Tsuboi N, Kodama I, Toyama J, Yamada K
Jpn Circ J. 1985 May;49(5):487-98. doi: 10.1253/jcj.49.487.
The effects of fiber direction on the conduction of excitation and the characteristics of both extracellular and intracellular action potentials were examined in isolated dog ventricular muscle preparations. Conduction velocity and amplitude of extracellular potentials during propagation in the direction parallel to the long axis of fibers (longitudinal propagation) were significantly greater than those during propagation in the direction perpendicular to it (transverse propagation). However, the maximum rate of rise and amplitude of intracellular action potential were significantly greater during transverse propagation than during longitudinal propagation. Compared with the transverse propagation, the longitudinal propagation was more susceptible to conduction failure under high extracellular K+ concentration, suggesting a lower safety factor of the latter mode of propagation in depolarized cardiac tissue. In contrast, high frequency stimulation caused a greater decrease in the conduction velocity during transverse than longitudinal propagation resulting in augmentation of anisotropic conduction properties. These results suggest that the anisotropic conduction properties of cardiac tissue may play important roles in conduction disturbances leading to arrhythmias under various pathological conditions.
在离体犬心室肌标本中，研究了纤维方向对兴奋传导以及细胞外和细胞内动作电位特征的影响。在平行于纤维长轴方向传播（纵向传播）时，细胞外电位的传导速度和幅度显著大于垂直于该方向传播（横向传播）时。然而，细胞内动作电位的最大上升速率和幅度在横向传播时显著大于纵向传播时。与横向传播相比，在高细胞外钾浓度下纵向传播更容易发生传导失败，这表明在去极化心脏组织中后一种传播方式的安全系数较低。相反，高频刺激导致横向传播时的传导速度比纵向传播时下降得更多，从而增强了各向异性传导特性。这些结果表明，心脏组织的各向异性传导特性可能在各种病理条件下导致心律失常的传导障碍中起重要作用。
