Developmental Trajectories of Electrocardiographic Parameters in Pediatric Patients.

BACKGROUND: Normative pediatric electrocardiographic (ECG) parameters have been established in prior studies, but lack fine temporal resolution during early life. Accurate age-specific values are critical for diagnosis, risk stratification, and management of cardiovascular diseases (CVD). OBJECTIVE: To derive high-temporal-resolution developmental trajectories of ECG parameters in early childhood and evaluate disease-related deviations. METHODS: Five ECG parameters (heart rate (HR), QRS, PR, QT, QTc) were retrospectively analyzed from 6,967 patients at a large pediatric hospital. ECGs were included only if adjudicated as normal by a pediatric cardiologist. Patients were stratified into 45 age groups: neonates (1-35 days, 35 groups), infants (2-6 months, 5 groups), and young children (1-5 years, 5 groups). Sensitivity analysis ranked parameters by age dependence. Z-scores quantified deviations in developmental trajectories between the clinically CVD-free cohort and patients with unrepaired tetralogy of Fallot (TOF, n=305). RESULTS: All five ECG parameters demonstrated significant developmental shifts, with marked differences between early (1-8 days) and late neonates (9-35 days). Sensitivity analysis identified the neonatal period as the most dynamic stage of electrophysiological maturation, followed by slower changes in infancy and childhood. Unrepaired TOF patients exhibited deviations from CVD-free children, including altered HR, PR, and QRS in late neonates and QTc outliers (≥ 2 SD), in 32.7% and 24.3% of early and late neonates, respectively. CONCLUSION: High-temporal-resolution ECG trajectories define age-specific norms in early life and enable the detection of disease-related deviations, particularly during the dynamic neonatal period.