Wagshal A B, Huang S K, Pires L A, Mittleman R S, Greene T O, Schuger C D
Department of Medicine, University of Massachusetts Medical Center, Worcester, USA.
Pacing Clin Electrophysiol. 1995 Nov;18(11):2041-52. doi: 10.1111/j.1540-8159.1995.tb03866.x.
The ability of single paced ventricular beats during tachycardia to penetrate the tachycardia circuit and reset the subsequent atrial depolarization (atrial preexcitation), enabling calculation of the "preexcitation index," can be helpful in analyzing supraventricular tachycardias. However, the ventricular refractory period often prevents ventricular capture of beats with the necessary prematurity to demonstrate atrial preexcitation, particularly in atrioventricular nodal reentrant tachycardia (AVNRT). We hypothesized that the use of double premature stimuli could overcome this limitation. In 25 consecutive patients with either AVNRT or atrioventricular reciprocating tachycardia (AVRT) we attempted to demonstrate atrial preexcitation with single and double ventricular extrastimuli. Whereas atrial preexcitation with a single extrastimulus could only be achieved in 3 of 11 patients with AVNRT, all but 1 patient demonstrated atrial preexcitation with the use of double ventricular extrastimuli. On the other hand, in all but 1 patient with AVRT, atrial preexcitation could be achieved with single and double extrastimuli. A formula was derived for obtaining a preexcitation index with double extrastimuli and shown to correspond closely with the preexcitation index obtained with a single extrastimulus in the 16 patients in whom atrial preexcitation could be achieved with single and double extrastimuli. Thus, this technique significantly enhances the ability to achieve atrial preexcitation and to calculate the preexcitation index in patients with AVNRT, and thus may be useful in deciphering tachycardia mechanism in some patients, as well as being a useful technique in studying the electrophysiological properties of the antegrade and retrograde limbs of AVNRT.
心动过速期间单起搏心室搏动穿透心动过速环路并重置随后的心房去极化（心房预激）的能力，使得能够计算“预激指数”，这有助于分析室上性心动过速。然而，心室不应期常常阻止心室夺获具有必要提前期以显示心房预激的搏动，特别是在房室结折返性心动过速（AVNRT）中。我们推测使用双重期前刺激可以克服这一限制。在连续25例患有AVNRT或房室折返性心动过速（AVRT）的患者中，我们试图用单心室和双心室额外刺激来显示心房预激。在11例AVNRT患者中，仅3例能用单个额外刺激实现心房预激，而除1例患者外，所有患者使用双心室额外刺激均显示心房预激。另一方面，在除1例患者外的所有AVRT患者中，单心室和双心室额外刺激均可实现心房预激。推导了一个用双额外刺激获得预激指数的公式，并且在16例能用单心室和双心室额外刺激实现心房预激的患者中显示该公式与用单个额外刺激获得的预激指数密切相关。因此，该技术显著增强了在AVNRT患者中实现心房预激和计算预激指数的能力，因而可能有助于解读某些患者的心动过速机制，也是研究AVNRT前传和逆传支电生理特性的有用技术。
