Here is some information on Double Aortic Arch that I found at the Cove Point Foundation website, part of the Helen B. Taussig Children's Heart Center at Johns Hopkins University:
In this defect, the aorta, the large vessel that carries blood from the heart to the body, separates into two branches above the heart. This splitting occurs where the aorta begins its curve downward on its way to the lower body - known as the Aortic Arch. Normally, the Aortic Arch consists of a single vessel, from which minor arteries carry blood to the upper body. In this case, the Aortic Arch consists of two vessels, each of which has smaller arteries leaving it.
The two branches of the Aortic Arch surround the esophagus (the tube which carries food to the stomach) and the trachea (the tube which carries air to and from the lungs). Before descending to the lower body, the two branches merge into one vessel, the Descending Aorta, as in a normal circulatory system.
This rare defect, which is one of the so-called Vascular Ring anomalies, affects boys and girls equally.
The symptoms associated with this defect involve the constriction of the trachea and/or esophagus by the surrounding branches of the aorta. In the former case, breathing may be difficult as the wind-pipe is compressed, resulting in wheezing or other respiratory distress. In the latter case, solid food may not be easily swallowed as the aortic branches narrow the esophagus, and vomiting or choking may occur.
This defect may take some time to be diagnosed as the symptoms are often mild. A Barium Swallow Study may be used to help identify the problem. If there is significant interference with breathing, surgery may be performed.
Surgical treatment involves the tying off and separation of one of the branches of the Double Aortic Arch. Sometimes, one of the branches is already closed (atretic), with no blood flowing through it. In this case, it is simply clipped or tied off and separated from the other branch.
We thank you for your prayers for our niece thus far, and ask you to continue praying for her and her parents. It's a relief to finally have some answers, and although surgery is necessary, we are confident that it will solve the problem and allow Charity to go home and join her family!