Ascending Aorta-Descending Aorta Outer/Internal Distance Index as a Potential Novel Method for Predicting Fetal Complete Transposition of the Great Arteries: A Pilot Study.

To investigate the ascending aorta (AAO)-descending aorta (DAO) outer/internal distance index (AAO-DAO ODI/IDI) prediction value for fetal complete transposition of the great arteries (D-TGA). Selected D-TGA fetuses between January 2019 and June 2024 as the D-TGA group and an equal number of normal fetuses (gestational age (GA) matched ± 1 week) as the control group. The AAO-DAO outer/internal distance (AAO-DAO OD/ID) and DAO diameter were measured in the aortic arch long-axis view, and the AAO-DAO ODI/IDI were calculated, which are the ratios of AAO-DAO OD/ID to DAO. The relationship between AAO-DAO OD/ID and AAO-DAO ODI/IDI and GA of the normal group was analyzed. The differences in AAO-DAO ODI/IDI between the D-TGA and the normal fetuses were compared, and the difference between the D-TGA with intact ventricular septum (D-TGA-IVS) and the D-TGA with ventricular septal defects (D-TGA-VSD) was compared. The sensitivity and specificity of the receiver operating characteristic (ROC) curve were applied to analyze the discrimination ability of AAO-DAO ODI/IDI for D-TGA and normal fetuses and D-TGA-IVS and D-TGA-VSD. In the normal control group, the DOA ICC was 0.972 (95% CI 0.958-0.982), the AAO-DAO OD ICC was 0.988 (95% CI 0.983-0.992), and the AAO-DAO ID ICC was 0.978 (95% CI 0.967-0.985); in the D-TDA group, the DAO ICC was 0.975 (95% CI 0.956-0.989), the AAO-DAO OD ICC was 0.994 (95% CI 0.991-0.996), and the AAO-DAO ID ICC was 0.991 (95% CI 0.987-0.994). The AAO-DAO OD (r = 0.811, P < 0.001) and AAO-DAO ID (r = 0.707, P < 0.001) increased with increasing GA. The linear regression equations are AAO-DAO OD = 0.087*GA-0.474 (R² = 0.758, N = 69), and AAO-DAO ID = 0.052*GA-0.319 (R² = 0.626, N = 69) respectively. The AAO-DAO ODI (r = 0.080, P = 0.511) and AAO-DAO IDI (r = 0.096, P = 0.433) did not significantly correlate with GA. In the D-TGA group, the AAO-DAO ODI/IDI were greater than the normal group (6.35 ± 0.43 vs 4.65 ± 0.35, t = - 25.385, P < 0.001) and (4.30 ± 0.42 vs 2.69 ± 0.30, t = - 26.050, P < 0.001). In the D-TGA-IVS group, the AAO-DAO ODI/IDI was greater than the D-TGA-VSD group (6.55 ± 0.32 vs 6.09 ± 0.43, t = 5.118, P < 0.001) and (4.50 ± 0.32 vs 4.04 ± 0.39, t = 5.425, P < 0.001). The AAO-DAO ODI AUC was 0.998 (95% CI 0.995-1), and the AAO-DAO IDI AUC was 0.999 (95% CI 0.996-1) for differentiating D-TGA from normal fetuses (twofold cross-validation). When the AAO-DAO ODI cutoff value was 5.34, the sensitivity was 98.6%, the specificity was 97.1%, the positive predictive value (PPV) was 97.1%, and the negative predictive value (NPV) was 98.5%, the positive likelihood ratio (PLR) was 34, and the negative likelihood ratio (NLR) was 0.015; when the AAO-DAO IDI cutoff value was 3.46, the sensitivity was 97.1%, the specificity was 100%, the PPV was 100%, the NPV was 97.2%, and the NLR was 0.029. The AAO-DAO ODI AUC was 0.807 (95% CI 0.696-918), and the AAO-DAO IDI AUC was 0.814 (95% CI 0.712-917) for differentiating D-TGA-IVS from D-TGA-VSD. When the AAO-DAO ODI cutoff value was 6.27, the sensitivity was 87.2%, the specificity was 70.0%, the PPV was 79.1%, the NPV was 80.8%, the PLR was 3.78, and the NLR was 0.24; when the AAO-DAO IDI cutoff value was 4.27, the sensitivity was 82.1%, the specificity was 73.3%, the PPV was 80.0%, the NPV was 75.9%, the PLR was 4, and the NLR was 0.32. AAO-DAO ODI/IDI is a sensitive predictive indicator for fetal D-TGA.