Double Aortic Arch

Double aortic arch is one of the most common forms of vascular ring, a class of congenital anomalies of the aortic arch system in which the trachea and esophagus are completely encircled by connected segments of the aortic arch and its branches. Although the double aortic arch has various forms, the common defining feature is that both the left and right aortic arches are present.

Embryology

The easiest way to understand the anatomy and development of double aortic arch and other forms of vascular ring is to begin by considering the bilateral system of pharyngeal arch vessels that exists in early embryogenesis.

Early in the course of embryonic morphogenesis, six pairs of pharyngeal arch arteries develop in conjunction with the branchial pouches. The first six arches appear in a fairly sequential fashion, with left-to-right symmetry and constitute the primitive vascular supply to the brachiocephalic structures, running from the aortic sac to the paired dorsal aortas. As normal cardiovascular morphogenesis proceeds, a patterned regression and persistence of the various arches and right-sided dorsal aorta occur, ultimately resulting in the mature configuration of the thoracic aorta and its branches. The third, fourth, and sixth arches, along with the seventh intersegmental arteries and the left dorsal aorta, are the primary contributors to the normal aortic arch and its major thoracic branches (see diagram below).

The segments of the bilateral aortic arch system that normally regress include the distal portion of the sixth arch and the right-sided dorsal aorta. Normally, the left fourth arch becomes the aortic arch, the right fourth arch contributes to the innominate artery, the distal left sixth arch becomes the ductus arteriosus, the proximal sixth arches bilaterally contribute to the proximal branch pulmonary arteries, the left dorsal aorta becomes the descending thoracic aorta, and the dorsal intersegmental arteries bilaterally become the subclavian arteries.

Vascular rings are formed when this process of regression and persistence does not occur normally, and the resulting vascular anatomy completely encircles the trachea and esophagus.[1] (Other forms of aortic arch anomalies occur in which a vascular ring is not present.) A double aortic arch is formed when both fourth arches and both dorsal aortas remain present. The reasons for the absence of regression are not clearly known.

Anatomy

Double aortic arch has various forms. Both arches may be patent, or an atretic (but persistent) segment may be present at one of several locations in either arch. When both arches are patent, the right or left arch may be larger, or they may be similar in size. A cervical arch on either side, variable laterality of the descending thoracic aorta, coarctation of the major arch, and/or discontinuity of the central pulmonary arteries may be present. In general, the apex of the right-sided arch is more superior than the left arch, and on occasion, a cervical arch may be present on either side.

In more than 75% of patients with double aortic arch, the right arch is dominant. Among patients with a right-dominant double arch, those with a patent minor arch outnumber those with an atretic minor arch. When the minor arch is atretic, the atretic segment almost always is distal to the left subclavian artery, although atresia may also occur between the left common carotid and subclavian arteries. In approximately 20% of patients, the left arch is dominant. In these patients, the minor right arch is typically patent.

Associated cardiovascular anomalies

Double aortic arch usually occurs without associated cardiovascular anomalies. Ventricular septal defect and tetralogy of Fallot are probably the most common associated defects, although truncus arteriosus, transposition of the great arteries, pulmonary atresia, and complex univentricular defects sometimes occur in conjunction with a double arch.

Associated syndromes and noncardiac conditions

Double aortic arch is associated with a chromosome 22q11 deletion in approximately 20% of patients (see Etiology). Chromosome 22q11 deletion is responsible for DiGeorge, velocardiofacial, and conotruncal anomaly face syndromes, which are often referred to using the unified terms CATCH-22 syndrome or chromosome 22q11 deletion syndrome. In patients with double aortic arch, the frequency of phenotypes satisfying the clinical criteria for these various syndromes is not known. Rather, the important point is that double aortic arch may be associated with chromosome 22q11 deletion, which has various other possible manifestations. These include, but are not limited to, palatal abnormalities, laryngotracheal anomalies, speech and learning delay, characteristic facial features, hypocalcemia, abnormalities of T-cell–mediated immune function, and neurologic defects.

Occasionally, patients with double aortic arch may have anomalies consistent with either vertebral, anal, cardiac, tracheal, esophageal, renal, and limb (VACTERL) or posterior coloboma, heart defect, choanal atresia, retardation, genital, and ear (CHARGE) associations. Double aortic arch has also been reported in association with other chromosomal anomalies, such as trisomy 21 and other syndromes.

One of the more important noncardiac features that sometimes is found in association with double aortic arch is esophageal atresia, insofar as an undiagnosed arch anomaly may complicate repair of the esophageal atresia, which is usually recognized earlier than the double aortic arch.

Another noncardiac anomaly that may be associated with vascular rings is a congenital laryngeal web, which may present with the same symptoms and signs as a vascular ring. Accordingly, patients with persistent stridor or upper airway obstruction after repair of a vascular ring, particularly those with a chromosome 22q11 deletion, should be evaluated for the presence of a congenital laryngeal web.

By definition, a vascular ring encircles the trachea and esophagus, usually causing compression of both structures. Compression of the trachea causes upper airway obstruction that impairs inspiratory and, to a lesser degree, expiratory airflow.[2] The extent of respiratory impairment depends on the severity of compression, which can widely vary. Significant compression of the trachea appears to be more common with double aortic arch than with other forms of vascular ring and is often more severe.

In addition to airway symptoms, patients may experience swallowing difficulties related to esophageal compression. These typically manifest as vomiting and feeding intolerance in infants and younger children and as dysphagia later in life. Swallowing dysfunction may contribute to respiratory symptoms as a result of aspiration and/or compression or irritation of the membranous portion of the trachea as a food bolus traverses the area of esophageal obstruction. Although respiratory or esophageal pathophysiology may predominate in any given patient, respiratory compromise usually is more problematic in younger patients. Patients with primarily esophageal symptomatology tend to be older at presentation.[3] The pathophysiology of double aortic arch does not differ in the various anatomic forms.

A persistent double aortic arch occurs when abnormal regression of the embryonic aortic arch segments is present, in which both the left and right aortic arches remain intact. With the different forms of double aortic arch, different segments of the embryonic aortic arch system, which normally regress, remain patent.

Factors responsible for the aberrant persistence of certain aortic arch segments have not been clearly identified, and the pathogenesis of this anomaly remains a mystery. Double aortic arch typically occurs without associated cardiovascular defects, although other lesions may be present, and accordingly, it is not usually found as part of a syndromic complex.

In one study, chromosome 22q11 deletions were found in 3 of 22 patients (14%) with double aortic arch.[4] This chromosomal anomaly is associated with aortic arch anomalies in patients with other forms of conotruncal heart disease and other isolated vascular abnormalities, and chromosome 22q11 deletion is likely to be an important etiologic factor in double aortic arch. Most such mutations arise de novo, and no recognizable inheritance pattern is present.

Familial recurrence of double aortic arch has been reported, supporting a genetic etiology for this anomaly. Teratogen-induced double aortic arch in animal models also has been reported. The mechanisms and significance of these models have not been elucidated.

United States data

Generally, incidence of double aortic arch and vascular rings is unknown, although vascular rings comprise an estimated 1% of cardiovascular malformations that are managed surgically. In most surgical series, 45-65% of patients undergoing repair of a vascular ring have a double aortic arch.

Race-, sex-, and age-related demographics

Based on limited data, no racial predilection is apparent.

No sex predilection has been documented in patients with double aortic arch or its various subtypes.

Double aortic arch is a developmental abnormality that is present in the fetus. The postnatal age at which the anomaly is identified may vary, although in most patients, double aortic arch is diagnosed in early infancy. Double aortic arch may also be identified on prenatal ultrasonography.[5]

Long-term prognosis for patients with repaired double aortic arch is excellent; persistent respiratory symptoms are the most common adverse outcomes.

In patients with a repaired double aortic arch, lifestyle implications are minimal and most likely are related to residual symptoms or associated anomalies.

Morbidity/mortality

The natural history of double aortic arch is not well defined. Vascular rings were among the first congenital cardiovascular anomalies repaired surgically, and surgical management has been the standard of care for more than 50 years. Patients with significant airway compression may die as a result of respiratory compromise, but such events are rare.

Preoperative morbidity generally is limited to respiratory symptoms, feeding problems, or both. Some patients may develop recurrent respiratory infections, and some may exhibit failure to thrive as the result of a combination of increased metabolic requirements from respiratory and feeding work and relatively poor oral intake.

Complications

Complications are uncommon after repair of vascular rings.

The major postoperative symptom is persistent respiratory symptoms, including cough, dyspnea, and wheezing. Pulmonary function testing reveals persistent upper airway obstruction in some patients. Others have evidence of lower airway obstruction that usually is responsive to bronchodilator therapy. Whether the incidence of lower airway obstruction is higher in patients who have undergone repair of vascular rings than in the population at large or whether such a pathologic condition in patients with rings has any relationship to prior anatomic and functional abnormalities is not known.

Rarely, patients with unrepaired double aortic arch may develop an aortoesophageal fistula, which causes fatal hemorrhage. Another rare complication is esophageal erosion.

Presentation of symptoms in patients with double aortic arch depends on several factors, including the severity of tracheal compression, esophageal compression, or both and whether associated anomalies are present. Note the following:

• Among patients with a vascular ring, those with double aortic arch tend to present earlier than those with other anatomic variations. The classic history in a patient with double aortic arch is noisy breathing noted by the parents during the first few weeks of life.

• Young patients may have experienced episodes that often are termed apparent life-threatening events (ALTE) or death spells, in which acute apneic or severe obstructive events are accompanied by cyanosis. Patients with less severe tracheal compression may give a history of persistent respiratory symptoms without frank stridor, often treated as asthma or bronchiolitis, or a history of recurrent lower respiratory infections.[6]

• Esophageal symptoms include emesis, choking, or dysphagia and are more common in older infants and children than in young infants.

• Occasionally, patients may reach older childhood or adulthood before developing persistent or progressive symptoms of dysphagia, respiratory symptoms, or both.

• Rarely, fetal echocardiography may reveal double aortic arch and types of vascular ring.

• In neonates with associated cardiac or noncardiac anomalies, a double aortic arch may be diagnosed incidentally during the course of evaluation.

Physical findings can vary, often in accordance with the patient's history.

Newborns with associated anomalies may have no evidence of a vascular ring on physical examination, but this situation is the exception because most patients have readily recognizable physical signs.

The classic sign of double aortic arch and of vascular rings in general is nonpositional stridor; however, many young infants with double aortic arch have adventitious expiratory breath sounds, as well as the characteristic inspiratory stridor. Respiratory findings typically do not improve with nebulized bronchodilator therapy and usually are more prominent with agitation or crying.

In differentiating double aortic arch from upper or lower respiratory infections, a white blood cell count and respiratory viral studies may be helpful. However, because patients with double aortic arch are predisposed to respiratory infections, the diagnosis of an infection does not exclude the possibility of double aortic arch.

As a result of the possible association between double aortic arch and chromosome 22q11 deletion, practitioners may wish to obtain a karyotype and a fluorescence in situ hybridization (FISH) test for deletions within chromosome 22q11. The diagnosis of chromosome 22q11 deletions allows targeted evaluation and follow-up care for conditions frequently found in patients with this anomaly.

No characteristic electrocardiography (ECG) findings are associated with double aortic arch, and ECG findings are usually normal, except in patients with associated cardiovascular anomalies.

Echocardiography

In most patients, the diagnosis of double aortic arch can be made reliably based on echocardiography; helpful information is obtained with suprasternal, high parasternal, and subcostal imaging. However, because patients with a vascular ring typically present with respiratory symptoms, the diagnosis is usually made based on other imaging modes.

Echocardiography is important in the evaluation of associated cardiovascular anomalies.[8]

Double aortic arch may also be identified on prenatal echocardiography[9, 6, 10] and ultrasonography.

Chest radiography

In patients with a double aortic arch, chest radiography may indicate the presence of a vascular ring. In some patients, lateral indentation of the tracheal air column may be revealed by anteroposterior or posteroanterior projection, usually in both the more superior right arch and the more inferior left arch. On lateral chest films, posterior indentation of the trachea by the right arch may be depicted.

Magnetic resonance imaging (MRI) and computed tomography (CT) scanning

MRI and CT scanning are the best single imaging studies for the diagnosis and characterization of vascular rings. MRI and CT scanning provide complete information with regard to the arterial branching pattern, clearly demonstrate the locations and extent of airway and esophageal obstruction, and can be used to delineate cardiac anatomy (see the image below). In addition to tomographic images, three-dimensional reconstruction of the aorta and airways can be a useful tool for preoperative planning.

A study by Chen et al indicated that multislice spiral CT (MSCT) scanning is an effective means of diagnosing double aortic arch and associated complications. In a study of 15 patients with double aortic arch, MSCT scanning identified all 15 cases and also revealed the presence of malformation and tracheobronchial stenosis. The investigators also found that ultrasonography successfully diagnosed only nine of the 15 cases.[11]

Barium esophagography

Frequently, the diagnosis of a vascular ring is made initially with barium esophagography. In patients with a double aortic arch, bilateral indentation of the esophagus is observed on the anteroposterior view, with the right-sided indentation superior to the left, and posterior indentation is observed on the lateral view.

Although this test is not necessary to make the diagnosis of double arch, it often is obtained in the preliminary evaluation of patients with symptoms of an upper airway and/or an esophageal pathologic condition. If a ring is strongly suspected on the basis of chest radiography or echocardiography findings, barium esophagography is not indicated. Rather, if additional imaging is desired, a more thorough diagnostic study, such as MRI, should be performed.

Diagnostic procedures are generally not necessary in the evaluation of patients with a double aortic arch.

Patients with a double aortic arch do not require a histologic tissue examination.

Bronchoscopy

Bronchoscopy may be obtained in the evaluation of a patient with a suspected airway pathologic condition but is not indicated in most patients. Pulsatile compression of the posterior and lateral walls of the trachea can be observed in patients with a double aortic arch, but the specific type of vascular ring cannot always be determined. Other imaging modalities, especially magnetic resonance imaging (MRI) and computed tomography (CT) scanning, permit characterization of the severity and location of tracheal obstruction while offering superior definition of vascular anatomy.

In some patients, depending on surgeon preference, bronchoscopy may be performed in the operating room before and after repair of the vascular ring to determine the efficacy of relief of tracheal compression. This is of particular value in young patients in whom persistent tracheomalacia is a concern.

Cardiac Catheterization

This is not usually indicated in patients with double aortic arch. Although angiography was once the criterion standard for the diagnosis of this anomaly, MRI is both less invasive and diagnostically superior. Angiograph findings may be somewhat confusing because of the overlapping projection of the various vascular structures. This problem may be somewhat ameliorated by the use of digital subtraction angiography or countercurrent brachial angiography, which provide sequential information that can help clarify the aortic branching pattern.

Medical care prior to surgical repair of double aortic arch depends on the clinical presentation. In most patients, only supportive care is required.

Catheter interventions are not used in the management of double aortic arch.

Aside from analgesic medications, pharmacologic therapy is not usually required after removal from mechanical ventilation. Relief from the pain of the thoracotomy incision may be achieved with age-appropriate narcotic and nonsteroidal anti-inflammatory medications.

After postoperative stabilization in the intensive care unit and removal from mechanical ventilatory support, the patient may be transferred to the regular inpatient care area for advancement of feedings and additional postoperative care.

Further inpatient care

Routine postthoracotomy care is provided following repair of double aortic arch.

Patients are removed from mechanical ventilation as soon as possible, and the chest tube usually is discontinued on the first postoperative day.

The remainder of the inpatient stay is focused on determining and managing any residual symptomatology, providing sufficient enteral nutrition, transitioning the patient to enteral analgesics, and educating the parents.

In patients with residual or recurrent obstruction of the airways, aortopexy may relieve the compression and associated symptoms.[12]

Consultations

Unless specific associated anomalies or problems are identified, consultations usually are not necessary. As noted above, chromosome 22q11 deletion is present in a substantial proportion of patients with double aortic arch.

Consultation with a geneticist is indicated in patients with other characteristic features of the chromosome 22q11 deletion syndrome and may be appropriate in young infants, in whom typical features of the syndrome may not yet be evident.

The first description of surgical relief of tracheal obstruction caused by vascular ring was reported by Gross in 1945.[13]

Indications

Surgical division of the vascular ring is indicated in any patient with symptoms of airway or esophageal compression and in patients undergoing surgery for repair of associated cardiovascular or thoracic anomalies.

Techniques

The fundamental principle of surgical management of double aortic arch is division of the ring to relieve compression of the trachea and esophagus. In general, this is achieved by dividing the minor arch through an ipsilateral thoracotomy. Note the following:

• When the minor arch is atretic, the atretic segment is ligated or clipped and then divided. When the minor arch is patent, it is usually ligated and divided between the subclavian artery and descending aorta. The ligamentum arteriosum, which is almost always left sided, is ligated and divided as well.

• Dissection should be carried down to the trachea and esophagus to ensure that no constricting fibrous bands remain.

• If necessary to minimize residual posterior compression of the trachea/esophagus, arteriopexy may be performed by suturing the retroesophageal aortic segment to the prevertebral fascia.

• Video-assisted thoracoscopic division of vascular rings is performed at several centers and appears to be an effective approach in most cases, but data on outcomes are limited. Robotically assisted division of vascular rings has also been reported.

• When associated intracardiac anomalies require surgery through a median sternotomy, division of the double arch is performed during the same procedure.

Results

In the current era, essentially no operative mortality is associated with repair of isolated double aortic arch.[14] Outcomes in patients with associated anomalies depend on the coexisting condition.

Postoperative care and precautions

Postoperative care after division of double aortic arch is similar to that for patients undergoing other cardiovascular procedures through a thoracotomy. Most patients experience immediate relief after surgery, although persistent respiratory symptoms and signs may be present, especially in very young infants with severe preoperative symptoms. Except in patients undergoing concurrent repair of associated anomalies, cardiopulmonary bypass is not used during the repair; therefore, postoperative cardiac function typically is not a problem.

Early postoperative complications

Complications in the early postoperative period are uncommon after division of a vascular ring.

The major issue is persistent respiratory symptoms, especially in neonates who are more susceptible to tracheomalacia.

Other rare operative complications include chylothorax resulting from injury to the thoracic duct, diaphragmatic paresis/paralysis secondary to phrenic nerve injury, and, following repair through a left thoracotomy (ie, in patients with a right-dominant double arch), vocal cord paresis/paralysis resulting from injury to the recurrent laryngeal nerve.

No special dietary considerations are indicated in patients with double aortic arch other than those dictated by associated conditions. Postoperatively, enteral feeding is resumed as soon as possible.

In patients with dysphagia or emesis as a presenting symptom, adequate oral intake should be verified, and feeding therapy should be instituted if necessary. In patients with chromosome 22q11 deletion, velopharyngeal insufficiency or cleft palate frequently is present; oral feedings should be resumed with the aid of feeding specialists.

Patients with double aortic arch are not subject to specific restrictions on activity. Prior to repair, activity may be limited by symptoms.

Following repair, any persistent respiratory symptoms resulting from tracheomalacia should dictate activity limitations.

For the early posthospital period, educate parents concerning the possible persistence of symptoms, the potential benefit of prone positioning in patients with tracheomalacia, signs and symptoms of aspiration, and management of the thoracotomy incision.

Close follow-up observation should be maintained after repair of double aortic arch, especially in young children with persistent tracheomalacia or other respiratory symptoms.

Additional imaging or bronchoscopic evaluation is not indicated unless residual symptoms persist or other mitigating circumstances are present.

No dietary or activity restrictions are indicated after repair of an isolated vascular ring.