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Majumder R. In silico thermal control of spiral wave dynamics in excitable cardiac tissue. BIOPHYSICAL REPORTS 2024; 4:100170. [PMID: 38960373 PMCID: PMC11304022 DOI: 10.1016/j.bpr.2024.100170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2024] [Revised: 06/26/2024] [Accepted: 06/28/2024] [Indexed: 07/05/2024]
Abstract
Self-organizing spiral waves of excitation occur in many complex excitable systems. In the heart, for example, they are associated with the occurrence of fatal cardiac arrhythmias such as tachycardia and fibrillation, which can lead to sudden cardiac death. The control of these waves is therefore necessary for the treatment of the disease. In this letter, I present an innovative approach to control cardiac arrhythmias using low (nonfreezing) temperatures. This approach differs from all previous established techniques in that it involves no drugs, no genetic modification, no injection of foreign bodies, no application of voltage shocks (high or low, single or pulsed), and no curative damage to the heart. It relies on regional cooling of cardiac tissue to create a transient inhomogeneity in the electrophysiological properties. This inhomogeneity can then be manipulated to control the dynamics of the reentrant waves. This approach is, to my knowledge, the most sustainable theoretical proposal for the treatment of cardiac arrhythmias in the clinic.
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Jenkins EV, Dharmaprani D, Schopp M, Quah JX, Tiver K, Mitchell L, Pope K, Ganesan AN. Understanding the origins of the basic equations of statistical fibrillatory dynamics. CHAOS (WOODBURY, N.Y.) 2022; 32:032101. [PMID: 35364849 DOI: 10.1063/5.0062095] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 02/07/2022] [Indexed: 06/14/2023]
Abstract
The mechanisms governing cardiac fibrillation remain unclear; however, it most likely represents a form of spatiotemporal chaos with conservative system dynamics. Renewal theory has recently been suggested as a statistical formulation with governing equations to quantify the formation and destruction of wavelets and rotors in fibrillatory dynamics. In this perspective Review, we aim to explain the origin of the renewal theory paradigm in spatiotemporal chaos. The ergodic nature of pattern formation in spatiotemporal chaos is demonstrated through the use of three chaotic systems: two classical systems and a simulation of cardiac fibrillation. The logistic map and the baker's transformation are used to demonstrate how the apparently random appearance of patterns in classical chaotic systems has macroscopic parameters that are predictable in a statistical sense. We demonstrate that the renewal theory approach developed for cardiac fibrillation statistically predicts pattern formation in these classical chaotic systems. Renewal theory provides governing equations to describe the apparently random formation and destruction of wavelets and rotors in atrial fibrillation (AF) and ventricular fibrillation (VF). This statistical framework for fibrillatory dynamics provides a holistic understanding of observed rotor and wavelet dynamics and is of conceptual significance in informing the clinical and mechanistic research of the rotor and multiple-wavelet mechanisms of AF and VF.
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Affiliation(s)
- Evan V Jenkins
- College of Medicine and Public Health, Flinders University, Adelaide 5042, Australia
| | - Dhani Dharmaprani
- College of Medicine and Public Health, Flinders University, Adelaide 5042, Australia
| | - Madeline Schopp
- College of Science and Engineering, Flinders University, Adelaide 5042, Australia
| | - Jing Xian Quah
- College of Medicine and Public Health, Flinders University, Adelaide 5042, Australia
| | - Kathryn Tiver
- Department of Cardiovascular Medicine, Flinders Medical Centre, Adelaide 5042, Australia
| | - Lewis Mitchell
- School of Mathematical Sciences, University of Adelaide, Adelaide 5005, Australia
| | - Kenneth Pope
- College of Science and Engineering, Flinders University, Adelaide 5042, Australia
| | - Anand N Ganesan
- College of Medicine and Public Health, Flinders University, Adelaide 5042, Australia
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Ng GA, Mistry A, Newton M, Schlindwein FS, Barr C, Bates MG, Caldwell J, Das M, Farooq M, Herring N, Lambiase P, Osman F, Sohal M, Staniforth A, Tayebjee M, Tomlinson D, Whinnett Z, Yue A, Nicolson WB. Rationale and study design of the MINERVA study: Multicentre Investigation of Novel Electrocardiogram Risk markers in Ventricular Arrhythmia prediction-UK multicentre collaboration. BMJ Open 2022; 12:e059527. [PMID: 34980634 PMCID: PMC8724816 DOI: 10.1136/bmjopen-2021-059527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 12/08/2021] [Indexed: 11/15/2022] Open
Abstract
INTRODUCTION The purpose of this study is to assess the ability of two new ECG markers (Regional Repolarisation Instability Index (R2I2) and Peak Electrical Restitution Slope) to predict sudden cardiac death (SCD) or ventricular arrhythmia (VA) events in patients with ischaemic cardiomyopathy undergoing implantation of an implantable cardioverter defibrillator for primary prevention indication. METHODS AND ANALYSIS Multicentre Investigation of Novel Electrocardiogram Risk markers in Ventricular Arrhythmia prediction is a prospective, open label, single blinded, multicentre observational study to establish the efficacy of two ECG biomarkers in predicting VA risk. 440 participants with ischaemic cardiomyopathy undergoing routine first time implantable cardioverter-defibrillator (ICD) implantation for primary prevention indication are currently being recruited. An electrophysiological (EP) study is performed using a non-invasive programmed electrical stimulation protocol via the implanted device. All participants will undergo the EP study hence no randomisation is required. Participants will be followed up over a minimum of 18 months and up to 3 years. The first patient was recruited in August 2016 and the study will be completed at the final participant follow-up visit. The primary endpoint is ventricular fibrillation or sustained ventricular tachycardia >200 beats/min as recorded by the ICD. The secondary endpoint is SCD. Analysis of the ECG data obtained during the EP study will be performed by the core lab where blinding of patient health status and endpoints will be maintained. ETHICS AND DISSEMINATION Ethical approval has been granted by Research Ethics Committees Northern Ireland (reference no. 16/NI/0069). The results will inform the design of a definitive Randomised Controlled Trial (RCT). Dissemination will include peer reviewed journal articles reporting the qualitative and quantitative results, as well as presentations at conferences and lay summaries. TRIAL REGISTRATION NUMBER NCT03022487.
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Affiliation(s)
- G Andre Ng
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- NIHR Leicester Biomedical Research Centre Cardiovascular Diseases, Leicester, UK
- Department of Cardiology, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Amar Mistry
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- Department of Cardiology, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Michelle Newton
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Fernando Soares Schlindwein
- NIHR Leicester Biomedical Research Centre Cardiovascular Diseases, Leicester, UK
- Department of Engineering, University of Leicester, Leicester, UK
| | - Craig Barr
- Cardiology, Dudley Group NHS Foundation Trust, Dudley, UK
| | | | - Jane Caldwell
- Cardiology, Castle Hill Hosptial, Hull and East Yorkshire NHS Trust, Hull, UK
| | - Moloy Das
- Cardiology, Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, UK
| | - Mohsin Farooq
- Cardiology, Kettering General Hospital, Kettering, UK
| | - Neil Herring
- Cardiology, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Pier Lambiase
- Cardiology, University College London Hospitals NHS Foundation Trust, London, UK
| | - Faizel Osman
- Cardiology, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK
| | - Manav Sohal
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Andrew Staniforth
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Muzahir Tayebjee
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - David Tomlinson
- Cardiology, University Hospitals Plymouth NHS Trust, Plymouth, UK
| | | | - Arthur Yue
- Cardiology, University Hospital Southampton, Southampton, UK
| | - Will B Nicolson
- NIHR Leicester Biomedical Research Centre Cardiovascular Diseases, Leicester, UK
- Department of Cardiology, University Hospitals of Leicester NHS Trust, Leicester, UK
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Connor MH, Connor CA, Eickhoff J, Schwartz GE. Prospective empirical test suite for energy practitioners. Explore (NY) 2020; 17:60-69. [PMID: 32798173 DOI: 10.1016/j.explore.2020.07.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 07/22/2020] [Accepted: 07/29/2020] [Indexed: 01/19/2023]
Abstract
OBJECTIVE To design a set of measures which were portable and cost-effective that scientists could use to determine competence of Energy Practitioners so that qualified practitioners could be employed in improving ongoing research accuracy. DESIGN This was a prospective study with sample of convenience. SUBJECTS 213 subjects, 185 women and 28 men, were tested in this study. OUTCOME MEASURES Empirical outcome measures included Triaxial Extra Low Frequency Magnetic Field meter, Data Logging Multimeter, RF Field Spectrum Analyzer, Acoustimeter, Broadcast Frequency counter, digital pH meter, digital TDS meter, GDV and physiology suite including heart rate variability, galvanic skin response, respiration, EMG, EKG, temperature and blood volume pulse. Additional questions on ethics and body reading were included in the test. RESULTS Results suggest a range of tests which could be used to determine practitioner competence. Many of the energy practitioners tested consistently produced changes in the areas being measured past the error rate of the devices being used. Across the 13 measures, practitioner success ranged from 56.8% on the Acoustimeter to 100% on the Broadcast Frequency Counter measures with 95% CI. Tri Axial ELF magnetic field meter showed significance with practitioners producing oscillations of amplitude from the L hand at p< 0.01 with and effect size D of 1.5 and R hand p< 0.001 and an effect size D of 1.6. Practitioners demonstrated the ability to produce a change in pH beyond ±.1pH in 10 minutes at a Mean of 0.5 and a SD of 0.4 at a 95% CI of 0.48-0.58 and changes in TDS beyond+/-2% at a Mean of 36.7 and a SD of 35.2 at a 95% CI of 31.9-41.5. Other measures are discussed in detail. CONCLUSIONS This test presents a possible way to demonstrate a level of practitioner competence and improve the selection of energy practitioners for use in scientific studies of energy healing in the areas of full spectrum healing, laying-on-of-hands healing, Reiki, Qi Gong and Tai Chi.
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Affiliation(s)
- Melinda H Connor
- CAM, Akamai University, Hilo Hawaii; Arizona School of Acupuncture and Oriental Medicine, Earthsongs Holistic Consulting, 31907 South Davis Ranch Rd., Marana, AZ 85658, USA.
| | - Caitlin A Connor
- Arizona School of Acupuncture and Oriental Medicine, Earthsongs Holistic Consulting, 31907 South Davis Ranch Rd., Marana, AZ 85658, USA; Health Science Research, Rewley House, University of Oxford, UK
| | - Jens Eickhoff
- Biostatistics & Medical Informatics, University of Wisconsin-Madison
| | - Gary E Schwartz
- Psychology, Medicine, Neurology, Psychiatry, and Surgery, The University of Arizona, USA
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Heikhmakhtiar AK, Abrha AT, Jeong DU, Lim KM. Proarrhythmogenic Effect of the L532P and N588K KCNH2 Mutations in the Human Heart Using a 3D Electrophysiological Model. J Korean Med Sci 2020; 35:e238. [PMID: 32715669 PMCID: PMC7384902 DOI: 10.3346/jkms.2020.35.e238] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 06/01/2020] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Atrial arrhythmia is a cardiac disorder caused by abnormal electrical signaling and transmission, which can result in atrial fibrillation and eventual death. Genetic defects in ion channels can cause myocardial repolarization disorders. Arrhythmia-associated gene mutations, including KCNH2 gene mutations, which are one of the most common genetic disorders, have been reported. This mutation causes abnormal QT intervals by a gain of function in the rapid delayed rectifier potassium channel (IKr). In this study, we demonstrated that mutations in the KCNH2 gene cause atrial arrhythmia. METHODS The N588K and L532P mutations were induced in the Courtemanche-Ramirez-Nattel (CRN) cell model, which was subjected to two-dimensional and three-dimensional simulations to compare the electrical conduction patterns of the wild-type and mutant-type genes. RESULTS In contrast to the early self-termination of the wild-type conduction waveforms, the conduction waveform of the mutant-type retained the reentrant wave (N588K) and caused a spiral break-up, resulting in irregular wave generation (L532P). CONCLUSION The present study confirmed that the KCNH2 gene mutation increases the vulnerability of the atrial tissue for arrhythmia.
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Affiliation(s)
- Aulia Khamas Heikhmakhtiar
- School of Computing, Telkom University, Bandung, Jawa Barat, Indonesia
- Research Center of Human Centric Engineering (HUMIC), Telkom University, Bandung, Jawa Barat, Indonesia
| | - Abebe Tekle Abrha
- Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Korea
| | - Da Un Jeong
- Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Korea
| | - Ki Moo Lim
- Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Korea.
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Comparison of Electromechanical Delay during Ventricular Tachycardia and Fibrillation under Different Conductivity Conditions Using Computational Modeling. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2020; 2020:9501985. [PMID: 32300375 PMCID: PMC7146094 DOI: 10.1155/2020/9501985] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 02/25/2020] [Indexed: 01/27/2023]
Abstract
Electromechanical delay (EMD) is the time interval between local myocyte depolarization and the onset of myofiber shortening. Previously, researchers measured EMD during sinus rhythm and ectopic pacing in normal and heart failure conditions. However, to our knowledge, there are no reports regarding EMD during another type of rhythms or arrhythmia. The goal of this study was to quantify EMD during sinus rhythm, tachycardia, and ventricular fibrillation conditions. We hypothesized that EMD under sinus rhythm is longer due to isovolumetric contraction which is imprecise during arrhythmia. We used a realistic model of 3D electromechanical ventricles. During sinus rhythm, EMD was measured in the last cycle of cardiac systole under steady conditions. EMD under tachycardia and fibrillation conditions was measured during the entire simulation, resulting in multiple EMD values. We assessed EMD for the following 3 conduction velocities (CVs): 31 cm/s, 51 cm/s, and 69 cm/s. The average EMD during fibrillation condition was the shortest corresponding to 53.45 ms, 55.07 ms, and 50.77 ms, for the CVs of 31 cm/s, 51 cm/s, and 69 cm/s, respectively. The average EMD during tachycardia was 58.61 ms, 58.33 ms, and 52.50 ms for the three CVs. Under sinus rhythm with action potential duration restitution (APDR) slope 0.7, the average EMD was 66.35 ms, 66.41 ms, and 66.60 ms in line with the three CVs. This result supports our hypothesis that EMD under sinus rhythm is longer than that under tachyarrhythmia conditions. In conclusion, this study observed and quantified EMD under tachycardia and ventricular fibrillation conditions. This simulation study has widened our understanding of EMD in 3D ventricles under chaotic conditions.
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Heikhmakhtiar AK, Lee CH, Song KS, Lim KM. Computational prediction of the effect of D172N KCNJ2 mutation on ventricular pumping during sinus rhythm and reentry. Med Biol Eng Comput 2020; 58:977-990. [PMID: 32095980 DOI: 10.1007/s11517-020-02124-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/07/2020] [Indexed: 01/30/2023]
Abstract
The understanding of cardiac arrhythmia under genetic mutations has grown in interest among researchers. Previous studies focused on the effect of the D172N mutation on electrophysiological behavior. In this study, we analyzed not only the electrophysiological activity but also the mechanical responses during normal sinus rhythm and reentry conditions by using computational modeling. We simulated four different ventricular conditions including normal case of ten Tusscher model 2006 (TTM), wild-type (WT), heterozygous (WT/D172N), and homozygous D172N mutation. The 2D simulation result (in wire-shaped mesh) showed the WT/D172N and D172N mutation shortened the action potential duration by 14%, and by 23%, respectively. The 3D electrophysiological simulation results showed that the electrical wavelength between TTM and WT conditions were identical. Under sinus rhythm condition, the WT/D172N and D172N reduced the pumping efficacy with a lower left ventricle (LV) and aortic pressures, stroke volume, ejection fraction, and cardiac output. Under the reentry conditions, the WT condition has a small probability of reentry. However, in the event of reentry, WT has shown the most severe condition. Furthermore, we found that the position of the rotor or the scroll wave substantially influenced the ventricular pumping efficacy during arrhythmia. If the rotor stays in the LV, it will cause very poor pumping performance. Graphical Abstract A model of a ventricular electromechanical system. This whole model was established to observe the effect of D172N KCNJ2 mutation on ventricular pumping behavior during sinus rhythm and reentry conditions. The model consists of two components; electrical component and mechanical component. The electrophysiological model based on ten Tusscher et al. with the IK1 D172N KCNJ2 mutation, and the myofilament dynamic (cross-bridge) model based on Rice et al. study. The 3D electrical component is a ventricular geometry based on MRI which composed of nodes representing single-cell with electrophysiological activation. The 3D ventricular mechanic is a finite element mesh composed of single-cells myofilament dynamic model. Both components were coupled with Ca2+ concentration. We used Gaussian points for the calcium interpolation from the electrical mesh to the mechanical mesh.
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Affiliation(s)
- Aulia Khamas Heikhmakhtiar
- Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
| | - Chung Hao Lee
- Department of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK, USA
| | - Kwang Soup Song
- Department of Medical IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea
| | - Ki Moo Lim
- Department of IT Convergence Engineering, Kumoh National Institute of Technology, Gumi, Republic of Korea.
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Ng GA, Mistry A, Li X, Schlindwein FS, Nicolson WB. LifeMap: towards the development of a new technology in sudden cardiac death risk stratification for clinical use. Europace 2018; 20:f162-f170. [PMID: 29684162 DOI: 10.1093/europace/euy080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 03/21/2018] [Indexed: 12/20/2022] Open
Abstract
Sudden cardiac death (SCD) is a major cause of mortality presenting a significant unmet clinical need. Patients at risk of SCD are implanted with implantable cardioverter-defibrillators (ICDs) according to international guidelines based on clinical trial evidence. Implantable cardioverter-defibrillators are not inexpensive and not without problem in terms of inappropriate shocks and infection risk. Also, only a minority of patients implanted with the ICD ever use the device during its battery lifetime highlighting the fact that methods used for SCD risk stratification are inadequate. Better ways of predicting who is at risk of SCD are needed. In addition, there is no effective prevention due to the lack of understanding of the electrical mechanisms underlying SCD. Our group has been investigating the electrophysiological basis of ventricular fibrillation and have successfully applied our preclinical findings to translational studies in patients with ischaemic cardiomyopathy. We have developed two ECG markers which have been shown to be strong predictors of ventricular arrhythmias and SCD. Ongoing clinical studies are being carried out including a multicentre UK study to consolidate the evidence base. They are being incorporated into the technology, LifeMap, with the aim to develop a successful clinical tool for the assessment of SCD risk. We hereby present the scientific data leading to the technology and the development to date. The information provided here was presented at the European Heart Rhythm Association (EHRA) Europace/Cardiostim conference at which LifeMap won the EHRA Inventors Award 2016.
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Affiliation(s)
- Ghulam André Ng
- Cardiology Group, Department of Cardiovascular Sciences, University of Leicester, Leicester LE39QP, UK.,NIHR Leicester Biomedical Research Centre, Leicester, UK.,Department of Cardiology, Glenfield Hospital, Leicester, UK
| | - Amar Mistry
- Cardiology Group, Department of Cardiovascular Sciences, University of Leicester, Leicester LE39QP, UK.,Department of Cardiology, Glenfield Hospital, Leicester, UK
| | - Xin Li
- Cardiology Group, Department of Cardiovascular Sciences, University of Leicester, Leicester LE39QP, UK.,Department of Engineering, University of Leicester, UK
| | - Fernando S Schlindwein
- NIHR Leicester Biomedical Research Centre, Leicester, UK.,Department of Engineering, University of Leicester, UK
| | - William B Nicolson
- Cardiology Group, Department of Cardiovascular Sciences, University of Leicester, Leicester LE39QP, UK.,NIHR Leicester Biomedical Research Centre, Leicester, UK.,Department of Cardiology, Glenfield Hospital, Leicester, UK
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Levin M. Molecular bioelectricity: how endogenous voltage potentials control cell behavior and instruct pattern regulation in vivo. Mol Biol Cell 2015; 25:3835-50. [PMID: 25425556 PMCID: PMC4244194 DOI: 10.1091/mbc.e13-12-0708] [Citation(s) in RCA: 221] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In addition to biochemical gradients and transcriptional networks, cell behavior is regulated by endogenous bioelectrical cues originating in the activity of ion channels and pumps, operating in a wide variety of cell types. Instructive signals mediated by changes in resting potential control proliferation, differentiation, cell shape, and apoptosis of stem, progenitor, and somatic cells. Of importance, however, cells are regulated not only by their own Vmem but also by the Vmem of their neighbors, forming networks via electrical synapses known as gap junctions. Spatiotemporal changes in Vmem distribution among nonneural somatic tissues regulate pattern formation and serve as signals that trigger limb regeneration, induce eye formation, set polarity of whole-body anatomical axes, and orchestrate craniofacial patterning. New tools for tracking and functionally altering Vmem gradients in vivo have identified novel roles for bioelectrical signaling and revealed the molecular pathways by which Vmem changes are transduced into cascades of downstream gene expression. Because channels and gap junctions are gated posttranslationally, bioelectrical networks have their own characteristic dynamics that do not reduce to molecular profiling of channel expression (although they couple functionally to transcriptional networks). The recent data provide an exciting opportunity to crack the bioelectric code, and learn to program cellular activity at the level of organs, not only cell types. The understanding of how patterning information is encoded in bioelectrical networks, which may require concepts from computational neuroscience, will have transformative implications for embryogenesis, regeneration, cancer, and synthetic bioengineering.
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Affiliation(s)
- Michael Levin
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA 02155-4243
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Levin M. Endogenous bioelectrical networks store non-genetic patterning information during development and regeneration. J Physiol 2015; 592:2295-305. [PMID: 24882814 DOI: 10.1113/jphysiol.2014.271940] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Pattern formation, as occurs during embryogenesis or regeneration, is the crucial link between genotype and the functions upon which selection operates. Even cancer and aging can be seen as challenges to the continuous physiological processes that orchestrate individual cell activities toward the anatomical needs of an organism. Thus, the origin and maintenance of complex biological shape is a fundamental question for cell, developmental, and evolutionary biology, as well as for biomedicine. It has long been recognized that slow bioelectrical gradients can control cell behaviors and morphogenesis. Here, I review recent molecular data that implicate endogenous spatio-temporal patterns of resting potentials among non-excitable cells as instructive cues in embryogenesis, regeneration, and cancer. Functional data have implicated gradients of resting potential in processes such as limb regeneration, eye induction, craniofacial patterning, and head-tail polarity, as well as in metastatic transformation and tumorigenesis. The genome is tightly linked to bioelectric signaling, via ion channel proteins that shape the gradients, downstream genes whose transcription is regulated by voltage, and transduction machinery that converts changes in bioelectric state to second-messenger cascades. However, the data clearly indicate that bioelectric signaling is an autonomous layer of control not reducible to a biochemical or genetic account of cell state. The real-time dynamics of bioelectric communication among cells are not fully captured by transcriptomic or proteomic analyses, and the necessary-and-sufficient triggers for specific changes in growth and form can be physiological states, while the underlying gene loci are free to diverge. The next steps in this exciting new field include the development of novel conceptual tools for understanding the anatomical semantics encoded in non-neural bioelectrical networks, and of improved biophysical tools for reading and writing electrical state information into somatic tissues. Cracking the bioelectric code will have transformative implications for developmental biology, regenerative medicine, and synthetic bioengineering.
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Affiliation(s)
- Michael Levin
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
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Nicolson WB, McCann GP, Smith MI, Sandilands AJ, Stafford PJ, Schlindwein FS, Samani NJ, Ng GA. Prospective evaluation of two novel ECG-based restitution biomarkers for prediction of sudden cardiac death risk in ischaemic cardiomyopathy. Heart 2014; 100:1878-85. [DOI: 10.1136/heartjnl-2014-305672] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Nicolson WB, McCann GP, Brown PD, Sandilands AJ, Stafford PJ, Schlindwein FS, Samani NJ, Ng GA. A novel surface electrocardiogram-based marker of ventricular arrhythmia risk in patients with ischemic cardiomyopathy. J Am Heart Assoc 2012; 1:e001552. [PMID: 23130163 PMCID: PMC3487358 DOI: 10.1161/jaha.112.001552] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 05/02/2012] [Indexed: 11/24/2022]
Abstract
Background Better sudden cardiac death risk markers are needed in ischemic cardiomyopathy (ICM). Increased heterogeneity of electrical restitution is an important mechanism underlying the risk of ventricular arrhythmia (VA). Our aim was to develop and test a novel quantitative surface electrocardiogram–based measure of VA risk in patients with ICM: the Regional Restitution Instability Index (R2I2). Methods and Results R2I2, the mean of the standard deviation of residuals from the mean gradient for each ECG lead at a range of diastolic intervals, was measured retrospectively from high-resolution 12-lead ECGs recorded during an electrophysiology study. Patient groups were as follows: Study group, 26 patients with ICM being assessed for implantable defibrillator; Control group, 29 patients with supraventricular tachycardia undergoing electrophysiology study; and Replication group, 40 further patients with ICM. R2I2 was significantly higher in the Study patients than in Controls (mean ± standard error of the mean: 1.09±0.06 versus 0.63±0.04, P<0.001). Over a median follow-up period of 23 months, 6 of 26 Study group patients had VA or death. R2I2 predicted VA or death independently of demographic factors, electrophysiology study result, left ventricular ejection fraction, or QRS duration (Cox model, P=0.029). R2I2 correlated with peri-infarct zone as assessed by cardiac magnetic resonance imaging (r=0.51, P=0.024). The findings were replicated in the Replication group: R2I2 was significantly higher in 11 of 40 Replication patients experiencing VA (1.18±0.10 versus 0.92±0.05, P=0.019). In combined analysis of ICM cohorts, R2I2 ≥1.03 identified subjects with significantly higher risk of VA or death (43%) compared with R2I2 <1.03 (11%) (P=0.004). Conclusions In this pilot study, we have developed a novel VA risk marker, R2I2, and have shown that it correlated with a structural measure of arrhythmic risk and predicted risk of VA or death in patients with ICM. R2I2 may improve risk stratification and merits further evaluation. (J Am Heart Assoc. 2012;1:e001552 doi: 10.1161/JAHA.112.001552.)
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Affiliation(s)
- William B Nicolson
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK (W.B.N., P.D.B., N.J.S., G.A.N.) ; National Institute for Health Research Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester, UK (W.B.N., G.P.M., N.J.S., G.A.N.)
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Biktashev VN, Biktasheva IV, Sarvazyan NA. Evolution of spiral and scroll waves of excitation in a mathematical model of ischaemic border zone. PLoS One 2011; 6:e24388. [PMID: 21935402 PMCID: PMC3174161 DOI: 10.1371/journal.pone.0024388] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 08/08/2011] [Indexed: 11/26/2022] Open
Abstract
Abnormal electrical activity from the boundaries of ischemic cardiac tissue is recognized as one of the major causes in generation of ischemia-reperfusion arrhythmias. Here we present theoretical analysis of the waves of electrical activity that can rise on the boundary of cardiac cell network upon its recovery from ischaemia-like conditions. The main factors included in our analysis are macroscopic gradients of the cell-to-cell coupling and cell excitability and microscopic heterogeneity of individual cells. The interplay between these factors allows one to explain how spirals form, drift together with the moving boundary, get transiently pinned to local inhomogeneities, and finally penetrate into the bulk of the well-coupled tissue where they reach macroscopic scale. The asymptotic theory of the drift of spiral and scroll waves based on response functions provides explanation of the drifts involved in this mechanism, with the exception of effects due to the discreteness of cardiac tissue. In particular, this asymptotic theory allows an extrapolation of 2D events into 3D, which has shown that cells within the border zone can give rise to 3D analogues of spirals, the scroll waves. When and if such scroll waves escape into a better coupled tissue, they are likely to collapse due to the positive filament tension. However, our simulations have shown that such collapse of newly generated scrolls is not inevitable and that under certain conditions filament tension becomes negative, leading to scroll filaments to expand and multiply leading to a fibrillation-like state within small areas of cardiac tissue.
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Affiliation(s)
- Vadim N Biktashev
- Department of Mathematical Sciences, University of Liverpool, Liverpool, United Kingdom.
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14
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Choi BR, Jang W, Salama G. Spatially discordant voltage alternans cause wavebreaks in ventricular fibrillation. Heart Rhythm 2007; 4:1057-68. [PMID: 17675081 PMCID: PMC2137164 DOI: 10.1016/j.hrthm.2007.03.037] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 03/28/2007] [Indexed: 11/20/2022]
Abstract
BACKGROUND Ventricular fibrillation (VF) is characterized by complex ECG patterns emanating from multiple, short-lived, reentrant electrical waves. The incessant breakup and creation of new daughter waves (wavebreaks) perpetuate VF. Dispersion of refractoriness (static or dynamic) has been implicated as a mechanism underlying wavebreaks. OBJECTIVE The purpose of this study was to investigate the mechanisms underlying wavefront instability in VF by localizing wave fractionation sites (the appearance of multiple waves) and their relationship to local spatial dispersion of voltage (V(m)) oscillations. METHODS Wave fractionations were identified by tracking V(m) oscillations optically at unprecedented spatial (100 x 100 pixels) and temporal (2,000 frames per second) resolution using a CMOS camera viewing the surface (1 x 1 cm(2)) of perfused guinea pig hearts (n = 6). VF was induced by burst stimulation, and wavefront dynamics were highlighted using region-based image analysis to automatically detect wavebreaks. Direct detection of wavebreak locations by image analysis was more reliable than the phase reconstruction method because baseline noise obstructed the correct identification of phase singularities by detecting false-positives. RESULTS Wave fractionations (34 +/- 4 splits/s.cm(2)) fell into three categories: decremental conduction (49% +/- 7%), wave collisions (32% +/- 8%), and wavebreaks (17 +/- 2%). Wavebreaks occurred at a frequency of 5.8 +/- 1 splits/s.cm(2) and did not preferentially occur at anatomic obstacles (i.e., coronary vessels) but coincided with discordant alternans where V(m) amplitudes and durations shifted from high to low to from low to high on opposite sides of wavebreak sites. CONCLUSION Spatial discordant alternans cause wavebreaks most likely because they are sites of abrupt dispersion of refractoriness.
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Affiliation(s)
- Bum-Rak Choi
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Woncheol Jang
- Department of Statistics, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Guy Salama
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania
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15
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Pumir A, Arutunyan A, Krinsky V, Sarvazyan N. Genesis of ectopic waves: role of coupling, automaticity, and heterogeneity. Biophys J 2005; 89:2332-49. [PMID: 16055545 PMCID: PMC1366734 DOI: 10.1529/biophysj.105.061820] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many arrhythmias are believed to be triggered by ectopic sources arising from the border of the ischemic tissue. However, the development of ectopic activity from individual sources to a larger mass of cardiac tissue remains poorly understood. To address this critical issue, we used monolayers of neonatal rat cardiomyocytes to create conditions that promoted progression of ectopic activity from single cells to the network that consisted of hundreds of cells. To explain complex spatiotemporal patterns observed in these experiments we introduced a new theoretical framework. The framework's main feature is a parameter space diagram, which uses cell automaticity and coupling as two coordinates. The diagram allows one to depict network behavior, quantitatively address the heterogeneity factor, and evaluate transitions between different regimes. The well-organized wave trains were observed at moderate and high cell coupling values and network heterogeneity was found to be qualitatively unimportant for these regimes. In contrast, at lower values of coupling, spontaneous ectopic activity led to the appearance of fragmented ectopic waves. For these regimes, network heterogeneity played an essential role. The ectopic waves occasionally gave rise to spiral activity in two different regions within the parameter space via two distinct mechanisms. Together, our results suggest that localized ectopic waves represent an essential step in the progression of ectopic activity. These studies add to the understanding of initiation and progression of arrhythmias and can be applied to other phenomena that deal with assemblies of coupled oscillators.
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Affiliation(s)
- Alain Pumir
- Institut Non-Lineaire de Nice, Valbonne, France
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16
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Kimura H, Kawahara K, Yamauchi Y, Miyaki J. On the mechanisms for the conversion of ventricular fibrillation to tachycardia by perfusion with ruthenium red. J Electrocardiol 2005; 38:364-70. [PMID: 16216614 DOI: 10.1016/j.jelectrocard.2005.05.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Revised: 04/24/2005] [Accepted: 05/09/2005] [Indexed: 11/19/2022]
Abstract
We have recently demonstrated that during pacing-induced sustained ventricular fibrillation (VF), perfusion of the heart with either ruthenium red (RR) or Ru 360, blockers of the mitochondrial Ca2+ uniporter, resulted in the reversible conversion of VF to ventricular tachycardia (VT). Here, we aimed at elucidating the electrophysiological mechanisms for the RR-induced conversion of VF to VT. The experiments were performed using Langendorff-perfused isolated rat hearts in which left ventricular pressure and left ventricular intracellular action potential were recorded. Perfusion with either RR or Ru 360 resulted in decreases in the action potential duration (APD), refractory period, and slope of APD restitution curves. These changes were antagonized by cotreatment with S(-)-Bay K8644. In addition, perfusion with verapamil produced the decreases in APD at 90% repolarization, refractory period and slope of APD restitution curves similar to the RR or Ru 360 perfusion. Such electrophysiological changes may be responsible for the reversible conversion of sustained VF to VT caused by perfusion with RR or Ru 360.
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Affiliation(s)
- Hiroyuki Kimura
- Laboratory of Cellular Cybernetics, Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan
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17
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Choi BR, Liu T, Salama G. Adaptation of Cardiac Action Potential Durations to Stimulation History with Random Diastolic Intervals. J Cardiovasc Electrophysiol 2004; 15:1188-97. [PMID: 15485446 DOI: 10.1046/j.1540-8167.2004.04070.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
INTRODUCTION The restitution hypothesis proposes that adaptation of cardiac action potential duration (APD) to rate changes is a predictor of ventricular fibrillation (VF). Conventional restitution kinetics plots the APD of a premature beat as a function of the previous diastolic interval (DI), and VF vulnerability is related to how rapidly APD shortens with decreasing DI. However, APD depends not only on the previous DI but also on the history of previous APDs and DIs. For a comprehensive understanding of APD restitution, we developed a random stimulation protocol and curve fitted each APD with the previous DIs and APDs using multiple autoregressive analyses. METHODS AND RESULTS Guinea pig hearts (n = 5) were perfused and stained with di-4 ANEPPS to record optical APs from 252 sites. Activation and repolarization times were detected in real time from one pixel and hearts were stimulated at random DIs (range 0-50 or 0-100 ms). We found that the first, second, and third previous APDs and DIs are required to obtain the best curve fit, which provides the most significant feedback control to APD and up to six previous beats contributed to curve fits (R > 0.8). The coefficients relating the previous DI to APD increased systematically in going from apex to base reflecting the intrinsic gradient of APD across the epicardium. CONCLUSION Random restitution is more comprehensive than steady-state restitution, being based on random and dynamic DIs, and makes possible characterization of restitution in only 32 seconds to track changes in restitution during time-varying conditions such as ischemia/reperfusion.
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Affiliation(s)
- Bum-Rak Choi
- Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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18
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19
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Fossa AA, Wisialowski T, Wolfgang E, Wang E, Avery M, Raunig DL, Fermini B. Differential effect of HERG blocking agents on cardiac electrical alternans in the guinea pig. Eur J Pharmacol 2004; 486:209-21. [PMID: 14975710 DOI: 10.1016/j.ejphar.2003.12.028] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2003] [Accepted: 12/19/2003] [Indexed: 11/18/2022]
Abstract
Beat-to-beat alternations of the cardiac monophasic action potential, known as electrical alternans, were studied at drug concentrations that have known arrhythmogenic outcomes. Electrical alternans were elicited from the heart of anesthetized guinea pigs, both in the absence and presence of drugs that inhibit the delayed rectifier K(+) channel encoded by the human ether a-go-go related-gene (HERG), and are associated with the fatal arrhythmia, Torsade de Pointes. Two other HERG inhibiting drugs not associated with Torsade de Pointes were also studied. At concentrations known to be proarrhythmic, E-4031 and bepridil increased mean alternans 10 and 40 ms at pacing frequencies </=160 ms. Terfenadine and cisapride both increased mean alternans up to 20 and 21 ms, respectively, at pacing frequencies of </=150 ms. On the other hand, verapamil and risperidone showed no increase in mean alternans while risperidone significantly reduced alternans at concentrations up to 74 times its therapeutic level. The magnitude of effect on rate-dependent alternans may allow the differentiation of proarrhythmia and non-arrhythmic HERG blockers at clinically relevant concentrations.
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Affiliation(s)
- Anthony A Fossa
- Pfizer Global Research and Development, Eastern Point Rd., Bldg. 118, MS 4036 Groton, CT 06340, USA.
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20
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Abstract
Sudden cardiac death, secondary to ventricular fibrillation (VF), remains the leading cause of death in the USA. Recent experimental and theoretical studies suggest that VF could be caused by spiral wave re-entry. The initiation and subsequent break-up of spiral waves has been linked to electrical alternans, a phenomenon produced in cardiac tissue that has a steeply sloped restitution relation. Agents that reduce the slope of the restitution relation have been shown to suppress alternans and, presumably by that mechanism, terminate VF. These results suggest that electrical restitution could be a promising new target for antiarrhythmic therapies.
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Affiliation(s)
- Robert F Gilmour
- Dept of Biomedical Sciences, T7 012C VRT, Cornell University, Ithaca, NY 14853-6401, USA.
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He D, Hu G, Zhan M, Ren W, Gao Z. Pattern formation of spiral waves in an inhomogeneous medium with small-world connections. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:055204. [PMID: 12059631 DOI: 10.1103/physreve.65.055204] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2001] [Indexed: 05/23/2023]
Abstract
Pattern formation of spiral waves in an inhomogeneous excitable medium with small-world connections is investigated. In both cases, with completely local regular connections and with completely random connections, spiral waves cannot survive in the given inhomogeneous medium. It is found that with small-world connections (basically local connections plus a small number of random connections) a well behaved spiral wave can be formed against the destructive role of the inhomogeneous medium. There also exists an optimal fraction of random connections which can greatly enhance the probability of spiral wave formation; this resembles the behavior of stochastic resonance.
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Affiliation(s)
- Daihai He
- Department of Physics, Beijing Normal University, Beijing, 100875, China
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22
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Amann A, Achleitner U, Antretter H, Bonatti JO, Krismer AC, Lindner KH, Rieder J, Wenzel V, Voelckel WG, Strohmenger HU. Analysing ventricular fibrillation ECG-signals and predicting defibrillation success during cardiopulmonary resuscitation employing N(alpha)-histograms. Resuscitation 2001; 50:77-85. [PMID: 11719133 DOI: 10.1016/s0300-9572(01)00322-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mean fibrillation frequency may predict defibrillation success during cardiopulmonary resuscitation (CPR). N(alpha)-histogram analysis should be investigated as an alternative. After 4 min of cardiac arrest, and 3 versus 8 min of CPR, 25 pigs received either vasopressin or epinephrine (0.4, 0.4, and 0.8 U/kg vasopressin versus 45, 45, and 200 microg/kg epinephrine) every 5 min with defibrillation at 22 min. Before defibrillation, the N(alpha)-parameter histogramstart/histogramwidth and the mean fibrillation frequency in resuscitated versus non-resuscitated pigs were 2.9+/-0.4 versus 1.7+/-0.5 (P=0.0000005); and 9.5+/-1.7 versus 6.9+/-0.7 (P=0.0003). During the last minute prior to defibrillation, histogramstart/histogramwidth of > or =2.3 versus mean fibrillation frequency > or =8 Hz predicted successful defibrillation with subsequent return of a spontaneous circulation for more than 60 min with sensitivity, specificity, positive predictive value and negative predictive value of 94 versus 82%, 96 versus 89%, 98 versus 93% and 90 versus 74%, respectively. We conclude, that N(alpha)-analysis was superior to mean fibrillation frequency analysis during CPR in predicting defibrillation success, and distinction between vasopressin versus epinephrine effects.
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Affiliation(s)
- A Amann
- Department of Anesthesiology and Critical Care, The Leopold-Franzens University, Anichstrasse 35, 6020, Innsbruck, Austria
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23
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Abstract
The spatial and dynamic properties of ventricular fibrillation (VF) may be random or related to cellular electrical properties of the normal heart. Local activation intervals (AIs) in VF may depend on the local refractory period (RP), and sustained VF may require a steep action potential (AP) restitution curve. In guinea pig hearts, AP durations (APDs) and RPs on the epicardium are shorter at the apex and progressively longer toward the base, producing gradients of RPs that may influence the spatial organization of VF. In the present study, the influence of APDs on VF dynamics is investigated in perfused guinea pig hearts stained with a voltage-sensitive dye by comparing APD gradients to the dynamics of VF elicited by burst pacing. In VF, AIs had no clear periodicity, but average AIs were shorter at the apex (57.5+/-8.1 ms) than the base (76.1+/-1.5 ms, n=6, P<0.05) and had gradients similar to APD gradients (correlation coefficient 0.71+/-0.04). Analysis of local velocity vectors showed no preferential directions, and fast Fourier transform (FFT) power spectra were broad (10 to 24 Hz) with multiple peaks (n=6). However, the selective inhibition of delayed K(+) rectifying currents, I(Kr) (E4031; 0.5 micromol/L, n=3), shifted FFT spectra from complex to a lower dominant frequency (10 Hz) and altered repolarization but retained the correlation between mean AIs and RPs. Thus, VF dynamics are consistent with a multiple wave-make and wave-break mechanism, and the local RP influences VF dynamics by limiting the range of VF frequencies and AIs at each site. The full text of this article is available at http://www.circresaha.org.
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Affiliation(s)
- B R Choi
- University of Pittsburgh, School of Medicine, 3500 Terrace St, S314 Biomedical Science Tower, Pittsburgh, PA 15261, USA
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24
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Qu Z, Kil J, Xie F, Garfinkel A, Weiss JN. Scroll wave dynamics in a three-dimensional cardiac tissue model: roles of restitution, thickness, and fiber rotation. Biophys J 2000; 78:2761-75. [PMID: 10827961 PMCID: PMC1300866 DOI: 10.1016/s0006-3495(00)76821-4] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Scroll wave (vortex) breakup is hypothesized to underlie ventricular fibrillation, the leading cause of sudden cardiac death. We simulated scroll wave behaviors in a three-dimensional cardiac tissue model, using phase I of the Luo-Rudy (LR1) action potential model. The effects of action potential duration (APD) restitution, tissue thickness, filament twist, and fiber rotation were studied. We found that APD restitution is the major determinant of scroll wave behavior and that instabilities arising from APD restitution are the main determinants of scroll wave breakup in this cardiac model. We did not see a "thickness-induced instability" in the LR1 model, but a minimum thickness is required for scroll breakup in the presence of fiber rotation. The major effect of fiber rotation is to maintain twist in a scroll wave, promoting filament bending and thus scroll breakup. In addition, fiber rotation induces curvature in the scroll wave, which weakens conduction and further facilitates wave break.
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Affiliation(s)
- Z Qu
- Department of Medicine (Cardiology), University of California, Los Angeles 90095, USA.
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25
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Callaway CW, Sherman LD, Scheatzle MD, Menegazzi JJ. Scaling structure of electrocardiographic waveform during prolonged ventricular fibrillation in swine. Pacing Clin Electrophysiol 2000; 23:180-91. [PMID: 10709226 DOI: 10.1111/j.1540-8159.2000.tb00799.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ventricular fibrillation (VF) is the most common arrhythmia causing sudden cardiac death. However, the likelihood of successful defibrillation declines with increasing duration of VF. Because the morphology of the electrocardiogram (ECG) waveform during VF also changes with time, this study examined a new measure that describes the VF waveform and distinguishes between early and late VF. Surface ECG recordings were digitized at 200 samples/s from nine swine with induced VF. A new measure called the scaling exponent was calculated by examining the power-law relationship between the summation of amplitudes of a 1,024-point (5.12 second) waveform segment and the time scale of measurement. The scaling exponent is a local estimate of the fractal dimension of the ECG waveform. A consistent power-law relationship was observed for measurement time scales of 0.005-0.040 seconds. Calculation of the scaling exponent produced similar results between subjects, and distinguished early VF (< 4-minute duration) from late VF (> or = 4-minute duration). The scaling exponent was dependent on the order of the data, supporting the hypothesis that the surface ECG during VF is a deterministic rather than a random signal. The waveform of VF results from the interaction of multiple fronts of depolarization within the heart, and may be described using the tools of nonlinear dynamics. As a quantitative descriptor of waveform structure, the scaling exponent characterizes the time dependent organization of VF.
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Affiliation(s)
- C W Callaway
- Department of Emergency Medicine, University of Pittsburgh, PA 15213, USA.
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26
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Koller ML, Riccio ML, Gilmour RF. Dynamic restitution of action potential duration during electrical alternans and ventricular fibrillation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:H1635-42. [PMID: 9815071 DOI: 10.1152/ajpheart.1998.275.5.h1635] [Citation(s) in RCA: 200] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The restitution kinetics of action potential duration (APD) were investigated in paced canine Purkinje fibers (P; n = 9) and endocardial muscle (M; n = 9), in isolated, perfused canine left ventricles during ventricular fibrillation (VF; n = 4), and in endocardial muscle paced at VF cycle lengths (simulated VF; n = 4). Restitution was assessed with the use of two protocols: delivery of a single extrastimulus after a train of stimuli at cycle length = 300 ms (standard protocol), and fixed pacing at short cycle lengths (100-300 ms) that induced APD alternans (dynamic protocol). The dynamic protocol yielded a monotone increasing restitution function with a maximal slope of 1.13 +/- 0.13 in M and 1.14 +/- 0.17 in P. Iteration of this function reproduced the APD dynamics found experimentally, including persistent APD alternans. In contrast, the standard protocol yielded a restitution relation with a maximal slope of 0.57 +/- 0.18 in M and 0.84 +/- 0.20 in P, and iteration of this function did not reproduce the APD dynamics. During VF, the restitution kinetics at short diastolic interval were similar to those determined with the dynamic protocol (maximal slope: 1.72 +/- 0.47 in VF and 1.44 +/- 0.49 in simulated VF). Thus APD dynamics at short coupling intervals during fixed pacing and during VF were accounted for by the dynamic, but not the standard, restitution relation. These results provide further evidence for a strong relationship among the kinetics of electrical restitution, the occurrence of APD alternans, and complex APD dynamics during VF.
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Affiliation(s)
- M L Koller
- Department of Physiology, Cornell University, Ithaca, New York 14853-6401, USA
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