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Right Aortic Arch with Bicarotid Trunk and Aberrant Left Subclavian ArteryFunding None.
Presence of bicarotid trunk has been previously reported in association with aberrant right subclavian artery (SCA) with no known in human description of bicarotid trunk in association with aberrant left SCA. We, hereby, describe one such rare aortic arch pattern highlighting the association of bicarotid trunk with aberrant left SCA and direct vertebral artery origin from the right aortic arch leading to four arch vessels, which to the best of our knowledge has not been reported so far in literature.
The development of aortic arch is a complex process with various congenital anomalies of aortic arch sidedness and its branching patterns. Most commonly encountered pattern is left-sided aortic arch with three arch branches—brachiocephalic artery that further gives rise to right common carotid artery (CCA) and right SCA, left CCA, and the left SCA. This case describes a rare right aortic arch branching pattern with bicarotid trunk, aberrant left SCA, and direct origin of right vertebral artery from the aortic arch.
A 7-month-old male infant patient with failure to thrive, suck-rest-suck cycles, and no cyanosis underwent computed tomography (CT) angiography in view of suspected congenital heart disease (CHD) on clinical grounds and echocardiography showing large ventricular septal defect (VSD) with echo dropout between aorta and pulmonary artery. CT angiography showed type II right sided aortic arch with four arch branches—bicarotid trunk (common trunk giving rise to bilateral common carotids), right vertebral artery, right SCA, and aberrant left SCA ([Fig. 1]). Additionally, it showed presence of large VSD with confluent dilated pulmonary arteries causing narrowing of lower trachea, right main bronchus with ostial occlusion of right upper lobe bronchus ([Fig. 2]). No patent ductus arteriosus or coarctation was seen with normal origin and course of coronary arteries.
Right aortic arch is a rare aortic arch anomaly with aberrant left SCA (type II) being the most common variation in a right-sided aortic arch followed by mirror image branch pattern (type I) and isolated left SCA (type III). Associated CHD is invariably seen with type I and is rarely seen with type II right aortic arch.
Association of bicarotid trunk with aberrant right SCA has been reported previously with origin of three or four arch vessels, including ectopic origin of vertebral arteries.   Moreover, associated CHD has been reported in 98.4% of patients with bicarotid trunk with VSD being the most common followed by pulmonary valve stenosis and atrial septal defect in a study including pediatric cardiology patients who underwent cardiac catheterization.
Literature search showed no known in human description of association of bicarotid trunk with aberrant left SCA; however, its occurrence in animals is well documented. Moreover, the association of bicarotid trunk with aberrant left SCA and direct vertebral artery origin from the right aortic arch, leading to four arch vessels, has not been reported so far. Our case also highlights the importance of CT in delineation of associated cardiovascular and tracheobronchial abnormalities. Thorough understanding and description of arch branching pattern, airway anatomy, and cardiovascular associations are extremely crucial while planning any endovascular or surgical procedure and intubation. It may require modification of surgical access or technique with careful observation during the usage of heart-lung machine or extracorporeal membrane oxygenation (e.g., aortic cannula may obstruct flow to both the carotid arteries in cases of bicarotid trunk). 
Article published online:
26 December 2022
© 2022. Indian Radiological Association. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)
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