The Drift Characteristics Of Spiral Wave In Cardiac Tissue Under Optical Feedback

Spiral wave is a natural phenomenon widely existing in nature,such as chemical waves in the reaction-diffusion system,neural signals in the cerebral cortex of primates,and ECG signals in the heart,etc.,the emergence of spiral waves can be observed in the system composed of these media.In heart tissue,the spiral wave is closely related to ventricular fibrillation,tachycardia,and other diseases.Discovering the nature of spiral waves is a necessary process to overcome these diseases.The exploration of the organism is not only confined to biological experiments.For the heart,a system composed of regular working cardiomyocytes,we can find appropriate equations to describe its characteristics and then simulate the working state of the whole heart system on the computer.Under special conditions,we can study this dynamic phenomenon in heart tissue by simulating spiral waves.Drift is an important feature of spiral wave mechanics.In previous studies(based on theoretical and experimental studies of Belousov-Zhabotinsky reactions),the spiral waves in chemical media can drift under the control of an applied electric field.Mathematically,this drift occurs because of the presence of additional gradient terms in the Laplacian operator of the reaction-diffusion equation describing excitable media.It is obvious that this method of controlling spiral waves is not suitable for cardiac mediators where external electric fields cannot generate gradient terms.In this paper,we propose a new method to induce spiral wave drift in the cardiac medium.In the Fitzhugh-Nagumo model,we add the simulation of photosensitive ion channels in cardiomyocytes.Under the action of photosensitive ion channels,we can realize the light feedback control of the system’s working state.In addition to researching the control effect of the continuous light source,we also simulate the spiral wave drift under discrete LED light sources,and propose how the number of LED and light intensity affect the drift.The results show that both continuous light sources and discrete light sources can control the directional drift of spiral waves in the heart.At the same time,we discuss how to eliminate the spiral wave under light feedback conditions,such as manipulating the spiral wave to collide with a tissue boundary or another spiral wave with specific properties.Based on these results,treating diseases such as cardiac arrhythmias caused by spiral waves by additional light fields may become a new direction of medical research.In the first chapter,we mainly introduce the necessary academic background for this research.It includes pattern dynamics,nonlinear science,reaction-diffusion systems,and excitable systems.As basic subjects,these subjects have been applied in a wide range of research directions.In addition,we describe how spiral waves in chemical media drift in electric fields,and the emerging application of optogenetics in the mammalian heart,which are the basis of our research.In chapter 2,we focus on our new cardiac system equation with light feedback properties.In this process,we refer to how the mathematical equations describing chemical mediators are modified under the action of electric fields,and we modify the normal cardiac tissue model in this process.This new set of equations is the basis of our simulation experiment.In Chapter 3,we conduct simulation experiments under a continuous light source and discrete light source respectively to explore whether light can manipulate spiral wave movement in photosensitive cardiac medium,and how light source parameters and ion channel types affect spiral wave drift.In addition,we also simulate the possible elimination of spiral waves.Finally,we summarize the main content and research significance of this paper and imagine the future development and application of this research direction.