James Watts, Consultant in Anaesthesia and Critical Care Medicine, East Lancashire NHS Trust, describes a rare intrathoracic vascular anomaly and its implications for anaesthetists
Introduction
A patient with a known genetic condition presented for surgery. Although the patient was completely asymptomatic from a cardiorespiratory point of view, an echocardiogram was performed to rule out any possibility of congenital heart disease.
The report suggested that the left atrium was being compressed by an extra-cardiac structure. Cardiac function was otherwise reported as normal. Original CT and PET scan reports had not highlighted any issue.
A review of the pre-operative CT scans confirmed that the patient had a rare vascular abnormality, which may have ramifications for future anaesthetic interventions. This article outlines the condition and its implications for anaesthetists.
Retroaortic Left Brachiocephalic Vein
Usually, the subclavian and internal jugular veins join to form the right and left Brachiocephalic Veins (BCV). These then merge to form the Superior Vena Cava (SVC) which then drains into the Right Atrium (RA). As the SVC is situated on the right of the midline, the left BCV (sometimes the ‘Innominate Vein’) is much longer than the right and runs superior and anteriorly across the Arch of the Aorta (AA) at a downward angle.
A Retroaortic Left Braciocephalic Vein (RALBCV) instead runs behind and inferior to the Aortic Arch, sometimes compressing it, and sometimes raising it into the thoracic inlet (see diagram). This is a rare variant of the usual circulation, first described by Kershner in 1888 (1).
RALBCV occurs in about 0.55% of cases of congenital cardiac abnormality; and is most often associated with Tetralogy of Fallot, or other conditions such as right sided aorta or anomalous cardiac venous return (2,3).
The anomaly can also be found in isolation in adults (4,5). In such cases it is normally asymptomatic and of no clinical concern in and of itself. As an incidental finding, however, it can complicate the interpretation of radiological and echocardiological images as it may be mistaken for a persistent left SVC, or anomalous pulmonary drainage; as the aorta is displaced, it may be mistaken for the right Pulmonary Artery, or an anomalous pulmonary supply. Alternatively, it may be mistaken for a non-vascular structure such as a lymph node or tumour.
Although anatomical variations of this type will obviously cause issues during cardiac or thoracic surgery, they can also cause technical difficulty in relation to non-surgical procedures such as insertion of pacemakers and pacemaker wires if the left sided approach is used; and left sided central venous cannulation (CVC). If CVC access is needed, it may be prudent to use the approach on the right side of the neck, or to use radiographic controlled insertion, or to avoid the neck altogether if possible. It is clear that if the anomaly is known about, the CVC inserter should know how to interpret and orientate themselves in relation to unusual ultrasound images.
In addition, if the Aortic Arch is indeed high in the thoracic inlet, this may preclude the percutaneous insertion of a tracheostomy. Certainly, expert advice should be taken before embarking on such a procedure, which may be better performed surgically in theatre rather than at the bedside in critical Care.
Conclusion
Unusual variations in vascular anatomy although rare can present for the first time in adulthood, where they may need consideration by the anaesthetic and surgical team if technical difficulties during surgery or on ITU are to be minimised.
References
- Kershner L. Morphologie der vena cava inferior. Anat Anz. 1888;3:808–23.
- Hacking C, Knipe H, Retro-aortic left brachiocephalic vein. Reference article, Radiopaedia.org (Accessed on 22 Aug 2024)
- Kulkarni S, Jain S, Kasar Pet al . Retroaortic Left Innominate Vein – Incidence, Association with Congenital Heart Defects, Embryology, and Clinical Significance. Ann Pediatr Cardiol. 2008;1(2):139-41.
- Semionov A & Kosiuk J. Incidental Retroaortic Left Innominate Vein in Adult Patient. Radiol Case Rep. 2017;12(3):475-8. doi:10.1016/j.radcr.2017.05.005 – Pubmed
- Srinivasan S, Kannivelu A, Ali SZ, See PL. Isolated retroaortic left innominate vein in an adult without cardiac or aortic anomalies. Indian J Radiol Imaging. 2013 Oct;23(4):308-9.
