Paediatric long QT syndrome: clinical outcomes and therapy in the Spanish National Registry

Abstract

BACKGROUND AND AIMS: Congenital long QT syndrome (LQTS) is a heterogeneous disorder in which genotype and QTc duration modulate the risk of major arrhythmic events (MAEs), but contemporary paediatric outcome data remain limited. This study aimed to characterize clinical features, management strategies, and predictors of MAEs in a nationwide paediatric LQTS cohort. METHODS: This retrospective multicentre study analysed children (<18 years) diagnosed with LQTS across 30 tertiary centres (2004-24) using 2022 European Society of Cardiology criteria. MAEs were defined as sudden cardiac death, aborted cardiac arrest, or appropriate implantable cardioverter-defibrillator (ICD) therapy. RESULTS: The cohort included 371 children (58% male; median diagnosis age 6.0 years; interquartile range .25-11 years). Pathogenic/likely pathogenic variants were identified in 86.5%, mainly in KCNQ1, KCNH2, or SCN5A, while 5.7% harboured high-risk genotypes (Jervell-Lange-Nielsen, calmodulinopathies, CACNA1C/Timothy). Beta-blockers were prescribed in 92.4%. Over a median 6-year follow-up, 14 children (3.8%) experienced MAEs, which occurred predominantly in those with high-risk genotypes, QTc ?550 ms or very early presentation. MAEs were rare in LQT1-3 with QTc <500 ms. Foetal/neonatal bradycardia (5.1%) correlated with high-risk genotypes and adverse outcomes. ICDs were implanted in 33 children (8.9%); 10 (30%) received appropriate therapies, and 8 (24%) experienced complications. Left cardiac sympathetic denervation was performed in 33 (8.9%), mainly high-risk patients, and was associated with >80% arrhythmia-free survival without major complications. CONCLUSIONS: In this nationwide paediatric LQTS cohort, MAEs were uncommon and clustered in children with malignant genotypes, markedly prolonged QTc and very early presentation, particularly foetal or neonatal bradycardia. These data support the current genotype and QTc-guided management strategy, with beta-blockers as the cornerstone therapy and selective use of left cardiac sympathetic denervation and ICDs in high-risk profiles.