Prenatal diagnosis of isolated inferior vena cava interruption with hemiazygos continuation – beware of association with dilated left innominate vein

Case report

A 27-year-old female patient, G1, P0, with no history of consanguineous marriage, was referred at 23 weeks of gestational age (GA) by last menstrual period (LMP) for dedicated foetal echocardiography.
An initial study showed absence of the hepatic segment of the inferior vena cava (IVC) with direct drainage of hepatic veins into the right atrium (Figure 1C and D). There was a dilated hemiazygos vein coursing left sided retro aortic in the posterior mediastinum filling into the left innominate vein and eventually through the right superior vena cava (SVC) into the right atrium (Figures 1A, B, E, F and 2).
The pulmonary veins have normal connections and drainage into the left atrium (LA) and no persistent left SVC or coronary sinus dilation (Figure 2I).
Also, situs solitus with usual discrete morphology of both atrial appendages is seen in such a situs arrangement (Fig- ures 1G, H, I).
No associated congenital cardiac abnormalities could be detected with normal sinus rhythm, regular normal heart rate for GA, and a normal 1:1 atrio-ventricular (AV) relationship.
Our final diagnosis was isolated interruption of the IVC with a rare continuation of the hemiazygos vein filling through the left superior intercostal vein into the left innominate vein.

Discussion

Herein, we describe a rare anatomical variant of IVC interruption with hemiazygos continuation to the left innominate vein, and to our knowledge, this represents the first prenatal report of such an association, compared to the previous single prenatal report about incidental detection of this hemiazygos variant by Lo Verso et al. [1].
Interruption of the IVC is a well-known rare systemic venous anomaly occurring with left isomerism, or it may be in isolation. Reconstitution of venous return, in such a condition, will be through the azygos or hemiazygos system [2].
Three different pathways of hemiazygos drainage are well understood. The least common route, which was encountered in this prenatal report, is to continue more cranially (instead of joining the azygos or left SVC) and join the accessory hemi azygos and left superior intercostal vein filling into the left innominate vein, the right SVC, and eventually into the right atrium [3], with consequent dilation of such central veins raising the possibilities of anomalous pulmonary venous connections or high-flow vascular malformations within the upper half of the body. Thorough evaluation of central veins helped reach this rare association of isolated IVC interruption with such a rare hemiazygos variant.
Knowledge of this systemic venous variant warrants careful assessment of possible association of left isomerism with a normal heart. Additionally, it was reported that these patients have increased risk of lower limb DVT or development of sick sinus syndrome in their future life. Moreover, paying attention to this variant has some clinical implications regarding the future need of catheter-assisted procedures requiring IVC access or left thoracotomy procedures for cardiothoracic surgical interventions [4, 5].

Disclosures

Ethical considerations: none.
This research received no external funding.
The author declares no conflict of interest.

REFERENCES