Double aortic arch  is a relatively rare congenital cardiovascular malformation. DAA is an anomaly of the aortic arch in which two aortic arches  form a complete vascular ring that can compress the trachea and/or esophagus. Most commonly there is a larger (dominant) right arch behind and a smaller (hypoplastic) left aortic arch in front of the trachea/esophagus. The two arches join to form the descending aorta which is usually on the left side (but may be right-sided or in the midline). In some cases the end of the smaller left aortic arch closes (left atretic arch) and the vascular tissue becomes a fibrous cord. Although in these cases a complete ring of two patent aortic arches is not present, the term ‘vascular ring’ is the accepted generic term even in these anomalies. The symptoms are related to the compression of the trachea, esophagus or both by the complete vascular ring. Diagnosis can often be suspected or made by chest x-ray, barium esophagram, or echocardiography. Computed tomography (CT) or magnetic resonance imaging (MRI) show the relationship of the aortic arches to the trachea and esophagus and also the degree of tracheal narrowing. Bronchoscopy can be useful in internally assessing the degree of tracheomalacia. Treatment is surgical and is indicated in all symptomatic patients. In the current era the risk of mortality or significant morbidity after surgical division of the lesser arch is low. However, the preoperative degree of tracheomalacia has an important impact on postoperative recovery.
Non-perfused elements of other types of vascular rings (e.g. left arch with atretic (closed) end) or the ligamentum arteriosum might be difficult to visualize by echocardiography. Computed tomography (CT):
Computed tomography after application of contrast media is usually diagnostically accurate. It shows the relationship of the arches to the trachea and bronchi. Magnetic resonance imaging (MRI):
Magnetic resonance imaging provides excellent images of the trachea and surrounding vascular structures and has the advantage of not using radiation for imaging compared to Computed tomography. Cardiac catherization/aortography:
Today patients with double aortic arch usually only undergo cardiac catherization to evaluate the hemodynamics and anatomy of associated congenital cardiac defects. Through a catheter in the ascending aorta contrast media is injected and the resulting aortography may be used to delineate the anatomy of the double aortic arch including sites of narrowing in the left aortic arch. Aortography can also be used to visualize the origin of all head and arm vessels originating from the two arches. Classification
Double aortic arch is a subtype of complete vascular ring. There are three types of double aortic arch:

Right dominant arch (about 70% of surgical cases)
Balanced or codominant (about 5%): both arches are of equal size
Left dominant (about 25%)Double aortic arch with right dominant arch:
Normally there is only one (left) aortic arch. In patients with double aortic arch the ascending aorta arises normally from the left ventricle but then divides into two arches, a left and a right aortic arch which join posteriorly to become the descending aorta.