Kléber A G, Fast V G, Kucera J, Rohr S
Physiologisches Institut, Universität Bonn, Bern, Schweiz.
Z Kardiol. 1996;85 Suppl 6:25-33.
Representation of cardiac tissue by a continuous electrical cable provides a simple tool to explain impulse propagation and to make a comparison between heart, skeletal muscle and nerve. Recent experimental and theoretical studies have shown, however, that the process of electrical impulse propagation in heart is complex, due to the presence of cell borders and septa of connective tissue. At sites where propagation deviates from a linear profile, action potential generation gets delayed, and in cases of decreased excitability, unidirectional block may occur. At such sites, propagation is carried by the slow Ca++ inward current, in addition to the rapid Na+ inward current. As a consequence, local propagation may become sensitive to inhibition of Ca++ channels. Moreover, computer simulations have shown that electrical cell-to-cell uncoupling an gap junctions can reverse unidirectional block at such sites to bidirectional conduction. This complex interaction between function and structure which is likely to play a major role in remodeled tissue (hypertrophy, chronic infarction) has to be taken into account in the evaluation of the mechanisms of action of antiarrhythmic drugs.
用连续的电缆来表示心脏组织，为解释冲动传播以及比较心脏、骨骼肌和神经提供了一个简单的工具。然而，最近的实验和理论研究表明，由于存在细胞边界和结缔组织间隔，心脏中的电冲动传播过程很复杂。在传播偏离线性分布的部位，动作电位的产生会延迟，并且在兴奋性降低的情况下，可能会发生单向阻滞。在这些部位，除了快速的Na⁺内向电流外，传播还由缓慢的Ca²⁺内向电流介导。因此，局部传播可能会对Ca²⁺通道的抑制敏感。此外，计算机模拟表明，细胞间电去耦联和缝隙连接可以将这些部位的单向阻滞逆转为双向传导。在评估抗心律失常药物的作用机制时，必须考虑到这种功能与结构之间的复杂相互作用，这种相互作用可能在重塑组织（肥大、慢性梗死）中起主要作用。
