Almendral J M, Gottlieb C D, Rosenthal M E, Stamato N J, Buxton A E, Marchlinski F E, Miller J M, Josephson M E
Clinical Electrophysiology Laboratory, Hospital of the University of Pennsylvania, Philadelphia 19104.
Circulation. 1988 Mar;77(3):569-80. doi: 10.1161/01.cir.77.3.569.
Transient entrainment was demonstrated during 59 pacing events in 18 episodes of sustained uniform ventricular tachycardia (VT) while recording electrograms from the site of origin of tachycardia (LE-SOO). During entrainment, the morphology of the initial component of the LE-SOO was identical to the morphology observed during the tachycardia in 13 VTs (group I), but in five VTs (group II), the initial component changed at a "critical" paced cycle length. The presence of the proposed surface electrocardiographic criteria for entrainment--fixed fusion and a first postpacing complex without fusion but occurring at the paced cycle length--were integrally dependent on the morphologic changes in the local presystolic electrogram. Fixed fusion of the surface electrocardiogram at one or more paced cycle lengths was detected during entrainment at 35 of 59 paced cycle lengths in 12 of 18 tachycardias, 10 of which were group I and two of which were group II VTs. Fixed fusion demonstrated by analysis of the LE-SOO was observed at one or more pacing cycle lengths in 17 of 18 VTs. In five tachycardias in which surface electrocardiographic fusion was not observed, fixed fusion was evident on analysis of the left ventricular LE-SOO during right ventricular pacing. The first postpacing interval, as measured at the surface electrocardiogram, was consistently equal to the paced cycle length in only one of 18 tachycardias and was greater than the VT cycle length in eight of 17 tachycardias. A pathway with a long conduction time was demonstrated during entrainment. However, in those 12 VTs in patients in whom pacing was performed at more than one cycle length and there was preservation of the LE-SOO morphology, the conduction time between the stimulus and presystolic electrogram remained constant. Thus, no evidence for "atrioventricular nodal-like" decremental conduction was observed over a wide range of pacing cycle lengths. We conclude that: (1) two of the previously proposed criteria for diagnosis of entrainment (fixed fusion on the surface electrocardiogram and a first postpacing interval equal to the paced cycle length) are overly restrictive criteria for definition of "entrainment" of VT, (2) analysis of endocardial recordings from the site of origin of tachycardia during attempted entrainment of VT is useful for documenting the presence of entrainment, and (3) such analysis provides a basis for the understanding of surface electrocardiographic phenomenon associated with entrainment.
在18次持续性单形性室性心动过速（VT）发作的59次起搏事件中，记录心动过速起源部位（LE-SOO）的电图时证实了短暂性夺获。在夺获过程中，13例VT（I组）的LE-SOO初始成分形态与心动过速时观察到的形态相同，但在5例VT（II组）中，初始成分在“临界”起搏周长时发生改变。所提出的用于夺获的体表心电图标准——固定融合以及第一个起搏后复合波无融合但在起搏周长时出现——完全依赖于局部收缩前电图的形态变化。在18次心动过速中的12次、59个起搏周长中的35个进行夺获时，在一个或多个起搏周长检测到体表心电图的固定融合，其中10次为I组，2次为II组VT。通过LE-SOO分析在18次VT中的17次观察到在一个或多个起搏周长存在固定融合。在5次未观察到体表心电图融合的心动过速中，右心室起搏时左心室LE-SOO分析显示存在固定融合。在体表心电图测量的第一个起搏后间期，在18次心动过速中只有1次始终等于起搏周长，在17次心动过速中有8次大于VT周长。夺获过程中显示存在传导时间长的径路。然而，在那些以多个周长进行起搏且LE-SOO形态得以保留的患者的12次VT中，刺激与收缩前电图之间的传导时间保持恒定。因此，在很宽的起搏周长范围内未观察到“房室结样”递减传导的证据。我们得出结论：（1）先前提出的用于诊断夺获的两个标准（体表心电图固定融合和第一个起搏后间期等于起搏周长）对于定义VT的“夺获”来说限制过严，（2）在尝试对VT进行夺获时分析心动过速起源部位的心内膜记录对于记录夺获的存在是有用的，（3）这种分析为理解与夺获相关的体表心电图现象提供了基础。
