急性心肌缺血时瞬时外向钾电流和跨壁复极离散度的变化及其计算机仿真研究

The study on the changes of transient outward potassium current and transmural dispersion of repolarization and computer simulation during the early acute myocardial ischemia in canine

目的探讨急性心肌缺血时犬左室心肌楔形组织块瞬时外向钾电流(Ito)、跨壁复极离散度(TDR)的变化及其计算机仿真研究。方法建立冠状小动脉灌注犬左室心肌楔形组织块模型,应用浮置玻璃微电极和心电图同步记录技术,观察急性无灌流心肌缺血对内中外三层心肌细胞Ito、动作电位时程(APD)、TDR和心律失常的影响,并结合急性心肌缺血Ito离子流和TDR的变化,应用修正Luo-Rody参数进行计算机仿真。结果急性心肌缺血早期犬左室内中外三层心肌细胞的Ito离子流增大,APD缩短,均以心外膜层细胞最明显,TDR增加,诱发R-on-T早搏和室性心动过速,并经计算机仿真可以证实与临床一致的心电图特点。结论急性心肌缺血时Ito离子流增大,TDR增加,产生2位相折返,是多型性室性心动过速发生的重要机制,计算机仿真可以显示这些特点。

Objective To explore the role of acute ischemia on transient outward potassium current （Ito）, transmural dispersion of repolarization （TDR） and ventricular arrhythmia in canine left ventricular wedge and computer simulation. Methods Observing the role of acute non-flow cardiac ischemia on Ito, action potential duration （APD） of Epi, Mid and Endo-myocardial cells, TDR and arrhythmia in arterially perfused canine left ventricular wedge preparation by using floating glass microelectrode, and recording electrocardiogram at same time, and conducting computer simulation using the Luo-Rady dynamic model. Results After 5 - 10 minutes acute ischemia, in canine left ventricular wedge preparation, APD of three layer cells shortened and Ito increased simultaneously, especially in Epi; TDR increased; Delayed afterdepolarization （ DAD）, R on T premature beat and ventricular tachycardia were induced. The computer simulation showed the similar action potential and ECG changes as in clinic. Conclusion The phase 2 reentry can be initiated by the increases of Ito and TDR during acute cardiac ischemia in arterially perfused canine left ventricular wedge preparation, and can be demonstrated with computer simulation.