A demographically adaptive QT correction formula (QTcAd) achieved 92% sensitivity for detecting congenital long QT syndrome in pediatric patients, nearly doubling the 46.7% sensitivity of the current standard QTcB formula. The enhanced approach analyzed 8,306 ECGs from cardiovascular disease-free children and was validated against 137 clinically confirmed long QT cases, maintaining high specificity at 96.9%. The formula incorporates age-specific parameters and dynamic thresholds rather than fixed cutoffs. This advancement addresses a critical gap in pediatric cardiology, where long QT syndrome can trigger life-threatening arrhythmias but often goes undetected with current screening methods. The improved sensitivity could prevent sudden cardiac death in children while the maintained specificity reduces unnecessary follow-up testing—the emergency department cohort showed 270 fewer repeat-testing triggers compared to standard methods. However, this preprint awaits peer review, and the retrospective design limits causal inferences. The finding represents a meaningful incremental advance that could reshape pediatric cardiac screening protocols, though broader validation across diverse populations will be essential before clinical implementation.