Effects of Low [K]o on Cardiac Excitation Conduction and Membrane Currents in the Vicinity of Vulnerable Window: A Computer Simulation Study

Unidirectional conduction block of cardiac excitation wave is a requisite condition leading to initiation of reentrant arrhythmia and even causing lethal ventricular arrhythmia. Temporal vulnerable window (VW_time) is an important measure for arrhythmia vulnerability. In this study, we show how low extracellular K concentration ([K]₀) affects the VW_time of conduction block by single extrasystole. Using computer simulation with modified LR91 one dimensional (1-d) heterogeneous virtual cardiac ventricular tissue model, we quantitatively investigate the relation of different [K]₀ with VW_time, conduction velocity (CV) of premature beat and then, observe the change of electrical dynamic factor action potential duration (APD) restitution and CV restitution. Also, we characterize theoretically the distribution of action potential and membrane currents of premature beat applied at different time of the VW_time with normal and low [K]₀. The results show that along with [K]₀ decreasing, the magnitude of VW_time enlarges gradually. The conduction velocity of premature beat slows down with the [K]₀ very obviously. The overall results of low [K]₀ hyperpolarizing resting membrane potential and decreasing repolarization reserve cause a steeper APD restitution and broader CV restitution curve, which induce larger transmural dispersion of refratoriness for the premature beat and enlarge the VW_time.