Neonatal Narrow-Complex Supraventricular Tachycardia as the Index Presentation of Concealed or Intermittent Accessory Pathway–Mediated Ventricular Pre-Excitation: Developmental Electrophysiology, Substrate Characterization, and Implications for Early Risk Stratification

Abstract Neonatal narrow-complex supraventricular tachycardia (SVT) often serves as the initial manifestation of concealed or intermittent accessory pathway (AP)–mediated ventricular pre-excitation, a condition rooted in developmental anomalies of the cardiac conduction system. This review explores the electrophysiological maturation of accessory pathways in neonates, characterizes the arrhythmogenic substrates, and discusses clinical implications for early risk stratification. Drawing from recent advances in pediatric electrophysiology, we highlight the decremental conduction properties of neonatal APs, their potential for spontaneous resolution, and the risks of progression to life-threatening arrhythmias such as pre-excited atrial fibrillation. Non-invasive and invasive diagnostic approaches are evaluated, alongside therapeutic strategies including pharmacological management and catheter ablation. Emphasis is placed on personalized risk assessment to guide interventions, particularly in asymptomatic or minimally symptomatic cases. By integrating developmental insights with substrate analysis, this article underscores the need for vigilant monitoring and multidisciplinary care to optimize outcomes in this vulnerable population. Keywords: Neonatal supraventricular tachycardia, accessory pathway, ventricular pre-excitation, developmental electrophysiology, risk stratification, Wolff-Parkinson-White syndrome