Research On Current Distribution Under External Defibrillation And Method For Locating The Position Of Intracardiac Catheter With Numerical Simulation Of Transthoracic Electric-field

The most two common complex arrhythmias in clinical practice are ventricular fibrillation(VF) and atrial defibrillation(AF).AF has substantial impact on the property or quality of patients' normal living,and with the severity events may very commonly leads to some associated malignant entities such as stroke,congestive heart failure,even to high morbidity and possible life threaten.Especially during VF,if wihout any effective and immediate treatments has been done to terminate fibrillation,in a few minutes,it will lead to be sudden cardiac death(SCD) of and bring the fatal losing to the family and society.According to the pertinent epidemiologic statistical data,more than 50%cardiovascular death are the incidence of SCD,of which the majority are due to an accidental malignant ventricular arrhythmia,such as VF,etc.Moreover,the stroke is the most serious associated entities of AF,about 15%～20%stroke can ascribe to AF. In the United States,the incidence of AF is about 0.5%for the population of the age lower than 60,and in China,it has a higher level more than 0.7%for the total population.Due to the ponderance and universality of the complex arrhythmias of VF and AF, the academic and clinical study have being placed much emphasis on the prevention and treatment these arrhythmias.With the improvement of computational modeling and numerical simulation technologies,the numerical simulation and analysis of bioelectric field are gradually attracting more attentions of international cardiac electrophysiologist and clinical biomedical engineering scholar.More importantly,the numerical modeling and simulation give an efficient and feasible method to study and even sovle those difficult problems possibly hampering the progress of the clinical technologies for electrophysiological diagnosis and treatment.In this dissertation,a numerical simulation method are proposed to study the transthoracic electrical defibrillation to analyze the current distribution during defibrillation,of which the main aim is to optimize the defibrillation current pathway within the torso,decrease the delivered electrical energy, eventually obtain more satisfying effecacy of defibrillation.Using the similar way,the method for locating the position of intracardiac catheter based on three orthogonal transthoracic electric-fields has also been studied in detail,of which the main aims are to analyze the locating error and the relationship between the current distribution of transthoracic electric-field and disturbance factors.In this way,a novel adaptive real-time method has been presented to compensate the contraction and respiration artifact,of which the feasibility and practicability has also been validated by a preliminary animal experiments.The major research works completed in this dissertation include:1.With the numerical simulation theory of bioelectrieal field,a numerical modeling and simualtion method of transthoracic electric-field under external defibrillation is presented based on three dimensional anatomic torso model.Using the simulation results of current distribution under transthoracic defibrillation,a set of quantitative criterions is constructed to evaluate the defibrillation effecacy.Furthermore, the dependence of defibrillation effecacy on current distribution within the heart is analyzed in detail.2.For decreasing the delivered electrical energy,reducing the damage of skin or myocardium,and eventually obtaining more satisfying effecaey of defibrillation,the optimum scheme of current pathway of defibrillation is explored,which includes a proposed electrode-pairing pattern in spatially placed on the torso surface,as well as multiple electrode-pairing pattern,and electrode size and electrode shape.3.In order to experimentally validate the obtained optimum scheme and the proposed simulation method,a series of preliminary experiments on pigs is carried out. The good agreement between the experimental results and the simulation results basically indicate that the simulation method is feasible,and the optimized electrode-pairing displacement of U8-D3(please see page 62 of this dissertation) is confirmed.These research achievements are expected as academic reference for clinical defibrillation and to guide the improvement design of defibrillation electrode and external defibrillator.4.Based on the principle for locating the position of intracardial catheter using three orthogonal transthoracic electric-fields,the numerical modeling and simulation method of bioelectric field is proposed firstly in this dissertation to analyze the the error and the disturbance factors during locating the position of intracardial catheter.A set of quantitative criterions is also constructed to evaluate the influence of disturbance factors on locating accurately.And then,the reasons of locating errors and the relationship between the current distribution of transthoracic electric-field and disturbance factors are studied and analyzed in detail.5.A novel solving method to the locating errors is proposed,which is beed defined as the local calibration of nonuniformity of electric-field and adaptive real-time compensation of the contraction and respiration artifacts.For the latter,a two-stages adaptive filter is designed and discussed emphatically.6.At last,another series of preliminary experiments on pigs is carried out to actually observe the displacment error during locating the position of intracardial catherter.The preliminary experimental results basically validate the simulation results and test the performance of the two-stages adaptive filter to compensate the artifacts. These research achievements are expected to be used in development of three dimensional locating and tracking system of intracardial catheter.The research works in this dissertation establish the theoretical foundation to numerically simulate and analyze the transthoracic electric-field used by the electrical electrophysiological management of clinical complex arrhythmias.More importantly, these works widen the research thought of external defibrillation and method for locating the position of intracardial catheter,and to some extent,the obtained achievements have practical engineering values to improve the defibrillation effecacy and decrease the locating error.We can image that more luther works based on this reseach may get more possible acheivement on many similar problems in this field about bioelectric field,such as the implantable defibrillation,the forward/inverse of electrocardiogram,and electrical impedance tomography,etc.