Introduction A double aortic arch is one the most common types of vascular ring [1]. The hypothetical double aortic arch system was suggested by Dr Jesse E.Edwards in 1964 (image 14) [2,3]. In this model the descending aorta is located posterior to the tracheoesophageal pedicle and connected bilaterally to the ascending aorta by lateral aortic arches. Subclavian arteries and common carotid arteries arise from both right and left arches and ductus arterisosus on each sides connects the arch to its ipsilateral pulmonary artery [4]. The right arch is larger and higher in approximately 75% of cases. Rarely, one arch is atretic. In the majority of cases the left ductus is patent. The descending aorta is usually deviated to the side of the patent ductus [5]. A double aortic arch is a complete vascular ring that encircles both the trachea and the esophagus [6, 7]. Aortic arch anomalies may lead to respiratory distress in the neonate or the development of milder symptoms and signs of tracheal or esophageal compression later in life, or they may remain clinically silent [8].
A literature review showed an association between double aortic arch and congenital heart diseases in approximately 20% of cases most often tetralogy of Fallot, transposition of great vessels, ventricular septal defects. Rarely there can be atresia of the segment of the aortic arch, which can be difficult to differentiate from other aortic arch anomalies associated with chromosomal abnormalities such as microdeletion of chromosome 22q11 [9, 10]. The condition affect males and females fetuses equally [11].
Pathogenesis
The occurance of this anomaly is probably related to persistence of both embryonic aortic arches [9, 11]. The aortic arches are usually symmetrical, the right arch being larger and higher in approximately 75% of cases. As a rule, the descending aorta is contralateral to the side of the dominant arch. In the majority of cases the left ductus is patent [5].
Ultrasound findings
The vascular ring diseases can be recognized in 3 vessels. The suspicion of a double aortic arch is raised by detecting the U-sign which is formed by the combination of both aortic arches and the left ductus arteriosus (images 2,3). In a plane cranial to the U-sign, the aortic root bifurcates in the two arches directly in front of the trachea as a Lambda [12]. The 4-chamber view appears normal, but the descending aorta is deviated medially. In the 3 vessels view the ascending aorta and aortic arch are pointing to the right, whereas the left arch points to the left, and the trachea is seen between. The bifurcation of the aortic arch can be recognized in the upper thorax. The pulmonary trunk bifurcate into left and right pulmonary arteries and gives rise to the ductus arteriosus on the left side of the trachea [12]. The diagnosis cannot be achieved in a longitudinal visualization of the arch, since an arch with a common carotid artery and subclavian artery is visualized both in a left and in a right parasagittal plane to the trachea [12]. A sweep downward in the upper thorax will then demonstrate how the bifurcated aortic arches fuse together to form the neutral descending aorta [12]. A longitudinal coronal plane can demonstrate how both arches merge together to form the descending aorta. However, one has to be careful with this coronal plane, because it is also found in a right arch and a left ductus arteriosus (in the U-sign). The esophagus and trachea are entrapped in this vascular ring [12].
Differential diagnosis
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Right aortic arch and left ductus which forms a ring (the U-sign).
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Large azygos arch in case of interrupted inferior vena cava (left isomerism). Following the right arch into the upper thorax and seeking the presence of the brachiocephalic arteries can help in the differentiation [12].
Dicussion
The 4-chamber view is used in the fetal sonographic screening examination for detection of congenital heart disease. The limitations of the 4-chamber view is, that we could not detect anomalies of the outflow tract and great arteries. Integration of the 3-vessel view, an axial view of the fetal upper mediastinum has been proposed in sequential segmental analysis to improve the antenatal detection of congenital heart disease. The location of the aortic arch in relation to the trachea can be easily visualized because the fetal airway is normally filled with fluid, allowing sonographic visualization [1, 9, 12]. In summary, the 3-vessel and trachea view in the upper mediastinum is useful in detecting abnormalities of the aortic arch [9, 2].This report describes the sonographic prenatal diagnosis of double aortic arch , showing the importance of 3 vessels view examination by detecting the anomalies of aortic arch.
Answer of the Nickolay Veropotvelyan, MD. We wanted to show this answer because we find it very accurate and it nicely shows the analytical process of thinking and finding the correct answer!
As usual I use the systematic consequal segmental approach for the fetal heart evaluation.
Image 1: 4-chamber view at diastola is almost normal
- Position & cardiac axis and heart size are normal
- normal size relationship of the left and right sides
- chambers are without any asymmetry and visible septal detects
- atrial septum primum (I) is present
- opened MV & TV valves are well recognized
- opened FO
- atrio-ventricular connection is concordant
- normal connection of the pulmonary veins to the LA
- no cardiac wall hypertrophy (endocardrium echogenecity is also - normal)
- descending Ao in abnormal position – is ring-sided relative to spine
Image 2-4: 3V+T view– are abnormal
- 3 vessels are located sequentially with normal vessels size decrease
- Crossing of great arteries is present, so TGA is excluded.
And the main point – we can see vascular right arising from Aorta around the trachea and esophagus.
The ring is shaped as the figure “9” or “6” in horizontal position. It is the most significant echosign.
The right part of the ring is bigger than the left one.
Image 5: 5-chamber view – LV outlet with the ascending Ao
Image 6: the same scan in CFM Doppler mode – and we can see the beginning of the small left Ao Arch branch.
Descending Ao is right-sided relative to spine
Image 7: “Pulmonary view” – RV outlet with arising PA root – is normal
So, (looking on images 5-7) the bulbo- ventricular and ventriculo- arterial connections are concordant
Image 8: Sagittal scan – Longitudinal view of the Ao Arch.
Unfortunately I can’t see the exact number of the vessels arising to the head and upper limbs. We can definitely observe only 1 vessel.
Image 9: axial scan of fetal upper abdominal plan
- abnormal central position of descending Ao;
- vena cava inferior in normal right-sided position, ventral and lateral to the Aorta
- stomach is absent, I thank it is due to eosophagal obstruction by the double Ao Arch ring – effect like in case of esophageal atresia. (Unfortunately in these pictures we can’t see a quantity of Amniotic fluid) Polyhydranion - is may be expected.
- Looking at the video (with normal Rhythm and heart contractility) my answer #1:
- It is right sided double Aortic arch with the dominant right branch and right sided descending aorta.
P.S.
Differential diagnose with the Aberrant right subclavian artery/ARSA/ or a.Lusoria.
(RAo Arch with the ALSA – has another “U” – shaped–sign-picture with the ring due to Kommerell’s divertirulum.
Besides it is possible to have here vascular ring with the narrower vessel branching from the left of Ascending Ao. (ARSA originate from the 4-th regressed Ao Arch, connected with delay dorsal Ao segmett, which are connect with the right 7 intrasegmental artery). The key to the correct Prenatal diagnose is the Ao Arch longitudinal scan evaluation, which allows not a 3,-but a 4 arising wessels from the Ao Arch. (Especcialy useful 4D+STIC).
But these anomalies have a different clinic and prognosis. For DAA it is more typical to have more severe obstructive trachea symptoms and dysphagia. The final postnatal diagnose give by CT and MRT, because neonatal echocardiography is useless. As usual, infants with DAA need for cardiosurgery treatment.
With respect, Nickolay.
References
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