Double aortic arch

Introduction

Double aortic arch is the most common type of vascular ring malformation. It involves the complete encirclement and compression of the trachea and/or esophagus by the aortic arch, its branches, or atretic ligamentous segments. Left untreated, it may lead to significant morbidity for the patient and can result in sudden death from airway compromise. Hommel described the first post-mortem case in 1737, with the first documented surgical repair only being carried out by Robert Gross in 1947.[1]

Etiology

Aortic arch development is a complex process that occurs between weeks two and seven of gestational life. Six pairs of arches emerge and regress in a sequential fashion leaving remnants that form important vessels. This setup forms the basis of the aortic arch variants and anomalies. The first two arches disappear early, leaving the maxillary, hyoid, and stapedial arteries. The third branch forms the common carotid arteries and a small portion of the internal carotid arteries. The fourth pair of arches give rise to the bilateral aortic arches. In week five of gestation, the right-sided arch regresses, and the left-sided arch remains, leaving a normal left-sided aortic arch.

Failure of the regression of the right-sided arch with the persistence of the left-sided arch leads to the formation of a double aortic arch. Conversely, a solitary right-sided aortic arch may remain if the left-sided arch regresses while the right-sided arch persists. Three types of double aortic arches have been described and include (in order of decreasing frequency) dominant right-arch with small left-arch, dominant left-arch with small right-arch and balanced aortic-arches. The fifth pair of arches do not contribute to significant vasculature, whereas the anterior bud of the sixth pair of arches gives rise to the pulmonary arterial trunk and ductal artery.[2][3][4]

Epidemiology

The incidence of double aortic arch is generally unknown. Published data estimates the prevalence of vascular rings to be 1%. Up to 55% of patients undergoing vascular ring repair have a double aortic arch. There is no predilection towards a particular sex or race. An underlying cardiac diagnosis is prevalent in up to 12.6% and includes ventricular septal defect, tetralogy of Fallot, and other complex congenital cardiac conditions. There is an association with chromosome 22q11 deletion, trisomy 21, and other syndromes in up to 20% of cases. A 2 to 3 fold increase in the incidence of double aortic arch has been reported with the use of routine first-trimester ultrasound compared to postnatal data, with risk increasing significantly in those conceived via in-vitro fertilization.[5][6]

History and Physical

The presentation of a double aortic arch depends largely on the existence of hemodynamic instability. Children with double aortic arch tend to present earlier than those with the other vascular ring pathology, the right-sided aortic arch.

They may remain undiagnosed, rarely may be diagnosed during fetal echocardiography, and often are identified as an incidental finding during routine imaging for other indications. There are reported cases of double aortic arch being diagnosed after foreign body ingestion, and in an adult with aortic dissection.[7][8]

Due to the anatomic nature of the lesion and based on the degree of compression on the trachea and/or esophagus, patients may present with respiratory failure shortly after birth, apneic episodes, apparent life-threatening events (ALTE) or brief resolved unexplained events (BRUE), noisy breathing which may include stridor or wheeze, cyanosis, persistent cough, recurrent lower respiratory tract infections, misdiagnosed ‘asthma’ resistant to therapy, choking, regurgitation, persistent dysphagia, and failure to thrive. Exercise tolerance may be limited due to symptoms.[5][9][10]

Physical examination may often be entirely normal but can include evidence of poor growth and feed intolerance, non-positional stridor, respiratory distress, and features of a lower respiratory infection such as bronchial breath sounds and crackle.[11]