在体兔心左室肌缺血中心区与边缘区跨膜电位的比较

实验在30只兔身上进行。利用浮置微电极技术,在心脏的缺血中心区、边缘区和非缺血区共记录了630个细胞的动作电位,其中270个细胞在阻断冠脉条件下进行记录,360个细胞在冠脉灌流条件下,造成心肌不同程度缺血后进行记录。同时,用棉线电极记录了各区心外膜电图ST段的变化。 阻断冠脉引起静息电位(RP)减小、动作电位振幅(APA)和零期最大除极速度(dv/dt)明显降低以及复极50％时程(APD_(50))和衰极90％时程(APD_(90))的显著缩短。缺血边缘区上述各指标的变化与ST 段抬高的程度均显著轻于缺血中心区。改变冠脉灌流血量造成心肌不同程度缺血的结果表明,当灌流血量为 50％时,在中心区所记录的静息电位和动作电位均与阻断冠脉后的边缘区相似;而灌流量为 0％时,在同一区所记录的静息电位和动作电位则与阻断冠脉后的中心区相似。另外,0％ 灌流时的ST 段抬高程度也显著高于灌流量为50％时的表现。这些结果提示,在兔急性心肌缺血早期,从缺血中心区和边缘区可记录到各具特征的动作电位,似有助于说明在缺血区有边缘区的存在。

COMPARISON BETWEEN THE TRANSMEMBRANE ACTION POTENTIALS RECORDED FROM CENTRAL ISCHEMIC ZONE AND ISCHEMIC BORDER ZONE OF RABBIT'S LEFT VENTRICULAR MUSCLE IN SITU

The transmembrane action potentials (TAPS) were recorded from centralischemic zone and ischemic border zone of rabbit's left ventricular muscle. TheseTAPs were compared with those recorded from the central ischemic zone duringcoronary perfusion with different perfusion rate. The experiments were performedon 30 rabbits. TAP was recorded by using floating intracellular microelectrode.Among 630 cells, 270 cells were recorded after coronary occlusion, and 360 cellswere recorded during coronary perfusion. At the same time, changes in ST segmentof epicardial electrograms were recorded from each zone by using cotton-wick elec-trode. Coronary occlusion resulted in a significant diminution in resting potential(RP), amplitude of action potential (APA), maximal depolarization rate of phaseO(dv /dt), and decrease in action potential duration at 50% repolarization (APD_(50))and 90% repolarization (APD_(90)). These changes of action potential andST elevation recorded from the central ischemic zone were more severe than thoseof the ischemic border zone. The experiment of coronary perfusion with differentperfusion rate showed that the TAPs recorded from the central zone during 50%perfusion rate were similar to that of the ischemic border zone, while the TAPsrecorded from the same zone during 0% perfusion rate were similar to that of thecentral ischemic zone. In addition, the degree of ST segment elevation during0% perfusion was more obvious than that during 50% perfusion. Our results suggest that characteristic action potentials can be recorded fromthe central ischemic zone and ischemic border zone respectively. These findingsprovide an evidence for the existence of the ischemic border zone.