Anomalies of inferior vena cava are uncommon in the absence of lateralization defects. The incidence varies from 0.3 to 2% in patients with normal visceroatrial situs [3] to 90% in those with heterotaxy syndromes [4]. Embryologically, inferior vena cava is formed from five different venous systems. Caudal to cranial, these are the posterior cardinal veins (draining the posterior part of the body), the right supra cardinal veins, the subcardinal veins (draining the mesonephros or urogenital system), the hepatic segment of IVC (formed by small vessels in the dorsal body lateral to the fold of mesentery), and the hepatic veins. The subcardinals, supracardinals, posterior cardinals, and vitelline veins (hepatic veins) initially begin as bilateral structures but remain only on the right side and involute on the left side with the growth of the embryo. Absence of the hepatic segment of IVC with azygous continuation into the right or left SVC leads to interrupted IVC. Very rarely the interrupted IVC may continue to both the right and left SVC as bilateral azygous veins [5].
The azygous vein is formed by the confluence of the suprarenal segment of the right supra cardinal vein and the cephalic part of the right posterior cardinal vein. It starts from the right lumbar or right renal vein, passes through the diaphragm till the fourth thoracic vertebrae where it arches anteriorly to open into the SVC [5]. IVC interruption leads to the enlargement of azygous vein which ultimately drains the abdomen and the lower part of the body into the superior vena cava. Although, isolated interruption of the IVC is usually asymptomatic, the clinical importance lies in planning the surgical procedures (Bidirectional Glenn and modified Fontan operations), during cardiac catheterization (device closure as in the index case), radiofrequency catheter ablations, inferior vena cava filter placement, and temporary pacing through transfemoral route.
Interrupted IVC poses technical challenges [6] during transcatheter closure of PDA and may require a change of access site to the internal jugular vein from the femoral vein [7]. The jugular venous route is associated with the risk of pneumothorax, may need intubation in a small child to avoid airway compression, may limit the sheath size, and can be disastrous in an already heparinized child.
Other options include transhepatic IVC access, but it is more invasive and needs experienced hands. The use of ADO II via the femoral artery is also reported to be convenient [8], but we wanted to avoid trauma to the artery with the use of bigger sheaths. We did not attempt the internal jugular route as the neck was short and anticipated complications in a heparinized child, also it might have needed general anesthesia considering the age and small size of the child. We continued with the femoral venous access as it allows usage of larger delivery sheath if needed. We found standard femoral access with femoral vein-azygous vein route safe and feasible, time convenient for crossing the PDA, and its closure by the device. Although the patient had not yet shown any major complications related to IVC anomaly, she may be at risk of bilateral venous insufficiency and deep venous thrombosis.