Approach to prolonged QT interval in paediatric and neonatal patients

Congenital Long QT Syndrome (LQTS) is a potentially life-threatening cardiac channelopathy and an important cause of sudden cardiac death in young individuals. It is characterised by delayed myocardial repolarization, seen as a prolonged QT interval on a standard 12-lead electrocardiogram. This prolongation increases the risk of ventricular arrhythmias, particularly Torsades de Pointes, which may result in syncope, cardiac arrest, or sudden death, often secondary to physical or emotional stress. In infants and children, the upper limit of normal for a heart rate-corrected QT (QTc) interval is generally considered to be 460 ms. Nevertheless, the diagnosis of long QT syndrome (LQTS) should not rely solely on QTc duration, but rather on a combination of findings, including QT prolongation, clinical features, and family history, as outlined by the Schwartz score. A markedly prolonged QTc (> 500 ms on at least two separate ECGs) strongly supports the diagnosis. In this review, we explore the common presentation of LQTS and how paediatricians should assess across paediatric subgroups, including neonates, children, athletes, and those with comorbidities such as anorexia nervosa or hypothermia. What is known: • Long QT syndrome is a potentially life-threatening arrhythmia in infants and children, yet its recognition and initial evaluation in general paediatric and neonatal settings remain challenging . • Accurate QTc measurement and appropriate early work-up are essential to avoid misdiagnosis, unnecessary referrals, or missed high-risk cases. What is new: • This article provides a practical, step-by-step paediatric and neonatal approach to recognising, measuring, and initially managing prolonged QT interval, including common pitfalls and actionable clinical decision points. • The guideline is specifically designed to improve confidence and consistency among general paediatricians and neonatologists, supporting safer early management before specialist cardiology review.