Longitudinal Cardiac Magnetic Resonance Imaging Demonstrates Differential Pulmonary Artery Growth in Patients with Bilateral Bidirectional Glenn Circulations.

Examine the relationship between the inter-superior vena cava (SVC) distance and pulmonary blood flow (PBF) splitting, post-Fontan outcomes, hemodynamics, Fontan geometry, and pulmonary artery (PA) growth in bilateral bidirectional Glenn (BBDG) patients compared to unilateral bidirectional Glenn (BDG) patients. A single center retrospective cohort study comparing demographic, hemodynamic, and post-Fontan outcome variables between BBDG patients and a randomized cohort of BDG patients was conducted. A simple linear regression model was created to evaluate the relationship between Fontan geometry and PBF splitting. Cardiac magnetic resonance images were segmented using Slicer 5.6.2 and center line distance between the right and left SVC was calculated using an in-house code. The relationship between SVC distance and PBF was examined. The Nakata index was compared for BBDG and BDG patients. 42 patients (21 BBDG and 21 BDG) were included. Demographics, post-Fontan complications, and hemodynamics between groups were not different. PBF flow splitting increased as a function of inter-SVC distance. Patients with BBDG experienced a decrease in PA size over time with the mean difference in Nakata index between groups of 128.5 ± 23.73 (95% CI: 75.66, 181.4; p = 0.0003). Patients with BBDG have poor central PA growth compared to BDG patients. Although outcomes and hemodynamics were equivalent between groups, inter-SVC distance impacts PBF. This study provides a foundation on which to direct further prospective, studies of flow efficiencies in patients with BBDG circulations to guide patient-specific reconstruction techniques that maximize pulmonary artery growth potential and Fontan efficiency.