Computer simulation of myocardial fibrillation using a one dimensional model of excitation and recovery processes

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.