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Biophys. J. BioFAST: First Published October 27, 2006. doi:10.1529/biophysj.106.091009
© 2006 by the Biophysical Society.

A more recent version of this article appeared on January 15, 2007.
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BIOPHYSICAL THEORY AND MODELING

Dynamic Origin of Spatially Discordant Alternans in Cardiac Tissue

Hideki Hayashi 1, Yohannes Shiferaw 2*, Daisuke Sato 3, Motoki Nihei 4, Shien-Fong Lin 4, Peng-Sheng Chen 1, Alan Garfinkel 5, James Weiss 5 and zhilin Qu 5

1 Cedars Sinai Medical Center
2 California State University, Northridge
3 Northeastern University
4 Cedars Sinai
5 UCLA

* To whom correspondence should be addressed. E-mail: yshifera{at}yahoo.com.

Submitted on June 9, 2006
Revised on July 14, 2006
Accepted on 10 October 2006


  Abstract
Alternans, a condition in which there is a beat-to-beat alternation in the electromechanical response of a periodically stimulated cardiac cell, has been linked to the genesis of life-threatening ventricular arrhythmias. Optical mapping of membrane voltage (Vm) and intracellular calcium (Cai) on the surface of animal hearts reveal complex spatial patterns of alternans. In particular, spatially discordant alternans has been observed, in which regions with a large-small-large action potential duration (APD) alternate out-of-phase adjacent to regions of small-large-small APD. However, the underlying mechanisms that lead to the initiation of discordant alternans, and govern its spatiotemporal properties, are not well understood. Using mathematical modeling, we show that dynamic changes in the spatial distribution of discordant alternans can be used to pinpoint the underlying mechanisms. Optical mapping of Vm and Cai in paced rabbit hearts revealed that spatially discordant alternans induced by rapid pacing exhibits properties consistent with a purely dynamical mechanism as shown in theoretical studies. Our results support the viewpoint that spatially discordant alternans in the heart can be formed via a dynamical pattern formation process which does not require tissue heterogeneity.

Key Words: cardiac arrhythmias, discordant alternans, nonlinear dynamics, pattern formation




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Copyright © 2006 by the Biophysical Society.