Iinuma H, Sekiguchi A, Kato K
Cardiovascular Institute, Minato-ku Tokyo, Japan.
Pacing Clin Electrophysiol. 1989 Aug;12(8):1331-46. doi: 10.1111/j.1540-8159.1989.tb05047.x.
Triggered activity (TA) has recently received increased attention as a mechanism responsible for cardiac arrhythmias. However, few studies have shown TA in the intact heart. In an ouabain-treated dog's heart we have shown: (a) overdrive acceleration, (b) a concordant relationship between the postpacing interval (PI) and pacing cycle length (CL), and (c) a discordant relationship between the PI and number of paced beats necessary to induce TA. These findings appear to agree with the distinctive characteristics of TA arrhythmias elucidated in previous in vitro studies and suggest TA rather than a reentrant tachycardia. In addition, it is possible that this heart preparation could be considered as a suitable model for the study of TA arrhythmias. These results were obtained using a programmed stimulation protocol in this dog model: (1) Following single programmed ventricular stimulation during sinus rhythm, a repetitive ventricular response (RVR) of more than 3 beats occurred in only 20% of hearts. The relationship between PI and the coupling interval (CI) of the extrastimulus was concordant in 80% (12/15) and discordant in 13% (2/15) of all experiments. The PI-CI relationship was influenced by the mutual relationship between the stimulating, recording, and originating sites of TA. (2) RVR of more than 3 beats was induced by consecutive overdrive ventricular stimulation during sinus rhythm (78%). In addition, the PI-pacing CL relationship was concordant (100%). (3) The transient termination of sustained VT that occurred spontaneously after administration of a large dose of ouabain was seen in only 15% of the cases after a single programmed premature ventricular stimulation. The return cycle-CI relationship was biphasic in 75% (15/20) experiments and discordant in 25% (5/20) of the experiments. (4) The termination of spontaneous sustained VT by overdrive ventricular stimulation occurred in only 8% of the cases. Transient overdrive acceleration of VT occurred after overdrive pacing (53%). In contrast, overdrive suppression occurred in only 13%. Thus, the characteristics of TA arrhythmias observed in the whole heart preparations differed, in some respects, from those obtained by in vitro studies. These quantitative observations could suggest a differentiation, based on probability, between TA and the reentrant mechanism that would respond to programmed stimulation in a similar manner. The differentiation between reentrant and triggered ventricular tachycardia can be made with reasonable assurance using these programmed stimulation techniques.
触发活动（TA）作为导致心律失常的一种机制，近来受到了更多关注。然而，很少有研究在完整心脏中显示出TA。在一只用哇巴因处理过的犬心脏中，我们已经证明：（a）超速驱动加速，（b）起搏后间期（PI）与起搏周期长度（CL）之间存在一致关系，以及（c）PI与诱发TA所需的起搏搏动次数之间存在不一致关系。这些发现似乎与先前体外研究中阐明的TA心律失常的独特特征相符，并提示为TA而非折返性心动过速。此外，这种心脏标本有可能被视为研究TA心律失常的合适模型。这些结果是在该犬模型中使用程控刺激方案获得的：（1）在窦性心律期间进行单次程控心室刺激后，仅20%的心脏出现了超过3次搏动的重复心室反应（RVR）。在所有实验中，PI与额外刺激的耦联间期（CI）之间的关系在80%（12/15）的实验中是一致的，在13%（2/15）的实验中是不一致的。PI-CI关系受TA的刺激、记录和起源部位之间的相互关系影响。（2）在窦性心律期间通过连续超速驱动心室刺激诱发了超过3次搏动的RVR（78%）。此外，PI-起搏CL关系是一致的（100%）。（3）在给予大剂量哇巴因后自发发生的持续性室性心动过速（VT），在单次程控室性早搏刺激后仅15%的病例中出现短暂终止。在75%（15/20）的实验中，回归周期-CI关系呈双相性，在25%（5/20）的实验中是不一致的。（4）通过超速驱动心室刺激终止自发的持续性VT仅在8%的病例中发生。超速起搏后出现VT的短暂超速驱动加速（53%）。相比之下，超速抑制仅发生在13%的病例中。因此，在全心标本中观察到的TA心律失常的特征在某些方面与体外研究获得的特征不同。这些定量观察结果可能提示基于概率对TA与以类似方式对程控刺激作出反应的折返机制进行区分。使用这些程控刺激技术可以有合理把握地区分折返性和触发型室性心动过速。
