Red blood cell distribution width in pediatric congenital heart disease: A review of clinical applications

Congenital heart disease (CHD) encompasses a heterogeneous spectrum of anatomical lesions ranging from simple shunts to complex cyanotic malformations, representing the most common congenital anomaly in children with variable clinical outcomes. Red blood cell distribution width (RDW), an indicator of erythrocyte volume heterogeneity, has demonstrated associations with cardiac dysfunction across diverse CHD phenotypes. This review synthesizes evidence (2015-2023) from PubMed, Web of Science, Cochrane Library, and China National Knowledge Infrastructure regarding RDW's clinical utility in pediatric CHD. Current evidence indicates that elevated RDW correlates with disease severity, particularly in heart failure and pulmonary hypertension cohorts, and shows potential for perioperative risk stratification (e.g., prolonged mechanical ventilation). However, reported cutoff values vary substantially across studies (13.9%-16.0%), likely reflecting the anatomical and physiological heterogeneity of CHD populations - wherein RDW elevation in cyanotic lesions may reflect chronic hypoxia-driven erythropoiesis, while in acyanotic shunts it indicates volume overload-mediated inflammation. Existing data predominantly derive from retrospective, single-center studies lacking anatomical stratification, limiting causal inference. RDW serves as an inexpensive, accessible biomarker for risk assessment in resource-limited settings, though interpretation requires contextualization by specific CHD subtype and confounding factors (anemia, nutritional status). Future prospective multicenter studies must establish anatomy-specific reference ranges and validate temporal predictive utility through stratified analyses of simple versus complex lesions, cyanotic versus acyanotic physiology, and preoperative versus postoperative stages.