Right ventricular afterload in repaired D-TGA is associated with inefficient flow patterns, rather than stenosis alone

Treatment of D- transposition of great arteries (DTGA) involves the Arterial Switch Operation (ASO), which can create PA branch stenosis (PABS) and alter PA blood fow energetics. This altered PA fow may contribute to elevated right ventricular (RV) afterload more signifcantly than stenosis alone. Our aim was to correlate RV afterload and PA fow characteristics using 4D fow cardiac magnetic resonance (CMR) imaging of a mock circulatory system (MCS) incorporating 3D printed replicas. CMR imaging and clinical characteristics were analyzed from 22 ASO patients (age 11.9±8.7 years, 68% male). Segmentation was performed to create 3D printed PA replicas that were mounted in an MRI-compatible MCS. Pressure drop across the PA replica was recorded and 4D fow CMR acquisitions were analyzed for blood fow inefciency (energy loss, vorticity). In post-ASO patients, there is no diference in RV mass (p=0.07), nor RV systolic pressure (p=0.26) in the presence or absence of PABS. 4D fow analysis of MCS shows energy loss is correlated to RV mass (p=0.01, r=0.67) and MCS pressure diferential (p=0.02, r=0.57). Receiver operating characteristic curve shows energy loss detects elevated RV mass above 30 g/m2 (p=0.02, AUC 0.88) while index of PA dimensions (Nakata) does not (p=0.09, AUC 0.79). PABS alone does not account for diferences in RV mass or afterload in post-ASO patients. In MCS simulations, energy loss is correlated with both RV mass and PA pressure, and can moderately detect elevated RV mass. Inefcient PA fow may be an important predictor of RV afterload in this population.Peer ReviewedPostprint (author's final draft