预激综合征1:2房室传导及其变异

Atrioventricular conduction at ratio of 1 to 2 and variation in pre-excitation syndrome

目的探讨预激综合征患者发生l∶2房室传导时的电生理表现及形成机制。方法分析在心内法和食管法心脏电生理检查中发现的3例预激综合征1∶2房室传导和1例1∶2室房传导现象。结果电生理改变为:①心房期前收缩偶联间期缩短到一定程度后才出现两次心室激动,QRS波群第1次呈预激型,第2次呈束支传导阻滞型,R2与R2'波之间无P波;②心房期前收缩偶联间期缩短10ms,出现突然延长的S2-R2'间期,表明存在房室结双径路传导;③房室结慢径路传导延缓程度不够,两条径路未形成足够的传导时间差,因激动无法脱离下部共同径路或心室肌不应期,致1∶2房室传导被掩盖;④一次室性期前收缩后出现两次激动顺序一致的旁道逆传性心房激动,并诱发顺向性房室折返性心动过速。结论①预激综合征患者存在房室结双径路传导是引起传导显著缓慢、形成1∶2房室传导的主要原因;②1∶2房室传导较少见,是因为旁道与房室结的传导速度之差不够大,致沿房室结下传的激动难以脱离心室不应期。此外,旁道和房室结两条径路之间的隐匿性折返也是激动无法再次下传的重要原因;③出现显著晚于V波的H2波表明两条径路发生了同步传导,虽然未形成R2波,但可称为隐匿性1∶2房室传导。

Objective To investgate mechanism and electrophysiological phenomena during atrioventricular conduction at ratio of 1 to 2 in patients with pre-exciation syndrome. Methods Phenomena of atrioventricular and ventriculatrial conduction at ratio of l to 2 in three patients and in one patient with pre-excitation syndrome respectively were analyzed by esophageal electrophysiological examination and endocardial mapping. Results Electrophysiologic examination showed follows. ① Tow ventricular activation was not occurred until the coupling interval of atrial premature beat was decreased to some extent,first QRS complex was pre-excitation wave,second was bundle branch block wave,and there was no P wave between R2 and R′2.② When coupling interval of atrial premature beat was decreased in 10 ms, Iump of S2-R′2 interval demonstrated that atrioveiltricular node AVN dual pathways onduction existed.③Conduction over slow pathway of AVN was not delayed enough to have sufficient condction gap in dual pathways,so phenomena of atrioventricular conduction at ratio of 1 to 2 was hidden because activation was always in range of refractory period of common pathway in AVN or ventricular myocardium.④Following a ventricular premature beat,two atrial activation retrograde over accessory pathway occurred and an anegrade atrioventricular re-entrant tachycardia was initiated. Conclusion ①In patients with pre-excitation syndrome,atrioventricular conduction at ratio of 1 to 2 is mainly due to AVN dual pathways. ② Phenomena of atrioventricular conduction at ratio of l to 2 are rare.One reason is that activation from AVN is always in range of ventricular refractory period,because conduction velocity is not enongh to make difference between AP and AVN.Other important reason is that there is concealed conduction over two pathways. ③ When H2 wave is significantly delayed after V wave,it show that synchronous conduction occurs in two pathways.Thongh R2 wave does not form,this can be considered as concealed atrioventricular condnction at ratio of 1 to 2.