Rudy Y, Quan W L
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106.
Circ Res. 1987 Dec;61(6):815-23. doi: 10.1161/01.res.61.6.815.
The effects of the discrete cellular structure on propagation of electrical excitation in cardiac muscle were studied in a one-dimensional fiber model containing a periodic intercalated disk structure. Globally, the macroscopic velocity of propagation follows the behavior associated with propagation in a continuous tissue (except for high values of disk resistance). In addition, the computed spatial extracellular potential along the fiber is a smooth biphasic waveform and does not reflect the underlying discrete cellular structure of the tissue. Other results of the simulations demonstrate the discontinuous nature of propagation and the importance of the structure in arrhythmogenesis. Vmax displays a biphasic behavior as a function of increasing intercalated disk resistance. An initial "paradoxical" increase in Vmax (with a simultaneous decrease in conduction velocity) is followed by a decrease that leads to decremental propagation and conduction block. The time constant of the foot of the action potential (tau foot) increases monotonically with increasing intercalated disk resistance. An increase in the leakage current to extracellular space brings about a significant decrease in the action potential duration and a loss of the plateau. This major effect is accompanied by a relatively smaller decrease in conduction velocity. Collision of two activation wavefronts results in a significant (100%) increase in Vmax and a very small (0.6%) decrease in tau foot.
在一个包含周期性闰盘结构的一维纤维模型中，研究了离散细胞结构对心肌电兴奋传播的影响。总体而言，宏观传播速度遵循与连续组织中传播相关的行为（除了高值的盘电阻情况）。此外，沿纤维计算的细胞外空间电位是一个平滑的双相波形，并未反映出组织潜在的离散细胞结构。模拟的其他结果表明了传播的不连续性以及该结构在心律失常发生中的重要性。Vmax 作为闰盘电阻增加的函数呈现双相行为。Vmax 最初出现“反常”增加（同时传导速度降低），随后是导致递减传播和传导阻滞的降低。动作电位起始段的时间常数（tau foot）随闰盘电阻增加而单调增加。向细胞外空间的漏电流增加会导致动作电位持续时间显著缩短以及平台期消失。这种主要影响伴随着传导速度相对较小的降低。两个激活波前的碰撞导致 Vmax 显著增加（100%），而 tau foot 非常小的降低（0.6%）。
