Patruno N, Pulignano G, Urbani P, Critelli G
II Cattedra di Malattie dell'Apparato Cardiovascolare, Università degli Studi La Sapienza, Roma.
Cardiologia. 1990 Jul;35(7):611-4.
Atrioventricular nodal reentry tachycardia (AVNRT) is a common form of paroxysmal supraventricular tachyarrhythmia. In this tachycardia, the atrium and ventricle are not necessary links of the reentry circuit, so that the arrhythmia may persist in spite of the occurrence of 2:1 AV ratio or AV dissociation. Only a few examples of 2:1 AV block during AVNRT have been described. We report on 2 patients with a history of paroxysmal supraventricular tachycardia in whom 2:1 AV block with persistence of the arrhythmia was documented. Transesophageal electrophysiologic study was performed after pharmacologic wash-out in both patients. During definition of refractory periods, reciprocating tachycardia was initiated when a critical lengthening of the Stimulus-R interval was reached. Tachycardia showed narrow QRS complexes at a rate of 200 (patient 1) and 180 (patient 2) bpm, with the ventriculo-atrial interval (VA) of 45 and 70 ms, respectively. During tachycardia, sustained episodes of 2:1 AV block, without termination of the arrhythmia, occurred in both patients. The tachycardia could be reproducibly terminated by means of extrastimulus technique, rapid burst pacing as well as intravenous injection of adenosine-5'-triphosphate (ATP) at doses of 0.15-0.20 mg/kg. Initiation of tachycardia after a critical lengthening of the Stimulus-R interval and the effectiveness of either rapid burst pacing or ATP injection in the interruption of the arrhythmia, suggested a reentry circuit involving the AV node. The unusual finding of 2:1 AV block during reciprocating tachycardia with a retrograde time conduction (VA interval) equal to or shorter than 70 ms suggested the presence of an intranodal reentry as the substrate of the tachycardia, and excluded the presence of an accessory AV pathway.
房室结折返性心动过速（AVNRT）是阵发性室上性快速心律失常的一种常见形式。在这种心动过速中，心房和心室并非折返环路的必要环节，因此即使出现2:1房室传导比例或房室分离，心律失常仍可能持续存在。仅有少数关于AVNRT期间2:1房室传导阻滞的病例被描述过。我们报告了2例有阵发性室上性心动过速病史的患者，其中记录到了伴有心律失常持续存在的2:1房室传导阻滞。在对两名患者进行药物洗脱后进行了经食管电生理研究。在确定不应期时，当刺激-R间期达到临界延长时诱发了折返性心动过速。心动过速时QRS波群狭窄，患者1的心率为200次/分，患者2的心率为180次/分，心室-心房间期（VA）分别为45毫秒和70毫秒。在心动过速期间，两名患者均出现了持续的2:1房室传导阻滞，且心律失常未终止。通过额外刺激技术、快速猝发起搏以及静脉注射剂量为0.15 - 0.20毫克/千克的腺苷-5'-三磷酸（ATP），可重复性地终止心动过速。在刺激-R间期达到临界延长后诱发心动过速，以及快速猝发起搏或ATP注射对心律失常的中断有效，提示存在涉及房室结的折返环路。在逆向时间传导（VA间期）等于或短于70毫秒的折返性心动过速期间出现2:1房室传导阻滞这一不寻常发现，提示存在结内折返作为心动过速的基质，并排除了房室旁路的存在。
