TRANSMEMBRANE POTENTIAL MAPPING OF DEFIBRILLATION

电除颤休克是停止心室颤动的唯一有效疗法。治疗的改进将需要了解电击如何与心肌相互作用以改变心脏跨膜电压。一种“激活功能”被假设来控制这种相互作用。该基金将通过以下方法来验证这一假设：1)开发一种光学标记心脏的方法，该方法将表明记录跨膜电压的位置；2)确定电击引起的心脏细胞外电压的一阶和二阶空间导数与跨膜电压变化的关系；3)确定心肌结构不均匀性与电击产生的跨膜电压变化的关系。4)确定在除颤过程中经常出现的由缺血引起的细胞间解耦是否会改变电击产生的跨膜电压的变化。兔心脏的跨膜电压变化将通过跨膜电压敏感染料荧光激光扫描测绘来测量。为了确定心肌结构与跨膜电压变化之间的关系，我们将用激光束光学标记记录位置。用透明氧化铟锡（ITO）和金属触电电极在一维和二维空间上产生冲击胞外电压的空间导数。衍生物将用金属和ITO记录电极测量。光漂白后细胞内6-羧基荧光素荧光恢复（FRAP）的定位将表明与心肌多细胞结构相对应的细胞内扩散在控制跨膜电压变化的关系中的作用。FRAP还将显示缺血期间细胞间解耦引入的扩散常数的变化。是否解耦对冲击产生的跨膜电压变化的影响将被确定为全局缺血和缺血区域边界。因此，将确定正常和缺血心脏除颤期间跨膜电压变化的主要因素。这些知识将有助于优化危及生命的心律失常的电疗法。

An electric defibrillation shock is the only effective therapy to halt ventricular fibrillation. Improvements in the therapy will require knowledge of how electric shocks interact with the myocardium to change cardiac transmembrane voltages. An "activating function" is hypothesized to govern this interaction. This grant will test the hypothesis by 1) developing a method to optically mark hearts that will indicate the locations from which transmembrane voltages were recorded, 2) determining the relationships of the first and second spatial derivatives of the cardiac extracellular voltages induced by electric shocks to the changes in transmembrane voltages, 3) determining the relationships of myocardial structural inhomogeneities to the changes in transmembrane voltages produced by electric shocks, and 4) determining whether cell-to-cell uncoupling by ischemia, often present during defibrillation, alters the changes in transmembrane voltages produced by electric shocks. Transmembrane voltage changes in rabbit hearts will be measured with laser-scanner mapping of transmembrane voltage-sensitive dye fluorescence. To determine relationships between myocardial structure and transmembrane voltage changes, we will optically mark recording locations with the laser beam. Spatial derivatives of shock extracellular voltages will be produced in one and two dimensions with transparent indium tin oxide (ITO) and metallic shocking electrodes. The derivatives will be measured with metallic and ITO recording electrodes. Mapping of intracellular 6-carboxyfluorescein fluorescence recovery after photobleaching (FRAP) will indicate roles of intracellular diffusion that corresponds to the myocardial multicellular structure in the relationships that govern transmembrane voltage changes. FRAP will also indicate changes in diffusion constants introduced by cell-to-cell uncoupling during ischemia. Whether the uncoupling impacts on transmembrane voltage changes produced by shocks will be determined for global ischemia and for borders of ischemic regions. Thus, major factors responsible for transmembrane voltage changes during defibrillation in normal and ischemic hearts will be determined. This knowledge will help to optimize electrical therapy for life-threatening arrhythmias.