Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session X7: Complex Spatio-Temporal Patterns in Cardiac Tissue |
Hide Abstracts |
Sponsoring Units: DBP Chair: Leon Glass, McGill University Room: LACC 408B |
Friday, March 25, 2005 8:00AM - 8:36AM |
X7.00001: Transitions between spatiotemporal patterns in cell culture Invited Speaker: Cardiac monolayers undergo transitions between different spatiotemporal states as experimental conditions are varied. Monolayers display periodic target pattern waves, stable spiral waves, spirals that spontaneously initiate and terminate, multiple interacting wavefronts, and quiescence. Transitions between these spatiotemporal states are observed during washout of beta-glycyrrhetinic acid, a pharmacological agent that reduces cell-cell coupling. Simple excitable media models undergo the same transitions as local connectivity is continuously varied. Similar mechanisms may be responsible for transitions between healthy and unhealthy rhythms in whole hearts. [Preview Abstract] |
Friday, March 25, 2005 8:36AM - 9:12AM |
X7.00002: Complex-periodic cardiac spiral waves mediated by static and dynamic defects Invited Speaker: Spiral wave activities arising on cardiac tissues have been the subject of numerous studies in the field of nonlinear dynamics as well as medical sciences for the reason that they are associated with cardiac arrhythmia and their dynamical properties are scientifically very intriguing. One of the important issues regarding these waves is to understand the role of system inhomogeneities. For example, localized inhomogeneities (in cell density or electrical conductivity) like infarcts can often initiate re-entrant spiral waves that become self-sustained once formed. Some localized inhomogeneities can also act as a pinning site anchoring spiral waves. In this lecture, I will discuss that besides the aforementioned two simple cases they can have a far more complex role of generating multiply periodic (period-2, -3, and -4) or chaotic waves. Our experimental observations suggesting this new possibility were obtained through dissociated cardiac cell cultures of rat ventricles. The wave activities were visualized by a non-invasive, non-interferometric phase-contrast macroscope that was developed recently by us. Similar situations could be also reproduced in a model simulation. [Preview Abstract] |
Friday, March 25, 2005 9:12AM - 9:48AM |
X7.00003: The dynamic behaviors of bound spiral waves in excitable media Invited Speaker: Recent large-scale computations have shown that at sufficiently high densities spiral waves spontaneously coalesce to form stable conglomerates (bound states) composed of spirals of similar or opposite chiralities. The most common form are pairs and triplets composed of spirals of the same chirality often called two-armed and three-armed spirals, respectively. The bound states generate waves with higher average frequencies than a single spiral and exhibit complex dynamic behaviors. My talk will concentrate on media with a single diffusing variable and Fitz-Hugh-Nagumo type kinetics, commonly used as a model of wave propagation in the heart. I will discuss the main types of bound states in such media and their dependence on the properties of the medium. In particular, I will describe newly discovered asymmetric bound states with one spiral orbiting the other at distances significantly exceeding the wavelength. A special emphasis will be given to bound spiral pairs, which have been recently discovered experimentally in monolayers of cardiac myocytes and in the intact heart. [Preview Abstract] |
Friday, March 25, 2005 9:48AM - 10:24AM |
X7.00004: Experimental and computational studies on complex spiral waves in 2-D cardiac substrates Invited Speaker: A variety of chemical and biological nonlinear excitable media including heart tissue can support stable, self-organized waves of activity in a form of rotating single-arm spirals. In the heart tissue, stable single-arm spirals can underlie highly periodic activity such as monomorphic ventricular tachycardia (VT), while unstable spirals that continuously form and break up are shown to underlie aperiodic and lethal heart activity, namely fibrillation. Although fast pacing from a point in the heart is commonly used to terminate VT, it can occasionally yield a transient or stable acceleration of tachicardia rate and/or fibrillation. In this study we tested the effect of rapid point pacing on sustained spiral waves in the uniformly anisotropic cultures of cardiac myocytes. In 15/79 cultures, rapid pacing induced a stable formation of multiple bound spiral waves (a complex spiral) and acceleration of overall excitation rate in the tissue, as assessed by pseudo ECG (pECG). The level of rate acceleration correlated with the number of rotating waves. Further rapid point pacing decelerated, terminated, or further accelerated the complex spiral activity via a change in the number of coexisting rotating waves. The dynamic restitution analysis revealed no alternans in action potential duration in any of the cultures. Stable formation of complex spirals was accomplished only in the cultures that showed relatively broad and steep impulse wavelength and conduction velocity restitutions. A necessary condition for rate acceleration in a medium with monotonic restitution is that the rate of rotation of a single spiral wave is significantly lower than maximum sustainable rate of excitation in the medium. Preliminary data in a homogeneous medium using 3-variable Fenton-Karma (FK) based model of cardiac tissue suggest that decrease of fast inward current (excitability) can shift the spiral rate away from the break point on the restitution curve, enabling a necessary condition for rate acceleration. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700