Spach M S, Dolber P C, Heidlage J F, Kootsey J M, Johnson E A
Circ Res. 1987 Feb;60(2):206-19. doi: 10.1161/01.res.60.2.206.
As yet there is no model or simulation that accounts for the anisotropic difference in the shape of the upstroke and safety factor of propagating cardiac action potentials: fast upstrokes occur with slow transverse propagation and slow upstrokes occur with fast longitudinal propagation. The purpose of this paper is to demonstrate, however, that a simplified cable model based on directional differences in the effective membrane capacitance predicts in detail the experimentally measured directionally dependent behavior of the upstroke in response to modification of the sodium conductance. Quinidine and lidocaine produced greater relative decreases in Vmax and conduction velocity with longitudinal propagation than with transverse propagation, as predicted on the basis that the shape differences should produce an anisotropic distribution in the membrane uptake of sodium channel binding drugs. The simulation predictions of the effects of positive shifts of the take-off potential due to premature action potentials were also confirmed experimentally: there was a greater relative decrease in conduction velocity, Vmax, and Vamp with a greater increase in tau foot during longitudinal propagation than with transverse propagation. The major anisotropic differences in shape occurred when the take-off potential approached the least negative value that produced a propagated response. The extensive experimental verification of the results of a simplified model based on directional differences of effective membrane capacitance, combined with directional differences in effective axial resistivity, provides an initial quantitative basis for the anisotropic behavior of propagating depolarization in response to modification of the sodium conductance in cardiac muscle.
快速上升支伴随着缓慢的横向传播，而缓慢上升支伴随着快速的纵向传播。然而，本文的目的是证明，基于有效膜电容方向差异的简化电缆模型详细预测了实验测量的响应钠电导改变时上升支的方向依赖性行为。奎尼丁和利多卡因在纵向传播时比横向传播时导致Vmax和传导速度的相对降低更大，这是基于形状差异应在钠通道结合药物的膜摄取中产生各向异性分布这一预测得出的。由早搏动作电位引起的起跳电位正向偏移效应的模拟预测也得到了实验证实：纵向传播期间，随着tau foot的增加，传导速度、Vmax和Vamp的相对降低比横向传播时更大。当起跳电位接近产生传播反应的最小负值时，形状上的主要各向异性差异出现。基于有效膜电容方向差异并结合有效轴向电阻率方向差异的简化模型结果得到了广泛的实验验证，为心肌中响应钠电导改变时传播去极化的各向异性行为提供了初步的定量基础。
