title: Dynamic origin of spatially discordant alternans in cardiac tissue.
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 (V(m)) and intracellular calcium (Ca(i)) on the surface of animal hearts reveals 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 V(m) and Ca(i) 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.
authors.affiliation: Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yohannes
authors.initials: Y
authors.lastname: Shiferaw
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sato
authors.forename: Motoki
authors.initials: M
authors.lastname: Nihei
authors.forename: Shien-Fong
authors.initials: SF
authors.lastname: Lin
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
authors.forename: Alan
authors.initials: A
authors.lastname: Garfinkel
authors.forename: James N
authors.initials: JN
authors.lastname: Weiss
authors.forename: Zhilin
authors.initials: Z
authors.lastname: Qu
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001683:Biological Clocks / Q000502:physiology*; D018780:Body Surface Potential Mapping; D020013:Calcium Signaling / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D066298:In Vitro Techniques; D008955:Models, Cardiovascular; D011817:Rabbits