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Wang L, Liu S, Zhao W, Li J, Zeng H, Kang S, Sheng X, Wang L, Fan Y, Yin L. Recent Advances in Implantable Neural Interfaces for Multimodal Electrical Neuromodulation. Adv Healthc Mater 2024; 13:e2303316. [PMID: 38323711 DOI: 10.1002/adhm.202303316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 01/29/2024] [Indexed: 02/08/2024]
Abstract
Electrical neuromodulation plays a pivotal role in enhancing patient outcomes among individuals suffering from neurological disorders. Implantable neural interfaces are vital components of the electrical neuromodulation system to ensure desirable performance; However, conventional devices are limited to a single function and are constructed with bulky and rigid materials, which often leads to mechanical incompatibility with soft tissue and an inability to adapt to the dynamic and complex 3D structures of biological systems. In addition, current implantable neural interfaces utilized in clinical settings primarily rely on wire-based techniques, which are associated with complications such as increased risk of infection, limited positioning options, and movement restrictions. Here, the state-of-art applications of electrical neuromodulation are presented. Material schemes and device structures that can be employed to develop robust and multifunctional neural interfaces, including flexibility, stretchability, biodegradability, self-healing, self-rolling, or morphing are discussed. Furthermore, multimodal wireless neuromodulation techniques, including optoelectronics, mechano-electrics, magnetoelectrics, inductive coupling, and electrochemically based self-powered devices are reviewed. In the end, future perspectives are given.
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Affiliation(s)
- Liu Wang
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Shengnan Liu
- School of Materials Science and Engineering, The Key Laboratory of Advanced Materials of Ministry of Education, State Key Laboratory of New Ceramics and Fine Processing, Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China
| | - Wentai Zhao
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Jiakun Li
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Haoxuan Zeng
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Shaoyang Kang
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Xing Sheng
- Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology, Institute for Precision Medicine, Laboratory of Flexible Electronics Technology, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, 100084, China
| | - Lizhen Wang
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Yubo Fan
- Key Laboratory of Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, P. R. China
| | - Lan Yin
- School of Materials Science and Engineering, The Key Laboratory of Advanced Materials of Ministry of Education, State Key Laboratory of New Ceramics and Fine Processing, Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China
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Koneru JN, Ellenbogen KA. First Among Equals?: Is Left Bundle Branch Pacing Superior to Biventricular Pacing for Heart Failure? JACC Clin Electrophysiol 2023; 9:1582-1584. [PMID: 37227341 DOI: 10.1016/j.jacep.2023.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/26/2023]
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Roth BJ. Bidomain modeling of electrical and mechanical properties of cardiac tissue. BIOPHYSICS REVIEWS 2021; 2:041301. [PMID: 38504719 PMCID: PMC10903405 DOI: 10.1063/5.0059358] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 10/15/2021] [Indexed: 03/21/2024]
Abstract
Throughout the history of cardiac research, there has been a clear need to establish mathematical models to complement experimental studies. In an effort to create a more complete picture of cardiac phenomena, the bidomain model was established in the late 1970s to better understand pacing and defibrillation in the heart. This mathematical model has seen ongoing use in cardiac research, offering mechanistic insight that could not be obtained from experimental pursuits. Introduced from a historical perspective, the origins of the bidomain model are reviewed to provide a foundation for researchers new to the field and those conducting interdisciplinary research. The interplay of theory and experiment with the bidomain model is explored, and the contributions of this model to cardiac biophysics are critically evaluated. Also discussed is the mechanical bidomain model, which is employed to describe mechanotransduction. Current challenges and outstanding questions in the use of the bidomain model are addressed to give a forward-facing perspective of the model in future studies.
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Affiliation(s)
- Bradley J. Roth
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
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Padala SK, Master VM, Terricabras M, Chiocchini A, Garg A, Kron J, Shepard R, Kalahasty G, Azizi Z, Tsang B, Khaykin Y, Pantano A, Koneru JN, Ellenbogen KA, Verma A. Initial Experience, Safety, and Feasibility of Left Bundle Branch Area Pacing. JACC Clin Electrophysiol 2020; 6:1773-1782. [DOI: 10.1016/j.jacep.2020.07.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/19/2020] [Accepted: 07/05/2020] [Indexed: 02/01/2023]
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Chiou YA, Cheng LK, Lin SF. Effects of high-frequency biphasic shocks on ventricular vulnerability and defibrillation outcomes through synchronized virtual electrode responses. PLoS One 2020; 15:e0232529. [PMID: 32357163 PMCID: PMC7194403 DOI: 10.1371/journal.pone.0232529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 04/16/2020] [Indexed: 11/19/2022] Open
Abstract
Electrical defibrillation is a well-established treatment for cardiac dysrhythmias. Studies have suggested that shock-induced spatial sawtooth patterns and virtual electrodes are responsible for defibrillation efficacy. We hypothesize that high-frequency shocks enhance defibrillation efficacy by generating temporal sawtooth patterns and using rapid virtual electrodes synchronized with shock frequency. High-speed optical mapping was performed on isolated rat hearts at 2000 frames/s. Two defibrillation electrodes were placed on opposite sides of the ventricles. An S1-S2 pacing protocol was used to induce ventricular tachyarrhythmia (VTA). High-frequency shocks of equal energy but varying frequencies of 125–1000 Hz were used to evaluate VTA vulnerability and defibrillation success rate. The 1000-Hz shock had the highest VTA induction rate in the shorter S1-S2 intervals (50 and 100 ms) and the highest VTA defibrillation rate (70%) among all frequencies. Temporal sawtooth patterns and synchronous shock-induced virtual electrode responses could be observed with frequencies of up to 1000 Hz. The improved defibrillation outcome with high-frequency shocks suggests a lower energy requirement than that of low-frequency shocks for successful ventricular defibrillation.
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Affiliation(s)
- Yu-An Chiou
- Department of Electrical and Computer Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
| | - Li-Kuan Cheng
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
| | - Shien-Fong Lin
- Department of Electrical and Computer Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
- * E-mail:
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Levin M, Pezzulo G, Finkelstein JM. Endogenous Bioelectric Signaling Networks: Exploiting Voltage Gradients for Control of Growth and Form. Annu Rev Biomed Eng 2017; 19:353-387. [PMID: 28633567 PMCID: PMC10478168 DOI: 10.1146/annurev-bioeng-071114-040647] [Citation(s) in RCA: 142] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Living systems exhibit remarkable abilities to self-assemble, regenerate, and remodel complex shapes. How cellular networks construct and repair specific anatomical outcomes is an open question at the heart of the next-generation science of bioengineering. Developmental bioelectricity is an exciting emerging discipline that exploits endogenous bioelectric signaling among many cell types to regulate pattern formation. We provide a brief overview of this field, review recent data in which bioelectricity is used to control patterning in a range of model systems, and describe the molecular tools being used to probe the role of bioelectrics in the dynamic control of complex anatomy. We suggest that quantitative strategies recently developed to infer semantic content and information processing from ionic activity in the brain might provide important clues to cracking the bioelectric code. Gaining control of the mechanisms by which large-scale shape is regulated in vivo will drive transformative advances in bioengineering, regenerative medicine, and synthetic morphology, and could be used to therapeutically address birth defects, traumatic injury, and cancer.
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Affiliation(s)
- Michael Levin
- Biology Department, Tufts University, Medford, Massachusetts 02155-4243;
- Allen Discovery Center, Tufts University, Medford, Massachusetts 02155;
| | - Giovanni Pezzulo
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome 00185, Italy;
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Wu F, Wang C, Xu Y, Ma J. Model of electrical activity in cardiac tissue under electromagnetic induction. Sci Rep 2016; 6:28. [PMID: 28442705 PMCID: PMC5431370 DOI: 10.1038/s41598-016-0031-2] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 10/31/2016] [Indexed: 11/09/2022] Open
Abstract
Complex electrical activities in cardiac tissue can set up time-varying electromagnetic field. Magnetic flux is introduced into the Fitzhugh-Nagumo model to describe the effect of electromagnetic induction, and then memristor is used to realize the feedback of magnetic flux on the membrane potential in cardiac tissue. It is found that a spiral wave can be triggered and developed by setting specific initials in the media, that is to say, the media still support the survival of standing spiral waves under electromagnetic induction. Furthermore, electromagnetic radiation is considered on this model as external stimuli, it is found that spiral waves encounter breakup and turbulent electrical activities are observed, and it can give guidance to understand the occurrence of sudden heart disorder subjected to heavily electromagnetic radiation.
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Affiliation(s)
- Fuqiang Wu
- Department of Physics, Lanzhou University of Technology, Lanzhou, 730050, China
| | - Chunni Wang
- Department of Physics, Lanzhou University of Technology, Lanzhou, 730050, China
| | - Ying Xu
- Department of Physics, Lanzhou University of Technology, Lanzhou, 730050, China
| | - Jun Ma
- Department of Physics, Lanzhou University of Technology, Lanzhou, 730050, China.
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Dura B, Chen MQ, Inan OT, Kovacs GTA, Giovangrandi L. High-frequency electrical stimulation of cardiac cells and application to artifact reduction. IEEE Trans Biomed Eng 2012; 59:1381-90. [PMID: 22345525 DOI: 10.1109/tbme.2012.2188136] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A novel modality for the electrical stimulation of cardiac cells is described. The technique is based on HF stimulation-burst of HF (1-25 kHz) biphasic square waves-to depolarize the cells and trigger action potentials (APs). HF stimulation was demonstrated in HL-1 cardiomyocyte cultures using microelectrode arrays, and the underlying mechanisms were investigated using single-cell model simulations. Current thresholds for HF stimulation increased at higher frequencies or shorter burst durations, and were typically higher than thresholds for single biphasic pulses. Nonetheless, owing to the decreasing impedance of metal electrodes with increasing frequencies, HF bursts resulted in reduced electrode voltages (up to four fold). Such lowered potentials might be beneficial in reducing the probability of irreversible electrochemical reactions and tissue damage, especially for long-term stimulation. More significantly, stimulation at frequencies higher than the upper limit of the AP power spectrum allows effective artifact reduction by low-pass filtering. Shaping of the burst envelope provides further reduction of the remaining artifact. This ability to decouple extracellular stimulation and recording in the frequency domain allowed detection of APs during stimulation-something previously not achievable to the best of our knowledge.
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Affiliation(s)
- Burak Dura
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
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Levin M, Stevenson CG. Regulation of cell behavior and tissue patterning by bioelectrical signals: challenges and opportunities for biomedical engineering. Annu Rev Biomed Eng 2012; 14:295-323. [PMID: 22809139 PMCID: PMC10472538 DOI: 10.1146/annurev-bioeng-071811-150114] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Achieving control over cell behavior and pattern formation requires molecular-level understanding of regulatory mechanisms. Alongside transcriptional networks and biochemical gradients, there functions an important system of cellular communication and control: transmembrane voltage gradients (V(mem)). Bioelectrical signals encoded in spatiotemporal changes of V(mem) control cell proliferation, migration, and differentiation. Moreover, endogenous bioelectrical gradients serve as instructive cues mediating anatomical polarity and other organ-level aspects of morphogenesis. In the past decade, significant advances in molecular physiology have enabled the development of new genetic and biophysical tools for the investigation and functional manipulation of bioelectric cues. Recent data implicate V(mem) as a crucial epigenetic regulator of patterning events in embryogenesis, regeneration, and cancer. We review new conceptual and methodological developments in this fascinating field. Bioelectricity offers a novel way of quantitatively understanding regulation of growth and form in vivo, and it reveals tractable, powerful control points that will enable truly transformative applications in bioengineering, regenerative medicine, and synthetic biology.
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Affiliation(s)
- Michael Levin
- Department of Biology, Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts 02155, USA.
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Bishop MJ, Boyle PM, Plank G, Welsh DG, Vigmond EJ. Modeling the role of the coronary vasculature during external field stimulation. IEEE Trans Biomed Eng 2010; 57:2335-45. [PMID: 20542762 PMCID: PMC2976591 DOI: 10.1109/tbme.2010.2051227] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The exact mechanisms by which defibrillation shocks excite cardiac tissue far from both the electrodes and heart surfaces require elucidation. Bidomain theory explains this phenomena through the existence of intramural virtual electrodes (VEs), caused by discontinuities in myocardial tissue structure. In this study, we assess the modeling components essential in constructing a finite-element cardiac tissue model including blood vessels from high-resolution magnetic resonance data and investigate the specific role played by coronary vasculature in VE formation, which currently remains largely unknown. We use a novel method for assigning histologically based fiber architecture around intramural structures and include an experimentally derived vessel lumen wall conductance within the model. Shock-tissue interaction in the presence of vessels is assessed through comparison with a simplified model lacking intramural structures. Results indicate that VEs form around blood vessels for shocks > 8 V/cm. The magnitude of induced polarizations is attenuated by realistic representation of fiber negotiation around vessel cavities, as well as the insulating effects of the vessel lumen wall. Furthermore, VEs formed around large subepicardial vessels reduce epicardial polarization levels. In conclusion, we have found that coronary vasculature acts as an important substrate for VE formation, which may help interpretation of optical mapping data.
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Affiliation(s)
- Martin J Bishop
- Computing Laboratory, University of Oxford, Oxford, OX1 3QD, UK.
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Abstract
Electrical shock has been the one effective treatment for ventricular fibrillation for several decades. With the advancement of electrical and optical mapping techniques, histology, and computer modeling, the mechanisms responsible for defibrillation are now coming to light. In this review, we discuss recent work that demonstrates the various mechanisms responsible for defibrillation. On the cellular level, membrane depolarization and electroporation affect defibrillation outcome. Cell bundles and collagenous septae are secondary sources and cause virtual electrodes at sites far from shocking electrodes. On the whole-heart level, shock field gradient and critical points determine whether a shock is successful or whether reentry causes initiation and continuation of fibrillation.
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Affiliation(s)
- Derek J Dosdall
- Departments of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
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Vančura V, Wichterle D, Brabec M, Bytešník J, Lefflerová K, Kautzner J. The relationship between right ventricular pacing voltage and QRS complex duration. Physiol Meas 2009; 30:517-27. [DOI: 10.1088/0967-3334/30/5/008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Mashburn DN, Hinkson SJ, Woods MC, Gilligan JM, Holcomb MR, Wikswo JP. A high-voltage cardiac stimulator for field shocks of a whole heart in a bath. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:104302. [PMID: 17979442 DOI: 10.1063/1.2796832] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Defibrillators are a critical tool for treating heart disease; however, the mechanisms by which they halt fibrillation are still not fully understood and are the subject of ongoing research. Clinical defibrillators do not provide the precise control of shock timing, duration, and voltage or other features needed for detailed scientific inquiry, and there are few, if any, commercially available units designed for research applications. For this reason, we have developed a high-voltage, programmable, capacitive-discharge stimulator optimized to deliver defibrillation shocks with precise timing and voltage control to an isolated animal heart, either in air or in a bath. This stimulator is capable of delivering voltages of up to 500 V and energies of nearly 100 J with timing accuracy of a few microseconds and with rise and fall times of 5 micros or less and is controlled only by two external timing pulses and a control computer that sets the stimulation parameters via a LABVIEW interface. Most importantly, the stimulator has circuits to protect the high-voltage circuitry and the operator from programming and input-output errors. This device has been tested and used successfully in field shock experiments on rabbit hearts as well as other protocols requiring high voltage.
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Affiliation(s)
- David N Mashburn
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
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14
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Cardiac Electrophysiology. Bioelectricity 2007. [DOI: 10.1007/978-0-387-48865-3_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Abstract
OBJECTIVES The definition of defibrillation shock "success" endorsed by the International Liaison Committee on Resuscitation since the publication of Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiac Care has been removal of ventricular fibrillation at 5 secs after shock delivery. Although this success criterion provides a direct assessment of the primary task of a shock, it may not be the only clinically useful measure of shock outcome. We evaluated a different defibrillation success criterion to determine whether it could provide additional insight into the relative performance of different defibrillation shocks. DESIGN A randomized study comparing monophasic and biphasic waveform shocks is reported with return of organized rhythm as the primary outcome measure of defibrillation success. PATIENTS A total of 120 patients with out-of-hospital ventricular fibrillation as the first recorded rhythm were treated with defibrillation with automated external defibrillators. MEASUREMENTS AND MAIN RESULTS Return of organized rhythm (two QRS complexes, <5 secs apart, <60 secs after defibrillation) was achieved in 31 monophasic shock (45%) and 35 biphasic shock (69%) patients (relative risk, 1.53, 95% confidence interval, 1.11-2.10). Logistic regression analysis revealed that shock waveform was the strongest independent predictor of return of organized rhythm (odds ratio, 4.0; 95% confidence interval, 1.67-10.0). Defibrillation success with the conventional International Liaison Committee on Resuscitation criterion was very high (91% and 98%, respectively) and not significantly different between groups. CONCLUSIONS Return of organized rhythm proved to be a more sensitive measure of relative defibrillation shock performance than the conventional shock success criterion. Inclusion of return of organized rhythm as an end point in future clinical research could help discern more subtle defibrillation shock effects and contribute to further optimization of defibrillation technology.
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Affiliation(s)
- Rudolph W Koster
- Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands
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16
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Trew M, Le Grice I, Smaill B, Pullan A. A Finite Volume Method for Modeling Discontinuous Electrical Activation in Cardiac Tissue. Ann Biomed Eng 2005; 33:590-602. [PMID: 15981860 DOI: 10.1007/s10439-005-1434-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper describes a finite volume method for modeling electrical activation in a sample of cardiac tissue using the bidomain equations. Microstructural features to the level of cleavage planes between sheets of myocardial fibers in the tissue are explicitly represented. The key features of this implementation compared to previous modeling are that it represents physical discontinuities without the implicit removal of intracellular volume and it generates linear systems of equations that are computationally efficient to construct and solve. Results obtained using this method highlight how the understanding of discontinuous activation in cardiac tissue can form a basis for better understanding defibrillation processes and experimental recordings.
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Affiliation(s)
- Mark Trew
- Bioengineering Institute, The University of Auckland, New Zealand.
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Ashihara T, Trayanova NA. Asymmetry in membrane responses to electric shocks: insights from bidomain simulations. Biophys J 2005; 87:2271-82. [PMID: 15454429 PMCID: PMC1304652 DOI: 10.1529/biophysj.104.043091] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Models of myocardial membrane dynamics have not been able to reproduce the experimentally observed negative bias in the asymmetry of transmembrane potential changes (DeltaVm) induced by strong electric shocks delivered during the action potential plateau. The goal of this study is to determine what membrane model modifications can bridge this gap between simulation and experiment. We conducted simulations of shocks in bidomain fibers and sheets with membrane dynamics represented by the LRd'2000 model. We found that in the fiber, the negative bias in DeltaVm asymmetry could not be reproduced by addition of electroporation only, but by further addition of hypothetical outward current, Ia, activated upon strong shock-induced depolarization. Furthermore, the experimentally observed rectangularly shaped positive DeltaVm, negative-to-positive DeltaVm ratio (asymmetry ratio) = approximately 2, electroporation occurring at the anode only, and the increase in positive DeltaVm caused by L-type Ca2+-channel blockade were reproduced in the strand only if Ia was assumed to be a part of K+ flow through the L-type Ca2+-channel. In the sheet, Ia not only contributed to the negative bias in DeltaVm asymmetry at sites polarized by physical and virtual electrodes, but also restricted positive DeltaVm. Inclusion of Ia and electroporation is thus the bridge between experiment and simulation.
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Affiliation(s)
- Takashi Ashihara
- Department of Biomedical Engineering, Tulane University, New Orleans, Louisiana 70118, USA.
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Kuijpers NHL, Keldermann RH, Arts T, Hilbers PAJ. Computer simulations of successful defibrillation in decoupled and non-uniform cardiac tissue. ACTA ACUST UNITED AC 2005; 7 Suppl 2:166-77. [PMID: 16102514 DOI: 10.1016/j.eupc.2005.03.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Revised: 02/03/2005] [Accepted: 05/03/2005] [Indexed: 11/19/2022]
Abstract
Abstract
Aim
The aim of the present study is to investigate the origin and effect of virtual electrode polarization in uniform, decoupled and non-uniform cardiac tissue during field stimulation.
Methods
A discrete bidomain model with active membrane behaviour was used to simulate normal cardiac tissue as well as cardiac tissue that is decoupled due to fibrosis and gap junction remodelling. Various uniform and non-uniform electric fields were applied to the external domain of uniform, decoupled and non-uniform resting cardiac tissue as well as cardiac tissue in which spiral waves were induced.
Results
Field stimulation applied on non-uniform tissue results in more virtual electrodes compared with uniform tissue. The spiral waves were terminated in decoupled tissue, but not in uniform, homogeneous tissue. By gradually increasing local differences in intracellular conductivities, the amount and spread of virtual electrodes increased and the spiral waves were terminated.
Conclusion
Fast depolarization of the tissue after field stimulation may be explained by intracellular decoupling and spatial heterogeneity present in normal and pathological cardiac tissue. We demonstrated that termination of spiral waves by means of field stimulation can be achieved when the tissue is modelled as a non-uniform, anisotropic bidomain with active membrane behaviour.
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Affiliation(s)
- N H L Kuijpers
- Department of Biomedical Engineering, Technische Universiteit Eindhoven, The Netherlands.
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Pak HN, Liu YB, Hayashi H, Okuyama Y, Chen PS, Lin SF. Synchronization of ventricular fibrillation with real-time feedback pacing: implication to low-energy defibrillation. Am J Physiol Heart Circ Physiol 2003; 285:H2704-11. [PMID: 12893637 DOI: 10.1152/ajpheart.00366.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Wavefront synchronization is an important aspect preceding the termination of ventricular fibrillation (VF). We evaluated the defibrillation efficacy of a novel multisite pacing algorithm using optical recording-guided synchronized pacing (SyncP) in the excitable gaps. We compared the effects of SyncP with traditional overdrive pacing (ODP) at 90% of the VF cycle length (VFCL) and high-frequency pacing (HFP; 43-215 Hz) on spontaneous VF termination in isolated rabbit hearts. For SyncP, the pacing current was triggered by the activation of a reference site and was delivered when the optical potential of the pacing site was in an excitable gap. We measured VFCL and the spatial dispersion of VFCL (SDCL) from five points (3 points in the paced area and 2 points in the nonpaced area) and the distribution of phase singularities during the prepacing, pacing, and postpacing periods. The results showed that 1) the VF termination rate of SyncP (16.0%, n = 106) was higher than that of ODP (2.1%, n = 48, P < 0.01) or HFP (1.6%, n = 129, P < 0.0001); 2) energy consumption for SyncP (7.6 +/- 9.3 mJ) was significantly lower than that of ODP (14.0 +/- 14.8 mJ, P < 0.0001); and 3) SyncP, but not ODP or HFP, decreased SDCL in the paced area during the pacing (P < 0.01) and postpacing (P < 0.05) periods compared with the prepacing period. We conclude that SyncP is effective in inducing wavefront synchronization and is more effective at facilitating spontaneous VF termination than non-SyncP.
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Affiliation(s)
- Hui-Nam Pak
- Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California, Los Angeles, 90048, USA
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Walcott GP, Killingsworth CR, Ideker RE. Do clinically relevant transthoracic defibrillation energies cause myocardial damage and dysfunction? Resuscitation 2003; 59:59-70. [PMID: 14580735 DOI: 10.1016/s0300-9572(03)00161-8] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Sufficiently strong defibrillation shocks will cause temporary or permanent damage to the heart. Weak defibrillation shocks do not cause any damage to the heart but also do not defibrillate. A relevant and practical question is what range of shock energies is most likely to defibrillate while not causing damage to the heart. This question is most difficult to answer in the pre-hospital defibrillation setting where the patients' size and shape vary, placement of the defibrillation patches vary, and the etiology of their arrhythmia varies. Unlike internal defibrillators, which are tested at implantation, efficacy of an external defibrillator is determined only once, when it is most needed. This review discusses shock damage and dysfunction caused by monophasic waveforms as well as biphasic waveforms. Evidence is presented suggesting that for perfused hearts, the threshold for damage is well above any shock size delivered clinically. For non-perfused hearts, both in humans and animals, evidence is presented that monophasic shocks of up to 5 J/kg do not cause any more cardiac damage/dysfunction than that associated with smaller shocks and that much of this damage is caused by the ischemic period itself rather than the shock. Although many patients can be defibrillated with 150 J (2.2 J/kg) biphasic shocks, some patients may require biphasic shocks up to 360 J (5 J/kg) to be defibrillated. Studies still need to be performed comparing the efficacy and damaging effects of 360 J biphasic shocks to 150 J biphasic shocks. Until those studies are completed, it seems reasonable to use the same 360 J (5 J/kg) energy limit for biphasic shocks as for monophasic shocks.
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Affiliation(s)
- Gregory P Walcott
- Cardiac Rhythm Management Laboratory, Division of Cardiovascular Diseases, Department of Medicine, University of Alabama at Birmingham, Volker Hall B140, 1670 University Blvd., Birmingham, AL 35294, USA.
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Kirchhof P, Milberg P, Eckardt L, Breithardt G, Haverkamp W. Effect of sotalol and acute ventricular dilatation on action potential duration and dispersion of repolarization after defibrillation shocks. J Cardiovasc Pharmacol 2003; 41:640-8. [PMID: 12658067 DOI: 10.1097/00005344-200304000-00018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Ventricular dilatation shortens action potential duration and increases the defibrillation threshold, whereas sotalol prolongs action potential duration and may decrease the defibrillation threshold. Whether these action potential changes remain after defibrillation shocks, and how they relate to defibrillation success, is not known. In this study, eight monophasic action potentials were recorded simultaneously during electrical defibrillation (shock strength: 20%-200% of the defibrillation threshold) in 16 normal and acutely dilated isolated rabbit hearts at baseline and after addition of sotalol (2 x 10-5 M). Post-shock action potential duration (PS-APD) and dispersion of PS-APD [Disp(PS-APD)] of monophasic action potentials were analyzed after 322 defibrillation shocks at different repolarization levels and related to defibrillation success. Acute ventricular dilatation shortened PS-APD, whereas sotalol prolonged PS-APD. Successful defibrillation was associated with lower Disp(PS-APD) at all repolarization levels in the normal and dilated heart at baseline and with sotalol (mean difference: 33%-46%, all P < 0.005). Minimal PS-APD was longer (mean difference: 5%-11%), while maximal PS-APD was shorter (mean difference: 2%-16%) after successful defibrillation shocks than after failing defibrillation shocks. Therefore, sotalol prolongs action potential duration after defibrillation shocks. Synchronization of repolarization, caused by both prolongation of short PS-APD and shortening of long PS-APD, is associated with successful defibrillation in the normal, acutely dilated, and sotalol-treated heart.
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Affiliation(s)
- Paulus Kirchhof
- Department of Cardiology and Angiology, University Hospital Münster, Germany.
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Kirchhof P, Eckardt L, Loh P, Weber K, Fischer RJ, Seidl KH, Böcker D, Breithardt G, Haverkamp W, Borggrefe M. Anterior-posterior versus anterior-lateral electrode positions for external cardioversion of atrial fibrillation: a randomised trial. Lancet 2002; 360:1275-9. [PMID: 12414201 DOI: 10.1016/s0140-6736(02)11315-8] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND External cardioversion is a readily available treatment for persistent atrial fibrillation. Although anatomical and electrophysiological considerations suggest that an anterior-posterior electrode position should create a more homogeneous shock-field gradient throughout the atria than an anterior-lateral position, both electrode positions are equally recommended for external cardioversion in current guidelines. We undertook a randomised trial comparing the two positions with the endpoint of successful cardioversion. METHODS 108 consecutive patients (mean age 60 years [SD 16]) with persistent atrial fibrillation (median duration 5 months, range 0.1-120) underwent elective external cardioversion by a standardised step-up protocol with increasing shock strengths (50-360 J). Electrode positions were randomly assigned as anterior-lateral or anterior-posterior. If sinus rhythm was not achieved with 360 J energy, a single cross-over shock (360 J) was applied with the other electrode configuration. A planned interim analysis was done after these patients had been recruited; it was by intention to treat. FINDINGS Cardioversion was successful in a higher proportion of the anterior-posterior than the anterior-lateral group (50 of 52 [96%] vs 44 of 56 [78%], difference 23.7% (95% CI 9.1-37.8, p=0.009). Cross-over from the anterior-lateral to the anterior-posterior electrode position was successful in eight of 12 patients, whereas cross-over in the other direction was not successful (two patients). After cross-over, cardioversion was successful in 102 of 108 randomised patients (94%). INTERPRETATION An anterior-posterior electrode position is more effective than the anterior-lateral position for external cardioversion of persistent atrial fibrillation. These results should be considered in clinical practice, for the design of defibrillation electrode pads, and when guidelines for cardioversion of atrial fibrillation are updated.
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Affiliation(s)
- Paulus Kirchhof
- Department of Cardiology and Angiology and Institute for Arteriosclerosis Research, University of Münster, Münster, Germany.
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Hooks DA, Tomlinson KA, Marsden SG, LeGrice IJ, Smaill BH, Pullan AJ, Hunter PJ. Cardiac microstructure: implications for electrical propagation and defibrillation in the heart. Circ Res 2002; 91:331-8. [PMID: 12193466 DOI: 10.1161/01.res.0000031957.70034.89] [Citation(s) in RCA: 204] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Our understanding of the electrophysiological properties of the heart is incomplete. We have investigated two issues that are fundamental to advancing that understanding. First, there has been widespread debate over the mechanisms by which an externally applied shock can influence a sufficient volume of heart tissue to terminate cardiac fibrillation. Second, it has been uncertain whether cardiac tissue should be viewed as an electrically orthotropic structure, or whether its electrical properties are, in fact, isotropic in the plane orthogonal to myofiber direction. In the present study, a computer model that incorporates a detailed three-dimensional representation of cardiac muscular architecture is used to investigate these issues. We describe a bidomain model of electrical propagation solved in a discontinuous domain that accurately represents the microstructure of a transmural block of rat left ventricle. From analysis of the model results, we conclude that (1) the laminar organization of myocytes determines unique electrical properties in three microstructurally defined directions at any point in the ventricular wall of the heart, and (2) interlaminar clefts between layers of cardiomyocytes provide a substrate for bulk activation of the ventricles during defibrillation.
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Affiliation(s)
- Darren A Hooks
- Bioengineering Research Group, Department of Physiology, School of Medicine, University of Auckland, Auckland, New Zealand.
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Ueda N, Kaji Y, Maruyama T, Shimoike E, Ito H, Fujino T, Niho Y, Harada M. Subthreshold stimulation in three types of reentrant supraventricular tachycardia: correlation with the results of catheter ablation. JAPANESE CIRCULATION JOURNAL 2001; 65:1057-63. [PMID: 11767998 DOI: 10.1253/jcj.65.1057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The effects of subthreshold stimulation (STS) by direct current were investigated in 20 patients with atrioventricular nodal reentrant tachycardia (AVNRT), 27 with atrioventricular reentrant tachycardia (AVRT) and 3 with idiopathic atrial reentrant tachycardia (IART) STS was delivered to each eligible site for ablation prior to radiofrequency application. STS was defined as 'positive' if it could terminate the tachycardia or disrupt the conduction of accessory pathways without myocardial capture and defined as 'negative' if it could not. Radiofrequency ablation was performed irrespective of a positive or negative result from STS and was successful in all 50 patients. Among the 50 successful ablation sites, STS was positive at 26 sites (11 sites in AVNRT, 12 in AVRT and 3 in IART). STS was positive at 4 sites where ablation failed in 3 patients with AVRT and was negative at 8 sites where ablation was successful in 4 patients with AVNRT and 4 with AVRT. The positive and negative predictive value of STS for the detection of the optimal ablation site were, respectively, 100% and 74% in AVNRT, 73% and 72% in AVRT, and both 100% in IART STS-guided mapping is a specific method to predict the successful catheter ablation of reentrant supraventricular tachycardia.
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Affiliation(s)
- N Ueda
- Department of Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
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