Right aortic arch anomalies occur in 0.01% to 0.1% of the general population. Abnormalities of aortic arch branching and sidedness are associated with other congenital heart defects (Tetralogy of Fallot, truncus arteriosus, and d-transposition of the great arteries) and chromosomal abnormalities such as DiGeorge syndrome (22q11 deletion). A right aortic arch in and of itself does not cause any physiologic cardiovascular effects; however, the right aortic arch can be associated with other congenital heart defects and/or a vascular ring.
The exact cause of right aortic arch is unknown because, often, there are no identifiable genetic abnormalities. However, a right aortic arch can be associated with 22q11 deletion and some conotruncal congenital heart defects such as Tetralogy of Fallot, truncus arteriosus, or d-transposition of the great arteries.
Isolated right aortic arch with mirror image branching occurs in 0.01% to 0.1% of the general population. This entity can be associated with left pulmonary stenosis/atresia, and it can be associated with a ductus arteriosus originating from the left innominate artery. A right aortic arch with an aberrant left subclavian causes a vascular ring.
A right arch occurs when the aortic arch traverses over the right bronchus instead of the left bronchus. Embryologically, this develops when the right dorsal aorta persists, and the left dorsal aorta regresses. Depending on the formation of the other branching of the aortic arch, various forms of the right aortic arch can develop. This would include a right aortic arch with mirror image branching, defined as a first branch the right innominate artery, second left carotid and third left subclavian. The ductus arteriosus in this scenario originates off the underside of the aortic arch or from the left innominate artery. In the latter scenario, left pulmonary artery stenosis or isolation from the main pulmonary artery can occur. If an aberrant left subclavian is present, the ductus arteriosus originates from the subclavian artery. This leads to an outpouching of the aorta. After the closure of the ductus arteriosus connection to the left pulmonary artery, a vascular ring is formed. The outpouching from the aorta is termed a Kommerell's diverticulum. An extremely rare form of a right aortic arch with isolation of the left subclavian from a ductal attachment to the left pulmonary artery can occur. Rarely, a double aortic arch with an atretic left segment can be misdiagnosed as a right aortic arch. This differentiation is very important as the expected symptomatology and treatment is different.
Right aortic arch with mirror image branching does not cause any cardiovascular, airway, or swallowing symptoms. It can be associated with left pulmonary artery flow abnormalities. Right aortic arch with an aberrant left subclavian causes a vascular ring can be associated with swallowing difficulties (dysphagia lusoria) in children after they begin to eat solid foods, especially meat. Rarely, it can be associated with stridor and recurrent croup if there are compression and malacia of the trachea.
History and physical examination show abnormalities associated with an underlying intracardiac congenital heart defect such as Tetralogy of Fallot or truncus arteriosus. Without an underlying intracardiac congenital heart defect, the cardiac examination in a patient with a right aortic arch is normal. Symptoms as of vascular ring include a history of croup and an examination finding stridor, more often noted in double aortic arch forms of vascular rings. A history of dysphagia is a more common finding in the right aortic arch and aberrant left subclavian form of a vascular ring.
A chest x-ray can demonstrate the trachea deviated to the left in the presence of right aortic arch. This occurs from the aortic arch crossing over the right bronchus instead of the more common right sided deviation from a left sided aortic arch. A barium swallow evaluation can demonstrate a posterior esophageal indentation from the aberrant left subclavian in patients who have a vascular ring. An echocardiogram evaluation will demonstrate any associated intracardiac abnormalities and can demonstrate the arch sidedness including the anatomy of the arch. By echocardiography, the first branch of the aorta defines the sidedness of the aortic arch. If the first branch of the aorta bifurcates to the left, then a right aortic arch is present. CT scans can be performed when there is a concern for a vascular ring causing important symptoms. This can be helpful in preoperative surgical planning, but it should be reserved for patients in whom vascular ring surgery is considered. CT scans can also demonstrate the airway and esophagus and yield an anatomic evaluation of narrowing or compression of these structures. MRI of the aorta can be performed en lieu of a CT scan to avoid a potential long-term radiation risk. Cardiac catheterization and angiography can be performed to image the aortic arch. However, due to its invasiveness, this imaging is reserved for patients with other congenital heart defects that require hemodynamic information of cardiac interventions.
A right aortic arch with an aberrant right subclavian that is symptomatic can undergo surgical division of the ligamentum arteriosus with plication of the diverticulum of Kommerell off of the esophagus. If stridor secondary to tracheomalacia is present, this symptom might not fully resolve immediately after surgery. Right aortic arch with mirror imaging branching does not typically require medical or surgical therapy unless an important left pulmonary abnormality is noted. In the case of left pulmonary artery stenosis, a transcatheter balloon or stent angioplasty intervention can be performed to alleviate the stenosis. In the scenario of left pulmonary artery isolation, a strategy of left pulmonary artery rehabilitation and reimplantation can be employed. Surgical treatment of a vascular ring is rarely associated with long-term morbidity. However, there is a small surgical risk of recurrent laryngeal nerve injury and vocal cord paralysis and thoracic duct injury, leading to chylous effusions.
In general, the isolated right aortic arch is a benign lesion. Right aortic arch and left pulmonary artery anomalies are more difficult to identify and may require more extensive evaluation and intervention. Vascular rings associated with right aortic arch anomalies are intervened upon for symptomatic benefit. Failure to identify a patient with a 22q11 deletion or DiGeorge syndrome can place the patient at risk for unrecognized hypocalcemia, development delay, or other future non-cardiac problems.