伊布利特对犬心脏电生理特性的影响

观察伊布利特对犬心脏电生理特性的作用特点,初步探讨其终止心房扑动(简称房扑)的机制。15只成年健康雄性杂种犬,麻醉后气管插管,开胸并缝合电极,伊布利特按0.10mg/kg静脉推注给药(10min缓推,给药30min后按照0.01mg/min静脉滴注维持),观察给药前后心率、房内房间传导时间、峡部缓慢传导区传导速度、各部位不应期的变化。结果:伊布利特对心率有明显的抑制作用,作用的高峰时间在给药后20~30min,2h后心率基本恢复到用药前的水平;伊布利特能显著延长心房肌、心室肌以及肺静脉的不应期(P<0.05~0.001),但对房内、房间以及峡部的传导作用影响不明显(P>0.05)。结论:伊布利特终止房扑的机制可能是由于该药造成不应期延长,使折返环可激动间隙兴奋性降低,进而使波锋不能向前推进,终止房扑。其房扑折返环传导的减慢可能不是房扑终止的主要作用。

The Effects of Ibutilide on Canine Electrophysiological Characters

The purpose was to observe the effects of ibutilide on canine electrophysiological characters, and further more, to explore the mechanism of ibutilide′s converting atrial flutter(AFL). 15 mongrel dogs were anesthetized and intubated with a tracheal tube. The heart was exposed through a thoracotomy and then electrodes were fixed by suture. The electrophysiologic variables were measured with and without ibutilide(for the 10-minute infusions the dose was 0.10mg/kg, and 30 minutes later, the maintaining dose was 0.01mg/min). These variables included the heart rate, the conduction of intraatrium and interatrium, the conduction ratio of isthmus, the effective refractory period, and so on. Results:Ibutilide had the significant suppressing effect for the sinus atrial node. The peak response time was 20~30 min and the heart rate recovered without drug administration. The atrial, ventricular and pulmonary vein effective refractory period were significantly prolonged(P<0.05~0.001).However, there were no significant difference on the conduction of intraatrium, interatrium and isthmus(P>0.05). Conclusion:The mechanism of ibutilide′s rapidly terminating AFL is speculated on the prolongation of the refractory period which could cause the whole excitable gap of the reentrant circuit to be affected by refractoriness, thus to terminate the AFL due to the reentrant wavefront′s inability to proceed.