Effects of electrical heterogeneity on transmural reentry during acute global ischemia.
Ventricular arrhythmias are commonly observed in patients with ischemia. It is reported that the electrophysiological changes evoked by ischemia are greater in the epicardium than in the endocardium. To investigate the effects of this heterogeneity on transmural reentry, the computer simulation method is used. A two-dimensional model which can reproduce the endocardial, epicardial and middle cell types, approximate the ischemic characteristics and distribution of the ischemic severity is developed by setting different ratios of the maximum conductance of the rapid and slow inward rectifier potassium currents and considering the three major component conditions of acute ischemia at the ionic level. The results demonstrate that action potentials of the ischemic cells have elevated resting potential, shortened duration, slowed upstroke and declined amplitude. Conduction velocity is much more depressed in the epicardium because of the ischemia-induced transmural gradient of excitability. The epicardially initiated activation has wider vulnerable window and more possibility to cause unidirectional propagation even reentry. Dispersion of the excitability is proposed to be the underlying mechanism.
Zhang
Hong
H
School of Electrical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, PR China. maxr@263.net
Jin
Yin-Bin
YB
Zhang
Zhen-Xi
ZX
Yang
Lin
L
Huang
Ye-Cho
YC
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000150:complications* / Q000503:physiopathology*; D003198:Computer Simulation; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007511:Ischemia / Q000150:complications* / Q000503:physiopathology*; D008955:Models, Cardiovascular; D032383:Myocytes, Cardiac / Q000378:metabolism*