title: Cardiac beat-to-beat alternations driven by unusual spiral waves.
abstract: Alternans, a beat-to-beat temporal alternation in the sequence of heartbeats, is a known precursor of the development of cardiac fibrillation, leading to sudden cardiac death. The equally important precursor of cardiac arrhythmias is the rotating spiral wave of electro-mechanical activity, or reentry, on the heart tissue. Here, we show that these two seemingly different phenomena can have a remarkable relationship. In well controlled in vitro tissue cultures, isotropic populations of rat ventricular myocytes sustaining a temporal rhythm of alternans can support period-2 oscillatory reentries and vice versa. These reentries bear "line defects" across which the phase of local excitation slips rather abruptly by 2pi, when a full period-2 cycle of alternans completes in 4pi. In other words, the cells belonging to the line defects are period-1 oscillatory, whereas all of the others in the bulk medium are period-2 oscillatory. We also find that a slowly rotating line defect results in a quasi-periodic like oscillation in the bulk medium. Some key features of these phenomena can be well reproduced in computer simulations of a nonlinear reaction-diffusion model.
authors.affiliation: National Creative Research Initiative Center for Neuro-Dynamics and Department of Physics, Korea University, Seoul 136-701, Korea.
authors.forename: Tae Yun
authors.initials: TY
authors.lastname: Kim
authors.forename: Sung-Jae
authors.initials: SJ
authors.lastname: Woo
authors.forename: Seong-Min
authors.initials: SM
authors.lastname: Hwang
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Hong
authors.forename: Kyoung J
authors.initials: KJ
authors.lastname: Lee
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003198:Computer Simulation; D004058:Diffusion; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000166:cytology; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D016276:Ventricular Function