Overview: Anomalies of the aortic arch and the cervical vessels are relatively common, with a prevalence estimated at 0.5% to 3%, depending on the inclusion criteria. Most variations, such as a left aortic arch with an aberrant right subclavian artery, common origin of the left common carotid and right innominate arteries (bovine arch), and ectopic origin of the left vertebral artery from the aortic arch, are of little or no clinical consequence.

“Vascular ring” is a term that refers to encirclement of the trachea and esophagus caused by the abnormal embryologic development of the aortic arch. The principal structural components responsible for this encirclement are derived from the aortic arch or arches, subclavian artery, circumflex aortic segment, ductus arteriosus, or ligamentum arteriosum. Structural anomalies of the aortic arch can be understood as the abnormal divisions in the totipotential arch, a theoretical construct proposed by Jesse Edwards (Fig. 77-1).¹ Only a small subset of aortic arch developmental anomalies leads to vascular rings, accounting for less than 1% of all congenital cardiovascular defects. Although about a dozen different types of vascular rings exist, double aortic arches and right aortic arch with left ligamentum arteriosum account for 90% of cases.²

Chromosome 22q11 deletion has been reported in 24% of patients with isolated arch anomalies.3,4 This deletion was first identified in persons with DiGeorge syndrome, which consists of various degrees of immunodeficiency, thymic hypoplasia or aplasia, hypoparathyroidism, outflow tract cardiac defects, and dysmorphic appearance. Chromosome 22q11 deletion is now recognized as a major factor in many congenital heart defects. For example, it is detected in up to 50% of patients born with interrupted aortic arch or truncus arteriosus. Testing for this chromosomal abnormality can be performed using fluorescence in situ hybridization.

Clinical Manifestations: The severity of symptoms and the age of onset depend on the extent of the compression about the esophagus and trachea.⁵ Because different ring arrangements have different constrictive effects, not all vascular rings produce the same degree of symptoms; in fact, some rings produce no symptoms. Conversely, symptomatic vascular compression of the trachea and esophagus does not require a complete ring, as can be seen in an anomalously placed or aneurysmal innominate artery or a retroesophageal subclavian artery. Most cases of vascular ring, if they are symptomatic, present during infancy or early childhood.

Clinical symptoms related to constriction of the trachea include stridor, exertional dyspnea, cyanosis, respiratory distress, reflex apnea, and chronic cough. In cases of severe obstruction, intercostal retractions and lung hyperinflation can occur. Some patients have a history of recurrent respiratory infections. The pathophysiology involves external vascular compression, which leads directly to a reduced luminal cross-sectional area, as well as cartilage breakdown, tracheomalacia, and stenosis as a result of chronic, pulsatile mechanical compression. Clinical symptoms related to constriction of the esophagus are dysphagia, recurrent vomiting, difficulty feeding, and failure to thrive. Because the trachea and esophagus share the same space within the ring, respiratory symptoms can worsen during feedings. Of the different types of rings, double aortic arches produce the most severe symptoms. It is not uncommon for infants and children with vascular rings to be misdiagnosed with reactive airway disease.

Imaging: Chest radiography may show tracheal compression by a vascular ring, but by itself a chest radiograph cannot confirm or exclude a vascular ring. Because a vascular ring is more likely in the presence of a right aortic arch, symptoms of tracheal compression in the presence of a right aortic arch should raise the possibility of a vascular ring.

In patients presenting with nonspecific symptoms, barium esophagography is a useful first test.⁶ A normal barium esophagram usually excludes a clinically significant vascular ring. Classic S-shaped indentations in the frontal projection of an esophagram are highly suggestive of double aortic arches. A posterior vascular indentation may or may not be a vascular ring but is more likely in the presence of a right aortic arch. An esophagram may reveal other causes of a patient’s symptoms, such as gastroesophageal reflux, aspiration, or tracheoesophageal fistula.

Mediastinal ultrasonography or echocardiography with gray scale and color Doppler imaging may visualize the vascular ring directly in neonates and infants because these patients have excellent sonographic windows.⁷ Echocardiography generally is not useful in older children or adolescents. Moreover, because ultrasound is primarily a two-dimensional imaging method, connecting tortuous vascular structures can be difficult, especially when ligamentous or interrupted vascular segments are present. The presence of a vascular ring has been diagnosed successfully in utero with fetal ultrasonography.⁸

Patients with severe symptoms or an abnormal results of an esophagram, chest radiograph, or mediastinal ultrasonography should undergo angiography to confirm the vascular abnormalities and to gather information for surgical planning. Conventional catheter angiography has been replaced by first-pass, contrast-enhanced computed tomographic angiography (CTA) or magnetic resonance angiography (MRA). Both modalities can visualize the aortic arch and the cervical arteries well. MRA is usually preferred because it does not subject the patient to ionizing radiation.9,10 However, in cases in which the airways and the lungs must be evaluated together with the vascular anomaly, CTA can accomplish both in a single scan and may be a better choice.

Treatment: The definitive treatment is surgical relief of the obstruction.¹¹ A double aortic arch is repaired by dividing the nondominant arch between its last cervical artery and the point where the nondominant arch joins the descending aorta. If the ductus arteriosus or the ligamentum arteriosum forms a border of the ring, it is ligated to relieve the constriction. A thoracotomy is performed at the side of the planned ligation. Persistent stenosis or tracheomalacia may develop in the constricted trachea, requiring additional repair.

Anatomic, clinical, and imaging considerations for specific aortic arch anomalies are discussed in the following section.