Continuing Education Activity

Aortic arch anomalies can give rise to vascular rings, a rare vascular anomaly with significant health implications. This activity deals with understanding the embryology of the aortic arch, the anatomy of a normal aortic arch and its anomalies, types of aortic arch anomalies that can give rise to a vascular ring, its symptomatology and how to diagnose and manage a patient with a vascular ring. It will also review the role of an interprofessional team.

Objectives:

• Describe the embryology of an aortic arch ring.
• Outline the typical imaging findings associated with an aortic arch ring.
• Review the management options available for an aortic arch ring.
• Summarize interprofessional team strategies for improving care coordination and communication to advance the care of patients with an aortic arch ring and improve outcomes.

Introduction

A vascular ring is a condition in which both the trachea and the esophagus are encircled by vascular structures or its remnants (ligamentous remnant, atretic chord like remnant).

Aortic Arch

The transverse aortic arch gives rise to three branches, the brachiocephalic artery, the left common carotid artery, and left subclavian artery. The brachiocephalic trunk then divides into the right common carotid artery and right subclavian artery.

Sidedness of the Aortic Arch

The side of the aortic arch is determined by the bronchus that is traversed by the aortic arch. This will lead to the left aortic arch (LAA) will be on the left of the trachea, and the right aortic arch (RAA) will be on the right of the trachea.

Anomalies of Aortic Arch

Due to several embryological alterations, the architecture of the aortic arch can be altered, giving rise to an array of different aortic arch anomalies.

Normal Variants

These include a common origin of the brachiocephalic artery and the left common carotid artery, and origin of the vertebral artery between the left common carotid artery and left subclavian artery.

Etiology

Embryology of Aortic Arch

The distal part of the truncus arteriosus is from the aortic sac. The aortic sac forms the right and left horns of the aorta, which form the aortic arches before terminating in the right and left dorsal aorta. Each pharyngeal arch receives its own artery, which is derived from the aortic arches.

Aortic Arches

The pharyngeal arches and its vessels (aortic arches) develop during the 4th to 5th week of gestation but are not present simultaneously. They develop from cranial to caudal fashion. Initially, there are 6 aortic arches connecting the ventral aorta and the dorsal aorta. The fifth aortic arch either never forms or forms incompletely and regresses. The first arch mostly disappears, leaving behind a small portion that forms the maxillary artery. The second arch mostly disappears as well and forms the hyoid and stapedial arteries. The third, fourth, and sixth arches remain large to give rise to the vessels of the aortic arch as well as the aorta.

Embryological Origin

Right horn - brachiocephalic artery

Left horn - proximal aortic arch

3rd arch - common carotid artery, external carotid artery and the proximal portion of the internal carotid artery on both the sides

Left 4th arch - arch between the left common carotid artery (LCCA) and left subclavian artery (LSCA)

Right 4th arch - proximal portion of right subclavian artery (RSCA)

Left sixth arch - proximal portion forms the left pulmonary artery (LPA). The distal portion forms the patent ductus arteriosus (PDA).

Right sixth arch - proximal portion forms the right pulmonary artery (RPA). The distal portion disappears.

Right dorsal aorta - right distal subclavian artery

Left dorsal aorta - left aortic arch distal to LSCA

Dorsal aorta - The cranial portion also forms the distal portion of internal carotid arteries on both sides. The portion of dorsal aorta between 3rd and 4th arches disappears. The portion of the right dorsal aorta between the origin of the 7th intersegmental artery and the junction with left dorsal aorta disappears as well.

Right seventh intersegmental artery - distal RSCA

Left seventh intersegmental artery - LSCA

The above embryological knowledge is essential in understanding the formation of vascular rings that can arise from various aortic arch anomalies.

Epidemiology

Incidence of aortic arch anomalies:

Approximately 1 to 3 percent of all congenital heart disease.[1]

Compared to females, males appear to have a 1.4 to 2 times greater risk of having a vascular ring than females.[2][3][4]

Among the aortic arch anomalies that can lead to a vascular ring, the following with the first two listed below comprising more than 90% of all vascular rings seen:

• Double aortic arch (DAA)
• RAA and aberrant LSCA and left PDA
• Circumflex aortic arch - Either a left-sided aortic arch with a right descending aorta and right-sided PDA (or) a right-sided aortic arch with a left descending aorta and left-sided PDA
• Pulmonary artery sling (It is not a vascular ring in a true sense and hence called vascular sling because it passes anterior to the esophagus behind the trachea)
• Left-sided aortic arch (LAA) with aberrant RSCA (ONLY if right-sided PDA is present)
• Right-sided aortic arch (RAA) with mirror image branching (ONLY if left-sided PDA arises from descending aorta)

History and Physical

A high index of suspicion is needed to get to a prompt diagnosis of an aortic arch anomaly. A clue to the diagnosis is an infant or a child presenting with a history of multiple visits to the pulmonologist or a gastroenterologist with no definitive diagnosis for the underlying long-standing symptoms.

History

Respiratory Symptoms[1][2][3][4][5][6]

Wheezing, stridor, pneumonia, upper respiratory tract infection, and respiratory distress are observed. Cough and respiratory cyanosis can also be seen. Respiratory arrest, choking, and bronchiolitis are rare. Apnea, tracheomalacia, and aspiration are extremely rare.

Gastrointestinal Symptoms

Vomiting, failure to thrive, dysphagia, and choking with feeds

Cardiac Symptoms

Murmurs, heart failure 

Physical Exam

Completely depend upon the severity of tracheal and esophageal compression from the vascular ring. Infants can develop tracheobronchomalacia secondary to compression that, in turn, leads to "noisy breathing," which on examination presents as inspiratory stridor and occasionally rhonchi, which worsens with agitation. 

As the severity of compression worsens, respiratory distress/failure signs become more apparent: nasal flaring, intercostal and subcostal retractions, tachypnea, hypoxia, and cyanosis.

Evaluation

Chest X-ray

Posteroanterior and lateral views are needed to rule out underlying respiratory pathologies, clues to any associated congenital heart disease. If a vascular ring is present, the anterior bowing trachea is noted on the lateral radiograph. 

Computed Tomography or Magnetic Resonance Angiography

These provide advanced imaging of the vascular ring in three-dimensional perspective leading to better visualization and localization

Advantages of CTA: better visualization of airways. Disadvantage of CTA: radiation exposure

Advantages of MRA: no radiation. Disadvantage of MRA: prolonged testing needing sedation/anesthesia

Echocardiography

Echocardiography at the hands of an experienced technician can detect vascular anomalies.[7] More commonly, preoperative echocardiography is often performed to identify the presence of congenital heart disease.  

Advantage of echocardiogram: Noninvasive, readily available, no radiation exposure. Disadvantage of echocardiogram: Cannot identify atretic segments and can also be affected due to poor acoustic windows 

Bronchoscopy

Bronchoscopy is not useful in the identification of vascular rings. It is done in certain institutes preoperatively to determine the level of compression to help in endotracheal tube placement. It also helps in some cases to rule out other causes of upper airway obstruction and is part of the work up carried by a pulmonary specialist.

Barium Swallow

This is not superior to CTA and MRA, and has no longer used in the evaluation of suspected vascular rings. Posterior indentation of the esophagus indicates a vascular ring. Precise identification of the anatomy of the vascular ring is not possible. Anterior indentation indicates a pulmonary vascular sling.

Treatment / Management

Since all symptoms result from mechanical compression, there is no role for medical treatment, and surgical correction is the only definitive treatment available with excellent clinical outcomes. Surgery is indicated only in symptomatic individuals.

Right Aortic Arch with Aberrant LSCA

Through a posterolateral left thoracotomy, the left-sided PDA or ligamentum or atretic segment is divided, which results in the release of the vascular ring.[5] Diverticulum of Kommerell, if prominent, has also been removed to avoid reoperation for persistent or recurrent esophageal or tracheal compression symptoms.[8]

Double Aortic Arch

Using preoperative imaging, the site of the surgical division is selected. This is usually an atretic segment in the smaller of the two arches, which is, in most cases, the left-sided arch. Using a left-sided posterolateral thoracotomy, the ductus or ligamentum must also be divided to release the ring. 

Pulmonary Artery Sling

Cardiopulmonary bypass and midline sternotomy approach are used. Relocation of the left pulmonary artery to anterior of the trachea is done in patients with extrinsic tracheal compression without fixed stenosis. In patients with a complete tracheal ring, tracheal resection of the affected portion is most often needed.[9][10]

Recent Advances

Video-assisted thoracoscopic surgical (VATS)[11] and endoscopic robotic-assisted surgical techniques[12] are being used as an alternative to open thoracotomy in advanced treatment centers and show initial promising results with reduced length of stay.

Differential Diagnosis

Otolaryngology

• Congenital or acquired laryngeal abnormalities 

Respiratory

• Asthma 
• Recurrent pneumonia 
• Tracheoesophageal fistula, tracheomalacia, congenital tracheal anomalies 

Gastrointestinal

• Gastroesophageal reflux disease
• Esophageal motility disorders 

Others

• External compression of the trachea or esophagus by mediastinal mass (e.g., Hodgkin lymphoma) 

Prognosis

In children with vascular rings, surgical correction is not associated with any mortality. Rare reported cases of mortality in the vascular ring have been associated with other congenital heart disease or underlying pulmonary pathology.[2][3][4][5][6][13]

More than 70% of patients become asymptomatic after one year after surgical correction. However, respiratory symptoms can persist up to four to six months after surgery.[4]

The need for reoperation is very low (8%), and the most common reasons for it include persistence of diverticulum, circumflex aortic arch, scarring, and tracheobronchomalacia needing aortopexy.[14]

Complications

• Recurrent laryngeal nerve injury and vocal cord paralysis
• Thoracic duct injury and chylous pleural effusion
• Vascular complications including narrowing of the vessel, bleeding, and thrombosis
• Tracheal and esophageal injury

Deterrence and Patient Education

Patients with aortic arch anomalies should be counseled about the risk of the vascular ring and the need for advanced imaging. Once the diagnosis is ruled out, reassurance is necessary. If a vascular ring is identified, necessary steps, including symptoms that need to be watched for, need, and timing of surgery, adequate follow-up needs to be advised to improve symptoms.

Enhancing Healthcare Team Outcomes

Evaluation and management of an individual with a symptomatic vascular ring require the involvement of multiple specialties needing an interprofessional approach.  

Once the patient is symptomatic, the following specialties are involved: pediatric cardiology, pediatric gastroenterology, pediatric otorhinolaryngology, pediatric pulmonology, and finally, the repair is performed by pediatric cardiovascular surgery.

Postoperative care and rehabilitation in pediatric ICU will be needed to recognize possible complications that occur immediately following surgical correction.