Roth B J
Biomedical Engineering and Instrumentation Program, National Institutes of Health, Bathesda, MD 20892, USA.
IEEE Trans Biomed Eng. 1995 Dec;42(12):1174-84. doi: 10.1109/10.476124.
Numerical simulations of electrical stimulation of cardiac tissue using a unipolar extracellular electrode were performed. The bidomain model with unequal anisotropy ratios represented the tissue, and the Beeler-Reuter model represented the active membrane properties. Four types of excitation were considered: cathode make (CM), anode make (AM), cathode break (CB), and anode break (AB). The mechanisms of excitation were: for CM, tissue under the cathode was depolarized to threshold; for AM, tissue at a virtual cathode was depolarized to threshold; for CB, a long cathodal pulse produced a steady-state depolarization under the cathode and hyperpolarization at a virtual anode. At the end (break) of the pulse, the depolarization diffused into the hyperpolarized tissue, resulting in excitation. For AB, a long anodal pulse produced a steady-state hyperpolarization under the anode and depolarization at a virtual cathode. At the end (break) of the pulse, the depolarization diffused into the hyperpolarized tissue, resulting in excitation. For AB stimulation, decay of the hyperpolarization faster than that of the depolarization was necessary. The thresholds for rheobase and diastolic CM, AM, CB, and AB stimulation were 0.038, 0.41, 0.49, and 5.3 mA, respectively, for an electrode length of 1 mm and a surface area of 1.5 mm2. Threshold increased as the size of the electrode increased. The strength-duration curves for CM and AM were similar except when the duration was shorter than 0.2 ms, in which case the AM threshold rose more quickly with decreasing duration than did the CM threshold. CM and AM resulted in similar strength-frequency curves. The model agrees qualitatively, but (in some cases) not quantitatively, with experiments.
使用单极细胞外电极对心脏组织进行电刺激的数值模拟已经完成。具有不等各向异性比的双域模型代表组织，而Beeler-Reuter模型代表活性膜特性。考虑了四种类型的刺激：阴极接通（CM）、阳极接通（AM）、阴极断开（CB）和阳极断开（AB）。刺激的机制如下：对于CM，阴极下方的组织去极化至阈值；对于AM，虚拟阴极处的组织去极化至阈值；对于CB，长阴极脉冲在阴极下方产生稳态去极化，并在虚拟阳极处产生超极化。在脉冲结束（断开）时，去极化扩散到超极化组织中，导致兴奋。对于AB，长阳极脉冲在阳极下方产生稳态超极化，并在虚拟阴极处产生去极化。在脉冲结束（断开）时，去极化扩散到超极化组织中，导致兴奋。对于AB刺激，超极化的衰减必须比去极化的衰减更快。对于电极长度为1 mm且表面积为1.5 mm2的情况，基强度和舒张期CM、AM、CB和AB刺激的阈值分别为0.038、0.41、0.49和5.3 mA。阈值随着电极尺寸的增加而增加。CM和AM的强度-持续时间曲线相似，除非持续时间短于0.2 ms，在这种情况下，AM阈值随持续时间的缩短比CM阈值上升得更快。CM和AM产生相似的强度-频率曲线。该模型在定性上（但在某些情况下不是定量上）与实验结果一致。
