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Page 6 of 14 Bader et al. Vessel Plus 2020;4:34 I http://dx.doi.org/10.20517/2574-1209.2020.36

Figure 5. Classic Rathke’s diagram representing embryological development of aortic arches

aortic arch; in circumflex aorta, the dorsal aorta contralateral to the aortic arch is the one that persists in
[40]
life . Therefore, based on this hypothetical model, involutions that occur in circumflex aorta with right
aortic arch are (1) the right sixth aortic arch; and (2) the left fourth aortic arch with persistence of the
left sixth aortic arch and left dorsal aorta (dorsal aortic root segment 8). Alternatively, it may also share a
common pathway with embryological formation of a cervical aortic arch or a double aortic arch [5,12,41] . In
the latter, if obliteration between the left common carotid and subclavian arteries occurs early in-utero, the
[12]
segment may completely involute giving rise to a true form of circumflex arch at birth .

As with other types of aortic obstruction, hemodynamic mechanisms resulting in reduced flow in the
[5]
ascending aorta during fetal life may contribute to the development of arch hypoplasia . In addition,
compression of the retrooesophageal component between oesophagus and spine during fetal development
may also contribute. The aetiology of hypoplasia, when it occurs, is probably not genetic but rather
acquired as a consequence of changes in fetal flow patterns.

TERMINOLOGY
The adjective ‘circumflex’ describes a structure that is curved or bends around another structure, in this
case, the aortic arch bending posteriorly around the oesophagus. The term circumflex aorta and circumflex
aortic arch are also used interchangeably and both terms have been used in the surgical literature to refer to
the much more common form of circumflex aorta with right aortic arch.

The term circumflex aorta or circumflex aortic arch should be used as a generic term to refer to a
congenital arch anomaly with high retroesophageal arch segment above the tracheal carina with both the