Typically, the distal components of the right IV and VI arches regress, with the left IV arch becoming the definitive aortic arch, and the left VI arch persisting as the patent ductus arteriosus, illustrated in [Figure 4]a.
However, dissolution of the right IV aortic arch with persistence of the distal right VI arch forming the right ductus arteriosus and pulmonary artery can lead to isolation of the RSCA, as illustrated in [Figure 4]b.
He was born via repeat cesarean section with Apgars 8 and 8 at 1 and 5 min, respectively.
After transfer to the intensive care unit, initial pulse oximetry demonstrated a right arm saturation of 99%; while right ear, left arm, and right leg saturations ranged from 50 to 60%.
The presence of an isolated RSCA arising from the pulmonary artery in association with d-transposition of the great arteries (d-TGA) is extremely unusual, with few cases previously reported in the literature.Figure 4: (a) Diagram of the normal embryological origin of the RSCA from the seventh (VII) intersegmental artery with subsequent cranial migration, and dissolution (in black) of the R-PDA and right fourth (IV) aortic arch (R-arch).(b) Isolation of the RSCA occurs when there is dissolution (in black) of the right IV aortic arch but persistence of the right sixth (VI) arch from which the R-PDA and RPA take their origin.Contrast-enhanced magnetic resonance imaging (MRI) with thin-slab three-dimensional surface rendering was performed the following day, confirming the origin of the RSCA from a ductus arteriosus arising from the proximal right pulmonary artery [Figure 2].
Figure 1: Transthoracic echocardiogram demonstrating a vessel arising from the proximal right pulmonary artery (RPA) and coursing superior and rightward, suggestive of an anomalous origin of the right subclavian artery (RSCA).Noninvasive imaging modalities such as transthoracic echocardiography and MRI can confirm the origin of the RSCA.