Clinical Spectrum of Arrhythmogenic Entities in Spanish Children Carrying Deleterious SCN5A Variants.

Deleterious variants in SCN5A lead to a wide clinical spectrum that includes pathologies characterized by life-threatening cardiac events (CEs). In the pediatric population, early identification, management, and risk stratification of these pathologies are the main current challenges. This study analyzed a Spanish pediatric cohort (≤18 years) carrying rare SCN5A variants to explore genotype-phenotype correlations. A retrospective descriptive cohort study, including clinical, demographic, and genetic data of probands and their relatives, was conducted. Out of 100 children studied, 69 had definitively deleterious SCN5A variants (26 females, 38%; median age: 3 years, IQR 1-12). The main diagnoses were isolated Brugada syndrome (BrS) (31; 45%); isolated long QT syndrome type 3 (LQT3) (5; 7%); isolated progressive cardiac conduction disease (PCCD) (1; 2%); isolated familial atrial fibrillation (1; 2%); overlapping phenotypes (7; 10%) including: BrS-PCCD (2; 2.8%); BrS-LQT3 (1; 1.4%); premature ventricular contraction-dilated cardiomyopathy (1; 1.4%); BrS-LQT3-PCCD (1; 1.4%); BrS-PCCD-sick sinus syndrome (SSS) (1; 1.4%) and BrS-PCCD-SSS-familial atrial fibrillation (1; 1.4%). Of them, 13 (19%) patients presented with CEs (cardiogenic syncope, ventricular tachycardia/fibrillation, sudden cardiac arrest/death, and appropriate implantable cardio defibrillator shock). These findings underscore the utility of genetic testing for early diagnosis, risk stratification, and personalized management, enhancing preventive strategies for CE prevention in pediatrics.