Malik M, Camm A J
Department of Cardiological Sciences, St George's Hospital Medical School, London.
Cardiovasc Res. 1989 Feb;23(2):132-44. doi: 10.1093/cvr/23.2.132.
A computer model of cardiac excitation sequences and recovery processes has been employed to reproduce chaotic behaviour of the simulated tissue and to investigate how different variables of the model influence the degree of disorganisation in modelled episodes. The model emphasises the electrophysiological features of excitation transmission and repolarisation processes and introduces phenomena which are omitted or seriously simplified in most of the existing models of cardiac tissue electrophysiology. These phenomena include abnormal shapes of action potential curves corresponding to premature excitation of cells which have not fully recovered, excitation transmission based on transmembrane voltages, and the electrotonic interactions between neighbouring cells during their repolarisation phases. The model has been used to examine a one dimensional cable of simulated cells in which a central area with shortened refractoriness was used to enable the "reflection" processes to initiate conduction and repolarisation disturbances. In some cases, the chaotic nature of the reproduced episodes resembled fibrillation myocardium. The degree of the simulated chaos depended on different variables of the model. This study included a systematic evaluation of the influence of the shapes of action potential curves, of the threshold of transmembrane voltages initiating an excitation wave, of the degree of the electrotonic interactions of neighbouring cells, and of various combinations of these variables. The results showed that in this model, the maximum disorganisation was achieved when combining the negative influences of all variables, and that changing the shape of the action potential curves prevented the modelled chaos more fully than changes in the other variables.
一种心脏兴奋序列和恢复过程的计算机模型已被用于重现模拟组织的混沌行为，并研究该模型的不同变量如何影响模拟事件中的无序程度。该模型强调兴奋传递和复极化过程的电生理特征，并引入了在大多数现有的心脏组织电生理模型中被忽略或严重简化的现象。这些现象包括对应于未完全恢复的细胞过早兴奋的动作电位曲线的异常形状、基于跨膜电压的兴奋传递以及相邻细胞在复极化阶段的电紧张相互作用。该模型已被用于检查一维模拟细胞电缆，其中使用具有缩短不应期的中心区域来使“反射”过程引发传导和复极化干扰。在某些情况下，重现事件的混沌性质类似于心肌颤动。模拟混沌的程度取决于模型的不同变量。这项研究包括对动作电位曲线形状、引发兴奋波的跨膜电压阈值、相邻细胞电紧张相互作用程度以及这些变量的各种组合的影响进行系统评估。结果表明，在该模型中，当所有变量的负面影响相结合时，实现了最大程度的无序，并且改变动作电位曲线的形状比改变其他变量更能充分防止模拟的混沌。
