https://orcid.org/0000-0002-8080-5276
We discuss the use of 4D flow magnetic resonance imaging (MRI) for quantifying a large systemic to pulmonary veno-venous collateral (VVC) in a case of severe Fontan obstruction. Thank you for considering this for publication in your journal.
A 14-year-old, with an extracardiac Fontan conduit, underwent MRI for evaluation of possible Fontan narrowing. As part of that study, a 4D flow MRI was performed and demonstrated severe Fontan stenosis with a large VVC from the left renal vein to the left lower lobe pulmonary vein. 4D flow MRI parameters included the following: echo time/repetition time = 2.6/4.3 ms, 1.56×1.56×2.00 mm3, velocity encoding gradient = 120 cm/s, temporal resolution = 39 ms with aliasing and eddy current correction.
4D flow MRI was utilized to quantify VVC (estimated to be 6.4 mL/cycle) and Fontan haemodynamics. Flow through the narrowed conduit exhibited increased velocity of 1.16 m/s and resulted in reversed superior vena cava (SVC) flow. These findings prompted catheter intervention on the Fontan with placement of a 14 mm Palmaz stent and occluder in the VVC. Six months following stent placement, a repeat 4D flow MRI demonstrated persistent smaller VVC, antegrade SVC flowLEfl, and increased flow through the inferior vena cava.
Discussion
4D flow MRI is an established technique for evaluating arterial haemodynamics in single ventricle physiology but not yet well established for VVC flow. Evaluation of VVC with 2D datasets is limited by low velocity and tortuosity of these vessels which would necessitate multiple acquisitions. In this case, 4D flow quantified a significant source of desaturation and facilitated post treatment surveillance. This case highlights the comprehensive flow information obtained with 4D flow MRI, despite complex anatomy and low velocities, and how this data influenced patient management in this complication of Fontan palliation.
Author notes
Conflict of interest: None declared.
