The smaller left arch passes anteriorly and to the left of the trachea in the usual position. It is often joined by the ligamentum arteriosum (or patent ductus arteriosus) where it forms the descending aorta. The left arch gives first origin to the left common carotid artery and then the left subclavian artery. The right aortic arch is completing the vascular ring by passing to the right and then behind the esophagus and trachea to join the usually left-sided descending aorta. The first vessel coming off the right arch is usually the right common carotid artery followed by the right subclavian artery. Double aortic arch with left dominant arch:
In this less common condition, as the name indicates, the left arch is the larger of the two aortic arches. The origins of the arm and head vessels are identical to the anatomy of double aortic arch with right dominant arch
Balanced or codominant double aortic arch:
In this rare condition both aortic arches are of the same diameter. Treatment
Surgical correction is indicated in all double aortic arch patients with obstructive symptoms (stridor, wheezing, pulmonary infections, poor feeding with choking). If symptoms are absent a conservative approach (watchful waiting) can be reasonable. Children with very mild symptoms may outgrow their symptoms but need regular follow-up. Anesthesia and intraoperative monitoring
The procedure is performed in general anesthesia. It is useful to place pulse oximeter probes on both hands and one foot so that test occlusion of one arch or its branches will allow confirmation of the anatomy.
Sometimes, in families with cleft hand with good function, operations for cosmetic aspects are considered marginal  and the families choose not to have surgery. Indications
Surgical treatment of the cleft hand is based on several indications:
Improving function
Absent thumb
Deforming syndactyly (mostly between digits of unequal length like index and thumb)
Transverse bones (this will progress the deformity; growth of these bones will widen the cleft)
Narrowed first webspace
The feetAesthetical aspects

Reducing deformity

Timing of surgical interventions
The timing of surgical interventions is debatable. Parents have to decide about their child in a very vulnerable time of their parenthood. Indications for early treatment are progressive deformities, such as syndactyly between index and thumb or transverse bones between the digital rays. Other surgical interventions are less urgent and can wait for 1 or 2 years. Classification and treatment
When surgery is indicated, the choice of treatment is based on the classification. Table 4 shows the treatment of cleft hand divided into the classification of Manske and Halikis. Techniques described by Ueba, Miura and Komada and the procedure of Snow-Littler are guidelines; since clinical and anatomical presentation within the types differ, the actual treatment is based on the individual abnormality.Table 4: Treatment based on the classification of Manske and Halikis

Snow-Littler
The goal of this procedure is to create a wide first web space and to minimise the cleft in the hand. The index digit will be transferred to the ulnar side of the cleft. Simultaneously a correction of index malrotation and deviation is performed.