心肌电特性参数对心律影响的定量仿真研究

QUANTITATIVE SIMULATION STUDIES OF EFFECT OF MYCARDIUM ELECTRICITY PARAMETERS ON ECG RHYTHM

心电场是由心肌的电活动产生的。心肌细胞的电特性及心肌细胞间的传导关系决定了体表电位的分布及心电图的变化。心肌电特性参数主要包括动作电位、兴奋传导速度、不应期及心肌细胞受激时间间隔与动作电位持续时间的关系（间隔－时间关系）等。由于很难通过实验方法来人为改变这些参数，因而临床上有关心肌细胞电特性参数对心律影响的定量知识相当缺乏。本文采用真实三维躯干模型及心脏模型，对心肌电特性参数与心律变化的关系进行定量仿真研究。结果表明，动作电位的持续时间与Ｓ－Ｔ间隔有关；动作电位分布与Ｔ波形状有关；兴奋传导速度决定了整个心电图的变化，而局部普通心肌的传导速度在相当范围内变化似乎对心电图影响不明显，但传导速度超过一定范围后可能产生突变；心肌不应期的变化对心律也有影响，当某心肌单元不应期延长到一定程度后甚至可能引起折返；另外，心肌细胞受刺激时间间隔的长短对动作电位持续时间产生影响。

Electrocardiofield is resulted from the electric activity of myocardium. The body surface potential map(BSPM) and electrocardiography(ECG) were determined by the electricity parameters and activation conduction of myocardial cells. Generally, the myocardial electricity parameters included action potential(AP), activation conduction velocity, refractory period and the relationship between action potential duration(APD) and the stimulated period of cardiac tissue (period time relation). Because of the difficulties in changing the parameters experimentally, the clinical quantitative knowledge of effect of myocardial electricity parameters on ECG rhythm was very poor. This study described the quantitative simulation of effect of myocardial electricity parameters on cardiac rhythm with threedimensional realistic torso heart geometry models. The results showed that: (1) S T period was affected by APD; (2) T wave was affected by AP; (3) ECG was determined by conduction velocity. The change of conduction velocity of regional myocardium was not obvious in a certain range, but it became critical when the change is out of the range; (4) The cardiac rhythm was also affected by the refractory period, and reentry would occur when the refractory period of some myocardial cells increased; and (5) the APD was influenced by the stimulated period, and consequently, the ECG would be affected also.