Discussion

Circumflex retroesophageal aortic arch is a rare form of aortic arch anomaly in which the aortic arch and the descending aorta are placed on opposite sides of the spine.^{Reference Wernovsky, Anderson and Kumar3} In the presence of an ipsilateral arterial duct with the descending aorta, as is often the case, it forms a complete vascular ring. Left aortic arch with right descending aorta associated with coarctation of the aorta is an even rarer congenital cardiac anomaly.^{Reference Miwa, Iwai and Nagashima2,Reference Sheth, Varghese and Sivakumar4} In our patient, the aortic arch and the descending aorta were on opposite sides of the midline, although the aorta did not course behind the oesophagus and the arterial duct was left-sided (contralateral to the descending aorta).

Left main bronchial stenosis is a well-known complication that may occur after repair of coarctation of the aorta. Usually, the mechanism is an external compression of the left main bronchus by the anteriorly relocated descending aorta. In patients with a circumflex aortic arch, this complication may occur more frequently because the descending aorta should be brought up towards the aortic arch after crossing the midline. Miwa et al reported three patients with left aortic arch, right descending aorta, and coarctation who were treated with conventional resection and direct anastomosis.^{Reference Miwa, Iwai and Nagashima2} In two patients, left main bronchial stenosis developed by gradual traction of the descending aorta towards the left side, thereby narrowing the space between the descending aorta and the right pulmonary artery. They suggested that alternative surgical techniques, such as arch reconstruction with an autologous pulmonary artery patch, should be considered in this situation to prevent postoperative left main bronchial stenosis.

Descending aortic translocation, first reported by McKenzie et al, is a procedure originally designed to relieve the airway compression by the midline-crossing descending aorta without associated coarctation of the aorta.^{Reference McKenzie, Roeser and Thompson5} In this procedure, the proximal descending aorta is transected, brought up through the transverse sinus caudad to the tracheal carina and pulmonary artery, and anastomosed in an end-to-side fashion to the proximal ascending aorta. In this way, the descending aorta is relocated away from the airway. Sheth et al reported successful use of this technique in a 5-month-old infant with left aortic arch, right descending aorta, coarctation of the aorta, and severe preoperative left main bronchial stenosis.^{Reference Sheth, Varghese and Sivakumar4} In our patient, there was no airway stenosis preoperatively. However, we were concerned about potential postoperative left main bronchial stenosis, given that we favour end-to-side repair technique^{Reference Lee, Brink and Galati1} for coarctation of the aorta with associated arch hypoplasia. Descending aortopexy to address this issue may be ineffective in cases with midline-crossing descending aorta. Therefore, we decided to perform descending aortic translocation to prevent postoperative left main bronchial stenosis. Although a little more dissection in the posterior mediastinum was required compared with conventional repair, this simple manoeuver relocated the descending aorta well away from the airway (Fig. 2). One of the potential complications of this procedure may be chylothorax due to extensive dissection of the descending aorta. We believe that descending aortic translocation may be a useful surgical option to prevent airway stenosis in patients with coarctation of the aorta and midline-crossing descending aorta. However, long-term effect of the resultant non-anatomical aortic arch geometry remains to be elucidated.^{Reference Ou, Celermajer and Raisky6}