Department of Biomedical Engineering, Maastricht University, Maastricht, The Netherlands.
Heart Rhythm. 2011 Mar;8(3):429-36. doi: 10.1016/j.hrthm.2010.11.020. Epub 2010 Nov 12.
Acute atrial dilation increases the susceptibility to atrial fibrillation (AF). However, the mechanisms by which atrial stretch may contribute to the initiation and perpetuation of AF remain to be determined.
The purpose of this study was to use a novel multiscale model of atrial electromechanics and mechanoelectrical feedback to test the hypothesis that acute stretch increases vulnerability to AF by heterogeneous activation of stretch-activated channels.
Human atria were represented by a triangular mesh obtained from magnetic resonance imaging data. Atrial trabecular bundle structure was incorporated by varying thicknesses of the atrial wall. Atrial membrane behavior was modeled by the Courtemanche-Ramirez-Nattel model with the addition of a nonselective stretch-activated cation current (I(sac)). Mechanical behavior was modeled by a series elastic, a contractile, and a parallel elastic element in which contractile force was related to intracellular concentration of free calcium and sarcomere length.
Acute atrial dilation was simulated by increasing stretch throughout the atrial wall. Stimulation near the pulmonary vein ostia at an interval of 600 ms induced AF at an overall stretch ratio of 1.10. Initiation and perpetuation of AF in our model were related to increased dispersion of effective refractory period, conduction slowing, and local conduction block, all related to heterogeneous activation of I(sac). Upon local contraction, mechanoelectrical coupling affects perpetuation of AF by temporarily changing local excitability.
During acute atrial dilation, heterogeneous activation of I(sac) enhances initiation and can affect perpetuation of AF.
急性心房扩张增加了心房颤动（AF）的易感性。然而，心房拉伸如何有助于 AF 的起始和维持的机制仍有待确定。
本研究旨在使用一种新的心房机电和力学电反馈多尺度模型来检验以下假设：急性拉伸通过异质性激活拉伸激活通道增加 AF 的易感性。
采用从磁共振成像数据获得的三角形网格来表示人类心房。通过改变心房壁的厚度来纳入心房小梁束结构。心房膜行为通过加入非选择性拉伸激活阳离子电流（I(sac)）的 Courtemanche-Ramirez-Nattel 模型来建模。机械行为通过串联弹性体、收缩性和并联弹性体建模，其中收缩力与细胞内游离钙浓度和肌节长度有关。
通过增加整个心房壁的拉伸来模拟急性心房扩张。在间隔 600 毫秒处刺激肺静脉口附近，在整体拉伸比为 1.10 时诱导 AF。我们的模型中 AF 的起始和维持与有效不应期的离散度增加、传导减慢和局部传导阻滞有关，所有这些都与 I(sac)的异质性激活有关。在局部收缩时，力学电耦合通过暂时改变局部兴奋性来影响 AF 的维持。
在急性心房扩张期间，I(sac)的异质性激活增强了起始，并可能影响 AF 的维持。
