A 23-year-old male patient presented with cyanosis and dyspnea on exertion since childhood. Trans-thoracic echocardiography depicted a peri-membranous ventricular septal defect, an aortic over-ride, and severe pulmonary stenosis, consistent with tetralogy of Fallot (TOF). The patient underwent cardiac computed tomography for further evaluation, which confirmed the findings of TOF. The patient had a right aortic arch (RAA) with the first and second branches being the right common carotid artery (CCA) and right subclavian artery (SCA). Interestingly, the left brachiocephalic artery (LBA) was not visualized. There was a blind-ending stump and a fibrous band originating from the main pulmonary artery. Cranial to this stump, left CCA and left SCA were visualized. The mediastinum showed an extensive network of aortopulmonary collaterals arising from the descending thoracic aorta, bilateral internal mammary and subclavian arteries Figures 1 and 2.Figure 1: Axial computed tomography angiography (a-c) depicting right-sided aortic arch, the arch vessels, and an extensive network of aortopulmonary collaterals in the mediastinum (depicted by arrows)Figure 2: Coronal oblique (a) and sagittal oblique (b) computed tomography image demonstrating nonvisualized left innominate artery from the right-sided aortic arch. There was a blind-ending stump and a fibrous band originating from the main pulmonary artery (marked by a thick arrowhead). Cranial to this stump, the left common carotid artery (LCCA) and left subclavian artery (LSCA) were visualized. Volume rendered images (c and d) showing right-sided aortic arch with the first and second branches being the right common carotid artery (RCCA) and right subclavian artery. There is an interruption of the connection between LCCA and LSCA with the main pulmonary artery (depicted by yellow asterisk). RAA: Right aortic arch, RSCA: Right subclavian artery, RCAA: Right common carotid artery, LSCA: Left subclavian artery, LCAA: Left common carotid artery, MPA: Main pulmonary artery, RPA: Right pulmonary artery“Isolation” implies no direct communication between the arch vessel and the aortic arch. The isolation of LBA is exceedingly rare, with very few cases reported in the literature.1 Interruption of the connection of LBA with the main pulmonary artery or an absent patent arterial duct, as seen in the present case, is even rarer.2 Perfusion in such a scenario is maintained via the retrograde filling of left SCA and left CCA via the left vertebral artery, which in turn is filled by the contralateral vertebral artery. Based on the presence or absence of connection between the LBA and the pulmonary artery and the sources of steal, isolated LBA can be divided into three types: single steal with no connection to the pulmonary artery, connection of LBA to pulmonary artery through a patent arterial duct and two sources of steal and the last one being triple steal type with two patent arterial ducts.2 The clinical manifestations can involve the neurologic system (cerebral insufficiency due to involvement of the vertebrobasilar system), heart (secondary to pulmonary overcirculation), and left upper limb (claudication due to decreased flow to the left SCA). In the present case of above-described pattern, conventional pulmonary steal is not observed. The present case highlights the role of computed tomography in depicting arch vessel anomalies, which have potential clinical implications. In the present case, along with surgical repair of TOF, the reimplantation of isolated LBA onto the ascending aorta to restore the normal flow remains the treatment of choice. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Sharma et al. (Wed,) studied this question.