Discussion

During foetal life, the pulmonary venous plexus, a part of the splanchnic plexus, has a connection to the pre-cardinal, post-cardinal and umbilicovitteline venous systems. These connections are lost after the pulmonary venous plexus establishes a connection to the common pulmonary vein. Anomalous pulmonary venous connections are felt to result from proximal obstruction to the pulmonary venous drainage, leading to persistence of these vestigial connections. If the obstruction to the pulmonary venous drainage is at the level of the heart, then persistence of these connections leads to egress of blood from the left atrium, thus forming the levoatriocardinal vein. The term levoatriocardinal vein was first recommended by Edwards and Dushane.Reference Edwards, Dushane, Alcott and Burchell ³ It typically runs posterior to the left pulmonary artery (as shown in Supplementary Figure S2) as it drains the left atrium to the left innominate vein. This is in contrast to the persistent left superior vena cava, which courses anterior to the left pulmonary artery and usually drains into the coronary sinus (Fig 1).

Figure 1 Three-dimentional reconstruction of the magnetic resonance imaging/angiography images showing the course of the levoatriocardinal vein connecting the left atrium to the left innominate vein and passing posterior to the left pulmonary artery (LPA). Compare it with another image where the left superior vena cava (LSVC) runs anterior to the left pulmonary artery (image taken from a different patient).

Levoatriocardinal vein has been described in association with hypoplastic left heart syndrome and intact atrial septum.Reference Bernstein, Moore, Stanger and Silverman ² An intact atrial septum is a rare finding in hypoplastic left heart syndrome, occurring only in 1% of the pathology specimens.Reference Rychik, Rome, Collins, DeCampli and Spray ⁴ In all, 10% of the patients with hypoplastic left heart syndrome were also noted to have aberrant subclavian artery with left aortic arch in previous studies.Reference Ramaswamy, Lytrivi and Thanjan ⁵ To our knowledge, no prior reports have identified a case with combination of the lesions as described in our case. Finding individually rare lesions in the same patient makes our case rare and unique.

A cardiac magnetic resonance imaging/angiography was obtained to confirm the venous anatomy and identify aortic arch branching, which could not be determined by echocardiogram. The magnetic resonance imaging confirmed the echocardiogram findings and identified previously unknown aberrant right subclavian artery (Figs 1, 2). The presence of a levoatriocardinal vein and dilated left innominate vein most likely obscured the aortic arch and its branches. Pre-operative identification of aortic arch sidedness and presence of aberrant subclavian arteries is critical in surgical planning, especially if a Blalock–Taussig shunt is incorporated into the palliation. In addition, during Norwood repair, it is prudent to identify and clamp the aberrant right subclavian artery to improve visualisation of the surgical field. From a monitoring standpoint during surgery, previous reports have suggested that a radial artery catheter be placed in the arm opposite the side of the aberrant subclavian artery to avoid it being compressed by a trans-oesophageal probe.Reference Bensky, O’Brien and Hammon ⁶ Prior knowledge of arch anatomy will enable the surgeon to optimally plan surgery. In addition, during follow-up after surgery, right arm to leg blood pressure gradient can no longer be used to identify the persistence or development of a recoarctation in a patient who has right aberrant subclavian artery.

Figure 2 Three-dimentional reconstruction from magnetic resonance imaging/angiography images showing the aortic arch with its branches; the aberrant right subclavian artery can be visualised coming distal to the left subclavian from the descending aorta.