Hayashi Hideki, Shiferaw Yohannes, Sato Daisuke, Nihei Motoki, Lin Shien-Fong, Chen Peng-Sheng, Garfinkel Alan, Weiss James N, Qu Zhilin
Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
Biophys J. 2007 Jan 15;92(2):448-60. doi: 10.1529/biophysj.106.091009. Epub 2006 Oct 27.
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.
交替现象是指在周期性刺激的心脏细胞的机电反应中出现逐搏交替的一种情况，它与危及生命的室性心律失常的发生有关。对动物心脏表面的膜电压（V(m)）和细胞内钙（Ca(i)）进行光学映射，揭示了交替现象的复杂空间模式。特别是，已经观察到空间不协调的交替现象，其中动作电位持续时间（APD）为大-小-大的区域与APD为小-大-小的区域相邻且异相交替。然而，导致不协调交替现象起始并控制其时空特性的潜在机制尚未得到很好的理解。通过数学建模，我们表明不协调交替现象空间分布的动态变化可用于确定潜在机制。对起搏兔心脏中的V(m)和Ca(i)进行光学映射发现，快速起搏诱导的空间不协调交替现象表现出与理论研究中所示的纯动力学机制一致的特性。我们的结果支持这样一种观点，即心脏中的空间不协调交替现象可通过不依赖组织异质性的动态模式形成过程形成。
