Cardiac Microstructure: Implications for Electrical Propagation and Defibrillation in the Heart

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 suffici...

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Bibliographic Details
Published in:Circulation research 2002-08, Vol.91 (4), p.331-338
Main Authors: Hooks, Darren A, Tomlinson, Karl A, Marsden, Scott G, LeGrice, Ian J, Smaill, Bruce H, Pullan, Andrew J, Hunter, Peter J
Format: Article
Language:English
Subjects:
Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy
Animals
Anisotropy
Biological and medical sciences
Computer Simulation
Electric Countershock
Emergency and intensive cardiocirculatory care. Cardiogenic shock. Coronary intensive care
Finite Element Analysis
Gap Junctions - metabolism
Heart - physiology
Heart Conduction System - physiology
Heart Conduction System - physiopathology
Heart Conduction System - ultrastructure
Intensive care medicine
Medical sciences
Membrane Potentials - physiology
Models, Cardiovascular
Myocardium - metabolism
Myocardium - ultrastructure
Rats
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Summary: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.
ISSN:0009-7330
1524-4571
DOI:10.1161/01.RES.0000031957.70034.89