CT imaging of a rare case of persistent fifth aortic arch in newborn

Abstract

Congenital persistence of the fifth aortic arch is an unusual, often misdiagnosed and underestimated pathological finding. It is usually associated with other cardiac or vascular anomalies, which makes every case quite unique in its clinical presentation and treatment. Our subject was a newborn (1-month-old male) who was referred to our hospital from a peripheral centre owing to difficulty in obtaining a clear diagnosis with traditional means (echocardiography). He presented with Type II left-sided malformation (atresia or interruption of the superior arch with patent inferior arch) and also showed an associated atrial septal defect with left-to-right-shunt. The investigation was carried out with a contrast-enhanced CT scan owing to the serious clinical condition (haemodynamic instability) of the subject that made an MRI examination too hazardous. The study succeeded in plainly depicting the malformation, providing a clear diagnosis and also giving the surgeons (especially with the assistance of three-dimensional volume rendering reconstruction) an accurate anatomical model, which played a crucial role in planning the operation. The ability of a multislice CT scan to rapidly perform a full, panoramic and minimally invasive study of the cardiovascular system is clearly demonstrated in this study. The only downside of this procedure is the use of ionizing radiation on a newborn, although it is justified in this case by the emergent need for a quick diagnosis. Furthermore, a CT scan is characterized by a higher spatial resolution compared with an MRI and for vascular anomalies, a CT scan is often preferred. An MRI is mainly used in case of functional imaging. Exactly for this reason, we planned the procedure in order to maintain the equivalent radiation dose as low as possible [equivalent dose (H) ≤ 1 mSV].

Figure 1.

Axial view of two aortic arches. On the left is the superior arch, which is the real one (with a reduced calibre); on the right is the inferior arch, which is the persistent fifth aortic arch (with a greater calibre but hypoplastic in its distal portion).

Figure 2.

Coronal view of two aortic arches. In these two subsequent images, in addition of what is described in Figure 1, we can see an anonymous arterial trunk arising from the proximal fusion of the two arches and the left carotid artery (of regular calibre) arising from the superior arch.

Figure 3.

Maximum intensity projection reconstruction. A double aortic arch is shown from a different viewpoint; it demonstrates the rise of supra-aortic branches (the left carotid and subclavian arteries from the superior arch and an anonymous arterial trunk from the proximal fusion of the two arches) and the presence of a hypoplasia in the distal portion of the inferior arch, which continued itself with the aortic isthmus that showed a significant coarctation and a related post-isthmic dilation. Also shown is a distal connection of the upper arch and the aortic isthmus, although it appears essentially atresic.

Figure 4.

Volume rendering reconstruction. Three-dimensional view of what was seen on maximum intensity projection images.