【作者】 赖大坤；

【导师】 方祖祥；

【作者基本信息】 复旦大学 ， 医学电子学， 2008， 博士

【摘要】 心室颤动(ventricular fibrillation-VF,简称室颤)、心房颤动(atrialdefibrillation-AF,简称房颤)等是临床常见的复杂性心律失常,发作时轻则影响患者生活质量,重则引起脑卒中(stroke,又称中风)、心功能衰竭等恶性并发症,甚至危机患者生命安全,尤其是室颤发作时,如不及时采取有效措施,常常导致患者(相当一部分是中青年患者)的心脏猝死(sudden cardiac death,SCD),给家庭和社会造成重大损失。临床流行病学研究表明,所有心血管病死亡中超过50%患者为SCD,其中绝大部分归因于各类心血管病变基础上发生的一时性恶性室性心律失常,如室颤等;而脑卒中则是房颤最严重的并发症,约15%～20%脑卒中是由房颤引起,美国60岁以下人群中房颤发病率为0.5%,我国普通人群房颤患病率则高达0.7%。由于室颤、房颤危害的严重性和广泛性,所以,与室颤、房颤等复杂性心律失常的临床防治密切相关电除颤技术(electrical defibrillation-ED,简称除颤)和介入导管技术(interventional catheter)的研究一直以来都受到国内外学者的广泛重视。尤其是近年来随着计算机建模与仿真技术的兴起,与电生理诊疗技术相关的生物电场问题的数值仿真研究正成为的心脏电生理工程领域的前沿课题和热点,也为解决电生理诊疗技术中的诸多难题提供了一套行之有效的解决办法。本文作者将生物电场的数值仿真方法用于室颤的电除颤技术及介入导管术的心内导管定位方法的研究,探讨了体外除颤时放电电流路径的优化和心内导管三维经胸电场定位的位置偏差问题分析。采用本文优化所得的放电电流路径有助于降低除颤能量、改善除颤效果,初步实验结果同时显示本文提出的定位偏差自适应实时补偿新方法具有一定的可行性。对于室颤的体外电除颤技术研究和心内导管三维经胸电场定位方法研究,本文的主要工作和研究成果包括:1、针对现有在体实验记录手段有限,而动物实验“猜摸”方式的除颤研究方法又非常盲目,在已有生物电场数值仿真方法的基础上,给出了基于三维真实人体胸腔模型的体外除颤数值仿真研究方法;结合除颤电场的仿真求解结果,建立了一套衡量一次除颤效果好坏的仿真评估指标,并探讨和分析了体外除颤时胸腔电场分布与除颤效果的关系。2、针对电击除颤时释放的高能电脉冲可能会对患者的皮肤和心脏造成伤害,甚至可能因此而诱发复杂度更高的室颤等问题,提出了降低除颤能量、改善除颤效果的优化放电电流路径方案,包括除颤电极对在胸腔体表高、中、低位的立体贴放模式(“高”位表示该电极位于锁骨和第三肋骨间定义的体表上部区域,“中”位表示第三肋骨和第七肋骨间体表中部区域,“低”表示第七到第十肋骨体表较下区域)、多电极分区除颤模式,以及除颤电极大小和形状的优化。3、在仿真研究的基础上,设计并开展了体外除颤动物实验,重点测试了除颤电极贴放位置与除颤电量阈值之间的关系。初步实验结果显示:U8-D3位置(右前胸第1到第3肋骨——左腋中线第9肋骨区)的除颤电量阈值最低,优于已有文献报道的M2-M6位置(左胸心前位置—右后背中部位置)。实验结果与仿真结果较好的一致性,在一定程度上说明了仿真结果的正确性和体外除颤仿真研究方法的可行性,相关结论有望用于除颤设备的改进设计和除颤操作方法的理论参考。4、结合心内导管三维经胸电场定位的基本原理和生物电场的数值仿真方法,提出了采用数值建模和仿真方法分析定位过程中的位置偏差问题,基于定位电场的仿真求解结果,构建了一套衡量导管定位性能的仿真评估方法,并探讨和分析了定位电场分布与导管定位偏差的相互关系,初步量化预估了各相关因素对定位准确度的影响程度25、基于定位偏差问题的仿真分析和定位干扰因素的系统认识,提出了解决导管定位偏差问题的分片实时校准补偿新方法,包括静态梯度系数畸变的分片校准思想和动态呼吸伪差的自适应实时补偿,着重探讨了后者的两级自适应滤波算法的实现。6、设计并开展了基于三维经胸低频电场的心内导管定位方法的系列基础实验,一方面从实验角度进一步分析了心内导管定位过程中的定位偏差问题;同时,通过动物实验对仿真结果和自适应补偿方法的验证,得到了一些初步的结果,这些研究成果有望用于指导心内导管三维经胸电场定位及心内膜标测系统的研制。本文的研究工作为基于经胸电场的临床电生理诊疗技术的研究与相关医疗仪器系统的改进设计提供了一套可参考的研究方法,开阔了目前体外电除颤及心内导管定位方法的研究思路,具有一定的理论意义;对于改善体外除颤效果、降低导管定位偏差等也具有一定的实际应用价值。本文研究方法可将其扩展到体内电除颤的效果评估及其电极配置模式的优化,以及心电正/逆问题、电阻抗成像等应用领域的相关问题研究。更多还原

【Abstract】 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.更多还原