基于动态心脏模型的体表心电图仿真研究

Simulation Study of Body Surface ECG Based on a Dynamic Heart Model

以往的电生理心脏模型大多是静态的,而非动态模型。这样在用准静电场理论求解体表电位时,整个心动周期中等效心电偶极子(源点)与体表(场点)之间的距离假设为恒定不变,从而会引入较大的系统误差。因此,为了更准确仿真心电图,有必要采用动态或跳动的心脏模型。基于原来静态心脏模型,构造了一个动态心脏模型,并对体表12导联心电图进行仿真比较研究。在动态心脏模型中考虑了心肌电兴奋引起的心脏机械力学收缩,通过计算心动周期中心室壁的位移,从而将心脏与体表之间的相对距离变化考虑进体表电位计算过程。仿真结果表明,对于正常心电图,基于动态心脏模型的仿真结果比基于静态心脏模型的仿真结果更符合临床记录心电图,特别是V1-V6胸导联的ST段和T波。对于前壁轻微缺血情况,在动态心脏模型的仿真心电图中能明显看出ST段和T波的变化,而在静态心脏模型的仿真心电图中与正常心电图相比看不出什么变化。本研究的仿真研究证实了动态心脏模型的确能更准确地仿真体表心电图。

Most previous electrical heart models were static, not beating ones. When computing body surface ECG based on quasi-static field theory, the distances between equivalent cardiac dipoles （source points） and body surface （field points） were supposed to be constant during the whole cardiac cycle. Large system errors could be introduced because of the significant relative position changes of source-field points during cardiac systole and diastole. Therefore, to improve the ECG simulation accuracy, a beating or dynamic heart model should be considered. In this investigation, a dynamic or beating heart model was constructed based on our previous static electrical heart model, and a comparative simulation study of 12-lead ECG based on dynamic and static heart models was presented. In the dynamic heart model, the eoupling of electrical excitation and mechanical contraction were considered, and the resulted relative position changes between heart wall and body surface during cardiac systole and diastole were employed to calculate body surface ECG afterwards. The results showed that, compared with ECG signals simulated from the static electrical heart model, the ECG signals obtained from the beating heart model was more accordant with clinical recorded ECG, especially for ST segment and T wave of V1-V6 lead ECG. For slight-degree myocardial ischemia, the ST segment and T wave changes were observed from the simulated ECG based on beating heart model, while the ST segment and T wave of simulated ECG based on static heart model was almost unchanged compared with normal ECG. These simulation results suggest that the beating heart model generate more accurate ECG signals.