Coarctation of persistent right fifth aortic arch and pulmonary sequestration

Persistent fifth aortic arch: the "great pretender" in clinical practice

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.

How frequent is the fifth arch artery?

Although usually shown in embryology textbooks, the presence of the fifth pair of pharyngeal arch arteries has long been controversial. To the best of our knowledge, six pairs of bilaterally symmetrical arteries developing within the pharyngeal arches are yet to be found in any mammalian or avian species. Collateral channels between the distal ends of the fourth and sixth arch arteries, in contrast, have been found in up to half of all developing mouse embryos. In only one human embryo, again to the best of our knowledge, has a channel been found that extends from the aortic sac to the dorsal aorta, and hence qualifies as an arch artery. Despite these confounding factors in terms of the developmental heritage of the fifth arch arteries, the purported channels are invoked with increasing frequency to describe various lesions discovered in the setting of the congenitally malformed heart. Persistence of the artery of the fifth arch was initially proposed to explain double-barrelled aorta. It was subsequently proposed to account for various systemic-to-pulmonary channels feeding the pulmonary circulation in the setting of pulmonary atresia. It has also been claimed to persist so as to explain abnormal branching of the brachiocephalic arteries from the aortic arch. In the light of the ongoing doubts concerning the existence of the arteries of the fifth arch themselves, we have reviewed the various descriptions of purported fifth arch arteries within the world literature. We have then sought to validate the descriptions on the basis of our own understanding of development, for this purpose providing images of the remoulding arch arteries in the mouse so as to substantiate our conclusions. While accepting that our own interpretations are speculative, we suggest that more convincing alternative explanations can be advanced to account for the majority of lesions currently interpreted on the basis of persistence of the arteries of the fifth arches. Although the interpretations do not necessarily change the therapeutic approaches to the channels, appropriate description is important in terms of their classification.

Regression of left ventricular dilation after percutaneous closure of a large intralobar pulmonary sequestration

We describe an infant of 8 months who presented with left ventricular dilation due to an extensive intralobar sequestration of the right lung. The pulmonary sequestration was associated with a patent arterial duct and a right aortic arch. Percutaneous closure of the anomalous aberrant artery feeding the sequestrated lung resulted in prompt regression of the left ventricular enlargement.

Truncus arteriosus with coarctation of persistent fifth aortic arch

Truncus arteriosus is a rare form of congenital heart defect. Among cases, 10% to 20% are associated with arch anomalies, such as interruption, coarctation, or patent ductus arteriosus. We treated a rare case of combined truncus with complex arch anomaly. The patient was a 2-month-old girl weighing 3.8 kg. Echocardiogram and computed tomogram showed interrupted aortic arch, truncus arteriosus, persistent fifth aortic arch, and its coarctation. One-stage total correction was performed under cardiopulmonary bypass without circulatory arrest. The operation consisted of a Rastelli procedure with a 12-mm valved conduit, coarctoplasty, and intraventricular baffling. The patient recovered well without complications.