Asymmetry in Membrane Responses to Electric Shocks: Insights from Bidomain Simulations

Models of myocardial membrane dynamics have not been able to reproduce the experimentally observed negative bias in the asymmetry of transmembrane potential changes (Δ V m) induced by strong electric shocks delivered during the action potential plateau. The goal of this study is to determine what me...

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Bibliographic Details
Published in:	Biophysical journal 2004-10, Vol.87 (4), p.2271-2282
Main Authors:	Ashihara, Takashi, Trayanova, Natalia A.
Format:	Article
Language:	eng
Subjects:	Action Potentials - physiology Animals Anisotropy Biomedical research Biophysical Theory and Modeling Cell Membrane - physiology Computer Simulation Electric Stimulation - methods Electroconvulsive therapy Electroporation - methods Heart Conduction System - physiology Humans Membrane Potentials - physiology Membranes Models, Cardiovascular Models, Neurological Muscle Fibers, Skeletal - physiology Myocytes, Cardiac - physiology Simulation
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Summary:	Models of myocardial membrane dynamics have not been able to reproduce the experimentally observed negative bias in the asymmetry of transmembrane potential changes (Δ V m) 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 Δ V m asymmetry could not be reproduced by addition of electroporation only, but by further addition of hypothetical outward current, I a, activated upon strong shock-induced depolarization. Furthermore, the experimentally observed rectangularly shaped positive Δ V m, negative-to-positive Δ V m ratio (asymmetry ratio) = ∼2, electroporation occurring at the anode only, and the increase in positive Δ V m caused by L-type Ca 2+-channel blockade were reproduced in the strand only if I a was assumed to be a part of K + flow through the L-type Ca 2+-channel. In the sheet, I a not only contributed to the negative bias in Δ V m asymmetry at sites polarized by physical and virtual electrodes, but also restricted positive Δ V m. Inclusion of I a and electroporation is thus the bridge between experiment and simulation.
ISSN:	0006-3495 1542-0086