Vascular Rings

Double aortic arch

Visualization through a left thoracotomy shows a normally positioned left (anterior) arch exiting the pericardium and joining the left-side descending thoracic aorta after giving off the left subclavian artery. The ligament arteriosum is positioned normally. The posterior (right) arch joins the descending thoracic aorta at the same level as the anterior arch but reaches that point from an extreme posterior course behind the esophagus. Often, the posterior arch is visible only after circumferential dissection of the aorta at the level of its junction with the anterior arch. (See the image below.)

Right aortic arch with retroesophageal left subclavian artery and left ligamentum arteriosum

The arch travels to the right and behind the esophagus, joining the left-side descending aorta. As it takes this course, it gives off the left carotid artery first. Then, it sequentially gives off the right carotid, right subclavian, and left subclavian arteries. This last branch often has a retroesophageal position. The ligamentum arteriosum courses from the base of the left subclavian artery to the left pulmonary artery. (See the image below.)

Through a left thoracotomy, the structures visible in normal position are the descending thoracic aorta and the distal portion of the left subclavian artery. These structures can be traced proximally to identify the site where the left subclavian artery exits the right arch as it joins with the descending aorta. The ligamentum arteriosum can be found at the base of the subclavian artery and traced towards the pulmonary artery.

Right aortic arch with mirror-image branching and retroesophageal ligamentum arteriosum

In the rightward and retroesophageal course, the aortic arch gives off a left innominate artery, which in turn branches into the left carotid and subclavian arteries. The right carotid artery then branches from the arch, followed by the right subclavian. The ligamentum arteriosum exits distal to this point from the area of the Kommerell diverticulum and courses to the left pulmonary artery. (See the image below.)

As viewed through a left thoracotomy, the descending thoracic aorta is visible and can be traced proximally to the area of its merger with the right aortic arch, which joins it from behind the esophagus. In this area, the ductus diverticulum and ligamentum arteriosum can be found.

Left aortic arch with right descending thoracic aorta and right ligamentum arteriosum

The arrangement of this anomaly is the mirror image of right aortic arch with retroesophageal left subclavian artery and left ligamentum arteriosum. Approached through a right thoracotomy, structures are identified and traced in the same manner. (See the image below.)

Left aortic arch with right descending aorta and atretic right arch

In a retroesophageal position, the left arch passes to the left of the trachea to join the right descending thoracic aorta. The surgical view is via a right thoracotomy. At the level of this junction and immediately superior to a right ligamentum arteriosum, an atretic right arch is found. The brachiocephalic vessels in this case exit the left arch in a normal sequence.

Anomalous innominate artery

The brachiocephalic vessels exit the left arch in the normal sequence. The innominate artery may be more distally positioned and leftward on the arch than normal.

Retroesophageal right subclavian artery with left aortic arch and left ligamentum arteriosum

Rather than an innominate artery exiting the arch as the normal first brachiocephalic branch, the right carotid is the first brachiocephalic vessel. It is followed by the left carotid and then the left subclavian artery. The right subclavian artery is the last brachiocephalic branch to exit the arch, and it takes a course rightward and posterior to the esophagus. The ligamentum arteriosum is normally positioned on the left. (See the image below.)

Anomalous left pulmonary artery (pulmonary artery sling)

Instead of the normal pulmonary artery configuration, in which the main pulmonary artery gives rise to the right and left pulmonary arteries, the main pulmonary artery continues behind the ascending aorta and rightward as the right pulmonary artery, which then gives off the left pulmonary artery. The left pulmonary artery passes from right to left between the trachea and esophagus in its course to the left lung. The ligamentum arteriosum takes a course from the junction of the main and right pulmonary arteries posteriorly to the aorta. (See the image below.)

In spite of the significant variability in this group of structural abnormalities of the aortic arch, they all possess a common feature: They all produce some degree of compression on the major airway structures, the esophagus, or both. The location and severity of compression varies with the configuration of the lesion. Individuals with anomalies producing more severe compression are likely to present earlier in life.

Tracheal or tracheobronchial malacia and stenosis may develop in association with some of these lesions in the areas where the greatest degree of compression exists. This is particularly true in cases of anomalous left pulmonary artery.

Other congenital cardiac anomalies may be present in association with aortic arch anomalies.

The presence of a right aortic arch should always raise the suspicion of additional congenital cardiac disease. Right aortic arch has been reported in as many as 34% of cases of tetralogy of Fallot. Other intracardiac lesions found in association with a right aortic arch include double-outlet right ventricle, truncus arteriosus, ventricular septal defect with pulmonary atresia, transposition of the great vessels, tricuspid atresia, and absent left pulmonary artery.

Anomalous left pulmonary artery has also been associated with other cardiac defects in as many as 50% of cases. These include the aforementioned lesions, as well as persistent left superior vena cava, atrial septal defect, and ventricular defect. Complete tracheal rings (congenital absence of the membranous trachea) resulting in tracheal stenosis are another anomaly reported in as many as 50% of infants with anomalous left pulmonary artery. The combination of these two lesions is often termed the ring-sling complex.

The various forms of this anomaly occur very early in embryologic development. They result from the abnormal or incomplete regression of one of the six embryonic branchial arches. Several papers have reported the close association of band 22q11 deletion with anomalies of the aortic arch, as well as other congenital cardiac abnormalities.[5]

Early in normal development, both a dorsal and a ventral aortic arch are present. The two arches are connected by six embryonic branchial arches (see the image below). The third, fourth, and sixth embryonic arches are the most crucial in the development of the aortic arch and several of its major branches, as well as the ductus arteriosus and the main pulmonary arteries.

In normal development, each primitive arch either progresses into a functional vascular structure or involutes as follows:

• The right and left first and second arches become a portion of the arterial supply to the face
• The third arches develop into the carotid arteries
• The dorsal aorta between the third and fourth arches involutes
• The fourth arches are the primary contributors to the aortic arch itself, with the proximal right fourth arch developing into the proximal right subclavian artery; the distal portion of the right fourth arch involutes at the point where it joins the dorsal arch; the left fourth arch remains as the aortic arch in normal development
• The fifth arches involute bilaterally
• The ventral right sixth arch becomes the proximal right pulmonary artery; the ventral portion of the left sixth arch develops into the left pulmonary artery, while the dorsal portion becomes the ductus arteriosus
• The entire left and the distal right subclavian arteries arise from the seventh segmental arterial branches of the dorsal aorta

Abnormal arch development (see Anatomy) results when one or more of the necessary involutions or other changes in embryonic arch structures does not occur.

Double aortic arch

The classic double aortic arch develops when involution of the distal right fourth arch does not take place. The fourth right and left arches both persist and join the left-side descending thoracic aorta. The right and left aortic arches encircle the trachea and esophagus. In about 30% of cases of double aortic arch, the smaller, or less dominant, of the arches is atretic but remains in continuity with the descending aorta, maintaining the complete ring.

The double aortic arch forms a ring around the trachea and esophagus, compressing both of these structures. Tracheoesophageal compression typically results in early symptoms. This type of defect is rarely associated with intracardiac defects.

The Kommerell diverticulum, though more commonly associated with a right aortic arch (see below), has been known to occur with a double aortic arch as well.[6]

Abnormalities associated with right aortic arch

When the left fourth branchial arch involutes and the right remains, a right aortic arch is present. Right aortic arch occurs less frequently than 1 in 100,000 times in the general population and may exist in the absence of any other anomalies. Its presence is suggestive of the existence of an associated anomaly. About 30% of patients with tetralogy of Fallot have an associated right aortic arch.

Persistence of the right arch with involution of the left creates a situation in which the origins of the left subclavian artery and ductus arteriosus can vary. Several of these configurations can produce a vascular ring.

Right aortic arch with aberrant left subclavian artery and left ligamentum arteriosum

In this anomaly, the right arch first gives off the left carotid artery, which travels anterior to the trachea. It then gives off the right carotid, followed by the right subclavian artery and, finally, the left subclavian artery, which courses in a retroesophageal position and gives rise to the ligamentum arteriosum from its base.

The ligamentum arteriosum connects the left subclavian or descending aorta to the left pulmonary artery. The trachea and esophagus are surrounded by the ascending aorta anteriorly, the aortic arch on the right, the descending aorta posteriorly, and the ligamentum arteriosum and left pulmonary artery on the left. Almost 10% of these defects are associated with an intracardiac defect.

Right aortic arch with mirror-image branching and retroesophageal ligamentum arteriosum

In these cases, only partial resorption of the distal left fourth arch occurs. The first brachiocephalic vessel originating from the right arch is the left innominate artery, which, in turn, branches into a left carotid and left subclavian artery. These vessels course anterior to the trachea.

Following these, a right carotid artery and then a right subclavian artery arise. The ligamentum arteriosum is the final structure arising from the arch in this sequence. It originates from the Kommerell diverticulum, an area that represents the nonresorbed remnant of the left fourth arch and is situated at the point of merger between the right arch and the proximal descending thoracic aorta.

The ligamentum passes leftward and behind the esophagus and then travels anteriorly to join with the left pulmonary artery and complete the ring. More commonly, in cases of right aortic arch with mirror-image branching, the ligamentum arteriosum travels from the mirror-image innominate or left subclavian artery to the left pulmonary artery. A complete ring is not present in these cases. This type of vascular ring has a greater than 90% association with intracardiac defects.

Vascular rings associated with left aortic arch

Two extremely rare complete rings occur in the presence of a left aortic arch, and both are associated with a right-side descending thoracic aorta.

Left aortic arch with right descending aorta and right ligamentum arteriosum

The first arch vessel to exit the left aortic arch is the right common carotid, which passes anterior to the trachea. The left carotid is next, followed by the left subclavian artery. The right subclavian artery arises more distally as a branch of the proximal right-side descending aorta. The ligamentum arteriosum arises from the base of the right subclavian artery or a nearby diverticulum and travels to the right pulmonary artery.

Left aortic arch, right descending aorta, and atretic right aortic arch

The brachiocephalic vessels arise from the left-side arch in a normal arrangement. The left arch passes behind the esophagus to join a right-side descending aorta. An atretic right arch is present and completes the ring.

Arch abnormalities producing compression symptoms without anatomic ring

Anomalous innominate artery

The actual prevalence of this abnormality has been widely debated. This is because in as many as 90% of cases where symptomatic tracheal compression is produced by the innominate artery, the vessel is noted angiographically to have a normal origin from the aorta. When an anatomic abnormality is noted in these cases, the innominate artery appears to originate from a more distal and leftward position on the arch than normal. As it takes its course from left to right, it crosses the trachea anteriorly and in doing so may produce compression of the trachea.

Retroesophageal right subclavian artery with left aortic arch and left ligamentum arteriosum

This is the most common of the arch-vessel anomalies, occurring in about 0.5% of the population. In these cases, the right subclavian artery does not arise from an innominate trunk with the right carotid artery but originates as the last brachiocephalic branch from the descending aorta and takes a retroesophageal route to its destination.

A normally positioned ligamentum arteriosum is present on the left. If a right ligamentum arteriosum were present instead of one on the left, its course would proceed from the base of this anomalous right subclavian artery to the right pulmonary artery and a complete ring would exist. Instead, no true vascular ring is present in these cases. Most patients are symptomatic, but the occasional patient may present with dysphagia.

Anomalous left pulmonary artery or pulmonary sling

This abnormality occurs when the left main pulmonary artery arises as a branch of the right pulmonary artery instead of originating from the main pulmonary artery. This is believed to be an abnormality related to sixth aortic arch development. In this anomaly, the left pulmonary artery leaves the right and courses in a position cephalad to the right mainstem bronchus, proceeding around the right side of the trachea. It then travels between the trachea and esophagus as it goes to the left lung.

This lesion is often associated with hypoplasia and other abnormalities of the tracheal and bronchial cartilages. Most patients are symptomatic by 1 month after birth. Because the most severe compression is on the trachea, respiratory symptoms predominate. More than 50% of infants also have severe tracheobronchial anomalies such as tracheomalacia, stenosis, webs, or complete tracheal rings. Intracardiac defects are also seen in 20% of these infants.

Vascular rings are uncommon anomalies and make up fewer than 1% of all congenital cardiac defects. They occur with about equal frequency in both sexes. No geographical or racial predominance exists. Some vascular rings are associated with other congenital heart defects; others may be isolated deficits.

The two most common types of complete vascular rings are double aortic arch and right aortic arch with left ligamentum arteriosum. These make up 85-95% of the cases.[7, 8, 2]

Two other complete vascular rings that are extremely rare (< 1%) are (1) right aortic arch with mirror-image branching and (2) left ligamentum arteriosum and left aortic arch with retroesophageal right subclavian artery, right-side descending aorta, and right ligamentum arteriosum.

Other named anomalies that produce symptoms but do not form a complete anatomic vascular ring make up the remainder and include the abnormally placed or anomalous innominate artery and the retroesophageal right subclavian artery with left-side aorta and left ligamentum arteriosum.

The anomalous left pulmonary artery or pulmonary artery sling makes up about 10% of cases, though the exact number is difficult to determine because there are so few case reports.[9] Although the pulmonary artery sling is not associated with the aortic arch or its branches, it arises from an abnormality of the sixth branchial arch and produces a complete ring. This anomaly is associated with intracardiac defects in 10-15% of cases.

About 95% of patients who undergo surgical correction of a vascular ring survive for long periods, and most of these are soon relieved of their symptoms. In those infants with no intracardiac or extracardiac defects, surgery for vascular rings carries essentially no mortality.

Among those with less optimal long-term results are patients with an anomalous left pulmonary artery with and without complete tracheal rings and those with severe associated congenital cardiac defects. In those patients with a severely deformed trachea or tracheomalacia, additional reconstruction procedures may be required in the future.

In a series reported by Backer et al, reoperation proved necessary for 26 of 300 patients who had undergone surgical intervention for vascular rings.[10]  The four primary indications for reoperation were Kommerell diverticulum (18 patients), circumflex aorta (two patients), residual scarring (two patients), and tracheobronchomalacia necessitating aortopexy (four patients).

A number of patients continue to show evidence of some pulmonary function abnormalities years after surgery. Several studies report that measured pulmonary function studies show some degree of airway obstruction in as many as 50% of patients 7-8 years postoperatively. Also, a large number of patients appear to have a pronounced bronchial responsiveness to histamine.

Naimo et al reported long-term outcomes of complete vascular ring division in 132 children from a 36-year experience at a single institution (median follow-up, 11.4 years; range, 44 days to 36 years).[11]  In-hospital mortality was 1.5% (2/132), and no late deaths occurred. Overall survival was 98.3 ± 1.2% at 20 years. After surgical treatment, three patients experienced persistent tracheal compression and 16 had tracheomalacia. The freedom-from-reoperation rate was 88.6 ± 4.0%. None of the patients required tracheal surgery during the follow-up period.

François et al assessed early and late outcomes (mean follow-up, 7.8 ± 5.8 years) in 62 patients (median age, 1 year) who underwent surgical treatment of a vascular ring (most commonly a double aortic arch [53%]).[12] Median extubation time was 4 hours, and median hospital stay was 5 days. Early mortality was 8% and was associated with the anatomic diagnosis, concomitant anomalies, and the need for preoperative intubation. At 1 month, 63% of patients were free of residual symptoms; at 6 months, 82% were. At final follow-up, the rate of freedom from inhalation therapy was 82%.

Symptoms and physical findings produced by vascular rings are primarily those of airway or esophageal compression. Individuals with a narrow or tight ring have a significant degree of constriction of one or both of these structures and present very early in life.

The vast majority of patients with a vascular ring present with symptoms in infancy or very early in childhood.[13]  However, a small number of patients do not manifest symptoms until later in life, and others remain entirely asymptomatic.[14]  Common symptoms include the following:

• Stridor
• Cyanosis
• Wheezing
• Respiratory distress
• Apnea
• Characteristic high-pitched, brassy cough

Additional findings include the following:

• History of asthma
• Recurrent pneumonia
• Evidence of dysphagia or difficulty with feedings

In some cases, airway symptoms are worsened or aggravated by feedings. Intercostal retractions during respiration are observed in some infants with severe obstruction. Others may try to maintain a position in which the head is hyperextended to improve breathing and minimize the obstruction. Air-trapping and evidence of pulmonary hyperinflation may also be present in one or both lungs in severe cases.

Symptoms of airway obstruction predominate in patients who present in infancy or the first few years of life. Dysphagia and symptoms related to the esophagus are the more likely presenting findings in older children and adults with vascular rings. Esophageal compression is usually posterior. Symptoms that are present soon after birth may include slow breast or bottle feeding, fatigue with feeding, frequent regurgitation, and aspiration pneumonias. In most cases, workup is initiated when solid foods are introduced, which causes more pronounced dysphagia.

The double aortic arch is the anomaly that usually produces the most severe airway compression in the youngest patients. The second most common configuration, right aortic arch and left ligamentum arteriosum with retroesophageal left subclavian artery, displays a spectrum of severity. Some individuals present in infancy or very early in childhood, whereas others do not present until adulthood.

Although patients with associated cardiac lesions may have additional symptoms secondary to that abnormality, symptoms of airway compression related to the constricting vascular ring are usually most prominent.

Finally, it should be kept in mind that some patients with a complete vascular ring have minimal symptoms or remain asymptomatic. In such cases, the abnormal arch anatomy is often discovered incidentally when the patient is undergoing diagnostic studies for another problem.

Conversely, if left aortic arch with associated retroesophageal right subclavian artery is incidentally found during diagnostic studies for symptoms of dysphagia, the clinician should not assume that this vascular abnormality, which is not a true vascular ring, is the source of the symptoms. Additional investigation for the true cause should be pursued. This arch abnormality, previously believed to be responsible for dysphagia symptoms and for which the term dysphagia lusoria was coined long ago, is rarely responsible for esophageal symptoms.

Because children usually present with symptoms of respiratory difficulty, chest radiography is always the first and most commonly performed test.

Look for the position of the aortic arch, which is usually identifiable on the plain chest radiograph. The identification of a right aortic arch on chest radiograph in a child with airway difficulties, respiratory distress or dysphagia should alert the clinician to the likelihood of a vascular ring.

An ill-defined arch location is often observed in patients with double aortic arch. Such a finding should raise the suspicion of an arch anomaly in a symptomatic child. Other radiographic findings that may be noted with vascular rings include compression of the trachea and hyperinflation or atelectasis of some of the lobes of either lung. A specific finding associated with an anomalous left pulmonary artery is hyperinflation of the right lung.

In general, chest radiography is not very sensitive in the diagnosis of vascular rings.

Most authorities consider barium esophagography to be the most important study in patients with a suspected vascular ring, and it is diagnostic in the vast majority of cases. (See the image below.)

Double aortic arch produces bilateral and posterior compressions of the esophagus, which remain constant regardless of peristalsis. The right indentation is usually slightly higher than the left, and the posterior compression is usually rather wide and courses in a downward direction as it goes from right to left.

Patients with one of the anomalies in which the right subclavian artery takes a retroesophageal course have a posterior defect slanting upward from left to right. The posterior defect in these cases is usually not as broad as that found in double aortic arch.

An anomalous left pulmonary artery produces a characteristic defect in the anterior wall of the esophagus at the level of the tracheal bifurcation. No posterior compression is present with this anomaly. Cases of abnormally located innominate artery causing tracheal compression have normal findings on esophagography.

Echocardiographic studies have been increasingly used for the diagnosis of a vascular ring.[15] At many centers, this study has replaced pulmonary angiography for determining the presence of an anomalous left pulmonary artery. It is also extremely useful in the diagnostic workup of associated congenital cardiac defects.

This study has some diagnostic limitations. Structures without a lumen, such as a ligamentum arteriosum or an atretic arch, have no blood flow and are difficult to identify with color-flow echocardiography. In addition, identification of compressed midline structures and their relations to encircling vascular anomalies may be difficult to detect, especially for the less experienced echocardiographer.

The addition of three-dimensional (3D) reconstruction techniques may improve the accuracy of echocardiography in diagnosing fetal aortic arch anomalies.[16, 17]  High antenatal detection rates are achievable.[18]

Computed tomography (CT), magnetic resonance imaging (MRI), and digital subtraction angiography (DSA) can be useful diagnostic tools because they reveal the positions of vascular, tracheobronchial, and esophageal structures and their relations to one another. However, these expensive imaging modalities are rarely necessary in the evaluation of vascular rings.[19]

Although CT, MRI, and DSA provide excellent delineation of all of the associated structures, they should be reserved for cases in which the results of barium esophagography do not provide a clear diagnosis. MRI has been proposed as an excellent substitute for angiography.[20] Multidetector CT (MDCT) is increasingly preferred to angiography in this setting.[21]

All of these studies have drawbacks. CT and DSA expose the patient to radiation and require intravenous (IV) contrast. MRI requires patients to remain very still, and thus, very young patients who are unable to understand verbal instructions must be sedated—a measure that may be particularly risky in young children with existing airway compromise. The expense associated with these investigations must also be considered.

In the past, diagnostic aortography was performed in selected cases to delineate the anomalous arch vasculature. At present, it is generally agreed that in the vast majority of cases, this study adds very little to the information obtained from barium esophagography. If additional studies are required, echocardiography, CT, or MRI can usually provide the information needed.

Nevertheless, cases of rare arch anomalies have been reported in which aortography was the only study capable of identifying the correct anatomic configuration.[22] This study may be required in cases where the diagnosis and arch configuration remain in question after other less invasive studies fail to provide a definitive answer.

Cardiac catheterization is useful in cases where associated cardiac abnormalities are known or suspected.

Bronchoscopy has been used in the evaluation of children with symptoms of airway obstruction or compression. It is most commonly applied to the diagnosis of an abnormally placed innominate artery or pulmonary sling but is rarely required in the diagnosis of the various types of complete vascular ring.

In the presence of a vascular ring, pulsatile external tracheal compression is easily observed. Compression of the airway by a vascular structure in the pediatric patient does not represent an unyielding obstruction and should not pose a problem for passage of the bronchoscope. In cases of an abnormally placed innominate artery, obvious pulsation is observed in the anterior wall of the trachea corresponding to the area of compression.

Surgical division of a vascular ring is indicated in all symptomatic patients. To avoid serious complications such as sudden death or significant tracheal or bronchial damage, surgery should not be delayed, especially in patients with symptoms of airway compression.

Individuals who have no symptoms from a vascular ring may not require surgical intervention.

In patients with vague symptoms of difficulty swallowing, the presence of a left aortic arch with retroesophageal right subclavian artery should not be regarded as the definitive cause of the patient's symptoms. Although surgical division of an anomalous retroesophageal right subclavian artery for treatment of such symptoms was reported in older surgical literature, it was found to be ineffective because the majority of these patients continued to have symptoms. Currently, this anomaly is believed not to cause such symptoms, and further evaluation should therefore be pursued.

Cases of anomalous innominate artery with evidence of tracheal compression do not warrant surgical treatment if the patient has few or no symptoms. Only about 10% of these patients require surgery.

Video-assisted thoracoscopic surgery (VATS) techniques have been used for some pediatric thoracic surgical procedures. Several centers have successfully employed this technology for patent ductus arteriosus ligation. Although some reported use of VATS for vascular ring division exists,[23, 24, 25]  this remains a controversial area. Most of the cases reported have been those in which an atretic arch or a ligamentum arteriosum was divided.

Use of this technology for division of a patent arch remains in question. The main objection to its use in such cases is the increased intraoperative risk of bleeding. The concern is that if vascular clips are applied to a patent arch and the arch is then divided, the amount of recoil of the divided ends that usually occurs may cause one of the clips to dislodge, resulting in severe hemorrhage.

Because of the constraints of video-assisted techniques, the surgeon may have difficulty ascertaining when complete occlusion of the arch by the vascular clips has occurred. Because present open techniques provide excellent operative results with extremely low mortality and low morbidity, minimally invasive methods will have to provide the same assurance of safety and efficacy to be applicable.

No medical therapy exists for the definitive treatment of vascular rings. Preoperatively, the patient should be given adequate nutritional support as well as general respiratory care and appropriate treatment of any respiratory tract infection. Surgery should not be delayed in the presence of a respiratory tract infection, because the division of the ring allows more adequate and complete clearing of respiratory secretions.

Surgical division of symptomatic vascular rings is the only appropriate form of therapy. Surgery should be performed promptly after the diagnosis is made, especially in patients with stridor, apnea, or other symptoms of respiratory distress. Delay in operative intervention can result in complications of a serious nature.

The first video below illustrates slide tracheoplasty and left pulmonary artery sling repair in a 13-month-old patient. The second illustrates single-stage correction of transposition of the great arteries with ventricular septal defect, a hypoplastic right aortic arch with bilateral ductuses, and an aberrant left subclavian artery arising from the left duct in a newborn. 

Preparation for surgery

In most cases, left thoracotomy is the surgical approach of choice for the division of a vascular ring. An anomalous left pulmonary artery has been corrected via the left thoracotomy approach in the past; however, the use of median sternotomy and cardiopulmonary bypass has been shown to yield better long-term results. The extremely rare configurations associated with left aortic arch and right descending thoracic aorta are the lesions that should be approached via a right thoracotomy for division of the ring.

Although a left thoracotomy can be used as the surgical approach for the vast majority of vascular rings, the surgeon must have exact delineation of the type of vascular ring present as well as associated tracheal or intracardiac abnormalities so that the proper surgical approach can be made.

Although a large percentage of vascular rings can be diagnosed with simple and inexpensive barium esophagography, additional studies should be performed if any question about the exact configuration of the abnormality exists before surgery.

Because the airway problems associated with vascular rings can cause the most severe complications, preoperative airway management is of paramount importance in these patients, especially those presenting with severe respiratory problems very early in life.

The infant with a vascular ring who requires preoperative intubation for respiratory distress should not be considered completely safe from airway complications simply because he or she is intubated. Small amounts of flexion or extension of the neck in these infants can change the position of the endotracheal tube in relation to the area of tracheal constriction, causing difficulties with ventilation and oxygenation. Endotracheal tube placement and patient ventilatory status must be carefully monitored in the operating room, especially during positioning for surgery.

Approaches to specific anomalies

Double aortic arch

The left chest is entered through the fourth intercostal space. The mediastinal pleura is opened, and the components of the vascular ring are visualized.

The right (posterior) arch need not be mobilized unless it is the lesser of the two arches and is to be divided. In such cases, the proximal descending aorta should be reflected anteriorly to visualize the area where the right arch enters.

In cases of double aortic arch, the nondominant, or smaller, arch is divided. If one arch is atretic, it is the obvious choice for division. A likely site for division of the minor, or atretic, arch is at its point of juncture with the descending aorta.

Division of the chosen arch should be performed between applied vascular clamps. Before the actual division, the strength of the right and left carotid and the radial pulses should be evaluated with the vascular clamps applied. Diminution or absence of the pulse in one or several of these areas indicates that division of the arch at the chosen location would result in interruption of blood flow to that area. In such cases, another site for division should be chosen.

Perfusion to the lower extremities should be assessed before division of one of two equal-sized patent arches.

The ends of the divided arch should be oversewn with fine, nonabsorbable vascular suture.

The ligamentum arteriosum and any other fibrous bands around the trachea or esophagus in that area should be divided as well.

The recurrent laryngeal and vagus nerves should be identified and avoided. Closure of the mediastinal pleura is not performed, so as not to foster the development of adhesive scarring in the already affected area of the trachea and esophagus.

Complete vascular ring with right aortic arch anatomy

In cases of complete vascular rings with right aortic arch anatomy, the primary structure to be divided is the ligamentum arteriosum.

After left thoracotomy, the anatomy should be dissected out and clearly visualized. The vagus and recurrent nerves should be visualized and preserved. The ligamentum is divided between vascular clamps and the ends oversewn. After ligamentum division, any associated fibrous or adhesive bands in the area are also divided.

In cases of right aortic arch with mirror-image branching and retroesophageal ligamentum arteriosum, a prominent or aneurysmal Kommerell diverticulum may be present. If so, it should be resected over a partially occluding vascular clamp and primarily oversewn or mobilized with the adjacent descending aorta so that it may be affixed to nearby vertebral fascia. If left alone, these diverticula can contribute to the compression on the trachea and esophagus.

A few authors have advocated division of the aberrant left subclavian artery in these cases as well, but the general view is that this is very rarely indicated for relief of the symptoms caused by the ring and may cause symptoms of subclavian steal later.

Ding et al, in a retrospective study of 48 children who had Kommerell diverticulum with right aortic arch and aberrant left subclavian artery, compared surgical treatment via left subclavian artery translocation (n = 26; median age, 12 months; median follow-up, 22 months) with treatment via aortopexy (n = 22; median age, 10 months; median follow-up, 14 months).[26] ​ They found that the two procedures relieved the pressure on the trachea and esophagus and had similar short-term outcomes, though the long-term outcomes remained unknown.

Anomalous left pulmonary artery

In the past, this abnormality was approached via either a right or a left thoracotomy. Presently, many centers utilize a median sternotomy approach with the aid of cardiopulmonary bypass. Others continue to report excellent results performing the corrective surgery via a left thoracotomy.

In cases using median sternotomy and bypass, aortic and single right atrial cannulation is employed. The infant is cooled to 32°C so that the normal cardiac rhythm is maintained.

The left pulmonary artery is identified at its junction with the right and is dissected out as far to the left as possible, with care taken to avoid injury to the membranous portion of the trachea. Its origin is often on the posterior surface of the right pulmonary artery and to the right of the trachea.

The pericardium is opened on the posterior left side near the site where the ligamentum arteriosum meets the pulmonary artery. The left pulmonary artery is identified in this area and freed from surrounding adhesions.

A partially occluding clamp is placed on the right pulmonary artery at the site of its junction with the left, which is then transected. The orifice left in the right pulmonary artery is closed primarily with fine interrupted polypropylene sutures.

The partial occluding clamp is released and replaced on the main pulmonary artery posteriorly where an arteriotomy is made. The location of the clamp on the main pulmonary artery is critical so that the left pulmonary artery is without deformity after the anastomosis.

The divided left pulmonary artery is brought through the path created for it behind the trachea and into the pericardium through the left-side pericardial opening. It is sewn to the arteriotomy with interrupted fine polypropylene sutures.

Tracheal anomalies associated with anomalous left pulmonary artery

As many as 50% of patients with aberrant left pulmonary artery may have the associated anomaly of complete tracheal rings. In these infants, the membranous portion of the trachea is congenitally absent. This abnormality results in tracheal stenosis or malacia and significantly adds to the morbidity of surgery.

The diagnosis of tracheal/bronchial malacia is made using rigid bronchoscopy.

The choice of repair depends upon the length of the trachea involved and may range from resection and end-to-end anastomosis in cases with short-segment involvement to a variety of tracheoplasty procedures in cases involving long-segment abnormalities.

When tracheal stenosis secondary to complete tracheal rings is found in association with an aberrant pulmonary artery, the two abnormalities may be repaired during the same operative procedure. The approach for this is median sternotomy, and cardiopulmonary bypass is used.

Congenital cardiac defects associated with anomalous left pulmonary artery

Intracardiac defects are commonly associated with an anomalous left pulmonary artery. Depending on the type of intracardiac pathology, the surgeon must use discretion in deciding whether to correct or palliate the cardiac defect at the same setting or to defer this until a later time.

Anomalous innominate artery

Tracheal compression from an aberrant innominate artery is most often approached via an anterolateral right thoracotomy. The right lobe of the thymus is removed, avoiding injury to the phrenic nerve. The pericardium immediately beneath this area is opened, and the innominate artery is identified near its junction with the aorta.

Treatment of this condition simply involves tacking the innominate artery to the posterior sternal surface. The innominate artery is affixed to the posterior periosteal layer of the sternum by using interrupted polypropylene sutures with pledgets. The sutures are each passed through the adventitia of the innominate artery and then through the periosteal layer of the sternum.

Usually, about three sutures are used and placed at intervals along the length of the artery, with the most proximal one placed at the junction of the innominate artery and the aorta. When these sutures are tied, the innominate artery is pulled away from the anterior surface of the trachea, relieving the compression.

Left aortic arch with right descending aorta lesions

These are extremely rare lesions, but they are the ones that must be approached via a right thoracotomy. Division of the ring in these cases is accomplished by dividing the right-side ligamentum arteriosum. Patients having this anomaly often have associated congenital cardiac defects and commonly receive extensive preoperative workup.

Operative details

When a thoracotomy is to be performed, a muscle-sparing incision is preferred.

In the thorax, it is important to delineate all of the anatomic features of the vascular ring before dividing the appropriate structure. In all cases, the phrenic, vagus, and recurrent laryngeal nerves should be identified and preserved intact.

Good communication between the surgeon and the anesthesiologist is essential during the operative procedure. This is especially true when vascular clamps are applied to a portion of an arch to be divided or to a ligamentum arteriosum prior to division.

The constricting effect of the vascular ring is temporarily increased by the placement of the clamps, and airway constriction may be transiently more severe. The surgeon should announce the time of clamp application, forewarning the anesthesiologist that oxygenation may worsen or ventilation may become more difficult. The anesthesiologist may then be able to compensate with other supportive measures.

Monitoring pulse oximetry and blood pressure in both upper extremities and one lower extremity is important in the case of a double aortic arch in which a patent arch is divided. These measurements help confirm the vascular anatomy and verify that no difference in blood pressure is produced when the arch to be divided is temporarily occluded.

Immediate postoperative management after division of a vascular ring is performed in an intensive care unit (ICU). The majority of patients can be extubated immediately or within a short time after the operation. Oxygen with high humidity should be administered, and chest physiotherapy should be provided as needed. For those infants with ongoing wheezing or stridor, nebulizer treatment is helpful. Pulse oximetry should be monitored.

About 10% of infants may continue to have noisy breathing for a while after the surgical procedure; it is important to inform the child's parents of this possibility. In some case, total relief of symptoms may take several months to 1 year. Many residual postoperative symptoms are related to the presence of some degree of malacotic change of the trachea or major bronchi at the site where the tightest constriction occurred. In the vast majority of cases, growth and appropriate stiffening of the tracheal cartilages take place.

Infants who must undergo tracheal reconstruction in addition to repair of a vascular ring have the trachea stented with an endotracheal tube for at least 1 week. When the infant is extubated, bronchoscopy is performed first to eliminate excess granulation tissue and any secretions present. Dilation may be performed at this time if necessary.

Serious surgical complications are rare in most reported surgical series of vascular ring division. Most complications associated with these problems occur in the preoperative setting and may even occur before the diagnosis is known. The majority of these are related to airway obstruction. Postoperatively, atelectases and pneumonias can and do occur. Pain from the thoracotomy incision can be long-lasting in some patients and can hamper breathing efforts.

Complications related to the surgical procedure itself are uncommon in most cases. Injury to the phrenic, vagus, or recurrent laryngeal nerve may occur. Disruption of the thoracic duct is also possible. Late vascular complications, such as subclavian steal, may be noted in cases where division of a brachiocephalic vessel, such as a retroesophageal subclavian artery, was deemed necessary.

Rare cases in which symptoms of airway obstruction persist may require resection of a severely malacotic segment of trachea or bronchus or a more complex tracheoplasty procedure.

One series reported two very rare cases in which a vascular ring that was originally identified as right arch with retroesophageal left subclavian artery and left ligamentum arteriosum was divided via a left thoracotomy with no postoperative improvement in symptoms. These patients were described as having a circumflex aorta in which it appeared that the posterior arch itself made up a portion of the obstructing ring.

Additional surgery was required in these patients. A second procedure was performed via median sternotomy with cardiopulmonary bypass support in which the posteriorly positioned aortic arch was divided at the point where it traveled around the right side of the trachea and esophagus. The divided leftward portion was brought anterior to the trachea and esophagus on the left and reanastomosed to the portion from which it was originally divided. Fortunately, such cases are extremely rare.

Most patients are essentially asymptomatic within a few weeks after surgery and can resume activity and feedings as tolerated.

A small group continues to have some symptoms postoperatively; however, these findings are less prominent than those noted preoperatively in the majority of cases. These patients should show gradual improvement over 6-12 months, and most eventually become asymptomatic. This group may require closer follow-up in the immediate postoperative outpatient period so that early diagnosis and treatment of common forms of pediatric airway infections that result in epiglottitis or tracheobronchitis may be performed.

Patients who undergo more extensive surgery, especially tracheal reconstruction, require long-term follow-up. They may require bronchoscopy at regular intervals for elimination of encroaching granulation tissue and for tracheal or bronchial stenosis.

Patients who have associated congenital cardiac disease require regular follow-up with a pediatric cardiologist.