Atrial Cell Modeling And Preminary Simulation Study Of Atrial Fibrillation Ablation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia in clinical practice. AF is characterized by rapid and irregular activation of the atria, with consequence deterioration of atrial mechanical function. The occurrence of AF increases with age, with a prevalence rising from0.5%of people in their50s to nearly10%of the octogenarian population, and its incidence is increasing in the last few years. Despite different hypotheses are proposed such as multiple wavelet hypothesis, mother rotor hypothesis and focal triggers and drivers from the PVs etc., the exact mechanisms leading to perpetuation of AF are still undetermined so far.There are two main pharmacological treatment strategies for patients with AF:rhythm control and rate control. Multiple pharmacological approaches have been tried to convert AF to sinus rhythm (SR). However, many of such drugs are relatively ineffective for maintaining sinus rhythm in the long term and are associated with significant side effects and complications.Clinicians have therefore pursued more definitive treatment options, both catheter based and surgical, to treat patients with AF. Surgical/Radiofrequency (RF) catheter ablation is a therapeutic procedure that consists of creating lines of conduction block to interrupt AF. Surgical therapies designed to cure AF have developed in parallel with an improved understanding of the key pathophysiological concepts important in initiation and maintenance of AF, largely as a result of advances in catheter ablation technology.The various treatments of AF remain largely based on empirical considerations and are usually evaluated in clinical study or in animal experiment. Heart modeling and simulation is one of the effective methods for AF research, it can be used to simulate AF and thus answer questions such as the mechanism involved in AF initiation or perpetration and the efficiency of therapy techniques. Compared to clinical and animal studies, an in silico approach has the advantages of repeatability and reproducibility under controlled conditions.This thesis is focus on modeling of atrial cells with different areas and simulation study of the AF therapies:Surgical/Radiofrequency catheter ablation.First, a brief review of the concepts and mechanisms of atrial fibrillation is presented, as well as a description of therapies aimed at AF including pharmacological treatments and non- pharmacological treatments.Second, based on the RNC model, which is only specific to canine right atrial region, we developed models of left atrial myocytes and myocardial sleeves in PVs for the first time, based on our own experiment data and other published data.Third, based on the published researches in recent years, ionic currents and action potential (AP) curves of normal human atrial myocytes are reproduced in our computer simulations. Then APs of human atrial myocytes with different anatomical regions of are simulated by changing ionic current parameters.Fourth, based on the phase spatial distribution theory developed by Iyer and Gray, an automatic method is proposed to identify the phase singularity in cardiac reentry simulation, and the efficiency, accuracy and parameter sensitivity of the method are studied and compared with another commonly used method developed by Fenton and Karma.Finally, based on3-D Cardiome-CN human heart model developed by our group,8different ablation patterns including the gold standard Cox-Maze Ⅲ are evaluated. Then several refined Cox-Maze Ⅲ ablation patterns are proposed.The work of this thesis is very useful for further understanding the mechanisms underlying AF as well as refining AF therapeutic techniques.