Rodefeld M D, Bromberg B I, Schuessler R B, Boineau J P, Cox J L, Huddleston C B
Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
J Thorac Cardiovasc Surg. 1996 Mar;111(3):514-26. doi: 10.1016/s0022-5223(96)70303-3.
Intraatrial reentrant tachycardia, or atrial flutter, is a common postoperative problem after Fontan repair, which involves an atriopulmonary connection. A modification of Fontan repair, total cavopulmonary connection, minimizes the portion of the right atrium exposed to stretch and hypertension; however, atrial flutter continues to occur after this procedure. We postulated that the intraatrial lateral tunnel suture line of total cavopulmonary connection, in the absence of physiologic alterations such as atrial hypertension or stretch, provides the necessary electrophysiologic substrate for atrial flutter. The purpose of this study was to produce a canine model of total cavopulmonary connection (1) to establish that the intraatrial suture line alone is sufficient to permit sustained atrial flutter and (2) to characterize the pathways of resulting reentrant arrhythmias. After induction of general anesthesia, 25 to 30 kg dogs (n = 17) underwent median sternotomy, cradling of the pericardium, and placement of a pacing electrode on the right atrial appendage. Normothermic cardiopulmonary bypass was initiated. The total cavopulmonary connection suture line was placed through a standard right atriotomy,simulating construcion of the lateral tunnel. After closure of the atriotomy, 253 point unipolar atrial endocardial form-fitting electrodes were placed through bilateral ventriculotomies. By means of atrial burst pacing and programmed extrastimulation, induction of atrial flutter was attempted. If atrial flutter could not be induced, isoproterenol was infused and the stimulation protocol was repeated. After induction of atrial flutter, mapping of the activation sequence was performed. Before suture line placement, no dog had inducible atrial flutter. After placement of the suture line, sustained atrial flutter was reproducibly induced in every dog, although isoproterenol was required for this in three (17.6%). The mean flutter cycle length was 177 +/- 30 msec. In each case, the atrial flutter circuit was limited to the right atrium, with the left atrium being passively activated. The atrial flutter circuit was dependent on a corridor of myocardium that resulted from conduction block on the free wall, created by the lateral margin of the total cavopulmonary connection. In no case was the atriotomy integral to the atrial flutter circuit. This study establishes that the total cavopulmonary connection baffle suture line alone, without alteration in circulatory physiology, creates a sufficient anatomic substrate for atrial flutter in a short-term canine model. Delineation of the anatomic boundaries of the reentrant circuit raises the possibility of targeting areas within the circuit that could be modified, potentially reducing the incidence of postoperative atrial flutter after total cavopulmonary connection.
房间隔折返性心动过速，即心房扑动，是Fontan修复术后常见的问题，Fontan修复术涉及心房与肺的连接。Fontan修复术的一种改良术式，即全腔静脉-肺动脉连接术，可将右心房暴露于牵张和高压的部分减至最小；然而，在此手术后心房扑动仍会发生。我们推测，在没有诸如心房高压或牵张等生理改变的情况下，全腔静脉-肺动脉连接术的房间隔侧隧道缝合线为心房扑动提供了必要的电生理基质。本研究的目的是建立一个全腔静脉-肺动脉连接术的犬模型，(1) 以证实仅房间隔缝合线就足以引发持续性心房扑动，(2) 并对由此产生的折返性心律失常的途径进行特征描述。在诱导全身麻醉后，体重25至30千克的犬（n = 17）接受正中胸骨切开术、心包的环抱以及在右心耳放置起搏电极。开始进行常温体外循环。全腔静脉-肺动脉连接缝合线通过标准的右心房切开术置入，模拟侧隧道的构建。在心房切开术关闭后，通过双侧心室切开术置入253个点的单极心房心内膜贴合电极。通过心房猝发起搏和程控期外刺激尝试诱发心房扑动。如果无法诱发心房扑动，则输注异丙肾上腺素并重复刺激方案。在诱发心房扑动后，进行激动顺序标测。在缝合线置入前，没有一只犬能诱发心房扑动。在缝合线置入后，每只犬都能重复诱发持续性心房扑动，尽管其中三只（17.6%）需要异丙肾上腺素才能诱发。平均扑动周期长度为177±30毫秒。在每种情况下，心房扑动环路都局限于右心房，左心房为被动激动。心房扑动环路依赖于一条心肌通道，该通道是由全腔静脉-肺动脉连接的外侧缘在游离壁上造成的传导阻滞形成的。在任何情况下，心房切开术都不是心房扑动环路所必需的。本研究证实，在短期犬模型中，仅全腔静脉-肺动脉连接术的挡板缝合线，在不改变循环生理的情况下，就为心房扑动创造了足够的解剖学基质。确定折返环路的解剖边界增加了针对环路内可进行改良的区域的可能性，这可能会降低全腔静脉-肺动脉连接术后心房扑动的发生率。
