人的肺静脉前庭心肌的病理组织学特点

Histological study of the pulmonary vein antrum in human

目的虽然导管消融治疗心房颤动（房颤）已取得了较高的成功率，但房颤的机制仍不十分明确，目前临床应用的导管消融术式多与肺静脉前庭有关，因此，肺静脉前庭的解剖结构与电生理特点成为人们关注的热点。本实验通过对比观察左心房、肺静脉及肺静脉前庭的组织学特点，探讨房颤发生与维持的机制。方法10例非心脏原因死亡的成人尸检标本。观察肺静脉的分布与走行，沿肺静脉走行剥离肺静脉与心包及周围结缔组织，剪下左心房与肺静脉。观察肺静脉前庭部肌束的分布与走行。并同时将标本由近至远心端分别环行剪取左上及右上肺静脉、左上及右上肺静脉前庭、左心房3mm宽组织标本。将组织置于4％的多聚甲醛溶液中固定1周以上进行取材。经酒精脱水，石蜡包埋，分别作纵向和横向连续切片，常规HE染色。选取部分标本进行Masson染色。随机选取肺静脉前庭部纵切3mm宽的组织标本，进行PGP9．5单克隆抗体S-P免疫组化染色。观察肺静脉前庭心肌厚度、细胞分布与排列特点、神经分布特点。结果（1）肺静脉前庭内心肌平均厚度较左心房薄[（2．6±0．4）mm对（3．0±0．5）mm，P=0．047]。（2）细胞分布：心肌纤维自左心房至肺静脉前庭向肺静脉连续延伸，逐渐变薄，心肌细胞数逐渐减少。与鼻心房心肌细胞分布相比较，肺静脉前庭处，从横切面上可以观察到心肌在肺静脉前庭内分布不均一，有的部分相对数量较多而有的部分则较稀疏。（3）细胞排列：从纵切面观察，在心房心肌纤维总体呈横行排列，密度均匀，而肺静脉前庭内的心肌纤维的走行方向呈横行、纵行或斜行等不规律排列，在近心内膜部分肌束排列较紧密，近心外膜部分则排列较疏松。随着向肺静脉延伸，心肌细胞分布逐渐稀疏，心内膜和心外膜的差别渐无。（4）特殊细胞：未观察到有结样细胞或形成传导束的特殊细胞。见到染色呈深褐色的特殊细胞。（5）免疫组化染色结果，肺静脉前庭的心肌细胞处存在PGP9．5免疫组化染色阳性的神经纤维。结论人的肺静脉前庭内心肌细胞的分布不均匀、排列紊乱，可能是发生心律失常的结构基础。有丰富的神经纤维分布，可能解释肺静脉前庭内易于出现自律性、不应期、传导速度等电生理特征异常的电活动，并触发或维持房颤。

Objective Pulmonary vein antrum has been regarded as an important target during ablation for atrial fibrillation. However, little is known about its anatomic and histological features. This study aimed to observe the anatomic and histological features of the left atrium. Methods The samples of left atrium,pulmonary vein and pulmonary vein antrum were obtained from 10 Chinese died of noncardiac causes. After observing the overall anatomy of the pulmonary veins, the pulmonary veins and the left atrium were peeled off. We took down the pulmonary veins and left atriums and observed the distribution of the muscular fascicle within the pulmonary vein antrum. Three milimeters specimens of the left atrium,the left upper and right upper pulmonary vein antrum,the left upper and right upper pulmonary vein were cut down. The specimens had been fixed using 4% formalin for more than a week. And then the specimens were dehydrated with ethanol and embedded in paraffin. The specimens were cut serially in longitudinal and transverse direction arid were stained with hematoxylin and eosin （HE）. Selected sections were stained with Masson-Trichrome. Also, the specimens of the pulmonary vein antrum were stained with general neural marker protein gene product 9.5 （PGP9.5）. The pulmonary vein antrum is defined as the part between the orifice of the pulmonary vein and the left atrium, which seems like a filter. Generally, Its edge is 0. 5 - 1.5 cm away from the orifice of each pulmonary vein. The observed data included the thickness of myocardium and the muscular distribution in pulmonary vein, pulmonary vein antrum and left atrium, and the distribution of nerve fibers in the pulmonary vein antrum. Results （ 1 ） The myocardium in the pulmonary vein antrum was thinner than that of the left atrium [ （ 2.6 ± 0.4 ） mm vs （ 3.0 ± 0.5 ） mm,P =0.047]. （2） The myocardium became thinner from the left atrium to the pulmonary vein. Also its number becme fewer and fewer. In transverse section, myocardium of the pulmonary vein and antrum distribute more inhomogenously by comparison with the left atrium. （ 3 ） In longitudinal section, myocardium of the left atrium arranged transversely in parallel, however,it disorganized in the pulmonary vein antrum. （4） No special node-like cells were observed, but some puce cells. （ 5 ） PGP9. 5-immunoreactive nerve fibers were distributed in the pulmonary vein antrum. Conclusions The myocardium of the pulmonary vein antrum distributes in disorganization which may contributes to the substrate of atrial arrhythmia. The abundant nerves distributing in the pulmonary vein antrum may play an important role in perpetuation and maintenance of atrial fibrillation.