Quan W L, Rudy Y
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio.
Pacing Clin Electrophysiol. 1991 Nov;14(11 Pt 2):1700-6. doi: 10.1111/j.1540-8159.1991.tb02751.x.
A computer model of a ring-shaped one-dimensional cardiac fiber was used to examine responses of reentrant propagation to premature stimuli applied under different degrees of head-tail interaction. Two different types (type I and type II) of termination window (TW) were identified. The type I TW was generated by functional inhomogeneity created by reentrant propagation. The width of the type I TW was proportional to the degree of cellular uncoupling. In contrast, uniform reduction in sodium channel conductance decreased the width of type I TW. The type II TW was generated by electrical alternans created by the head-tail interaction of the reentrant action potential. It was demonstrated that electrical alternans were most significant in medium degree head-tail interaction. For stronger or weaker head-tail interaction, the electrical alternans tended to decrease. The type II TW was located in excitable gaps following reentrant action potentials of short duration. Its size was proportional to the degree of electrical alternans. The type II TW was usually much larger than the type I TW. A premature conditioning stimulus induced alternans and created a type II TW. This response implies that a conditioning stimulus could facilitate greatly the termination of clinical reentrant arrhythmias by programmed electrical stimulation.
利用环形一维心脏纤维的计算机模型，研究了在不同程度的头尾相互作用下施加过早刺激时折返传播的反应。识别出了两种不同类型（I型和II型）的终止窗（TW）。I型TW是由折返传播产生的功能不均匀性所致。I型TW的宽度与细胞去偶联程度成正比。相比之下，钠通道电导的均匀降低会减小I型TW的宽度。II型TW是由折返动作电位的头尾相互作用产生的电交替所致。结果表明，电交替在中等程度的头尾相互作用中最为显著。对于更强或更弱的头尾相互作用，电交替倾向于减少。II型TW位于短持续时间折返动作电位后的可兴奋间隙中。其大小与电交替程度成正比。II型TW通常比I型TW大得多。过早的条件刺激会诱发交替并产生II型TW。这种反应意味着条件刺激可通过程控电刺激极大地促进临床折返性心律失常的终止。
