Double aortic arch (DAA) represents a rare congenital heart disease, distinguished by the division of the ascending aorta into right and left branches anterior to the trachea and esophagus. These branches encircle both structures before converging to form the descending aorta. This condition typically arises from abnormal embryonic development of the fourth pair of aortic arches (1). The incidence of DAA is approximately 0.005–0.007%, accounting for 33–75% of fetal vascular ring malformations (2, 3). According to the classification proposed by Backer and colleagues, DAA is categorized into three types: right arch dominant, left arch dominant and double arch balanced. The right arch dominant type is the most common, representing about 75% of all cases (4, 5). Approximately 16.6% of DAA cases may be associated with intracardiac malformations, such as tetralogy of Fallot, transposition of the great arteries, and ventricular septal defects, while 24% may be linked to chromosomal abnormalities, including 22q11 deletion syndrome (6, 7).

Most patients affected by DAA present with symptoms early in infancy. However, DAA can also be asymptomatic and found incidentally later in life through chest imaging or echocardiography. When the double aortic arch compresses the trachea and esophagus, it can lead to a variety of symptoms, including dysphagia, asthma, and dyspnea (4, 8). Repeated episodes of wheezing may affect bronchopulmonary development, potentially causing bronchial dysplasia and, in severe cases, respiratory failure or death. Studies have shown that children with DAA are more likely to present earlier with symptoms and experience residual respiratory morbidity post-operation compared to those with a right aortic arch (RAA). Some surgical centers advocate for universal early surgery in these cases. Prenatal diagnosis aids perinatal management by enabling parental education, early identification of clinical features, and timely assessment and treatment. Additionally, it has been associated with reduced residual respiratory morbidity after surgical repair, especially in children with DAA. Early surgical intervention is crucial to prevent long-term morbidity. Therefore, accurate prenatal diagnosis of DAA is crucial for neonatal prognosis (9–14).

To improve the accuracy of prenatal diagnosis of DAA, several new ultrasound techniques and indices have been proposed. High-resolution flow (HD-Flow) and time-space composite imaging (STIC) are among the methods used for diagnosis (15–18). Furthermore, the fetal tracheal internal diameter Z-score has been employed to quantitatively assess tracheal compression due to DAA (15). Additionally, differentiating the different pinch angles of DAA from those of the mirrored right aortic arch (RAA-MB) can improve the diagnostic accuracy of these vascular structures (19). Although multiple tests are available, making a comprehensive and accurate prenatal diagnosis of DAA remains challenging.

We conducted a retrospective analysis to study the prenatal ultrasound features of fetal DAA in conjunction with postnatal computed tomography angiography (CTA) features of CTA characteristics, associated abnormalities, and clinical outcomes. We also analyzed the Z-score of fetal tracheal internal diameter and measurements of the DAA pinch angle. The aim was to refine the prenatal diagnosis of DAA and to provide support for perinatal management.

There were 31 DAA cases, including 2 left arch dominant (6.5%), 15 right arch dominant (48.39%), 14 double arch balanced (45.16%). All 31 cases had left-position arterial conduits. There were 24 cases (77.4%) in the simple DAA group and 7 cases (22.6%) in the non-simple DAA group. Among the Non-simple DAA cases, 2 fetuses were confirmed by autopsy after termination of pregnancy. A total of 29 live birth were recorded, with a live birth rate of 93.5% (29/31). Postnatal echocardiography, CTA, or surgery confirmed the diagnostic accuracy of 93.5% (29/31) for prenatal ultrasonography. Two cases were misdiagnosed or missed prenatally, for a misdiagnosis rate of 6.5% (2/31).

In recent years, significant progress has been made in prenatal and postnatal studies on DAA. In the realm of prenatal diagnosis, advancements in fetal cardiac ultrasound technology have led to early identification of DAA. Moreover, the utilization of three-dimensional ultrasound and color doppler ultrasound has refined hemodynamic assessment. for postnatal diagnosis, transthoracic and transesophageal echocardiography severe as primary diagnostic tools, allowing confirmation of the presence of a DAA, as well as the evaluation of vascular anatomy, size, and interrelationships. In some cases, more sophisticated imaging techniques such as MRI or CT may be required to obtain detailed information about the vascular structure. Despite these technical advances, challenges remain in the diagnosis of DAA, particularly in early cases where accurate diagnosis may not be feasible. Furthermore, while surgery is the mainstay of treatment for DAA, the choice of surgical approach and timing continues to be a subject of refinement.

In this study, the right arch dominant type was the most common, with 15 cases (48.39%), which is generally consistent with the literature. However, it is noteworthy nothing that the proportion of double arch balanced type has increased as compared to previous studies. The observation that children with double arch balanced type tend to present earlier with symptoms such as shortness of breath and coughing in the neonatal period suggests that critically ill infants may not be diagnosed in time due to respiratory failure, potentially leading to an underestimation of the prevalence of this type. Therefore, in the integrated prenatal and postnatal management of DAA, a clear prenatal diagnosis and staging are particularly important. Additionally, it was noted that approximately 16.6% of DAA cases may be associated with intracardiac malformations such as tetralogy of Fallot, transposition of the great arteries and ventricular septal defects. In the present study, the percentage of combined intracardiac malformations was 12.9%, which is slightly lower than that reported in the literature, and this discrepancy may not adequately reflect the actual incidence of intracardiac malformations due to the small sample size.

We have found that although the majority of DAA can be successfully diagnosed through prenatal ultrasound, the diagnostic process remains challenging. In particular, the three-vessel-tracheal view, which is a key aspect of DAA diagnosis, is not always sufficient to confirm the condition on its own, this is particularly true in cases of left arch atresia, where typical vascular ring ultrasound manifestations may not be present due to interrupted blood flow. Therefore, the differential diagnosis between DAA from other vascular ring diseases such as pulmonary artery sling (PAS) and right aortic arch with mirror-image branches, is crucial. In this context, both the three-vessel-tracheal and three-vessel-pulmonary artery branch views are essential for differential diagnosis. For example, the key to the diagnosis of a pulmonary artery sling is that the three-vessel-pulmonary artery branching view fails to show the normal pulmonary artery bifurcation, but instead shows the left pulmonary artery originating from the right pulmonary artery and wrapping around the trachea. Conversely, identifying a right aortic arch with mirror-image branches hinges on observing whether the cephalic brachial artery is directly connected to the descending aorta. In addition, left ventricular outflow tract views of DAA may reveal changes in aortic bifurcation, which need to be differentiated from pulmonary artery originating from the ascending aorta (AOPA) and complete transposition of the great arteries (TGA). We also note that most of the double arches in DAA are unevenly developed, with approximately 75% being right arch dominant and generally located higher than the left arch. To reduce misdiagnosis, the number of branches of the cephalic and brachial arteries emanating from the aortic arch should be carefully identified during screening, and once two cephalic and brachial arteries are probed, high vigilance should be exercised for the presence of atresia of one side of the arches; moreover, the probe should be moved laterally in three-vessel-tracheal views to make both arches visible, to avoid missed diagnosis due to the high position of one side of the arches. Although studies have shown that the preoperative ultrasound detection rate of DAA is as high as 96% (24), some patients are still misdiagnosed or underdiagnosed in practice due to the lack of awareness of DAA by some sonographers or equipment limitations. Among the 31 fetuses with DAA in this study, 29 were born alive, of which 27 were compatible with prenatal ultrasound and 2 were confirmed by autopsy after induction of labor, resulting in a diagnostic accuracy of 93.5%. The misdiagnosed case was prenatally diagnosed with a right-sided aortic arch and underwent surgical treatment at 1 year and 10 months old due to the onset of cough and other symptoms. In contrast, the missed case had no detectable intra- or extracardiac malformations prenatally and was diagnosed with a double aortic arch postnatally. This condition was not surgically treated because the symptoms were mild. Research has demonstrated that the “Z” sign is the most predictive marker in fetal echocardiography (sensitivity: 100%, specificity: 81%) (25, 26). The “Z” sign is a common feature in fetal echocardiograms of double aortic arch, which helps to differentiate between a right aortic arch and a double aortic arch. The “6/9” sign is typically used to identify common variations of the aortic arch, whereas the “Z” sign is particularly helpful in identifying the complex condition of a double aortic arch. However, based on the data and case analyses we collected, we found the “6/9” sign to be more prominent and common in our fetal samples (Figures 4, 5).

DAA is a common type of intact vascular ring that often compresses the trachea or esophagus, causing infants to experience symptoms such as difficulty swallowing, asthma, and respiratory distress. In severe cases, infants may even develop respiratory failure, which constitutes a life-threatening condition. In this study, we used the tracheal internal diameter z-scores proposed by Yin et al. and found that there was a significant difference in the tracheal internal diameter z-scores of DAA fetuses in the symptomatic and asymptomatic groups, which not only agrees with the findings of Yin et al. but also further deepens our understanding of tracheal pressure in DAA fetuses, which may have an important impact on clinical diagnosis and treatment strategies. Repeatability is one of the basic principles in scientific research, and our study not only further validates the reliability and validity of the tracheal internal diameter z-scores, but also reduces the random error by having a larger sample size, thus making the results more credible. Recognizing and understanding neonatal respiratory symptoms caused by DAA is the key to this study, and by applying the tracheal internal diameter z-scores, physicians can predict the onset of these symptoms earlier and intervene in a timely manner, thus significantly improving the prognosis of the children and reducing the risk of associated complications.

In this study, by measuring the DAA pinch angle, we found that the double arch pinch angle in the symptomatic group was significantly smaller than that in the asymptomatic group, which is consistent with the findings of Han et al. (19). This study emphasizes the importance of prenatal ultrasound in predicting whether a child is exhibiting symptoms or not, and by measuring the double-arch pinch angle and comparing it with the cutoff value, we can arrive at a more accurate diagnosis. The experimental design differed from previous studies in that only the angle between the left and right arterial arches was measured and not compared with the RAA-MB, which provides a new perspective on this issue. Given the potential importance of dual aortic arch angle in the prediction of symptomatology in children, further studies are necessary. To further enrich the body of knowledge in this area, we plan to increase the sample size and further improve the measurement methods in future studies, which will help to validate our current findings and also hopefully reveal new insights and findings. In addition, by comparing the area under the ROC curve of the tracheal internal diameter Z-value and DAA pinch angle, we found that the tracheal internal diameter Z-value was more efficacious than DAA pinch angle in predicting symptoms (Figure 7). Therefore, when we are unable to measure both parameters, it is more important to prioritize the measurement of fetal tracheal internal diameter Z-value.

This study explored the association between DAA and genetic abnormalities, particularly chromosome 22q11 deletions. It was shown that the percentage of 22q11 deletions in patients with DAA is approximately 6%, which is lower than the 6.1–10% in fetuses with right aortic arch (27–29). In our study, only in the non-simple DAA group, 2 cases (10.5%) showed genetic abnormalities, but no 22q11 deletion was found (Table 4). Statistical analysis showed that there was no significant difference in the detection of genetic abnormalities between simplex and non-simplex DAA, a result that may be related to the small sample size. In addition, we found one case of ichthyosis gene carriage combined with heterozygous deletion and one case of Turner syndrome, which did not appear in previous related studies; therefore, further exploration of the association between DAA and genetic abnormalities is necessary. The present study also revealed the phenomenon of gender differences, i.e., DAA seems to be more common in males, which is not only reflected in our study (male-to-female ratio of 21:10), but is also consistent with the study of Helen Bornaun et al. (male-to-female ratio of 11:3). This finding suggests that sex chromosomes may play an important role in DAA occurrence and warrants further investigation. However, this study faced the limitation of a small sample size, which may affect the overall understanding of the relationship between DAA and genetic abnormalities. Future studies should expand the sample size and use gene editing technology and big data analysis to explore the genetic mechanism of DAA in depth, with the aim of deepening the understanding of DAA’s genetic factors.

Echocardiography is the routine postnatal diagnostic method for DAA, but it has limitations in identifying specific anatomical features (e.g., fibrous cords and tracheal compression), and air in the lungs may interfere with image quality. In contrast, CTA provides more comprehensive information, including vascular structures and spatial relationships with neighboring organs (especially the airway and esophagus), and is able to clearly show details of the compressed trachea, esophagus, and vascular rings (30, 31). There were 2 special cases of interest in this study, one of which was DAA with left arch atresia and the other was DAA with Kommerell diverticulum formation (Figures 3, 8). These two cases were misdiagnosed prenatally as right aortic arch and double aortic arch (right arch dominant type), respectively, but the correct diagnosis was obtained by CTA after birth. According to previous studies, Kommerell’s diverticulum (KD) is most commonly seen in patients with right aortic arch, whereas concomitant DAA is very rare, with only two case reports (32, 33). It has been suggested that DAA with Kommerell’s diverticulum is more likely to lead to compression of the esophagus or trachea, leading to symptoms, which is an important indication for surgical treatment. In patients with DAA, Kommerell’s diverticulectomy is safe and effective and also helps to prevent recurrence of symptoms after surgery (34, 35). The patient in this study, who presented with significant coughing symptoms in daily life, underwent surgery 1 year ago and is currently in good condition.

Fetal echocardiography is a reliable method for diagnosing fetal DAA. In particular, three-vessel-tracheal views and aortic arch coronal views are particularly important for screening. Aortic arch long-axis views help in the differential diagnosis of DAA. It is important to note that the prognosis of children with DAA depends not only on the DAA itself, but also on the presence and severity of other intra- and extracardiac malformations, as well as the presence of chromosomal abnormalities. For children with simple DAA or only other simple intra- and extracardiac malformations, surgical intervention usually yields satisfactory results, and induction of labor is generally not recommended. In symptomatic children, early surgical intervention usually yields favorable results. In children without symptoms of airway or esophageal compression, the condition can be monitored through long-term follow-up. In addition, close collaboration between cardiologists, geneticists, pediatricians, surgeons, and imaging physicians is essential for comprehensive management from prenatal to postnatal periods. The importance of long-term follow-up, including regular cardiac evaluations and psychosocial support when necessary, should not be overlooked, as these can have a profound impact on the quality of life of the child and his or her family.

The limitations of the study were highlighted, including its single-center design with a small sample size. The genetic testing results did not conclusively determine the cause of fetal DAA, indicating that further investigation is necessary. there is a clear need for larger multicenter studies to validate the genetic findings and to provide a more comprehensive understanding of the genetic underpinnings of DAA. Additionally, the study raised questions about the management of asymptomatic DAA cases, particularly regarding whether these cases would require surgery in the future. this is an important issue that needs to be addressed by future research, as it directly impacts clinical decision-making and patient outcomes. longer-term follow-up studies are essential to understand the natural history of asymptomatic DAA and to determine the most appropriate interventions, if any, for these patients.

Prenatal ultrasonography is invaluable for diagnosing fetal DAA. The three-vessel view, three-vessel tracheal view and aortic arch long-axis view, and aortic arch coronal view are crucial for exam DAA. The prevalence of fetal DAA is low and most cases are simple DAA with a low association with chromosomal abnormalities. However, when non-simple DAA is detected, genetic testing to explore the correlation is necessary. There are significant differences in the tracheal internal diameter Z-value and double arch pinch angles between infants with asymptomatic and symptomatic DAA, and prenatal monitoring of both can provide important information for clinical management in the perinatal period. Postnatal CTA provides a more accurate picture of tracheal compression, which is essential for guiding the timing of surgery. The presence or absence of combined intra- and extracardiac abnormalities and the degree of tracheoesophageal compression can affect the prognosis of DAA. Therefore, when dealing with children with DAA, a comprehensive consideration of these factors is important to ensure optimal outcome and prognosis.