Gilmour R F, Riccio M L, Locati E H, Maison-Blanche P, Coumel P, Schwartz P J
Instituto di Clinica Medica Generale e Terapia Medica, Universitá di Milano, Italy.
J Am Coll Cardiol. 1997 Jul;30(1):209-17. doi: 10.1016/s0735-1097(97)00105-8.
The purpose of this study was to determine whether the QT interval dynamics that precede torsade de pointes are consistent with the initiation of this arrhythmia by early afterdepolarization-induced triggered activity.
Early afterdepolarization-induced triggered activity has been suggested as an electrophysiologic mechanism for torsade de pointes. Consequently, the initiation of torsade de pointes should involve time- and rate-dependent alterations of ventricular repolarization similar to those known to modulate the development of early afterdepolarizations.
RR and QT intervals were measured in digitized 24-h ambulatory electrocardiographic recordings obtained from seven patients with acquired prolongation of ventricular repolarization. Each patient had one or more episodes of torsade de pointes. The relation between RR and QT intervals was determined before, during and after multiple episodes of torsade de pointes.
In patients with multiple episodes of ventricular arrhythmias, the onset of the arrhythmias was associated with a critical prolongation of the QT interval. In some episodes, prolongation of the QT interval was associated with sudden prolongation of the sinus cycle length, whereas in other episodes, the QT interval prolonged progressively at a constant cycle length.
The association between a critically prolonged QT interval and the onset of ventricular arrhythmias suggests that the initial complex of torsade de pointes is an early afterdepolarization-induced triggered response. However, prolongation of the QT interval itself was not sufficient to account for the initiation of torsade de pointes, suggesting that other, as yet unidentified factors are required.
本研究的目的是确定尖端扭转型室速之前的QT间期动态变化是否与早期后除极诱发的触发活动引发这种心律失常相一致。
早期后除极诱发的触发活动已被认为是尖端扭转型室速的一种电生理机制。因此，尖端扭转型室速的起始应涉及心室复极的时间和速率依赖性改变，类似于已知调节早期后除极发生的那些改变。
在从7例获得性心室复极延长患者中获取的数字化24小时动态心电图记录中测量RR和QT间期。每位患者有一次或多次尖端扭转型室速发作。在多次尖端扭转型室速发作之前、期间和之后确定RR和QT间期之间的关系。
在有多次室性心律失常发作的患者中，心律失常的发作与QT间期的临界延长有关。在某些发作中，QT间期延长与窦性周期长度的突然延长有关，而在其他发作中，QT间期在恒定周期长度下逐渐延长。
QT间期的临界延长与室性心律失常发作之间的关联表明，尖端扭转型室速的初始复合波是早期后除极诱发的触发反应。然而，QT间期本身的延长不足以解释尖端扭转型室速的起始，这表明还需要其他尚未确定的因素。
