Postnatal evolution of electrocardiographic parameters in preterm infants: a prospective longitudinal cohort study.

UNLABELLED: Electrocardiography (ECG), an indispensable bedside tool in neonatal intensive care, complements echocardiography by providing assessment of cardiac rhythm and conduction, and when advanced imaging is unavailable, serves as a screening tool. Preterm birth alters cardiac and autonomic maturation. Applying term-based ECG norms may misclassify physiological findings in preterm. We aimed to characterise serial ECG maturation in preterms from birth to term-equivalent age and define gestational- and postnatal-age-specific patterns relevant to clinical interpretation. In this prospective cohort, infants between 28⁰/₇ and 36⁶/₇ weeks' gestation without congenital heart disease underwent serial 11-lead ECG recording within 24 h of birth, on day 7, day 28 and at term-equivalent age. Postnatal and gestation-based differences in ECG parameters were analysed and centile charts were generated. Among 249 infants (mean gestation-334/₇ weeks), 213 completed follow-up until term-equivalent age. ECG parameters demonstrated consistent maturation across time points. The mean QRS axis shifted leftward from 117° at birth to 82° at term-equivalent age (p < 0.001). PR-interval, QRS and P-wave duration remained stable across all time points. Mean QTc showed minimal overall change. Transient QTc prolongation occurred in 8.1% of infants and resolved by term-equivalent age. Right precordial R-wave amplitudes declined over time, whereas left precordial amplitudes increased. At term-equivalent age, very preterm infants exhibited a more leftward QRS axis compared with late preterm infants. Infants with bronchopulmonary dysplasia showed trends toward right ventricular dominance.

CONCLUSION

Preterm ECG findings are dynamic, gestation-dependent markers of cardiovascular transition. This study characterises longitudinal ECG maturation in preterms and provides reference values, supporting improved decision-making in preterm care.

WHAT IS KNOWN: • Electrocardiographic reference nomograms used in neonatal practice are primarily based on paediatric cohorts or cross-sectional studies of term infants. These references provide limited information on longitudinal electrophysiologic maturation in preterm neonates.

WHAT IS NEW: • In a cohort of 249 preterm infants, serial ECG measurements demonstrated changes in axes, QTc, and precordial voltages from birth to term-equivalent age. • These gestation and age-specific trajectories support cautious interpretation of preterm ECGs using term-derived standards.