EXPERIMENTAL AND NUMBERICAL ANALYSES OF DEFIBRILLATION

这一建议的目的是确定心肌细胞的分布 除颤过程中的电流密度及其对除颤的影响 成功。这项研究的一个假设是，最小电流密度 必须到达心肌内才能实现除颤。一个 第二个假设是这个阈值电流密度不随 在动态平衡条件下对给定物种的尊重。 给定的情况下是否达到心肌电流阈值密度 除颤尝试取决于整个过程中的电流分布 心肌。这种分布是复杂的，因为 心脏容量导体和心肌电导率的各向异性 此外，可能会因电极大小和放置位置等因素而改变 以及急性缺血和梗死组织的存在。一个系统的 将进行研究以确定两者之间的数量关系 这些参数和心肌电流分布。长期的 目的是优化除颤脉冲的传递 给出了一组临床情况。 由于实验和数值方法的局限性 问题，这项调查将结合这两种方法在互补 时尚。将为有限元开发一个数值躯干模型。 分析。这个模型最终将能够预测当前的 一组给定的经胸腔或心脏内的分布 有心脏方面的问题。与这项工作并行的是发展 用于绘制三分量图的256通道数据采集系统 心外膜电流密度，心外膜内单分量电流密度 除颤前后的心肌和激活波前 脉搏。 数值模型将与实验数据进行核对并进行修改 直到数值结果与实验数据完全匹配。这个 将结合两种方法来检验假设和确定 电流密度阈值。然后，该模型将被用于执行 任意除颤条件下的数值实验。

The aims of this proposal are to determine the distribution of myocardial current density during defibrillation and its effect on defibrillation success. One hypothesis of this study is that a minimum current density must be reached within the myocardium in order to achieve defibrillation. A second hypothesis is that this threshold current density is invariant with respect to a given species under homeostatic conditions. Whether threshold myocardial current density is achieved for a given defibrillation attempt depends on the distribution of current throughout the myocardium. This distribution is complex due to inhomogeneity of the heart volume conductor and anisotropy of myocardial conductivity and, in addition, may be altered by such factors as electrode size and placement as well as the presence of acute ischemia and infarcted tissue. A systematic study will be performed to determine the quantitative relationships between these parameters and the myocardial current distribution. The long-term objective is to optimize the delivery of the defibrillation pulse for a given set of clinical conditions. Due to limitations of both experimental and numerical approaches to this problem, this investigation will combine both methods in a complementary fashion. A numerical torso model will be developed for finite element analysis. This model will ultimately be able to predict the current distribution throughout the heart for a given set of transthoracic or transcardiac conditions. In parallel with this work will be the development of a 256 channel data acquisition system for mapping three-component epicardial current density, one-component current density within the myocardium, and activation wavefronts before and after the defibrillatory pulse. The numerical model will be checked against experimental data and modified until the numerical results sufficiently match the experimental data. The two methods will be combined to test the hypotheses and to determine the current density threshold. The model will then be used to perform numerical experiments for any set of defibrillation conditions.