The simplest way to understand the anatomy and development of double aortic arch and other forms of vascular ring is to begin by considering the bilateral system of pharyngeal arch vessels in the early embryo.
Early in the course of embryonic morphogenesis, 6 pairs of pharyngeal arch arteries develop in conjunction with the branchial pouches. The first through sixth arches appear in a more or less sequential fashion, with left-to-right symmetry, and constitute the primitive vascular supply to the brachiocephalic structures, running from the aortic sac to the paired dorsal aortas. As normal cardiovascular morphogenesis proceeds, a patterned regression and persistence of the various arches and right-sided dorsal aorta occur, ultimately resulting in the mature configuration of the thoracic aorta and its branches. The third, fourth, and sixth arches, along with the seventh intersegmental arteries and the left dorsal aorta, are the primary contributors to the normal aortic arch and its major thoracic branches (see Image 1).
The segments of the bilateral aortic arch system that normally regress include the distal portion of the sixth arch and the right-sided dorsal aorta. Normally, the left fourth arch becomes the aortic arch, the right fourth arch contributes to the innominate artery, the distal left sixth arch becomes the ductus arteriosus, the proximal sixth arches bilaterally contribute to the proximal branch pulmonary arteries, the left dorsal aorta becomes the descending thoracic aorta, and the dorsal intersegmental arteries bilaterally become the subclavian arteries.
Vascular rings are formed when this process of regression and persistence does not occur normally, and the resulting vascular anatomy completely encircles the trachea and esophagus. (Other forms of aortic arch anomalies occur in which a vascular ring is not present.) A double aortic arch is formed when both fourth arches and both dorsal aortas remain present.
Various forms of double aortic arch exist. Both arches may be patent, or an atretic (but persistent) segment may exist at one of several locations in either arch. When both arches are patent, the right or left arch may be larger, or they may be similar in size. A cervical arch on either side, variable laterality of the descending thoracic aorta, coarctation of the major arch, and/or discontinuity of the central pulmonary arteries may be present. In general, the apex of the right-sided arch is more superior than the left arch, and on occasion, a cervical arch may be present on either side.
In more than 75% of patients with double aortic arch, the right arch is dominant. Among patients with a right-dominant double arch, those with a patent minor arch outnumber those with an atretic minor arch. When the minor arch is atretic, the atretic segment almost always is distal to the left subclavian artery, although atresia also may occur between the left common carotid and subclavian arteries. In approximately 20% of patients, the left arch is dominant. In these patients, the minor right arch typically is patent.
Double aortic arch usually occurs without associated cardiovascular anomalies. Ventricular septal defect and tetralogy of Fallot probably are the most common associated defects, although truncus arteriosus, transposition of the great arteries, pulmonary atresia, and complex univentricular defects sometimes occur in conjunction with a double arch.
What signs and symptoms does it cause?
nearly constant non-positional stridor, in inspiration more than expiration (usually noted at 2-6 weeks old)
recurrent respiratory infections and pneumonia
widened superior mediastinum on chest radiograph
vomiting and feeding intolerance (infants)
dysphagia or choking (in children old enough to eat solid food)
Anatomy of the AortaClinical Anatomy of the Aorta (PDF file) College of Osteopathic Medicine, University of Ohio
Links to Articles About Various Types of Vascular RingsVascular Rings The Child's Doctor- Journal of Children's Memorial Hospital (Chicago) - Spring 1998Vascular Ring, Double Aortic Arch eMedicine (Pediatric Cardiology) - July 17, 2002Vascular Ring eMedicine (Thoracic Surgery) - June 10, 2002Pulmonary Sling & Double Aortic Arch Learning Radiology.com
Patient/Family Education ResourcesDouble Aortic Arch Johns Hopkins Children's Center (includes surgical information)Double Aortic Arch University of Virginia Children's Heart Centre - March 18, 2003Double Aortic Arch Mayo Clinic - August 27, 2004
Case StudiesRecurrent Coins and Recurrent Respiratory Infections Radiology Cases in Pediatric Emergency Medicine (University of Hawaii)Difficulty Breathing Throughout Infancy Radiology Cases in Pediatric Emergency Medicine (University of Hawaii)Biphasic stridor in infancy Medical Journal of Australia - 2004Double Aortic Arch University Hospitals of Cleveland - Department of RadiologyBalanced type of double aortic arch Schweiz Med Wochenschr - 1999Adult with history of CABG University of Pittsburgh - March 2001