Henthorn R W, Okumura K, Olshansky B, Plumb V J, Hess P G, Waldo A L
Department of Medicine, Case Western Reserve University, Cleveland, OH.
Circulation. 1988 May;77(5):1003-12. doi: 10.1161/01.cir.77.5.1003.
Prior data pertaining to transient entrainment and associated phenomena have been best explained by pacing capture of a reentrant circuit. On this basis, we hypothesized that rapid pacing from a single site of two different constant pacing rates could constantly capture an appropriately selected bipolar electrogram recording site from one direction with a constant stimulus-to-electrogram interval during pacing at one rate, yet be constantly captured from another direction with a different constant stimulus-to-electrogram interval when pacing at a different constant pacing rate. To test this hypothesis, we studied a group of patients, each with a representative tachycardia (ventricular tachycardia, circus-movement tachycardia involving an atrioventricular bypass pathway, atrial tachycardia, and atrial flutter). For each tachycardia, pacing was performed from a single site for at least two different constant rates faster than the spontaneous rate of the tachycardia. We observed in these patients that a local bipolar recording site was constantly captured from different directions at two different pacing rates without interrupting the tachycardia at pacing termination. The evidence that the same site was captured from a different direction at two different pacing rates was supported by demonstrating a change in conduction time to that site associated with a change in the bipolar electrogram morphology at that site when comparing pacing at each rate. The mean conduction time (stimulus-to-recording site electrogram interval) was 319 +/- 69 msec while pacing at a mean cycle length of 265 +/- 50 msec, yet only 81 +/- 38 msec while pacing at a second mean cycle length of 233 +/- 51 msec, a mean change in conduction time of 238 +/- 56 msec. Remarkably, the faster pacing rate resulted in a shorter conduction time. The fact that the same electrode recording site was activated from different directions without interruption of the spontaneous tachycardia at pacing termination is difficult to explain on any mechanistic basis other than reentry. Also, these changes in conduction time and electrogram morphology occurred in parallel with the demonstration of progressive fusion beats on the electrocardiogram, the latter being an established criterion for transient entrainment.(ABSTRACT TRUNCATED AT 400 WORDS)
先前有关短暂性夺获及相关现象的数据，最好用折返环路的起搏夺获来解释。在此基础上，我们推测，从两个不同的固定起搏频率的单个部位进行快速起搏，在以一种频率起搏期间，能以恒定的刺激-电信号间期持续从一个方向夺获适当选择的双极电信号记录部位，而在以不同的固定起搏频率起搏时，则能以不同的恒定刺激-电信号间期持续从另一个方向被夺获。为验证这一假设，我们研究了一组患者，每位患者都有一种代表性的心动过速（室性心动过速、涉及房室旁路途径的折返性心动过速、房性心动过速和心房扑动）。对于每种心动过速，均从单个部位以至少两种比心动过速自发频率更快的不同固定频率进行起搏。我们在这些患者中观察到，在两个不同的起搏频率下，一个局部双极记录部位能持续从不同方向被夺获，且在起搏终止时不会中断心动过速。当比较每种频率起搏时，传导至该部位的时间发生改变，且该部位双极电信号形态也发生改变，这支持了在两个不同起搏频率下从不同方向夺获的是同一部位这一证据。起搏时平均周期长度为265±50毫秒，平均传导时间（刺激-记录部位电信号间期）为319±69毫秒，而在第二个平均周期长度为233±51毫秒起搏时，平均传导时间仅为81±38毫秒，传导时间平均改变238±56毫秒。值得注意的是，更快的起搏频率导致传导时间更短。除了折返之外，很难从任何机制基础上解释在起搏终止时自发心动过速未中断的情况下，同一电极记录部位能从不同方向被激活这一事实。此外，传导时间和电信号形态的这些变化与心电图上逐渐出现的融合波同时出现，后者是短暂性夺获的既定标准。（摘要截选至400字）
