Fontaine G, Frank R, Lascault G, Tonet J L, Fillette F, Grosgogeat Y
Arch Mal Coeur Vaiss. 1983 Aug;76(8):918-24.
The authors report a case of isolated and probably congenital complete heart block with spontaneous torsades de pointes preceded by an increase in the QT interval. During positioning of a temporary pacing catheter mechanically induced extrasystoles were observed, which seem to favor ventricular extrasystoles and unsustained runs of torsades de pointes. When the basal rhythm showed no extrasystoles, electrical stimulation delivered late in diastole captured the ventricle normally and was then followed in reproducible fashion by episodes of torsades de pointes or minor equivalents. The mechanism of this phenomenon is thought to be related to a concealed phase 4 intramyocardial block. It may have important practical consequences in paced patients predisposed to torsades de pointes. If the pacemaker is programmed at too slow a rate, with stimulation falling late in diastole, torsades de pointes could occur, some attacks of which are known to degenerate to true ventricular fibrillation.
作者报告了一例孤立且可能为先天性的完全性心脏传导阻滞病例，其在QT间期延长后出现自发性尖端扭转型室速。在放置临时起搏导管过程中，观察到机械诱发的期前收缩，这似乎有利于室性期前收缩和非持续性尖端扭转型室速发作。当基础心律无期前收缩时，舒张晚期给予的电刺激能正常夺获心室，随后可重复出现尖端扭转型室速或轻微类似情况。这种现象的机制被认为与隐匿性4相心肌内阻滞有关。对于易发生尖端扭转型室速的起搏患者，这可能具有重要的实际意义。如果起搏器编程频率过慢，刺激落在舒张晚期，则可能发生尖端扭转型室速，其中一些发作已知会恶化为真正的心室颤动。
