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Bader et al. Vessel Plus 2020;4:34 I http://dx.doi.org/10.20517/2574-1209.2020.36 Page 7 of 14

proximal descending aorta and ductal ligamentum on the opposite side to the arch, to form a vascular
ring. It only refers to the proximal segment of the descending aorta that is on the contralateral side of the
aortic arch, and the subsequent descending aorta may or may not cross back to the other side of the spine.
Not all retroesophageal arch is morphologically a circumflex arch, such as double aortic arch. A circumflex
aorta can be described as a constellation of abnormal lie and development of both the aortic arch as well as
the descending aorta, keeping in mind that the course of the descending aorta may have implications on
therapeutic management strategies.

In describing circumflex aorta, the following need to be specified further: (1) the laterality of the arch -
either “circumflex aorta with right aortic arch” or “circumflex aorta with left aortic arch” - (2) the presence
of any aberrant subclavian artery; (3) the caliber of the arch - unobstructed, or degree of hypoplasia, e.g.,
“Circumflex aorta with right aortic arch with aberrant left subclavian artery - unobstructed”; “Circumflex
aorta with left aortic arch with aberrant right subclavian artery - critical hypoplasia”. Such a morphological
description will summarize the potential deleterious physiological effects of this anomaly on the patient:
(1) a vascular ring that causes tracheal or esophageal compression; and (2) any degree of arch obstruction if
present, which causes haemodynamic compromise.

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION
The clinical manifestation of circumflex aortic arch is associated with pathophysiology that results from
vascular compression; Kommerell’s diverticulum; associated arch hypoplasia and intra-cardiac lesions. The
constellation of this pathophysiology, as well as ductal patency, will therefore dictate the severity and timing
of clinical presentation.

The hallmark of circumflex aortic arch is a high retrooesophageal arch segment. This crowds the
mediastinal space posteriorly, and may result in aortic compression of the oesophagus and the trachea.
Older children or adults can report long-standing, intermittent noisy breathing. Although severe airway
symptoms are uncommon in young children, a sudden presentation with acute respiratory distress has
[18]
been reported in infancy without major preceding symptoms . The mechanism of acute deterioration is
not clear but we postulate that this could due to closure of arterial duct and subsequent tightening of the
vascular ring with ductal ligamentum. When compression is severe, the underlying tracheobronchomalacia
could result in severe residual airway obstruction in the infant despite relief of vascular ring, which may
[7]
persist despite full anatomical correction of circumflex aortic arch .

[35]
Paediatric patients, who need intervention, usually present with significant airway symptoms . Dysphagia
[19]
is an uncommon presentation in children but likely to be under reported . In the authors’ experience,
parents may describe intermittent “choking” when the infant starts to take solid food and some toddlers
with a vascular ring develop an aversion to solid food.

Severe arch hypoplasia is uncommon, but could result in cardiovascular collapse during neonatal period
or early infancy [5,29] . As opposed to the usual situation with coarctation of the aorta, the timing and
mechanism of obstructive symptoms is much more akin to that of interruption of the aortic arch, as for
[5]
type B aortic interruption, and the two may be very easily confused on echocardiographic assessment . The
hypoplastic distal circumflex aortic arch does not exhibit the dynamic obstruction that occurs with classical
coarctation; however, treatment with prostaglandin to open and maintain ductal patency to the descending
aorta is just as important in cases of severe arch hypoplasia presenting with signs of heart failure or shock
and variably diminished pulses. Stenosis and hypoplasia in different sites or even multiple sites in patients
with circumflex arch has been reported. When the base of aberrant subclavian is stenosed or obstructed,
there will be differentiation of blood pressure between two arms; when presented without chest pain and
[42]
diminished pulse in one arm, it simulates an asymptomatic chronic dissecting aortic aneurysm .