Mechanism of idiopathic ventricular tachycardia of the left ventricular origin and the effect of antiarrhythmic agents on it. A study using an entrainment phenomenon.

利用心动过速夹带现象研究了左心室起源的特发性室性心动过速的机制。在4例心动过速患者中，在心动过速期间从右心室流出道进行比心动过速快5-25次/分钟的快速心室起搏，导致除最后一次捕获的心跳外的持续融合心跳。此外，随着起搏速率的增加，观察到逐渐融合。因此，这种类型的室性心动过速的机制最好的解释是再入与兴奋间隙。在心动过速夹带期间，测量起搏部位（右心室流出道）至心动过速最早激活部位及右心室心尖的传导间隔：前者为395 ~ 430 msec，随起搏速率的增加而增加；后者为70 ~ 90 msec，随起搏速率的增加而保持不变。因此，强烈建议在心动过速再入回路中存在具有递减传导特性的慢传导区域。为了检验维拉帕米在中断心动过速方面的效果，在心动过速期间给予小剂量（1.0 mg）的药物，这导致心动过速减慢，并重复了夹带研究。使用维拉帕米后，虽然起搏部位至右心室心尖的传导间隔保持不变，但所有患者从起搏部位至心动过速时最早激活部位（即经慢传导区传导）的传导间隔均增加。这表明维拉帕米选择性地抑制传导，通过传导缓慢的区域，从而减缓心动过速的速度。心动过速夹带有助于检查抗心律失常药物在再入回路中的选择性作用。少

The mechanism of idiopathic ventricular tachycardia of the left ventricular origin was studied using a tachycardia entrainment phenomenon. In 4 patients with the tachycardia, rapid ventricular pacing at rates 5-25 beats/minute faster than the tachycardia rate was performed from the right ventricular outflow tract during the tachycardia and resulted in constant fusion beats except for the last captured beat. Moreover, progressive fusion was observed with the increment of the pacing rate. Thus, the mechanism of this type of ventricular tachycardia was best explained by reentry with an excitable gap. During entrainment of the tachycardia, the conduction intervals from the pacing site (right ventricular outflow tract) to the earliest activation site during the tachycardia and to the right ventricular apex were measured: The former interval was 395-430 msec and increased with the increment of the pacing rate, while the latter one was 70-90 msec and was constant even with the increment of th … More e pacing rate. Therefore, an area of slow conduction with a property of decremental conduction was strongly suggested to be present within the reentry circuit of the tachycardia.To examine the effect of verapamil which has been shown to be effective in interrupting the tachycardia, a small dose (1.0 mg) of the drug was administered during the tachycardia, which resulted in slowing the tachycardia rate, and entrainment study was repeated. After administration of verapamil, although the conduction interval from the pacing site to the right ventricular apex remained unchanged, that from the pacing site to the earliest activation site during the tachycardia (i.e., conduction via an area of slow conduction) was increased in al patients. This indicates that verapamil selectively suppressed the conduction through an area of slow conduction and thereby slowed the rate of the tachycardia. Tachycardia entrainment is useful to examine a selective effect of antiarrhythmic agents within the reentry circuit. Less