Simulation analysis of excitation conduction in the heart: Propagation of excitation in different tissues |
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Authors: | Mitsuo Kawato Atsushi Yamanaka Seiichi Urushibara Osamu Nagata Hiroshi Irisawa Ryoji Suzuki |
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Institution: | 1. Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560, Japan;2. National Institute for Physiological Sciences, Myodaiji, Okazaki, Aichi 444, Japan;1. State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, PR China;2. Laboratory of Bioinspired Smart Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China;1. Institute of Materials in Electrical Engineering 1 (IWE1), RWTH Aachen University, Sommerfeldstrasse 24, 52074, Aachen, Germany;2. Institute of Molecular Pharmacology, RWTH Aachen University, Wendlingweg 2, 52074, Aachen, Germany;3. Institute of Biological Information Processing (IBI-2): Mechanobiology, Forschungszentrum Jülich GmbH, Leo-Brandt-Strasse, 52425, Jülich, Germany;4. Institute of Pharmacology and Toxicology, RWTH Aachen University, Wendlingweg 2, 52074, Aachen, Germany;1. MEMS and Nanotechnology Laboratory, School of Mechanical Engineering, Chonnam National University, Gwangju, 61186, Republic of Korea;2. Center for Next-Generation Sensor Research and Development, Chonnam National University, Gwangju, 61186, Republic of Korea;1. Department of Civil and Water Engineering, Université Laval, Québec, Québec G1V 0A6, Canada;2. Department of Civil, Geological and Mining Engineering, École Polytechnique de Montréal, Montréal, Québec H3T 1J4, Canada;1. School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA;2. Department of Biomedical Engineering, Emory University, Atlanta, GA, USA |
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Abstract: | The normal excitation and conduction in the heart are maintained by the coordination between the dynamics of ionic conductance of each cell and the electrical coupling between cells. To examine functional roles of these two factors, we proposed a spatially-discrete model of conduction of excitation in which the individual cells were assumed isopotential. This approximation was reasoned by comparing the apparent space constant with the measured junctional resistance between myocardial cells. We used the four reconstruction models previously reported for five kinds of myocardial cells. Coupling coefficients between adjacent cells were determined quantitatively from the apparent space constants. We first investigated to what extent the pacemaker activity of the sinoatrial node depends on the number and the coupling coefficient of its cells, by using a one-dimensional model system composed of the sinoatrial node cells and the atrial cells. Extensive computer simulation revealed the following two conditions for the pacemaker activity of the sinoatrial node. The number of the sinoatrial node cells and their coupling coefficients must be large enough to provide the atrium with the sufficient electric current flow. The number of the sinoatrial node cells must be large so that the period of the compound system is close to the intrinsic period of the sinoatrial node cell. In this simulation the same sinoatrial node cells produced action potentials of different shapes depending on where they were located in the sinoatrial node. Therefore it seems premature to classify the myocardial cells only from their waveforms obtained by electrical recordings in the compound tissue. Second, we investigated the very slow conduction in the atrioventricular node compared to, for example, the ventricle. This was assumed to be due to the inherent property of the membrane dynamics of the atrioventricular node cell, or to the small value of the coupling coefficient (weak intercellular coupling), or to the electrical load imposed on the atrioventricular node by the Purkinje fibers, because the relatively small atrioventricular node must provide the Purkinje fibers with sufficient electric current flow. Relative contributions of these three factors to the slow conduction were evaluated using the model system composed of only the atrioventricular cells or that composed of the atrioventricular and Purkinje cells. We found that the weak coupling has the strongest effect. In the model system composed of the atrioventricular cells, the propagation failure was not observed even for very small values of the coupling coefficient.(ABSTRACT TRUNCATED AT 400 WORDS) |
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