Transmembrane potential changes and ventricular fibrillation during repetitive myocardial ischaemia in the dog.
Transmembrane potential changes and ventricular fibrillation during repetitive myocardial ischaemia in the dog.
复制标题
狗重复心肌缺血期间的跨膜电位变化和心室颤动。
作者：
D. Russell;J. Smith;M. Oliver
用心外膜动作电位、心内膜-心外膜传导时间和左冠状动脉前降支连续阻断5分钟时心外膜ST段抬高相结合的方法，观察了13只犬冠状动脉结扎后即刻的电生理变化。随着ST段进行性抬高，动作电位时程由182±9ms缩短至113±9ms，传导时间由241ms延长至71±17ms。随后出现“慢反应”型电位，动作电位时程和波幅交替，心外膜和心内膜ST段抬高交替，间歇性传导阻滞。95%的室颤患者出现动作电位交替，65%的患者出现传导阻滞，且发生在最大传导延迟时。这些数据有力地支持了在早期室颤发病机制中折返的概念。在第一次闭塞期间，动作电位时程和传导时间的变化明显大于随后的闭塞。然而，来自闭塞2、3、4或5的数据之间没有显著差异。这质疑了基于以第一次闭塞为对照的连续冠脉闭塞的心肌缺血实验研究的有效性。
Electrophysiological changes occurring soon after experimental coronary occlusion have been examined in 13 dogs by combined recording of epicardial action potential, endocardial-epicardial conduction time, and epicardial ST segment elevation during successive 5-minute occlusions of the left anterior descending coronary artery. Mter initial coronary occlusion, action potential duration shortened from 182 ± 9 ms to 113 ± 9 ms at 2 minutes and conduction time was prolonged from 24 i 1 ms to 71 ± 17 ms associated with progressive ST segment elevation. These changes were followed by the appearance of potentials of 'slow response' type morphology, alternans of action potential duration and amplitude, alternans of epicardial and endocardial ST segment elevation, and intermittent conduction block. Ventricular fibrillation was preceded by action potential alternans in 95 per cent and by conduction block in 65 per cent of instances and occurred at a time of maximum conduction delay. These data strongly support the concept of re-entry in the pathogenesis of early ventricular fibrillation. Changes in action potential duration and conduction time were significantly greater during the first occlusion compared with subsequent occlusion periods. There was no significant difference however between data taken from occlusions 2, 3, 4, or 5. This questions the validity of experimental studies of myocardial ischaemia based on comparisons of sequential coronary occlusions using the first as the control.