Stimulatory current at the edge of an inactive conductor in an electric field: role of nonlinear interfacial current-voltage relationship.
Stimulatory current at the edge of an inactive conductor in an electric field: role of nonlinear interfacial current-voltage relationship.
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DOI：
10.1109/tbme.2009.2025965
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发表时间：
2010-02
期刊：
影响因子：
--
通讯作者：
Knisley SB
中科院分区：
文献类型：
--
作者：
Sims JA;Pollard AE;White PS;Knisley SB
心脏电场刺激对于除颤机制至关重要。在除颤期间，场中存在某些不活动的心外膜导体会降低除颤阈值。我们假设这种减少是由于场刺激期间非活动导体和心脏之间的界面上的电流的刺激效应所致。为了检查这种电流及其可能的刺激效应，我们对氧化铟锡 (ITO) 导体的透射率进行了成像，用 X 射线衍射测试了铟，创建了包含真实 ITO 界面特性的计算机模型，并在 ITO 导体存在的情况下以光学方式绘制了电场刺激期间兔子心脏的兴奋情况。当跨界面电压超过标准还原电位时，ITO 还原成铟会降低面向阳极电击电极的边缘的透射率。界面电流-电压关系是非线性的，在较高电流下产生较大电导。这种非线性将界面电流集中在图像和计算机模型的边缘附近。边缘电流是刺激性的，产生兔子心室的早期电击后兴奋。因此，ITO 变暗表明因铟还原而产生界面电流。界面非线性将电流集中在可以激发心脏的边缘附近。边缘处的刺激电流可能是报告中不活动导体导致除颤阈值降低的原因。
Cardiac electric field stimulation is critical for the mechanism of defibrillation. The presence of certain inactive epicardial conductors in the field during defibrillation can decrease the defibrillation threshold. We hypothesized this decrease is due to stimulatory effects of current across the interface between the inactive conductor and the heart during field stimulation. To examine this current and its possible stimulatory effects, we imaged transmittance of indium-tin-oxide (ITO) conductors, tested for indium with x-ray diffraction, created a computer model containing realistic ITO interfacial properties, and optically mapped excitation of rabbit heart during electric field stimulation in the presence of an ITO conductor. Reduction of ITO to indium decreased transmittance at the edge facing the anodal shock electrode when trans-interfacial voltage exceeded standard reduction potential. The interfacial current-voltage relationship was nonlinear, producing larger conductances at higher currents. This nonlinearity concentrated the interfacial current near edges in images and in a computer model. The edge current was stimulatory, producing early postshock excitation of rabbit ventricles. Thus, darkening of ITO indicates interfacial current by indium reduction. Interfacial nonlinearity concentrates current near the edge where it can excite the heart. Stimulatory current at edges may account for the reported decrease in defibrillation threshold by inactive conductors.