Target-oriented contrast enhancement strategies for pediatric cardiac CT angiography in congenital heart disease: a narrative review

Congenital heart disease (CHD) often requires precise anatomical assessment from the neonatal and infant periods. Although echocardiography remains the first-line imaging modality, cardiac computed tomography angiography (CTA) plays an important complementary role in evaluating complex cardiovascular anatomy, coronary artery origin anomalies, great vessel abnormalities, and postoperative anatomy. However, contrast enhancement behavior in neonates and infants differs substantially from that in adults because of low body weight, high heart rate, small-caliber veins, limited circulating blood volume, and short circulation time. In addition, disease-specific flow patterns such as right-to-left shunting, Glenn circulation, Fontan circulation, and surgically altered pathways further modify contrast arrival, mixing, and washout. This narrative review summarizes practical strategies for optimizing contrast enhancement in pediatric cardiac CTA for CHD. Key considerations include iodine dose, contrast concentration, injection rate, injection duration, venous access, saline flush, timing method, and CT technology. The available literature suggests that contrast protocol design should be individualized according to body size, circulation pattern, target anatomy, and scanner performance. In normal neonatal and infant circulation, reproducible enhancement may be supported by body-weight-based iodine dosing, low-kV imaging, diluted contrast material, and stable low-flow injection. In abnormal circulation, particularly Glenn and Fontan physiology, protocol design should additionally consider access-site selection, delayed arrival, heterogeneous mixing, and bolus shaping tailored to the hemodynamic setting. Because the current evidence base remains heterogeneous and is largely derived from single-center studies, the protocol ranges summarized in this review should be interpreted as a practical framework rather than as formal guideline-level recommendations.