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

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.

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.

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.

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.