Department of Cardiology, The 2nd Affiliated Hospital of Harbin Medical University, Harbin, China.
The Key Laboratory of Myocardial Ischemia, Chinese Ministry of Education, Harbin, China.
J Cardiovasc Electrophysiol. 2021 Jul;32(7):1896-1906. doi: 10.1111/jce.15117. Epub 2021 Jun 6.
The complex electrophysiological phenomena related to the atrioventricular node (AVN) are due to its complex anatomical structures. Aside from the inferior nodal extension (INE), other node-like tissues, such as the retroaortic node (RN), have been described less extensively and may also share the mechanism of normal conduction and abnormal conduction in AVN re-entrant tachycardia.
High-density sections of the entire AVN were obtained from rats and rabbits. Fibrosis was analyzed by Masson's trichrome staining. Connexin (Cx43, Cx40, and Cx45) and ion channel (Na 1.5, Ca 3.1, and HCN4) proteins were immunohistochemically labeled for the analysis of tissue features. Three-dimensional (3D) reconstruction of the AV junction was performed to clarify the relationships among different structures.
The RN expressed the same connexin isoforms as the compact node (CN) and INE. Na 1.5 labeling was observed at low levels in the CN, RN, and INE, where Ca 3.1 and HCN4 were expressed. The CN connected with the RN in a narrow strip pattern at the start of the CN. The RN presented as a shuttle shape and was the only tissue directly connected with the atrium in the anterior septum.
The RN connects with the AVN anatomically, suggesting that direct electrical conduction occurs between them. The entrance of the atria into the AVN is distal to the RN, which may form the fast AVN pathway.
房室结（AVN）的复杂电生理现象归因于其复杂的解剖结构。除了下结延伸（INE）外，其他类似结的组织，如主动脉后结（RN），也已被描述得较少，但也可能具有 AVN 折返性心动过速中正常传导和异常传导的机制。
从大鼠和兔中获得整个 AVN 的高密度切片。采用 Masson 三色染色分析纤维化。免疫组织化学标记连接蛋白（Cx43、Cx40 和 Cx45）和离子通道（Na 1.5、Ca 3.1 和 HCN4）蛋白，分析组织特征。对 AV 连接进行三维（3D）重建，以阐明不同结构之间的关系。
RN 表达与致密结（CN）和 INE 相同的连接蛋白同工型。在 CN、RN 和 INE 中观察到低水平的 Na 1.5 标记，而 Ca 3.1 和 HCN4 表达。CN 以 CN 起始处的窄带模式与 RN 相连。RN 呈梭形，是前间隔中唯一与心房直接相连的组织。
RN 在解剖上与 AVN 相连，提示它们之间存在直接电传导。心房进入 AVN 的部位位于 RN 远端，这可能形成快速 AVN 途径。
