(LAA; A) and a right aortic arch (RAA; B) The trachea shows slight indentation on the same side of the aortic arch and is bent slightly to the other side when there is an LAA or RAA The aortic arch can be traced downward to the vertical linear stripe of the descending aorta on the same side (arrows) In the setting of a double aortic arch (C), the distal trachea shows narrowing on both sides In this case the descending aorta can be traced down the left side (arrows) and pneumonic consolidation is seen in the right middle lobe (C) FIG 47.16 Lateral chest radiographs, corresponding to those shown in Fig 47.15, show (A) a normal left aortic arch and a normal trachea, which takes a straight course without narrowing (B) When the aortic arch is right sided and an aberrant left subclavian artery arises from a diverticulum of Kommerell, the trachea is bowed forward by the diverticulum (arrows) (C) In the setting of a double aortic arch, the distal trachea in this case shows diffuse narrowing (arrow), and pneumonic consolidation is seen in the right middle lobe Although the barium esophagography was previously used as a valuable adjunct, its use is almost abandoned currently because it does not provide a definitive diagnosis while exposing the patient to radiation.6 The definitive diagnosis can be made by using echocardiography, x-ray angiography, computed tomography, or magnetic resonance imaging Echocardiography is always indicated with aortic arch anomalies to exclude any associated intracardiac anomaly A standardized echocardiographic approach to locate the position of the aortic arch and its pattern of branching is always an essential component of the evaluation of suspected congenital cardiac disease.61 For this purpose, the transducer is positioned transversely in the suprasternal notch, and, starting with downward angulation, a gentle sweep upward allows identification of the aortic arch position relative to the trachea and the origins and branching pattern of the head and neck branches (Fig 47.17) In the normal left aortic arch, the first branch heads rightward and bifurcates into the right common carotid and subclavian arteries However, in the right aortic arch with mirror-image branching, the first branch heads leftward and bifurcates into the left common carotid and subclavian arteries If the first branch does not bifurcate, then an aberrant subclavian artery should be suspected (Fig 47.18) Alternatively, a common origin of the right brachiocephalic and left carotid arteries, or a separate origin of the left vertebral artery proximal to the left subclavian artery, can both occur in approximately 10% of otherwise normal left aortic arches In a double aortic arch, if both are patent, both can be identified in this transverse suprasternal view Echocardiography has the advantage that it can often be performed with no or minimal sedation at the bedside, and a complete diagnosis can be reached with echocardiography alone when the vascular anatomy is simple, as in classic form of double aortic arch.8 Often the information provided by echocardiography is incomplete, and the assessment of the anatomy of the airways is not possible with ultrasound FIG 47.17 Standardized echocardiographic approach to show the anatomy of the aortic arch in a patient with right aortic arch (RAA) and mirror-image branching The position of the aortic arch relative to the trachea is identified in a downward tilted transverse view from a suprasternal approach (A) Sweeping upward with the transducer permits ascertainment of the origins of the brachiocephalic arteries (B) The first branch in this case is the left brachiocephalic artery (LBA), which bifurcates into the left common carotid artery (LCCA) and left subclavian artery (LSA) With a further sweep upward, the carotid and subclavian arteries can be imaged in an almost symmetric arrangement in the lower neck (C) The transducer is rotated clockwise or counterclockwise to align the ascending and descending aorta with the aortic arch (D) In this instance, the sonographer has mirror-imaged the transducer clearly to demonstrate that there is an RAA LIA, Left innominate artery; LIV, left innominate vein; RCCA, right common carotid artery; RPA, right pulmonary artery; RSA, right subclavian artery; SCV, superior caval vein