Vascular Rings, Pulmonary Slings, and Other Vascular Abnormalities

Double Aortic Arch

Double aortic arch (DAA) is the most common cause of tracheoesophageal compression, with an incidence of 46% to 76% in reports of vascular rings. Here, persistence of segment A (see Fig. 42.1B ) will result in a DAA ( Fig. 42.3 ), completely encircling the trachea and esophagus, sometimes leading to severe obstruction. Each aortic arch gives rise to respective common carotid and subclavian arteries. The arterial duct and the descending aorta are frequently left sided. The right (posterior) arch is usually dominant, although the two arches can be of the same size. The left (anterior) arch is dominant in approximately 20% of cases. Occasionally, the right or left arch (or a segment) can be atretic. This is more common on the left side, and it is worth remembering that these atretic segments cannot be visualized by any current imaging modality. Hence, it is sometimes difficult to differentiate the following:

• 1.

  Right arch with a mirror image branching from a DAA with atresia of the segment beyond the LSCA (segment H, see Fig. 42.1B )

• 2.

  Right arch with an aberrant LSCA from a DAA when the atretic segment is between the LCCA and LSCA (segments F and G, see Fig. 42.1B ).

DAA is commonly an isolated anomaly but can be seen occasionally in patients with tetralogy of Fallot, transposition of the great arteries, cervical arch, common arterial trunk, and coarctation of the aorta.

Right Aortic Arch with Aberrant Left Subclavian Artery

Right aortic arch with aberrant LSCA is the next most common cause of vascular ring (30% to 40%) and is a result of the absence of the fourth arch on the left side (segments F and G, see Fig. 42.1B ) with persistence of segments A and H (see Fig. 42.1B ). The aberrant LSCA has a retroesophageal course and forms an incomplete vascular ring if the arterial duct is right sided. However, in the presence of a left-sided arterial duct connecting the origin of the aberrant subclavian artery to the left pulmonary artery (LPA), the vascular ring becomes complete ( Fig. 42.4 ). This is usually loose, but it is tight when coming from a diverticulum of Kommerell, which is an outpouching from the distal remnant of the left aortic arch (see Fig. 42.4A ). The presence of the diverticulum of Kommerell is indicative of the existence of an arterial ligament (a DAA with atretic segment between the LCCA and LSCA). It is also worth remembering that the diverticulum of Kommerell can independently cause tracheoesophageal compression; hence, the symptoms might persist in some patients, despite the surgical division of the left-sided ligamentum.

The right aortic arch with aberrant LSCA and the right-sided arterial duct can occur in patients with tetralogy of Fallot, with or without pulmonary atresia or a common arterial trunk.

Right Aortic Arch with Mirror Image Branching

It is worth noting that a right-sided aortic arch with mirror image branching, caused by atresia of segment H (see Fig. 42.1B ), is seen in 2% to 3% of the population. The ductus arteriosus is usually left sided, arising from the LSCA. A right-sided arch on its own does not produce a vascular ring, although it may do so in association with other vascular anomalies. Extremely rarely, a duct may originate from a diverticulum of Kommerell and pass retroesophageally to join the LPA leading to a tight ring obstructing the left main bronchus ( Fig. 42.5 ).

Left Aortic Arch With Aberrant Right Subclavian Artery

A left aortic arch with aberrant RSCA is found in 0.5% of the normal population and is usually an incidental finding. Usually there is a left duct and no ring. There is persistence of segment A with atresia of segments B and C (see Fig. 42.1B and Fig. 42.6 ). It is also found commonly in association with tetralogy of Fallot (see Chapter 47 ). The aberrant RSCA usually takes a retroesophageal course and may cause symptomatic airway compression at the level of the arch and the RSCA (anteroposterior compression). Very rarely it may pass between the esophagus and trachea to cause dysphagia.

In the presence of a right-sided arterial duct from the RSCA, a complete but loose vascular ring is formed (see Fig. 42.6 ).

Left Aortic Arch with Retroesophageal Right Descending Aorta

This is an extremely rare anomaly in which the ascending aorta and the descending aorta are on the opposite sides of the spine with the aortic arch looping posterior to the esophagus. With a right duct there can be posterior indentation of the esophagus, but it is usually insufficient to cause symptoms ( Fig. 42.7A ). However, in the presence of an aberrant right subclavian and right duct from a diverticulum of Kommerell, there can be a complete ring (see Fig. 42.7B ).

Aberrant Left Brachiocephalic (Innominate) Artery

A right aortic arch with an aberrant left brachiocephalic artery (retroesophageal) and left duct can cause a loose vascular ring. Symptoms are variable depending on the extent of compression.

Cervical Arch

Very rarely a third arch component assumes the role of the definitive arch and presents as an abnormal pulsating feature in the neck, the so-called cervical arch. A right-sided cervical arch is more common than a left-sided arch. The descending aorta has a retroesophageal course, contralateral or ipsilateral, and commonly there is an aberrant subclavian artery. Where the arterial duct arises from the descending aorta contralateral to the side of the arch and with an aberrant subclavian artery, a vascular ring is formed ( Fig. 42.8 ). Even without the presence of a complete ring there may be tracheal compression secondary to overcrowding of vascular structures in the upper mediastinum. It is not uncommon to find associated arch tortuosity or even obstruction (coarctation) in the setting of the cervical arch. A double arch can sometimes be in a cervical position.