Persistence of the embryonic “fifth aortic arch” in postnatal life is a rare, enigmatic – and at times controversial – condition, with variable anatomical forms and physiological consequences. First described in humans over 40 years ago by Van Praagh, the condition was labelled the “great pretender” by Gerlis 25 years later, because of its apparent propensity to mimic anatomically similar structures. Despite many subsequent case reports citing the condition, the true developmental origin of these structures remains unresolved, and has been the subject of debate among embryologists for more than a century. A persistent fifth aortic arch has been defined as an extrapericardial structure, arising from the ascending aorta opposite or proximal to the brachiocephalic artery, and terminating in the dorsal aorta or pulmonary arteries via a persistently patent arterial duct. This description may therefore encompass various anatomical forms, such as a unilateral double-lumen aortic arch, an unrestrictive aortopulmonary shunt, or a critical vascular channel for either the systemic or pulmonary circulation. The physiological properties of these vessels, such as their response to prostaglandins, may also be unpredictable. In this article, we demonstrate a number of cases that fulfil the contemporary definition of “persistent fifth aortic arch” while acknowledging the embryological controversies associated with this term. We also outline the key diagnostic features, particularly with respect to the use of new cross-sectional imaging techniques.

A symptomatic neonate was referred for aortic coarctation and, at cineangiography, was shown to have an interruption of the aortic arch at the isthmus together with coarctation related to a persistent fifth aortic arch. Balloon dilation of the coarctation was performed, but the coarctation was still evident after six months. A graft was then interposed between the left subclavian artery and the descending aorta. Balloon dilation was repeated five years later leaving a residual gradient of 11 mm Hg.

We describe a male infant with the combination ofan aortic interruption proximal to the brachiocephalic artery and a persistent fifth aortic arch providing a pulmonary-to-systemic shunt. As far as we know, interruption of the aorta at this site has not previously been reported. Documented cases of a persistent fifth aortic arch itself are few, although failure of recognition may account for its apparent rarity.

We report the first case of double-barrelled aorta associated with tetralogy of Fallot and pulmonary atresia, and we discuss the difficulties in the terminology of this fascinating anomaly.