胎儿主动脉弓离断的超声心动图和病理学超微结构特征

Echocardiographic features and pathological ultrastructural characteristics of fetal interruption of aortic arch

目的:主动脉弓离断(interruption of aortic arch,IAA)是一种罕见的先天性心脏疾病。本研究探讨IAA胎儿的超声心动图和病理学超微结构特征,并进一步分析其演变的病理过程。方法:回顾性分析产前诊断并经手术或尸体解剖确诊的IAA胎儿的产前超声心动图、术后病理检查或尸体解剖结果等资料。采用产前超声心动图追踪观察IAA胎儿主动脉弓各节段内径及Z值,以及狭窄段主动脉弓的变化情况,结合尸体解剖及病理检查结果,探讨胎儿IAA可能的宫内演变过程及其发生的细胞学基础。结果:纳入34例IAA胎儿,分别有3、3、28例产前超声诊断为主动脉弓发育不良(aortic arch dysplasia,AAD)、主动脉缩窄(coarctation of aorta,CoA)、IAA。3例AAD和3例CoA胎儿均在产前超声检查1~2周后选择引产,并经尸体解剖证实为IAA。28例产前超声诊断为IAA的胎儿中6例为CoA进行性加重,在超声心动图追踪复查的过程中发现逐渐演变为A型IAA;其他22例首次产前超声即诊断为IAA。3例胎儿分娩后经手术矫正,27例选择终止妊娠,4例宫内死亡。胎儿IAA的超声心动图主要表现包括:心脏四腔心切面左心室明显小于右心室或差别不明显;三血管切面显示主动脉明显小于肺动脉;三血管-气管切面和主动脉弓切面显示主动脉与降主动脉不能相连;主动脉弓切面显示主动脉弓弯曲度变小、走行僵直,主动脉、动脉导管和降主动脉之间失去正常的“V”字形结构。彩色多普勒超声检查显示主动脉弓中断处无连续血流信号,动脉导管内可见血流反转。对7例IAA胎儿进行透射电镜检测,结果显示主动脉弓近离断处的弹力膜之间存在大量平滑肌细胞,数量较升主动脉近端明显增多且排列紊乱,弹力膜较升主动脉近端增厚、走行扭曲;离断处系带无明显正常的内皮细胞和管腔,只有少量断裂坏死内皮细胞的痕迹,大量粗短且排列紊乱的弹力膜和纵横交错的平滑肌细胞无规律分布。结论:产前超声心动图是诊断胎儿IAA的主要手段,通过术后追踪和尸体解剖发现胎儿IAA的并发症和疾病特征,有利于提高其诊断率;部分胎儿IAA可由AAD或CoA逐步演变而来,其发病机制可能与缺血缺氧和动脉导管收缩成分迁移有关。

Objective:Interruption of aortic arch(IAA)is a rare congenital heart disease.This study aims to investigate echocardiographic features and pathological ultrastructural characteristics of fetal IAA and to further analyze its pathological evolution.Methods:A retrospective analysis was conducted on prenatal echocardiographic,post-surgical,or autopsy findings of fetuses prenatally diagnosed with IAA.Prenatal echocardiographic tracking was used to observe the internal diameters and Z-scores of different segments of the aortic arch and the changes in the narrowed section.These observations were combined with autopsy and pathological findings to explore the potential intrauterine evolution of IAA and its cytological basis.Results:The study included 34 fetuses with IAA,with 3,3,and 28 fetuses prenatally diagnosed with aortic arch dysplasia(AAD),coarctation of aorta(CoA),and IAA,respectively.The 3 AAD and 3 CoA fetuses chose termination of pregnancy 1 to 2 weeks after prenatal ultrasound diagnosis,and autopsy confirmed IAA.Among the 28 fetuses prenatally diagnosed with IAA,6 cases of CoA progressively worsened,eventually evolving into type A IAA as observed through echocardiographic follow-up.The remaining 22 cases were diagnosed as IAA on the first prenatal ultrasound.Postnatal surgery corrected 3 cases,while 27 cases opted for pregnancy termination,and 4 cases resulted in intrauterine death.Echocardiographic features of the fetal IAA included a significantly smaller left ventricle compared with the right or negligible difference on the four-chamber view,a significantly smaller aorta than the pulmonary artery on the three-vessel view,and a lack of connection between the aorta and the descending aorta on the three-vessel-trachea and aortic arch views.The aortic arch appears less curved and more rigid,losing the normal“V”shape between the aorta,ductus arteriosus,and descending aorta.Color Doppler ultrasound showed no continuous blood flow signal at the interruption site,with reversed blood flow visible in the ductus arteriosus.Transmission electron microscopy of 7 IAA fetuses revealed numerous disorganized smooth muscle cells between the elastic membranes near the aortic arch interruption site,significantly increased in number compared with the proximal ascending aorta.The elastic membranes were thicker and more twisted near the interruption site.The interruption area lacked normal endothelial cells and lumen,with only remnants of necrotic endothelial cells,disorganized short and thick elastic membranes,and randomly arranged smooth muscle cells.Conclusion:Prenatal echocardiography is the primary diagnostic tool for fetal IAA.Post-surgical follow-up and autopsy help identify complications and disease characteristics,enhancing diagnostic accuracy.Some fetal IAA may evolve from AAD or CoA,with potential pathogenesis related to ischemia,hypoxia,and migration of ductal constrictive components.