Muller-Borer B J, Johnson T A, Gettes L S, Cascio W E
University of North Carolina at Chapel Hill, USA.
J Cardiovasc Electrophysiol. 1995 Dec;6(12):1101-12. doi: 10.1111/j.1540-8167.1995.tb00388.x.
It is suggested that heterogeneous extracellular potassium concentration, cell-to-cell coupling, and geometric nonuniformities of the ischemic border zone contribute to the incidence of unidirectional block and subsequent development of lethal ventricular arrhythmias.
A discrete electrical network was used to model a single cardiac fiber with a [K+]e gradient characteristic of an ischemic border zone. Directional differences in propagation were evaluated by creating discrete regions with increased gap junctional resistance within the [K+]e gradient. Furthermore, the effect of homogeneity/heterogeneity of call length on impulse propagation through the [K+]e gradient in the presence of increased gap junctional resistance was evaluated. The results indicate that failure of impulse propagation occurs at the junction between partially uncoupled and normally coupled cells. Furthermore, propagation failure was more likely to occur as the impulse propagated from a region of high [K+]e to low [K+]e. Heterogeneity in cell length contributes to the variability in the occurrence of unidirectional and bidirectional block.
The onset of cellular uncoupling in an ischemic border zone may interact with the inherent [K+]e gradient leading to unidirectional conduction block. This mechanism may be important for the generation of reentrant arrhythmias at the ischemic border zone.
有人提出，细胞外钾浓度不均一、细胞间耦联以及缺血边缘区的几何形状不均一，均会导致单向阻滞的发生以及随后致死性室性心律失常的发展。
采用离散电网络对具有缺血边缘区特征性[K⁺]e梯度的单个心肌纤维进行建模。通过在[K⁺]e梯度内创建间隙连接电阻增加的离散区域，评估传播的方向差异。此外，在间隙连接电阻增加的情况下，评估细胞长度的均一性/不均一性对冲动通过[K⁺]e梯度传播的影响。结果表明，冲动传播失败发生在部分去耦联细胞和正常耦联细胞之间的交界处。此外，当冲动从高[K⁺]e区域向低[K⁺]e区域传播时，传播失败更有可能发生。细胞长度的不均一性导致单向和双向阻滞发生的变异性。
缺血边缘区细胞去耦联的发生可能与固有的[K⁺]e梯度相互作用，导致单向传导阻滞。这种机制可能对缺血边缘区折返性心律失常的产生很重要。
