Modeling And Studying For Myocardial Signal With Cellular Automata

The myocardial information transfers in the form of electric signal in the heart.The normal myocardial signal is traveling wave.The spiral wave of myocardial signal is the possible reason of arrhythmia.And the spatial-temporal chaos caused by the break up of the spiral waves will lead to the fibrillation,which will result the sudden death.Studying on the dynamics of spiral waves has been a hot spot in cardiology.Experiment is the primary method of studying cardiac electrical signal.Experiment is intuitive and reliable,but it is easy to damage the object of experiment and difficult to repeat.Importantly,experimental method is difficult to a unitary factor excluding the effects of other factors.Numerical simulation methods can effectively avoid the shortcomings of experimental method.So it has been an important assistant approach for the study of myocardial signal.Cellular automaton is a numerical simulation method which is efficient and simple.The Greenberg-Hastings cellular automaton is the simplest cellular automaton model for excitable media.Many studies have proved the correctness of cellular automaton for the study of the excitable media,such as the heart.In this paper,we study myocardial signal of a tissue slice using cellular automaton.The effects of mechanical deformation and cell memory for spiral waves will be explored,and the cellular automaton model for the electrocardiogram will be constructed,too.The works and results of this paper are as follows:First of all,the dynamics of spiral waves in myocardial tissue are studied using Greenberg-Hastings cellular automaton.The computer simulation results show that for stable spiral waves existing in a regular lattices system,the physiological deformation will lead to the meandering but not breakup of the spiral waves,however,the pathological deformation will result in the breakup,the meandering,or the disappearance of the spiral waves.The computer simulation results also turn to the conclusion that the spiral waves are more sensitive to the amplitude than to the angular frequency of the mechanical deformation.The reason of the quick recovery of the sportsman after the hitting for the breast and the reason of the fibrillation coming from the violent hitting for the breast are explained.In the second part,a cellular automaton model is established to reflect the conduction memory of the cardiac cells.In this model,the conduction velocity of the electrical cardiac signal depends on the preceding state period of the myocardial cells.With this model,the production and maintenance of stable spiral waves in myocardial tissue are imitated,and the phenomena of the Doppler and Eckhaus instability of spiral waves are exhibited,which can not be produced by the traditional Greenberg-Hastings cellular automata.The mechanisms underlying above results are provided.This work provides a model basis for the further study for the electrical cardiac signal in the future.In the third part,a cellular automaton model for the electrocardiogram considering the atria,the ventricle,the ventricular septum,and the atrioventricular orifices has been established.With this model,the conduction of the myocardial electrical activation is simulated,and the field potentials under normal and diseased conditions are followed.The computer simulation results showed that:under the healthy conditions,the field potential appears as a normal ECG,that is to say,it presents the P wave,QRS wave group,T wave,and J wave.The endocardium ischemia results the T wave inversion,the epicardium ischemia leads to the higher T wave,and the T wave appears earlier under the through wall ischemia.Above phenomena agree with the clinic results,and the mechanisms are analyzed briefly.