Comparative study of the properties in ischemic fibers with different transition forms

Simulated regional ischemic models with abrupt transition between normal and ischemic region are often used to study mechanisms of arrhythmia. Whether the simplified models could better approximate the real ischemic myocardium was our concern in this paper. Two kinds of regional ischemic fibers were constructed in our simulation research. One had abrupt change between normal and ischemic region. The other transition was gradual with linear change. The ischemic cells were developed by decreasing the intracellular ATP concentration, reducing conductance of the inward Na⁺ current and increasing the extracellular K⁺ concentration. The operator splitting method was used to integrate the models. The duration, resting potential, and amplitude of the cellular action potential along gradually changed fiber were in between the corresponding value of the normal and severely ischemic cell in sudden transitional fiber. The conduction velocity of the wave slowed while the width of the vulnerable window increased with the ischemic aggravation. It proved that due to electrotonic interaction the transitional portion actually existed even if the change between different tissues was assumed to be abrupt. The two constructed models had the similar properties. Therefore, the simplified regional ischemic models with abrupt transition could not influence the qualitative results of the simulation study.