A Unique Constellation of Venous Anomalies Associated with Tetralogy of Fallot: A Case Presentation

Description of Clinical Presentation: A 37-year-old man with a history of repaired Tetralogy of Fallot (TOF), right-sided aortic arch, and pulmonary valve replacement in 2010, presented for routine cardiovascular MRI. The patient was asymptomatic at the time of CMR, but two months later developed right lower extremity pain and edema. A CTA of the abdomen/pelvis and lower extremities was performed for further evaluation.

Diagnostic Techniques and Their Most Important Findings: In addition to standard cine and phase contrast imaging, the previously described image-based navigator (iNAV)/variable density Cartesian with spiral-like trajectory (VD-CASPR) research framework was utilized for contrast enhanced (CE) inversion recovery MRA[1] on a 1.5T scanner (MAGNETOM Sola , Siemens Healthineers, Forchheim, Germany) . Segmental anatomy was S, D, S. Relevant cardiac findings included a patch in the interventricular septum consistent with prior defect repair, right-sided aortic arch, and bioprosthetic pulmonary valve with mild regurgitation (regurgitant fraction of 15%) (Fig 1). Left and right ventricular volumes were within normal limits (LV EDVi 86 ml/m², RV EDVi 108 ml/m²), with mildly reduced LVEF (46%) and low-normal RVEF (48%).


Interestingly, iNAV CE-MRA demonstrated dual inferior vena cava (IVC)- the left IVC was constituted from an azygos continuation into the vertebral venous plexus, and the right IVC had the anatomically correct connection with the right atrium. The right and left renal venous drainage was into right and left IVCs respectively (Fig 2). The pelvis and thigh station was beyond the MRA field of view. However, CTA additionally demonstrated paraumbilical venous collateralization between the superficial epigastric and hepatic portal veins (Fig 3). The iliofemoral venous system drained into the vertebral venous plexus and left IVC, while collateral tributaries from the lower extremity terminated into the paraumbilical vein and right IVC. Occlusive venous thrombosis of the external right iliac vein was identified and treated with staged thrombectomy and thrombolysis.

Learning Points from this Case:

1. 
   In TOF population, interrupted IVC is found in 0.02% of TOF patients and a dual IVC system in 0.6% [2,3]. To our knowledge, this is the first described MRA case of dual IVC anatomy in TOF.
   
   

2. 
   Anomalies of the IVC are usually silent, although these patients are at higher risk for DVT[4]. Due to MRA findings, clinical suspicion for DVT was high leading to prompt CT imaging when the patient became symptomatic.
   
   

3. 
   Although, in general, intravascular contrast agents may be more suitable for venous imaging, in our case, iNAV CE-MRA, using extracellular gadolinium-based contrast agent was able to identify the relevant structural venous abnormalities.
   
   

Fig 1- 37-year-old man, with a history of Tetralogy of Fallot. (A) Normal configuration of the ascending aorta (AO) and pulmonary artery (PA) with right sided aortic arch. (B) A patch related to previous ventricular septal defect repair (asterisk) is present.. (C) A bioprosthetic valve is present in the pulmonary valve position (PVR).
Fig 2- Demonstration of dual inferior venal cava anatomy using image-based navigator (iNAV) gadolinium enhanced MRA. (A) The azygos continuation joins the vertebral venous plexus (VVP), from which the left inferior vena cava (LIVC) originates. There is drainage of the left renal vein (LRV) into the LIVC. Inset- there is normal connection of the hemiazygos to the azygos vein. (B) Axial maximal intensity projection reformats demonstrate the relationship between the left renal artery (LRA), right renal artery (RRA), LIVC, and VVP. (C) The right renal vein (RRV) is a branch of the right inferior vena cava (RIVC), which terminates into the right atrium (RA). Notice continuation of the RIVC inferior to the origin of the RRV.
Fig 3- Twin curved multiplanar reformats from CTA imaging also demonstrated collateralization through the paraumbilical vein; proximal connection with the superficial epigastric vein (white arrow) and distal connection with the hepatic portal vein (black arrow).