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Vascular Ring and Sling


Section I

Vascular Ring

Definition

Vascular ring is a congenital anomaly in which the aortic arch and its branches completely or incompletely encircle and compress the trachea or esophagus or both.

Historical Note

Double aortic arch was apparently first described by Hommel in 1737 (cited by Turner) and a century later by Von Siebold. Wolman is credited with describing the syndrome of tracheal and esophageal compression produced by a double arch in 1939. A description of a patient with dysphagia thought to be due to a retroesophageal right subclavian artery was published in 1794 by Bayford, although the vessel was illustrated to pass between the esophagus and trachea rather than in its actual position posterior to the esophagus.

Modern interest in these anomalies was prompted by the first surgical correction of a double aortic arch by Gross in 1945. Subsequently, he pioneered surgical treatment of most other forms of vascular ring. The basis for radiologic diagnosis was initially described by Neuhauser.

The complex development and regression of the aortic arches during fetal development was elucidated by Congdon in 1922, but until Gross's pioneering surgical work, this information was little used by clinicians. In 1948, Edwards introduced the hypothetical double aortic arch scheme to conceptualize the numerous anomalies of the arch complex. This was further elaborated by Kirklin and Clagett in 1950 and by Stewart, Kincaid, and Edwards in 1964. In 1951, Barry provided a clear anatomic summary and review of Congdon's basic work. In 1999, Momma and colleagues, followed by McElhinney and colleagues, identified chromosome 22q11 deletions associated with isolated anomalies of laterality or branching of the aortic arch.

Morphology

Variations in arrangement of the ascending, transverse, and descending aorta and its branches are numerous in patients with vascular rings. Several of these may produce compression of the trachea or esophagus, or both, and are of surgical importance. They may be grouped as (1) complete or (2) incomplete vascular rings, including compression by the brachiocephalic artery or left common carotid artery ( Box 51-1 ). Of 301 patients with vascular ring or sling reported by Backer and Mavroudis, 84% fit into the categories of double aortic arch (30%), right arch with retroesophageal component (27%), and brachiocephalic artery compression syndrome (27%).

Box 51-1
Classification of Vascular Ring

Complete Vascular Ring

  • Double aortic arch

  • Right aortic arch with retroesophageal component:

    • Mirror-image branching with retroesophageal ligamentum arteriosum

    • Retroesophageal left subclavian artery with ligamentum arteriosum

    • Retroesophageal left brachiocephalic artery

  • Left aortic arch and right descending aorta with right ligamentum arteriosum or patent ductus arteriosus

  • Cervical aortic arch complex

Incomplete Vascular Ring

  • Left aortic arch and retroesophageal right subclavian artery

  • Tracheal compression by brachiocephalic or left common carotid artery

  • Ductus arteriosus sling

  • Malrotation of heart with patent ductus arteriosus

Complete Vascular Ring

Double Aortic Arch

In patients with double aortic arch, the ascending aorta arises normally, but as it leaves the pericardium it divides into two branches, a left and right aortic arch, that join posteriorly to form the descending aorta. The left arch passes anteriorly and to the left of the trachea in the usual position and is joined by the ductus arteriosus (or more often a ligamentum arteriosum), where it becomes the descending aorta. The right aortic arch passes to the right and then posterior to the esophagus to join the left-sided descending aorta, thus completing the vascular ring ( Fig. 51-1 ). Occasionally the descending aorta is right sided, in which case the left arch (or its remnant) passes behind the esophagus. This was the case in 13 of 19 cases reported by Lincoln and colleagues. Alternatively, the descending aorta may be essentially a midline structure.

Figure 51-1, Double aortic arch with right dominant arch. Right common carotid and right subclavian arteries arise from right arch. Left common carotid and left subclavian arteries arise from smaller left arch. The two arches join as the descending thoracic aorta, forming a complete vascular ring.

The right arch gives origin to two vessels, the right common carotid and right subclavian arteries, and the left arch gives origin to the left common carotid and left subclavian arteries in that order. The right aortic arch is most often (75% of cases) larger (right dominant) than the left, which usually becomes narrow or atretic in its distal part beyond the origin of the left subclavian artery ( Fig. 51-2 ; see also Fig. 51-1 ). This portion may remain patent or be represented by a fibrous chord that joins the descending aorta, often at the site of a diverticulum. This fibrous chord, at its origin from the base of the left subclavian artery, lies close to the ligamentum arteriosum. The latter structure passes from this point to the adjacent proximal part of the left pulmonary artery ( Fig. 51-3 ; double arch, left dominant). Less commonly (20% of cases) the left aortic arch is larger (left dominant) than the right, which although smaller in its distal part after the origin of the right subclavian artery, is rarely atretic ( Fig. 51-4 ; see also Fig. 51-3 ). Size of the right and left aortic arches is nearly equal (balanced) in about 5% of cases.

Figure 51-2, Aortogram of right dominant double aortic arch in (A) frontal view and (B) lateral view with cranial tilt. Left aortic arch is distinctly narrowed beyond origin of left subclavian artery. Key: LA, Left arch; LCCA, left common carotid artery; LSA, left subclavian artery; RA, right aortic arch; RCCA, right common carotid artery; RSA, right subclavian artery.

Figure 51-3, Double aortic arch with left dominant arch. Smaller right arch passes posterior to esophagus, forming a complete vascular ring.

Figure 51-4, Aortogram of balanced double aortic arch in (A) frontal and (B) lateral views. Right aortic arch is slightly smaller than left (left dominant) where it joins left-sided descending aorta. Right and left common carotid arteries arise from a large common trunk. Key: LA, Left arch; LCCA, left common carotid artery; LSA, left subclavian artery; LVA, left vertebral artery; RA, right arch; RCCA, right common carotid artery; RSA, right subclavian artery; RVA, right vertebral artery.

Associated cardiovascular anomalies are uncommon but include tetralogy of Fallot and transposition of the great arteries.

Right Aortic Arch with Retroesophageal Component

In the situation of right aortic arch with a retroesophageal vascular or ligamentous component, a vascular ring is usually present, but the anatomic details vary depending on site of regression (interruption) of the embryonic left arch.

In the common situation of right aortic arch without retroesophageal segment, no vascular ring is present. The arch branches arise in mirror image of the normal ( Fig. 51-5 ). This arrangement is the result of interruption of the embryonic left arch distal to the ductus arteriosus, in which the anterior ligamentum courses from the brachiocephalic artery to the proximal left pulmonary artery ( Fig. 51-6, A , type 1 right aortic arch). This type is particularly common in tetralogy of Fallot (see Chapter 38 ) and truncus arteriosus (see Chapter 43 ).

Figure 51-5, Common type of right aortic arch with mirror-image branching. This anomaly is frequently associated with tetralogy of Fallot and truncus arteriosus. Ligamentum arteriosum is anterior, coursing from brachiocephalic artery to pulmonary artery. There is no vascular ring.

Figure 51-6, Vascular ring associated with right aortic arch. Center drawing depicts a double aortic arch with descending thoracic aorta as a midline or left-sided structure. Ligamentum arteriosum (dashed line) is shown originating from junction of right or left arch and descending aorta. Right-sided ligamentum arteriosum to right pulmonary artery usually forms in association with a right-sided descending aorta. Left-sided ligamentum arteriosum is the common configuration connecting midline or left descending thoracic aorta to left pulmonary artery near bifurcation. The four possible sites (dotted lines) of regression (interruption) of left arch during fetal development are shown. Various types of right aortic arch are depicted depending on site of interruption. Vascular ring results from a retroesophageal component of left arch giving rise to the ligamentum. A, Type 1 right aortic arch. Aortic arch branches arise in mirror image of normal. Anterior ligamentum arteriosum courses from brachiocephalic artery to proximal left pulmonary artery (see Fig. 51-5 ). There is no vascular ring. B, Type 2 right aortic arch. Left arch regresses just distal to left subclavian artery, leaving a retroesophageal aortic diverticulum. Ligamentum (ductus) arteriosum arises posteriorly from descending aorta and courses to left pulmonary artery, completing a vascular ring. C, Type 3 right aortic arch. Left arch regresses between left common carotid and left subclavian arteries, leaving a retroesophageal subclavian artery, with ligamentum (ductus) arteriosum forming a complete vascular ring. D, Type 4 right aortic arch. Left arch regresses between right arch and left common carotid artery. Complete vascular ring is present in this rare anomaly.

Mirror-Image Branching and Retroesophageal Ligamentum Arteriosum

Interruption of the left arch is proximal (upstream) to the ductus arteriosus ( Fig. 51-6, B , type 2 right aortic arch). The left-sided ligamentum arteriosum extends from a diverticulum (Kommerell) on the upper descending thoracic aorta, behind the esophagus, forward to the left pulmonary artery. The vascular ring is formed by the ascending portion of the right arch and brachiocephalic artery anteriorly, by the aortic diverticulum posteriorly, and by the ligamentum arteriosum laterally. In the surgical series reported by Backer and colleagues, this anomaly represented about one third of right arch vascular rings.

Retroesophageal Left Subclavian Artery and Ligamentum (Ductus) Arteriosum

Here the interruption of the left arch occurs between the left subclavian and left common carotid arteries ( Fig. 51-6, C , type 3 right aortic arch). The first branch of the right arch becomes the left common carotid artery, and the descending aorta gives origin to the retroesophageal left subclavian artery as the fourth branch. The ductus or ligament arises with the left subclavian artery from an aortic diverticulum or from the left subclavian artery itself near its origin, where the subclavian artery may be narrowed. The descending aorta can be left or right sided.

This is the most common type of vascular ring associated with right arch (see Fig. 51-6, C ), accounting for about two thirds of right arch vascular rings. It is usually loose, so compression of either the esophagus or trachea is uncommon. Associated cardiac anomalies are rare.

Retroesophageal Left Brachiocephalic Artery

Here interruption occurs between the left common carotid and the right arch ( Fig. 51-6, D , type 4 right aortic arch). A vascular ring is present, but the anomaly is rare. Bein and colleagues reported a case of long-segment coarctation with this anomaly.

Left Aortic Arch and Right Descending Aorta

Vascular rings are likely in the uncommon combination of left aortic arch and right descending aorta. The left arch crosses behind the esophagus. In combination with right patent ductus arteriosus or ligamentum arteriosum, a vascular ring is formed.

Cervical Aortic Arch Complex

Cervical aortic arch is a developmental entity consisting of persistence of the right or left third branchial arch and regression of the fourth branchial arch. The cervical aortic arch complex consists of a cervical position of the apex of the aortic arch with separate origin of the contralateral carotid artery, a retroesophageal descending aorta coursing contralaterally to the arch, and anomalous origin of the subclavian artery from the descending aorta. The cervical arch usually is right sided. The aorta is usually redundant and crosses to the opposite side posterior to the esophagus. The retroesophageal segment of the aorta may be tortuous and severely narrowed. A vascular ring is formed when there is an aberrant subclavian artery on the side contralateral to the aortic arch and a ligamentum arteriosum. There is considerable variability in anatomic configuration of the aortic arch and its branches. Abnormalities of brachiocephalic arterial branching and arch laterality are common in patients with cervical aortic arch. Vascular ring is frequently present, usually formed by the right aortic arch and aberrant left subclavian artery, but occasionally by double aortic arch. Rarely, a left cervical aortic arch, right ligamentum arteriosum, and right descending aorta form the vascular ring (see also discussion under “ Left Aortic Arch and Right Descending Aorta ”).

Incomplete Vascular Ring

Left Aortic Arch and Retroesophageal Right Subclavian Artery

The relatively common (0.5% of the general population ) retroesophageal right subclavian artery arising as the fourth branch of an otherwise normal aortic arch and passing upward and to the right behind the esophagus was once thought to be a cause of dysphagia (dysphagia lusoria, or “difficulty swallowing due to a trick of nature”). This condition does not form a complete ring and is generally not considered the true cause of vague symptoms related to swallowing. Rarely, a right ligamentum arteriosum passing from the retroesophageal right subclavian artery to the right pulmonary artery forms a vascular ring that is symptomatic.

Tracheal Compression by Brachiocephalic or Left Common Carotid Artery

The brachiocephalic or left common carotid artery may be drawn taut across the anterior wall of the trachea, a potential but uncommon cause of respiratory obstruction. It is not known why they occasionally compress the trachea. Presumably, the brachiocephalic artery originates more posteriorly from the aortic arch than usual, so it crosses the trachea more posteriorly.

Ductus Arteriosus Sling

Binet and colleagues described an infant with respiratory obstruction in which an anomalous vessel (presumed to be the ductus arteriosus) originated from the right pulmonary artery, crossed to the left between the esophagus and trachea, and joined the descending aorta adjacent to the origin of a retroesophageal right subclavian artery.

Severe Malrotation of Heart with Patent Ductus Arteriosus

Compression of the lower trachea can occur with a normal left arch when there is severe malrotation of the heart into the right chest in association with agenesis or hypoplasia of the right lung. Scherer and Westcott described a patient with dextrocardia and normal lungs in whom the pulmonary trunk lay anterior to the trachea and somewhat to the right. The patent ductus arteriosus connecting with a normally positioned descending aorta pulled the pulmonary trunk backward, compressing the front of the trachea. Compression was relieved by dividing the patent ductus arteriosus.

Clinical Features and Diagnostic Criteria

Symptoms and Signs

Symptoms of vascular ring relate to the consequences of tracheal and esophageal compression. Presentation is usually within the first 6 months of life and often within the first month. Inspiratory stridor may be present at birth, often in association with an expiratory wheeze and tachypnea. Stridor may be worse in various positions—for example, when the baby is lying on his or her back rather than side. Often, stridor is relieved by extending the neck. The baby's cry may be hoarse and, in the absence of frank stridor, the breathing noisy. Persistent barking cough is frequently present. There may be episodes of apnea, severe cyanosis, and unconsciousness. When obstruction is severe, subcostal retraction is obvious. Recurrent respiratory infections are common and aggravate the respiratory obstruction; when obstruction is less severe, obstructive symptoms may be apparent only at such times.

The baby often feeds poorly, and there may be obvious difficulty in swallowing liquids, with episodes of choking and increased respiratory obstruction at these times. Dysphagia for solids is common (most severe cases are operated on before the babies are old enough to be offered solid food), with the baby refusing to swallow them or choking and regurgitating.

Dysphagia lusoria is often attributed to retroesophageal origin of the right subclavian artery from the upper descending thoracic aorta. The artery courses to the right, posterior to the esophagus, producing an indentation of the esophagus that has been blamed for vague symptoms in children, but that is usually not the cause. Should it become ectatic or aneurysmal later in life, difficulty swallowing is more likely.

Symptomatic vascular rings manifesting in adults are rare, and reports often emphasize dysphagia as the predominant symptom. Grathwohl and colleagues reviewed case reports of 24 adults with vascular rings. Two thirds had symptoms, 63% respiratory. Dysphagia was less prominent, occurring in 33%. Vascular rings occurring in adults may mimic chronic asthma.

Chest Radiography

Plain chest radiograph in the frontal view is either normal (10%) or shows a right aortic arch (85%). Anterior tracheal bowing is present on 92% of lateral views, and tracheal narrowing on 77%.

Esophagography

The esophagram is a useful diagnostic measure. Video esophagography at the time of cineangiography is optimal because it permits a detailed study showing the pulsatile nature of the obstruction and trachea.

With double aortic arch, the esophagram shows left- and right-sided indentations, with that for the right arch usually higher and deeper ( Fig. 51-7, A ). In addition, the retroesophageal component produces a prominent posterior indentation that courses downward and to the left. In contrast, a retroesophageal left subclavian artery arising from the right arch produces a narrower esophageal impression that courses upward and rightward. Right arch and left ligamentum arteriosum show more marked right-sided than left-sided indentation ( Fig. 51-7, B ).

Figure 51-7, Esophagrams in anteroposterior (AP) and lateral (LAT) projections. A, Double aortic arch. B, Right aortic arch with retroesophageal aortic diverticulum giving origin to a retroesophageal left subclavian artery and ligamentum arteriosum. AP views show typical bilateral indentations, lateral views a posterior indentation. Key: ANT, Anterior aspect of patient; L, left side of patient; POST, posterior aspect of patient; R, right side of patient.

Bronchoscopy

Bronchoscopy is rarely done, although it does identify sites of tracheal compression and shows its pulsatile nature.

Two-Dimensional Echocardiography

Two-dimensional echocardiography is useful in diagnosing vascular ring, at least in neonates and infants, and is critically important for identifying associated cardiac anomalies. However, it is inferior to computed tomography (CT) in demonstrating details of arch anatomy.

Computed Tomography

CT with contrast usually provides an excellent image of the structures and complements two-dimensional echocardiography. Ultrafast CT with three-dimensional reconstruction provides even greater anatomic detail. In many institutions, CT has become the standard modality for delineating details of vascular ring anatomy.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is diagnostic and delineates severity of tracheal narrowing.

Aortography

Because of the accuracy of noninvasive imaging, aortography is rarely necessary. Aortography may be performed via a catheter positioned in the ascending aorta and is usually combined with cineangiography to assess associated congenital cardiac anomalies. Using biplane techniques, the first injection depicts both lateral and anteroposterior views, and the second both left and right oblique views. A degree of cranial tilt may separate the arches better in oblique views. Aortography can establish that the anomaly is a complete double aortic arch and show sites of narrowing in the left or (rarely) right arch (see Figs. 51-2 and 51-4 ). It cannot distinguish between a double arch with an atretic segment and a right aortic arch with a retroesophageal component. Sharp angulation of one of the brachiocephalic arteries may indicate the site of an atretic segment in a double arch or a constricting ligamentum arteriosum in a right arch with retroesophageal component ( Fig. 51-8 ).

Figure 51-8, Aortogram of right aortic arch with retroesophageal left subclavian artery and ligamentum arteriosum arising from a retroesophageal aortic diverticulum. Frontal views (A-B) and right anterior oblique views (C-D) are at different phases in cardiac cycle. Angulation at origin of left subclavian artery from diverticulum suggests presence of a ligamentum arteriosum under tension passing forward to left pulmonary artery (as was the case at operation). Angulation is downward in frontal view and anterior in right anterior oblique view. Absence of a similar angulation along course of left common carotid artery suggests that this artery is not connected to the diverticulum by an atretic ligament that forms part of a complete left aortic arch.

Natural History

Vascular rings of aortic arch origin account for 1% to 2% of cases of congenital heart disease. Only fragmentary information exists concerning the natural history of these anomalies. Untreated severe respiratory obstruction in the first 6 months of life is presumably fatal before age 1 year, particularly when symptoms are present from birth. Symptoms first appearing after age 6 months are less severe and rarely progressive, except at times of respiratory infection or regurgitation and choking.

When symptoms are of borderline severity, they usually disappear as the child grows. Godtfredsen and colleagues followed 11 patients with symptoms not severe enough to justify surgery. Of the six who had either double aortic arch or right arch with retroesophageal component, four outgrew their symptoms by age 4 years, and two with persistent symptoms had other anomalies to explain them.

Generally, symptoms are milder and of later onset, and dysphagia is less prominent, in patients having right aortic arch with retroesophageal component than in those with double aortic arch.

Technique of Operation

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