实验性甲状腺机能减退犬的心室电生理效应及其抗颤动作用

Effects of hypothyroidism on ventricular electrophysiology and its antifibrillatory properties in canine

应用心脏电刺激和单相动作电位记录技术，观察了实验性甲状腺机能减退大的在体心室电生理效应。结果表明，甲状腺机能减退状态呈现出与胺碘酮相似的电生理效应。包括同步均一地延长心室复极化（且主要是复极化前期），延长心室有效不应期，并具有抗心室纤颤作用。研究结果为深入认识甲状腺机能减退状态的心电生理效应及其潜在的抗心律失常作用提供了实验依据。

Abstract A study on ventricular electrophysiologic effects of hypothyroidism was made in vivo in dogs with the techniques of electrical stimulation and monophasic actionpotential (MAP) recording.The animals were randomly divided into 3 groups :Group 1 (n= 8) served as normal controls.Group 2 (n = 9) were the hypothyroid models by total thyroidectomy. Group 3 (n= 7) were given amiodarone orally 400mg a day for 4 weeks. The results showed that in anesthetized, open-chest dogs:(1)Hypothyroidism lengthened ventricular repolarization synchronousiy and homogeneously and the lengthening is observed mainly in the plateau phase of action potentials;(2)Hypothyroidism increased ventricular effective refractory period (ERP) by 32.6%,whereas it had no effect on intraventricular conduction time;(3)Hypothyroidism increased ventricular fibrillation threshold (VFT) by 48%;(4) Cardiac electrophysiologic effects of hypothyroidism were similar to those of amiodarone, but amiodarone suppressed myocardial conduction velocity and prolonged repolarization both in phase 2 and phase 3.