An infant with severe respiratory distress is found to have double aoic arch during investigation. Double aoic arch is due to persistence and continued patency of the segment of ?
**Core Concept**
Double aortic arch is a congenital anomaly resulting from the persistence and continued patency of a segment of the embryological aortic arches. Specifically, it involves the failure of regression of the right fourth aortic arch, which normally regresses and disappears during embryonic development.
**Why the Correct Answer is Right**
In the development of the aortic arches, the right fourth aortic arch typically gives rise to the proximal part of the right subclavian artery, while the left fourth aortic arch contributes to the aortic arch itself. However, in the case of double aortic arch, the right fourth aortic arch persists and forms a complete ring around the trachea and esophagus, leading to compression of these structures and resulting in respiratory distress. This persistence is due to the failure of the normal regression of the right fourth aortic arch during embryonic development.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because the persistence of the left fourth aortic arch is not associated with double aortic arch. The left fourth aortic arch contributes to the formation of the aortic arch and the proximal part of the descending aorta.
* **Option B:** This is incorrect because the distal part of the right subclavian artery is not directly involved in the formation of the double aortic arch. The right subclavian artery is derived from the right seventh intersegmental artery.
* **Option D:** This is incorrect because the ductus arteriosus is not involved in the formation of the double aortic arch. The ductus arteriosus connects the pulmonary artery to the aortic arch and typically regresses after birth.
**Clinical Pearl / High-Yield Fact**
Double aortic arch is a rare congenital anomaly that can cause severe respiratory distress in infants, and it requires prompt recognition and surgical intervention to relieve the compression of the trachea and esophagus. It is essential to consider this anomaly in the differential diagnosis of infants with respiratory distress and a normal cardiac silhouette.
**Correct Answer:** C.