Paroxysmal Starting and Stopping of Circulating Waves in Excitable Media

Abstract

Levels of intracellular Ca2+ were monitored using fluorescence from Ca2+-sensitive dyes in chick embryonic heart cells cultured in an annular geometry. There was spontaneous starting and stopping of reentrant waves of activity. The results are modeled using modified FitzHugh-Nagumo equations representing pacemakers embedded in a conducting medium. These results provide a potential mechanism for spontaneous abnormal cardiac rhythms in which there are rapid heart beats (tachycardias) that repetitively start and stop.

Complex temporal patterns of spontaneous initiation and termination of reentry in a loop of cardiac tissue

“…The pacer, as we have already remarked, can be natural or artificial. A number of prior studies of a different nature from ours also discover complex SITR patterns in simple settings, such as in sheets (Bub et al, 2003;Hwang et al, 2005), loops (Nagai et al, 2000) and aggregates (Kunysz et al, 1997) of animal cardiac tissue. In Bub et al (2003) and Hwang et al (2005) complex patterns in monolayers of growing cell cultures are linked to changing densities and to local inhomogeneities, respectively.…”

“…The relative simplicity of RC and their importance in clinical arrhythmogenesis have made them objects of frequent study (Cain, 2007;Chen et al, 2005;Cytrynbaum and Keener, 2002;Courtemanche et al, 1993Courtemanche et al, , 1996Courtemanche and Vinet, 2003;Frame and Simson, 1988;Ito and Glass, 1992;Keener, 2002;Mines, 1913;Nagai et al, 2000;Qu et al, 1997;Quan and Rudy, 1990;Sedaghat et al, 2005;Vinet, 2000). Studying spontaneous initiation and termination of reentry (SITR) patterns in the loop context is more focused and simpler than in the whole heart and can offer potentially useful insights into the clinically observed patterns of VT occurrences.…”

Multistable spatiotemporal patterns of cardiac activity

“…Cardiac tissue-culture preparations enable long-term observation of spontaneous activity using a variety of experimental techniques, including varying the geometry of growing cells and using pharmacologic agents to modify physiological cellular properties leading to novel dynamic behaviors (14,(16)(17)(18). Consequently, studies of dynamics in cardiac tissue culture should lead to a better understanding of the origin of spontaneous transitions in dynamics observed clinically.…”

Resonance Induced Pacemakers: A New Class of Organizing Centers for Wave Propagation in Excitable Media

“…They need to be considered, included, and studied as one of the probable causes for spontaneous pattern formation in an excitable media. This is of practical interest in biological (excitable) media where such abrupt pattern formation could have pathological implications [4,8]. For example, it is possible to envisage a scenario where a part of the media is active (exhibiting oscillations) and the remaining is passive (fixed point behavior).…”

“…The underlying mechanisms for the inception of these patterns are of practical interest as they provide valuable insight into relevant problems such as ventricular tachycardias [4]. For example, paroxysmal starting and stopping of circulating waves of activity can give rise to serious complex rhythms in the cardiac system [8]. Although, wave propagation from a source point is reasonably well understood, some curiosity persists regarding the emergence of the pacemaker (source) regions [1].…”