherwise identical pacing conditions, a periodically beat-to-beat changing CL is more effective than a random one in stabilizing repolarization. In summary, we propose a novel view of short-term AP memory, differentially stored between systole and diastole, which opens a number of methodological and theoretical implications for the understanding of arrhythmia development.
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Affiliation(s)
- Massimiliano Zaniboni
- Department of Chemistry, Life Sciences and Environmental Sustainability - University of Parma Parco Area delle Scienze, Parma, Italy
- Center of Excellence for Toxicological Research (CERT) - University of Parma, Parma, Italy
- * E-mail:
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11
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Wilson D, Ermentrout B. Stochastic Pacing Inhibits Spatially Discordant Cardiac Alternans. Biophys J 2017; 113:2552-2572. [PMID: 29212008 DOI: 10.1016/j.bpj.2017.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 09/28/2017] [Accepted: 10/02/2017] [Indexed: 12/19/2022] Open
Abstract
Depressed heart rate variability is a well-established risk factor for sudden cardiac death in survivors of acute myocardial infarction and for those with congestive heart failure. Although measurements of heart rate variability provide a valuable prognostic tool, it is unclear whether reduced heart rate variability itself is proarrhythmic or if it simply correlates with the severity of autonomic nervous system dysfunction. In this work, we investigate a possible mechanism by which heart rate variability could protect against cardiac arrhythmia. Specifically, in numerical simulations, we observe an inverse relationship between the variance of stochastic pacing and the occurrence of spatially discordant alternans, an arrhythmia that is widely believed to facilitate the development of cardiac fibrillation. By analyzing the effects of conduction velocity restitution, cellular dynamics, electrotonic coupling, and stochastic pacing on the nodal dynamics of spatially discordant alternans, we provide intuition for this observed behavior and propose control strategies to inhibit discordant alternans.
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Affiliation(s)
- Dan Wilson
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania.
| | - Bard Ermentrout
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania
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12
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Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
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Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
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13
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Kanaporis G, Blatter LA. Alternans in atria: Mechanisms and clinical relevance. MEDICINA-LITHUANIA 2017; 53:139-149. [PMID: 28666575 DOI: 10.1016/j.medici.2017.04.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 04/25/2017] [Indexed: 12/29/2022]
Abstract
Atrial fibrillation is the most common sustained arrhythmia and its prevalence is rapidly rising with the aging of the population. Cardiac alternans, defined as cyclic beat-to-beat alternations in contraction force, action potential (AP) duration and intracellular Ca2+ release at constant stimulation rate, has been associated with the development of ventricular arrhythmias. Recent clinical data also provide strong evidence that alternans plays a central role in arrhythmogenesis in atria. The aim of this article is to review the mechanisms that are responsible for repolarization alternans and contribute to the transition from spatially concordant alternans to the more arrhythmogenic spatially discordant alternans in atria.
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Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, USA.
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, USA
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14
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Orini M, Taggart P, Srinivasan N, Hayward M, Lambiase PD. Interactions between Activation and Repolarization Restitution Properties in the Intact Human Heart: In-Vivo Whole-Heart Data and Mathematical Description. PLoS One 2016; 11:e0161765. [PMID: 27588688 PMCID: PMC5010207 DOI: 10.1371/journal.pone.0161765] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 08/11/2016] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND The restitution of the action potential duration (APDR) and conduction velocity (CVR) are mechanisms whereby cardiac excitation and repolarization adapt to changes in heart rate. They modulate the vulnerability to dangerous arrhythmia, but the mechanistic link between restitution and arrhythmogenesis remains only partially understood. METHODS This paper provides an experimental and theoretical study of repolarization and excitation restitution properties and their interactions in the intact human epicardium. The interdependence between excitation and repolarization dynamic is studied in 8 patients (14 restitution protocols, 1722 restitution curves) undergoing global epicardial mapping with multi-electrode socks before open heart surgery. A mathematical description of the contribution of both repolarization and conduction dynamics to the steepness of the APDR slope is proposed. RESULTS This study demonstrates that the APDR slope is a function of both activation and repolarization dynamics. At short cycle length, conduction delay significantly increases the APDR slope by interacting with the diastolic interval. As predicted by the proposed mathematical formulation, the APDR slope was more sensitive to activation time prolongation than to the simultaneous shortening of repolarization time. A steep APDR slope was frequently identified, with 61% of all cardiac sites exhibiting an APDR slope > 1, suggesting that a slope > 1 may not necessarily promote electrical instability in the human epicardium. APDR slope did not change for different activation or repolarization times, and it was not a function of local baseline APD. However, it was affected by the spatial organization of electrical excitation, suggesting that in tissue APDR is not a unique function of local electrophysiological properties. Spatial heterogeneity in both activation and repolarization restitution contributed to the increase in the modulated dispersion of repolarization, which for short cycle length was as high as 250 ms. Heterogeneity in conduction velocity restitution can translate into both activation and repolarization dispersion and increase cardiac instability. The proposed mathematical formulation shows an excellent agreement with the experimental data (correlation coefficient r = 0.94) and provides a useful tool for the understanding of the complex interactions between activation and repolarization restitution properties as well as between their measurements.
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Affiliation(s)
- Michele Orini
- Institute of Cardiovascular Science, University College London, London, United Kingdom
- Barts Heart Centre, St Bartholomews Hospital, London, United Kingdom
| | - Peter Taggart
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Neil Srinivasan
- Institute of Cardiovascular Science, University College London, London, United Kingdom
- Barts Heart Centre, St Bartholomews Hospital, London, United Kingdom
| | - Martin Hayward
- The Heart Hospital, University College London Hospitals, London, United Kingdom
| | - Pier D. Lambiase
- Institute of Cardiovascular Science, University College London, London, United Kingdom
- Barts Heart Centre, St Bartholomews Hospital, London, United Kingdom
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15
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KIM MINSU, KIM JUN, LEE JIHYUN, HWANG YOUMI, KIM MINSEOK, NAM GIBYOUNG, CHOI KEEJOON, KIM JAEJOONG, KIM YOUHO. Impact of Improved Left Ventricular Systolic Function on the Recurrence of Ventricular Arrhythmia in Heart Failure Patients With an Implantable Cardioverter-Defibrillator. J Cardiovasc Electrophysiol 2016; 27:1191-1198. [DOI: 10.1111/jce.13037] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Revised: 06/07/2016] [Accepted: 06/13/2016] [Indexed: 11/27/2022]
Affiliation(s)
- MINSU KIM
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - JUN KIM
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - JI HYUN LEE
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - YOU MI HWANG
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - MIN-SEOK KIM
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - GI-BYOUNG NAM
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - KEE-JOON CHOI
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - JAE-JOONG KIM
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - YOU-HO KIM
- Heart Institute, Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
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16
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Narayan SM, Zaman JAB. Mechanistically based mapping of human cardiac fibrillation. J Physiol 2016; 594:2399-415. [PMID: 26607671 PMCID: PMC4850202 DOI: 10.1113/jp270513] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 11/20/2015] [Indexed: 12/02/2022] Open
Abstract
The mechanisms underpinning human cardiac fibrillation remain elusive. In his 1913 paper ‘On dynamic equilibrium in the heart’, Mines proposed that an activation wave front could propagate repeatedly in a circle, initiated by a stimulus in the vulnerable period. While the dynamics of activation and recovery are central to cardiac fibrillation, these physiological data are rarely used in clinical mapping. Fibrillation is a rapid irregular rhythm with spatiotemporal disorder resulting from two fundamental mechanisms – sources in preferred cardiac regions or spatially diffuse self‐sustaining activity, i.e. with no preferred source. On close inspection, however, this debate may also reflect mapping technique. Fibrillation is initiated from triggers by regional dispersion in repolarization, slow conduction and wavebreak, then sustained by non‐uniform interactions of these mechanisms. Notably, optical mapping of action potentials in atrial fibrillation (AF) show spiral wave sources (rotors) in nearly all studies including humans, while most traditional electrogram analyses of AF do not. Techniques may diverge in fibrillation because electrograms summate non‐coherent waves within an undefined field whereas optical maps define waves with a visually defined field. Also fibrillation operates at the limits of activation and recovery, which are well represented by action potentials while fibrillatory electrograms poorly represent repolarization. We conclude by suggesting areas for study that may be used, until such time as optical mapping is clinically feasible, to improve mechanistic understanding and therapy of human cardiac fibrillation.
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Affiliation(s)
| | - Junaid A B Zaman
- Stanford University, Palo Alto, CA, USA.,Imperial College London, London, UK
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17
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Piers SRD, Everaerts K, van der Geest RJ, Hazebroek MR, Siebelink HM, Pison LAFG, Schalij MJ, Bekkers SCAM, Heymans S, Zeppenfeld K. Myocardial scar predicts monomorphic ventricular tachycardia but not polymorphic ventricular tachycardia or ventricular fibrillation in nonischemic dilated cardiomyopathy. Heart Rhythm 2015; 12:2106-14. [PMID: 26004942 DOI: 10.1016/j.hrthm.2015.05.026] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Indexed: 12/12/2022]
Abstract
BACKGROUND The relation between myocardial scar and different types of ventricular arrhythmias in patients with nonischemic dilated cardiomyopathy (NIDCM) is unknown. OBJECTIVES The purpose of this study was to analyze the effect of myocardial scar, assessed by late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR), on the occurrence and type of ventricular arrhythmia in patients with NIDCM. METHODS Consecutive patients with NIDCM who underwent LGE-CMR and implantable cardioverter-defibrillator (ICD) implantation at either of 2 centers were included. LGE was defined by signal intensity ≥35% of maximal signal intensity, subdivided into core and border zones (≥50% and 35%-50% of maximal signal intensity, respectively), and categorized according to location (basal or nonbasal) and transmurality. ICD recordings and electrocardiograms were reviewed to determine the occurrence and type of ventricular arrhythmia during follow-up. RESULTS Of 87 patients (age 56 ± 13 y, 62% male, left ventricular ejection fraction 29% ± 12%), 55 (63%) had LGE (median 6.3 g, interquartile range 0.0-13.8 g). During a median follow-up of 45 months, monomorphic ventricular tachycardia (VT) occurred in 18 patients (21%) and polymorphic VT/ventricular fibrillation (VF) in 10 (11%). LGE predicted monomorphic VT (log-rank, P < .001), but not polymorphic VT/VF (log-rank, P = .40). The optimal cutoff value for the extent of LGE to predict monomorphic VT was 7.2 g (area under curve 0.84). Features associated with monomorphic VT were core extent, basal location, and area with 51%-75% LGE transmurality. CONCLUSIONS Myocardial scar assessed by LGE-CMR predicts monomorphic VT, but not polymorphic VT/VF, in NIDCM. The risk for monomorphic VT is particularly high when LGE shows a basal transmural distribution and a mass ≥7.2 g. Importantly, patients without LGE on CMR remain at risk for potentially fatal polymorphic VT/VF.
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MESH Headings
- Cardiomyopathy, Dilated/complications
- Cardiomyopathy, Dilated/diagnosis
- Cardiomyopathy, Dilated/physiopathology
- Cicatrix/complications
- Cicatrix/pathology
- Defibrillators, Implantable
- Diagnosis, Differential
- Electrocardiography
- Female
- Follow-Up Studies
- Humans
- Magnetic Resonance Imaging, Cine/methods
- Male
- Middle Aged
- Myocardium/pathology
- Predictive Value of Tests
- Retrospective Studies
- Risk Factors
- Tachycardia, Ventricular/diagnosis
- Tachycardia, Ventricular/etiology
- Tachycardia, Ventricular/therapy
- Ventricular Fibrillation
- Ventricular Function, Left/physiology
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Affiliation(s)
- Sebastiaan R D Piers
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Kimberly Everaerts
- Department of Cardiology, University Medical Centre Maastricht, Maastricht, The Netherlands
| | - Rob J van der Geest
- Division of Image Processing, Leiden University Medical Centre, Leiden, The Netherlands
| | - Mark R Hazebroek
- Department of Cardiology, University Medical Centre Maastricht, Maastricht, The Netherlands
| | - Hans-Marc Siebelink
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Laurent A F G Pison
- Department of Cardiology, University Medical Centre Maastricht, Maastricht, The Netherlands
| | - Martin J Schalij
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
| | | | - Stephane Heymans
- Department of Cardiology, University Medical Centre Maastricht, Maastricht, The Netherlands; Netherlands Heart Institute (ICIN), Utrecht, The Netherlands
| | - Katja Zeppenfeld
- Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands.
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18
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Abstract
RATIONALE Alternans is a risk factor for cardiac arrhythmia, including atrial fibrillation. At the cellular level alternans manifests as beat-to-beat alternations in contraction, action potential duration (APD), and magnitude of the Ca(2+) transient (CaT). Electromechanical and CaT alternans are highly correlated, however, it has remained controversial whether the primary cause of alternans is a disturbance of cellular Ca(2+) signaling or electrical membrane properties. OBJECTIVE To determine whether a primary failure of intracellular Ca(2+) regulation or disturbances in membrane potential and AP regulation are responsible for the occurrence of alternans in atrial myocytes. METHODS AND RESULTS Pacing-induced APD and CaT alternans were studied in single rabbit atrial and ventricular myocytes using combined [Ca(2+)]i and electrophysiological measurements. In current-clamp experiments, APD and CaT alternans strongly correlated in time and magnitude. CaT alternans was observed without alternation in L-type Ca(2+) current, however, elimination of intracellular Ca(2+) release abolished APD alternans, indicating that [Ca(2+)]i dynamics have a profound effect on the occurrence of CaT alternans. Trains of 2 distinctive voltage commands in form of APs recorded during large and small alternans CaTs were applied to voltage-clamped cells. CaT alternans was observed with and without alternation in the voltage command shape. During alternans AP-clamp large CaTs coincided with both long and short AP waveforms, indicating that CaT alternans develop irrespective of AP dynamics. CONCLUSIONS The primary mechanism underlying alternans in atrial cells, similarly to ventricular cells, resides in a disturbance of Ca(2+) signaling, whereas APD alternans are a secondary consequence, mediated by Ca(2+)-dependent AP modulation.
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Affiliation(s)
- Giedrius Kanaporis
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL
| | - Lothar A Blatter
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL.
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19
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Cappiello G, Das S, Mazomenos EB, Maharatna K, Koulaouzidis G, Morgan J, Puddu PE. A statistical index for early diagnosis of ventricular arrhythmia from the trend analysis of ECG phase-portraits. Physiol Meas 2014; 36:107-31. [DOI: 10.1088/0967-3334/36/1/107] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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20
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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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21
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Heart rate variability and alternans formation in the heart: The role of feedback in cardiac dynamics. J Theor Biol 2014; 350:90-7. [DOI: 10.1016/j.jtbi.2014.02.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Revised: 01/28/2014] [Accepted: 02/13/2014] [Indexed: 11/18/2022]
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22
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Finlay MC, Xu L, Taggart P, Hanson B, Lambiase PD. Bridging the gap between computation and clinical biology: validation of cable theory in humans. Front Physiol 2013; 4:213. [PMID: 24027527 PMCID: PMC3761165 DOI: 10.3389/fphys.2013.00213] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/25/2013] [Indexed: 11/13/2022] Open
Abstract
Introduction: Computerized simulations of cardiac activity have significantly contributed to our understanding of cardiac electrophysiology, but techniques of simulations based on patient-acquired data remain in their infancy. We sought to integrate data acquired from human electrophysiological studies into patient-specific models, and validated this approach by testing whether electrophysiological responses to sequential premature stimuli could be predicted in a quantitatively accurate manner. Methods: Eleven patients with structurally normal hearts underwent electrophysiological studies. Semi-automated analysis was used to reconstruct activation and repolarization dynamics for each electrode. This S2 extrastimuli data was used to inform individualized models of cardiac conduction, including a novel derivation of conduction velocity restitution. Activation dynamics of multiple premature extrastimuli were then predicted from this model and compared against measured patient data as well as data derived from the ten-Tusscher cell-ionic model. Results: Activation dynamics following a premature S3 were significantly different from those after an S2. Patient specific models demonstrated accurate prediction of the S3 activation wave, (Pearson's R2 = 0.90, median error 4%). Examination of the modeled conduction dynamics allowed inferences into the spatial dispersion of activation delay. Further validation was performed against data from the ten-Tusscher cell-ionic model, with our model accurately recapitulating predictions of repolarization times (R2 = 0.99). Conclusions: Simulations based on clinically acquired data can be used to successfully predict complex activation patterns following sequential extrastimuli. Such modeling techniques may be useful as a method of incorporation of clinical data into predictive models.
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Affiliation(s)
- Malcolm C Finlay
- Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Science, University College London London, UK
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23
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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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24
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Dorenkamp M, Morguet AJ, Sticherling C, Behrens S, Zabel M. Long-term prognostic value of restitution slope in patients with ischemic and dilated cardiomyopathies. PLoS One 2013; 8:e54768. [PMID: 23349967 PMCID: PMC3548796 DOI: 10.1371/journal.pone.0054768] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 12/14/2012] [Indexed: 11/30/2022] Open
Abstract
Background An action potential duration (APD) restitution curve with a steep slope ≥1 has been associated with increased susceptibility for malignant ventricular arrhythmias. We aimed to evaluate the “restitution hypothesis” and tested ventricular APD restitution slope as well as effective refractory period (ERP)/APD ratio for long-term prognostic value in patients with ischemic (ICM) or dilated cardiomyopathy (DCM). Methodology/Principal Findings Monophasic action potentials were recorded in patients with ICM (n = 32) and DCM (n = 42) undergoing routine programmed ventricular stimulation (PVS). Left ventricular ejection fraction was 32±7% and 28±9%, respectively. APD and ERP were measured at baseline stimulation (S1) and upon introduction of one to three extrastimuli (S2–S4). ERP/APD ratios and the APD restitution curve were calculated and the maximum restitution slope was determined. After a mean follow-up of 6.1±3.0 years, the combined end-point of mortality and and/or implantable cardioverter-defibrillator shock was not predicted by restitution slope or ERP/APD ratios. Comparing S2 vs. S3 vs. S4 extrastimuli for restitution slope (1.5±0.6 vs. 1.4±0.4 vs. 1.3±0.5; p = NS), additional extrastimuli did not lead to a steepening restitution slope. ERP/APD ratio decreased with additional extrastimuli (0.98±0.09 [S1] vs. 0.97±0.10 [S2] vs. 0.93±0.11 [S3]; p = 0.03 S1 vs. S3). Positive PVS was strongly predictive of outcome (p = 0.006). Conclusions/Significance Neither ventricular APD restitution slope nor ERP/APD ratios predict outcome in patients with ICM or DCM.
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Affiliation(s)
- Marc Dorenkamp
- Department of Cardiology, Charité - Universitätsmedizin Berlin, Campus Virchow-Klinikum, Berlin, Germany.
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25
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Shusterman V. Spatial heterogeneity of electrical restitution as a predictor of ventricular tachyarrhythmias: a lumped-parameter approach. J Am Heart Assoc 2012; 1:e002949. [PMID: 23130173 PMCID: PMC3487361 DOI: 10.1161/jaha.112.002949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Vladimir Shusterman
- School of Medicine, Division of Cardiology, University of Pittsburgh Pittsburgh, PA
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26
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Weinberg SH, Tung L. Oscillation in cycle length induces transient discordant and steady-state concordant alternans in the heart. PLoS One 2012; 7:e40477. [PMID: 22792346 PMCID: PMC3390356 DOI: 10.1371/journal.pone.0040477] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 06/08/2012] [Indexed: 11/19/2022] Open
Abstract
Alternans is a beat-to-beat alternation of the cardiac action potential duration (APD) or intracellular calcium (Cai) transient. In cardiac tissue, alternans can be spatially concordant or discordant, of which the latter has been shown to increase dispersion of repolarization and promote a substrate for initiation of ventricular fibrillation. Alternans has been studied almost exclusively under constant cycle length pacing conditions. However, heart rate varies greatly on a beat-by-beat basis in normal and pathological conditions. The purpose of this study was to determine if applying a repetitive but non-constant pacing pattern, specifically cycle length oscillation (CLO), promotes or suppresses a proarrhythmic substrate. We performed computational simulations and optical mapping experiments to investigate the potential consequences of CLO. In a single cell computational model, CLO induced APD and Cai alternans, which became “phase-matched” with the applied oscillation. As a consequence of the phase-matching, in one-dimensional cable simulations, neonatal rat ventricular myocyte monolayers, and isolated adult guinea pig hearts CLO could transiently induce spatial and electromechanical discordant alternans followed by a steady-state of concordance. Our results demonstrated that under certain conditions, CLO can initiate ventricular fibrillation in the isolated hearts. On the other hand, CLO can also exert an antiarrhythmic effect by converting an existing state of discordant alternans to concordant alternans.
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Affiliation(s)
- Seth H. Weinberg
- Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail: (SHW); (LT)
| | - Leslie Tung
- Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail: (SHW); (LT)
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27
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Wang YT, Efimov IR, Cheng Y. Electroporation induced by internal defibrillation shock with and without recovery in intact rabbit hearts. Am J Physiol Heart Circ Physiol 2012; 303:H439-49. [PMID: 22730387 DOI: 10.1152/ajpheart.01121.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Defibrillation shocks from implantable cardioverter defibrillators can be lifesaving but can also damage cardiac tissues via electroporation. This study characterizes the spatial distribution and extent of defibrillation shock-induced electroporation with and without a 45-min postshock period for cell membranes to recover. Langendorff-perfused rabbit hearts (n = 31) with and without a chronic left ventricular (LV) myocardial infarction (MI) were studied. Mean defibrillation threshold (DFT) was determined to be 161.4 ± 17.1 V and 1.65 ± 0.44 J in MI hearts for internally delivered 8-ms monophasic truncated exponential (MTE) shocks during sustained ventricular fibrillation (>20 s, SVF). A single 300-V MTE shock (twice determined DFT voltage) was used to terminate SVF. Shock-induced electroporation was assessed by propidium iodide (PI) uptake. Ventricular PI staining was quantified by fluorescent imaging. Histological analysis was performed using Masson's Trichrome staining. Results showed PI staining concentrated near the shock electrode in all hearts. Without recovery, PI staining was similar between normal and MI groups around the shock electrode and over the whole ventricles. However, MI hearts had greater total PI uptake in anterior (P < 0.01) and posterior (P < 0.01) LV epicardial regions. Postrecovery, PI staining was reduced substantially, but residual staining remained significant with similar spacial distributions. PI staining under SVF was similar to previously studied paced hearts. In conclusion, electroporation was spatially correlated with the active region of the shock electrode. Additional electroporation occurred in the LV epicardium of MI hearts, in the infarct border zone. Recovery of membrane integrity postelectroporation is likely a prolonged process. Short periods of SVF did not affect electroporation injury.
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Affiliation(s)
- Yves T Wang
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland, Ohio, USA
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28
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Cherry EM, Fenton FH, Gilmour RF. Mechanisms of ventricular arrhythmias: a dynamical systems-based perspective. Am J Physiol Heart Circ Physiol 2012; 302:H2451-63. [PMID: 22467299 PMCID: PMC3378269 DOI: 10.1152/ajpheart.00770.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 03/26/2012] [Indexed: 01/23/2023]
Abstract
Defining the cellular electrophysiological mechanisms for ventricular tachyarrhythmias is difficult, given the wide array of potential mechanisms, ranging from abnormal automaticity to various types of reentry and kk activity. The degree of difficulty is increased further by the fact that any particular mechanism may be influenced by the evolving ionic and anatomic environments associated with many forms of heart disease. Consequently, static measures of a single electrophysiological characteristic are unlikely to be useful in establishing mechanisms. Rather, the dynamics of the electrophysiological triggers and substrates that predispose to arrhythmia development need to be considered. Moreover, the dynamics need to be considered in the context of a system, one that displays certain predictable behaviors, but also one that may contain seemingly stochastic elements. It also is essential to recognize that even the predictable behaviors of this complex nonlinear system are subject to small changes in the state of the system at any given time. Here we briefly review some of the short-, medium-, and long-term alterations of the electrophysiological substrate that accompany myocardial disease and their potential impact on the initiation and maintenance of ventricular arrhythmias. We also provide examples of cases in which small changes in the electrophysiological substrate can result in rather large differences in arrhythmia outcome. These results suggest that an interrogation of cardiac electrical dynamics is required to provide a meaningful assessment of the immediate risk for arrhythmia development and for evaluating the effects of putative antiarrhythmic interventions.
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Affiliation(s)
- Elizabeth M Cherry
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA
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Otani NF. Termination of reentrant cardiac action potential propagation using far-field electrical pacing. IEEE Trans Biomed Eng 2011; 58:2013-22. [PMID: 21402503 PMCID: PMC3296456 DOI: 10.1109/tbme.2011.2126044] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Several different types of rapid cardiac rhythm disorders, including atrial and ventricular fibrillation, are likely caused by multiple, rapidly rotating, action potential (AP) waves. Thus, an electrical pacing therapy, whose effectiveness is based on being delivered with a particular timing relative to one of these waves, is unlikely to be useful in terminating the remaining waves. Here, we develop pacing protocols that are designed to terminate rotating waves independently of when the sequences of stimuli are imposed or where each wave is in its rotation at the time the sequences are initiated. These protocols are delivered as far-field stimuli, and therefore are capable of simultaneously influencing all the waves present. The pacing intervals for these protocols are, in general, of unequal duration and are determined through examination of the dynamics of AP propagation in a 1-D ring model. Series of two or three stimuli with interstimulus intervals chosen in this way are shown to be effective in terminating these waves over a wide range of ring circumferences and AP dynamical parameters. Stimulus sequences of this type may form the basis for developing new defibrillation protocols to test in experiments or more realistic models of the electrical heart.
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Affiliation(s)
- Niels F Otani
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA.
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Toward prediction of the local onset of alternans in the heart. Biophys J 2011; 100:868-74. [PMID: 21320430 DOI: 10.1016/j.bpj.2011.01.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 01/05/2011] [Accepted: 01/07/2011] [Indexed: 11/23/2022] Open
Abstract
A beat-to-beat variation in the cardiac action potential duration is a phenomenon known as alternans. Alternans has been linked to ventricular fibrillation, and thus the ability to predict the onset of alternans could be clinically beneficial. Theoretically, it has been proposed that the slope of a restitution curve, which relates the duration of the action potential to the preceding diastolic interval, can predict the onset of alternans. Experimentally, however, this hypothesis has not been consistently proven, mainly because of the intrinsic complexity of the dynamics of cardiac tissue. It was recently shown that the restitution portrait, which combines several restitution curves simultaneously, is associated with the onset of alternans in isolated myocytes. Our main purpose in this study was to determine whether the restitution portrait is correlated with the onset of alternans in the heart, where the dynamics include a spatial complexity. We performed optical mapping experiments in isolated Langendorff-perfused rabbit hearts in which alternans was induced by periodic pacing at different frequencies, and identified the local onset of alternans, B(onset). We identified two regions of the heart: the area that exhibited alternans at B(onset) (1:1(alt)) and the area that did not (1:1). We constructed two-dimensional restitution portraits for the epicardial surface of the heart and measured the spatial distribution of three different slopes (the dynamic restitution slope, S(dyn)(RP), and two local S1-S2 slopes, S(12) and S(12)(max)) separately for these two regions. We found that the S(12) and S(12)(max) slopes differed significantly between the 1:1(alt) and 1:1 regions just before the onset of alternans, and S(dyn)(RP) slopes were statistically similar. In addition, we found that the slopes of the dynamic restitution curve S(dyn) were also statistically similar between these two regions. On the other hand, the quantitative values of all slopes were significantly different from the theoretically predicted value of one. These results demonstrate that the slopes measured in the restitution portrait correlate with the onset of alternans in the heart.
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OSAKA TOSHIYUKI, YOKOYAMA ERIKO, HASEBE HIDEYUKI, KODAMA ITSUO. Effects of Chronic Amiodarone on the Electrical Restitution in the Human Ventricle With Reference to Its Antiarrhythmic Efficacy. J Cardiovasc Electrophysiol 2011; 22:669-76. [DOI: 10.1111/j.1540-8167.2010.01990.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Zheng Y, Wei D, Fang Z, Zhu X. Influences of sites and protocols on inducing ventricular fibrillation: A computer simulation study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:2005-8. [PMID: 21097216 DOI: 10.1109/iembs.2010.5627858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In cardiac electrophysiological study, several electrical stimulation protocols have been employed to induce ventricular fibrillations (VF). In addition, sites of inducing may have different impacts on inducing results as well as different inducing protocols. To study whether VF inducing method is determinant of induced outcome, we simulated VFs induced with different protocols at different sites based on the Wei-Harumi whole heart model. Simulations showed that only certain combinations of pacing protocols and sites could induce sustainable VFs, which had similar frequency distributions. This result suggested that the interactions between protocols and sites determine the odds of successful inducing but once the VF was induced, the pattern was solely determined by inner cardiac properties.
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Affiliation(s)
- Yi Zheng
- Department of Electronic Engineering, Fudan University, Shanghai, China.
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Alternans resonance and propagation block during supernormal conduction in cardiac tissue with decreased [K(+)](o). Biophys J 2010; 98:1129-38. [PMID: 20371312 DOI: 10.1016/j.bpj.2009.12.4280] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 12/02/2009] [Accepted: 12/03/2009] [Indexed: 11/20/2022] Open
Abstract
Cardiac restitution is an important factor in arrhythmogenesis. Steep positive action potential duration and conduction velocity (CV) restitution slopes promote alternans and reentrant arrhythmias. We examined the consequences of supernormal conduction (characterized by a negative CV restitution slope) on patterns of conduction and alternans in strands of Luo-Rudy model cells and in cultured cardiac cell strands. Interbeat intervals (IBIs) were analyzed as a function of distance during S1S2 protocols and during pacing at alternating cycle lengths. Supernormal conduction was induced by decreasing [K(+)](o). In control [K(+)](o) simulations, S1S2 intervals converged toward basic cycle length with a length constant determined by both CV and the CV restitution slope. During alternant pacing, the amplitude of IBI alternans converged with a shorter length constant, determined also by the action potential duration restitution slope. In contrast, during supernormal conduction, S1S2 intervals and the amplitude of alternans diverged. This amplification (resonance) led to phase-locked or more complex alternans patterns, and then to distal conduction block. The convergence/divergence of IBIs was verified in the cultured strands, in which naturally occurring tissue heterogeneities resulted in prominent discontinuities of the spatial IBI profiles. We conclude that supernormal conduction potentiates alternans and spatial analysis of IBIs represents a powerful method to locate tissue heterogeneities.
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Coronel R, Wilms-Schopman FJG, Janse MJ. Anti- or profibrillatory effects of Na(+) channel blockade depend on the site of application relative to gradients in repolarization. Front Physiol 2010; 1:10. [PMID: 21423353 PMCID: PMC3059930 DOI: 10.3389/fphys.2010.00010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 05/06/2010] [Indexed: 11/16/2022] Open
Abstract
Sodium channel blockers are associated with arrhythmic sudden death, although they are considered antiarrhythmic agents. The mechanism of these opposing effects is unknown. We used a model of induction of ventricular fibrillation (VF) based on selective perfusion of the vascular beds of isolated porcine hearts (n = 8). One bed was perfused with sotalol (220 μM), the adjacent bed with pinacidil (80 μM), leading to repolarization heterogeneity (late repolarization in the sotalol-, early in the pinacidil-area). Premature stimulation from the area with the short action potential was performed. Epicardial activation/repolarization mapping was done. In three of the eight hearts VF was inducible prior to infusion of flecainide. In those hearts the Fibrillation Factor (FF), the interval between the earliest repolarization of the premature beat (S2) in the early repolarizing (pinacidil) domain, and the last S2-activation in the late repolarizing (sotalol) domain, was significantly shorter than in the hearts without VF (33 ± 22 vs 93 ± 11 ms, m ± SEM, p < 0.05). In the three hearts with VF flecainide was infused in the pinacidil domain after defibrillation. This led to shortening of the line of block, local delay of S2 activation and repolarization, an increase in FF and failure to induce VF. In the five hearts without VF, flecainide was subsequently infused in the sotalol domain. This led to a local delay of S2 activation, a shortening of FF (by 47 ± 3 ms) and successful induction of VF in three hearts. In the two remaining hearts FF did not decrease enough (maximally 13 ms) to allow re-entry. Sodium channel blockade applied to myocardium with a short refractory period is antifibrillatory whereas sodium channel blockade of myocardium with a long refractory period is profibrillatory. Our study provides a mechanistic basis for pro- and antiarrhythmic effects of sodium channel blockers in the absence of structural heart disease.
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Affiliation(s)
- Ruben Coronel
- Experimental Cardiology Group, Academic Medical Center Amsterdam, Netherlands.
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Gelzer A, Otani N, Koller M, Enyeart M, Moise N, Gilmour R. Dynamically-Induced Spatial Dispersion of Repolarization and the Development of VF in an Animal Model of Sudden Death. COMPUTERS IN CARDIOLOGY 2009; 2009:309-312. [PMID: 20622925 PMCID: PMC2899698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Spatial dispersion of refractoriness and discordant action potential duration (APD) alternans, resulting in local conduction block, have been shown to cause wavebreak that can lead to ventricular fibrillation (VF). Previously, we developed a theory, based on action potential restitution functions, that predicts when the requisite conduction block can be created through a series of premature beats. The theory was applied successfully to normal beagle dogs; however, restitution functions in these animals were similar, both between right and left ventricles in a given animal and across animals. Consequently, for the present study we tested the theory on a population of German shepherds that, due to inherited cardiac abnormalities, presented with a wide variation of APD restitution functions. We found that the theory, when applied to restitution functions determined individually for each animal, reliably generated premature stimulation predictions that frequently resulted in the induction of VF in in vivo experiments.
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Affiliation(s)
- Arm Gelzer
- Department of Clinical Sciences, Cornell University, Ithaca, NY, USA
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Krogh-Madsen T, Christini DJ. Pacing-induced spatiotemporal dynamics can be exploited to improve reentry termination efficacy. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:021924. [PMID: 19792168 DOI: 10.1103/physreve.80.021924] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 05/30/2009] [Indexed: 05/25/2023]
Abstract
Some potentially fatal cardiac arrhythmias may be terminated by a series of premature stimuli. Monomorphic ventricular tachycardia, which may be modeled as an excitation wave traveling around in a ring, is one such arrhythmia. We investigated the mechanisms and requirements for termination of such reentry using an ionic cardiac ring model. Termination requires conduction block, which in turn is facilitated by spatial dispersion in repolarization and recovery time. When applying short series of two or three stimuli, we found that for conduction block to robustly occur, the magnitude of the spatial gradient in recovery time must exceed a critical value of 20 ms/cm. Importantly, the required spatial gradient can be induced in this homogeneous system by the dynamics of the stimulus-induced waves-we show analytically the necessary conditions. Finally, we introduce a type of pacing protocol, the "aggressive ramp," which increases the termination efficacy by exploiting such pacing-induced heterogeneities. This technique, which is straightforward to implement, may therefore have important clinical implications.
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Affiliation(s)
- Trine Krogh-Madsen
- Department of Medicine, Greenberg Division of Cardiology, Weill Cornell Medical College, New York, New York 10021, USA
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Gilmour RF. Restitution, heterogeneity and unidirectional conduction block: New roles for old players. Heart Rhythm 2009; 6:544-5. [DOI: 10.1016/j.hrthm.2009.01.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Indexed: 10/21/2022]
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Ahrens-Nicklas RC, Clancy CE, Christini DJ. Re-evaluating the efficacy of beta-adrenergic agonists and antagonists in long QT-3 syndrome through computational modelling. Cardiovasc Res 2009; 82:439-47. [PMID: 19264765 DOI: 10.1093/cvr/cvp083] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
AIMS Long QT syndrome (LQTS) is a heterogeneous collection of inherited cardiac ion channelopathies characterized by a prolonged electrocardiogram QT interval and increased risk of sudden cardiac death. Beta-adrenergic blockers are the mainstay of treatment for LQTS. While their efficacy has been demonstrated in LQTS patients harbouring potassium channel mutations, studies of beta-blockers in subtype 3 (LQT3), which is caused by sodium channel mutations, have produced ambiguous results. In this modelling study, we explore the effects of beta-adrenergic drugs on the LQT3 phenotype. METHODS AND RESULTS In order to investigate the effects of beta-adrenergic activity and to identify sources of ambiguity in earlier studies, we developed a computational model incorporating the effects of beta-agonists and beta-blockers into an LQT3 mutant guinea pig ventricular myocyte model. Beta-activation suppressed two arrhythmogenic phenomena, transmural dispersion of repolarization and early after depolarizations, in a dose-dependent manner. However, the ability of beta-activation to prevent cardiac conduction block was pacing-rate-dependent. Low-dose beta-blockade by propranolol reversed the beneficial effects of beta-activation, while high dose (which has off-target sodium channel effects) decreased arrhythmia susceptibility. CONCLUSION These results demonstrate that beta-activation may be protective in LQT3 and help to reconcile seemingly conflicting results from different experimental models. They also highlight the need for well-controlled clinical investigations re-evaluating the use of beta-blockers in LQT3 patients.
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Affiliation(s)
- Rebecca C Ahrens-Nicklas
- Greenberg Division of Cardiology, Weill Cornell Medical College, 1300 York Ave., Box 161, New York, NY 10065, USA
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Siso-Nadal F, Otani NF, Gilmour RF, Fox JJ. Boundary-induced reentry in homogeneous excitable tissue. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:031925. [PMID: 18851083 PMCID: PMC2697449 DOI: 10.1103/physreve.78.031925] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Indexed: 05/26/2023]
Abstract
Heterogeneity of cardiac electrical properties can lead to heart rhythm disorders. Numerical studies have shown that stimuli chosen to maximize dynamic heterogeneity terminate wave propagation. However, experimental investigations suggest that similar sequences induce fragmentation of the wave fronts, rather than complete wave block. In this paper we show that an insulating boundary in an otherwise homogeneous medium can disrupt dynamically induced wave block by breaking a symmetry in the spatial pattern of action potential duration, leading to unidirectional block and reentrant activation.
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