Color Doppler Patterns’ Recognition Indicative of Congenital Heart Defects at the First-Trimester Referral Scan

Background/Objectives: First-trimester referral scans in high-risk pregnancies are performed by expert fetal medicine operators using an extended protocol that includes direct fetal heart assessment. This study evaluated inter-operator agreement in characterizing the four-chamber view (4CV) and three vessels and trachea view (3VTV) using color Doppler during such scans in both normal and abnormal cases. Methods: Two independent operators and a fetal cardiologist, all blinded to final diagnoses, retrospectively reviewed 2D images and video clips of the 4CV and 3VTV in 90 fetuses (45 with congenital heart disease [CHD] and 45 controls). The 4CV was classified into four patterns: (1) two atrioventricular (A-V) inflows of similar size, (2) one A-V inflow filling two ventricles, (3) one A-V inflow filling one ventricle, and (4) two A-V inflows with disproportion. The 3VTV was assessed for (1) normal V-sign, (2) abnormal vessel number, (3) abnormal vessel dimension, (4) abnormal spatial relationships, and (5) ductal dependence. Agreement was measured using Cohen's Kappa. Results: Perfect agreement (K = 1) was seen in normal cases. In CHD cases, inter-operator and operator-cardiologist agreement was almost perfect for 4CV (K = 0.83-0.96) and substantial for 3VTV (K = 0.77-0.80). The lowest agreement occurred with ventricular disproportion in 4CV and abnormalities in vessel number and size in 3VTV. Conclusions: Expert operators show strong agreement in interpreting 4CV and 3VTV patterns in first-trimester scans using color Doppler. However, certain abnormalities-particularly ventricular disproportion and vessel anomalies-remain challenging to consistently interpret.