Pathology
Vascular ring refers to a group of anomalies of the aortic arch that cause respiratory symptoms or feeding problems. A rare anomaly of the left pulmonary artery L(PA) that causes symptoms is also included in this group, although it does not involve the aortic arch. The vascular ring may be divided into two groups, complete (or true) and incomplete.
- 1.
Complete vascular ring refers to conditions in which the abnormal vascular structures or their remnants form a complete circle around the trachea and esophagus. Double aortic arch and right aortic arch with left ligamentum arteriosum are examples of complete vascular ring.
- 2.
Incomplete vascular ring refers to vascular anomalies that do not form a complete circle around the trachea and esophagus but do compress the trachea or esophagus. These include anomalous innominate artery, aberrant right subclavian artery, and anomalous left PA (“vascular sling” or “pulmonary sling”).
Five major vascular rings will be discussed in this chapter.
- 1.
Double aortic arch is the most common vascular ring (40%) ( Fig. 16-1 ). This anomaly is caused by a failure of regression of both the right and left fourth branchial arches, resulting in right and left aortic arches, respectively. These two arches completely encircle and compress the trachea and esophagus, producing respiratory distress and feeding problems in early infancy. The right arch gives off two arch vessels, the right common carotid and the right subclavian arteries, and the left arch gives off the left common carotid and left subclavian arteries (see Fig. 16-1 ). The right aortic arch is usually larger than the left arch (seen in 75% of patients), but on rare occasions, partial obstruction or complete atresia of the left arch (with a ligamentous remnant) may occur. Double aortic arch is commonly an isolated anomaly but is rarely associated with a variety of congenital heart defects (CHDs) such as transposition of the great arteries, ventricular septal defect (VSD), persistent truncus arteriosus, tetralogy of Fallot (TOF), and coarctation of the aorta (COA).
FIGURE 16-1
Clinical summary of vascular ring. In the anatomy of right aortic arch with left ligamentum arteriosum (in the second row), thick short black bands (indicated by thick arrows) are left-sided ductal ligaments. Aber., aberrant; Ba-Esophag., barium esophagogram; Lat., lateral view; Lig., ligamentum; LPA, left pulmonary artery; MPA, main pulmonary artery; P-A, posteroanterior view; Post., posterior; RPA, right pulmonary artery; Rt., right; Subclav., subclavian.
- 2.
Right aortic arch with left ligamentum arteriosum. One of the major components of most vascular rings is a right aortic arch. Vascular ring with a right arch with left ligamentum arteriosum has several different forms; two common types are described here. Although rare, right aortic arch may occur without forming a vascular ring if the aorta stays and descends on the right of the vertebrae.
- a.
In the most frequent form of vascular ring with right aortic arch with left ligamentum arteriosum (occurring in ≈65% of cases), the right arch first gives off the left carotid artery, then the right carotid artery followed by the right subclavian artery, and last, the left subclavian artery (see Fig. 16-1 ). The aberrant left subclavian artery often arises from a retroesophageal diverticulum (called diverticulum of Kommerell). The ring is completed by a left-sided ductus arteriosus (or its remnant ligamentum arteriosum) passing from the subclavian artery to the proximal LPA (see Fig. 16-1 ). The descending aorta usually courses to the left of the vertebral column to pass through the diaphragm in the usual location of the aortic hiatus. About 10% of this type of vascular ring is associated with an intracardiac defect.
- a.
As a rare variant of this type, an aberrant innominate artery, rather than subclavian artery, may arise from the upper descending, and the ligamentum arteriosum connects the base of the innominate artery and the proximal left PA completing a vascular ring. Clinical manifestations are similar to the one described above.
- b.
In the second type of vascular ring with right aortic arch and ligamentum arteriosum (occurring in ≈35%), the left innominate artery originates from the right arch in mirror image fashion as the first branch followed by the right carotid and right subclavian arteries. A left-sided ductus or ligamentum arteriosum passes between the descending aorta and the proximal LPA (see Fig. 16-1 ). More than 90% of patients with this type of vascular ring have associated intracardiac defects, notably TOF and truncus arteriosus.
- b.
- 3.
Anomalous innominate artery occurs in about 10% of patients with vascular ring (see Fig. 16-1 ). If the innominate artery takes off too far to the left from the aortic arch or more posteriorly, it may compress the trachea, producing mild respiratory symptoms. This anomaly is commonly associated with other congenital heart defects such as VSD.
- 4.
Aberrant right subclavian artery is the most common arch anomaly (accounting for 0.5% of the general population, but its true incidence may be higher if asymptomatic patients are included). Most cases are asymptomatic. When the right subclavian artery arises independently from the descending aorta, it courses behind the esophagus, compressing the posterior aspect of the esophagus and producing mild feeding problems ( Figs. 16-1 and 16-2 ). Often, a larger compression is found behind the esophagus by an aortic diverticulum at the take-off of the right subclavian artery. This anomaly usually is an isolated anomaly, but it has a high association with coarctation of the aorta or interrupted aortic arch. Its incidence is very high (38%) in patients with Down syndrome with CHDs.
FIGURE 16-2
Barium esophagogram in a child with aberrant right subclavian artery. A, Anteroposterior view shows an oblique indentation of the esophagus (arrow) at the level slightly higher than the carina produced by the subclavian artery. The indentation proceeds upward and to the right toward the right shoulder. B, Lateral projection shows a relatively shallow, long retroesophageal impression produced by the aberrant artery.
- 5.
Anomalous left PA (also called “vascular sling” ) is a rare anomaly in which the left PA arises from the right PA ( Figs. 16-1 and 16-3 ). To reach the left lung, the anomalous artery courses over the proximal portion of the right mainstem bronchus, behind the trachea, and in front of the esophagus to the hilum of the left lung. Therefore, both respiratory symptoms and feeding problems (e.g., coughing; wheezing; stridor; episodes of choking, cyanosis, or apnea) may occur. About 10% to 20% of patients with this anomaly have associated cardiac defects, such as patent ductus arteriosus, VSD, atrial septal defect (ASD), atrioventricular canal, single ventricle, or aortic arch anomalies.
