The formal pathogenesis of isolated common carotid or innominate arteries: the concept of malseptation of the aortic sac

Abstract

Deficient connections (= isolation) of the innominate artery or the common carotid artery to the aorta are rare congenital anomalies of the human aortic arch complex that are usually associated with a patent vascular connection between the isolated artery and a pulmonary artery. In the present study we demonstrate chick fetuses with a corresponding anomaly, the isolation of the brachiocephalic artery. In our chick fetuses the left brachiocephalic artery did not arise from the aortic arch, but was connected to the pulmonary trunk proximal (upstream) to the patent left and right ductus arteriosus. These cases are of interest because the presence of a congenital pulmonary-systemic arterial connection proximal (upstream) to the ductus arteriosus cannot be explained by the traditional concept of the morphogenesis of the aortic arch complex. The development of the normal and abnormal branching patterns of the aortic arch arteries is traditionally explained by transformation of the primitive embryonic pharyngeal arch arterial system due to obliteration of some of its vascular segments. Based on this concept, the isolation of an aortic arch artery can be explained by obliteration of vascular segments proximal and distal to this artery, whereas its connection to a pulmonary artery can be explained only by deficient obliteration (persistence) of the distal portion of the right or left sixth pharyngeal arch artery. The connecting "vascular segment" between an isolated aortic arch artery and the pulmonary circulation, therefore, is traditionally interpreted as a patent ductus arteriosus. The formal pathogenesis of congenital pulmonary-systemic arterial connections proximal (upstream) to the ductus arteriosus is discussed. The presented cases of isolation of the brachiocephalic artery are explained by disturbances in the partition of the embryonic aortic sac, possibly due to abnormal development of the "cardiac" neural crest.

Isolated left brachiocephalic artery with the right aortic arch

“…Abnormal partition of primitive truncoaortic sac giving rise to pulmonary-brachiocephalic connection is alternative proposed mechanism giving rise to this anomaly. [8] The left arch variant with isolation of right subclavian is even rarer[9] and arises from regression of the right fourth arch and right dorsal aorta with persistence of right sixth arch.…”

Isolation of Left Common Carotid Artery with Its Origin Proximal to Patent Ductus Arteriosus Presenting in Adult Age

“…Only eight cases of isolated left common carotid artery have been documented in the literature [ 2 – 8 ] till now. None of these cases were reported in adults.…”

“…According to Männer et al [ 2 ], isolation of any aortic arch artery is explained not only by the regression of arch proximal and distal segments to it, but also by “deficient regression” that is persistence of ductus arteriosus. Presence of ductus arteriosus explains the communication with the pulmonary artery whereas regression of both proximal and distal segments explains the noncommunication to the arch.…”

“…Another variant is right sided aortic arch with aberrant left subclavian artery. Rare anomalies include isolation of either left subclavian artery, left common carotid artery, or innominate artery; that is, they do not have their origin from aorta or its major branches [ 2 ]. Isolation of left common carotid artery is the rarest of the three.…”

Echocardiographic diagnosis of left carotid artery arising from the pulmonary trunk

“…CHARGE association, also present in our patient, is an anomaly of migration of cells from the neural crest. Manner et al, 1 by ablation of such cells migrating from the neural crest in chicken embryos, have induced abnormal formation of the arterial pole resulting in origin of a left brachiocephalic artery from the pulmonary trunk in association with right aortic arch and aberrant left subclavian artery.…”