CARDIAC CURRENT DENSITY: DETERMINANT OF DEFIBRILLATION

高能直流电胸腔内送入的实践 用于脑室转流的病人 房颤转为血流动力学稳定的室上性心动过速 在过去的30年里，节律一直在临床上使用。 然而，这些电击可能导致MB-肌酸激酶的释放 和坦率的心肌坏死。当前的能级用于 除颤是经验性的和高度可变的。这在一定程度上， 是由于对电剂量进行量化的惯例 以能量为单位的除颤；然而，电流而不是 能量使心脏除颤。从年长到个人 优化电击的幅度，这是必要的 为了表征输送到 真正穿过心脏的胸腔，是必要的 心脏除颤所需的跨心肌电流 改变这些变量的因素。这其中的假设 研究发现：1)跨心肌电流是依赖的 关于经胸结构的相对阻力，2) 胸腔和胸腔内结构可以建模为3 并联可变电阻器，可以预测有效的 经胸电击产生的跨心肌电流， 3)除颤取决于达到最佳状态 心脏细胞团中的电流密度。这项建议 将测量跨心肌的电流流量并将其与 数量与输送到胸腔的总电流之比。 通过心肌的电流密度将在#年确定 通过三轴电极系统关闭胸腔的狗 在4.0平方厘米的范围内测量三维电流密度 12个同时的左心室部位的区域。这个 实现以下目标所需的最小心肌电流密度 除颤将被确定。两者之间的关联性 电流密度阈值和前瞻性测量对象 可预测最优电气参数的相关参数 将检查每个人的脉搏。这些信息 从这项研究中获得的数据应该进一步阐明 因此为除颤的生理学提供了基础 获取更复杂的方法来前瞻性地确定 除颤所需的最小能量(或电流) 一个单独的主题。

The practive of delivering high energy DC shocks to the thorax of patients for the purpose of converting ventricular fibrillation to a hemodynamically stable supraventricular rhythm has been clinically employed for the past 30 years. These shocks, however, can result in MB-creatine kinase release and frank myocardial necrosis. Present energy levels used for defibrillation are empiric and highly variable. This, in part, is due to the convention of quantifying the electrical dose for defibrillation in units of energy; however, current rather than energy defibrillates the heart. In older to individually optimize the magnitude of the electrical shock, it is necessary to characterize the percent of total current delivered to the thorax that actually traverses the heart, the requisite transmyocardial current needed to defibrillate the heart, and the factors that alter these variables. The hypotheses of this study are that: 1) transmyocardial current flow is dependent on the relative resistances of the transthoracic structures, 2) the thorax and intrathoracic structures can be modeled as 3 parallel, variable resistors that can predict the effective transmyocardial current delivered from transthoracic shocks, and 3) defibrillation is dependent on achieving on optimal current density in a ceitical mass of the heart. This proposal will measure transmyocardial current flow and compare this quantity to the total current delivered to the thorax. Transmyocardial current density will be determined in closed-chest dogs by a triaxial electrode system that will measure current density in three dimensions over a 4.0 cm2 region from 12 simultaneous left ventricular sites. The minimal myocardial current density necessary to achieve defibrillation will be determined. The correlation between current density thresholds and prospectively measured subject related parameters that may predict the optimal electrical pulse for each individual will be examined. The information obtained from this study should further elucidate the physiology of defibrillation and therefore provide the basis for more sophisticated methods in prospectively determining the minimal amount of energy (or current) required to defibrillate an individual subject.