Clinical Characteristics and Outcomes of Pediatric Patients With Long QT Syndrome: A Korean Multicenter Cohort Study

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BACKGROUND AND OBJECTIVES: Most studies on long QT syndrome (LQTS) have been conducted in Western populations, with limited data from Asian countries. We aimed to investigate the clinical characteristics, outcomes, and risk factors for arrhythmic events in Korean pediatric patients with LQTS. METHODS: We conducted a retrospective multicenter cohort study of 202 pediatric patients with LQTS. Risk factors for life-threatening arrhythmic events (LAEs) and breakthrough cardiac events (BCEs) were analyzed. RESULTS: The mean age at diagnosis was 8.2±5.6 years. Among 179 patients who underwent genetic testing, 72% carried pathogenic variants-most commonly LQT1 (35%), followed by LQT2 (15%) and LQT3 (8%). Independent risk factors for lifetime LAEs included LQT2 and LQT3 (vs. LQT1, hazard ratio [HR], 5.5; 95% confidence interval [CI], 2.08-14.68; and HR, 8.38; 95% CI, 2.79-25.19; respectively), fetal arrhythmia (HR, 14.8), QTc ≥500 ms (HR, 2.6), and propranolol or nadolol (HR, 0.25). BCEs occurred in 29% of patients; female sex, prior arrhythmic syncope or seizure, and QTc ≥500 ms were identified as risk factors. Pathogenic KCNQ1 S6-segment variants were associated with a higher risk of LAEs than other LQT1, LQT2, and LQT3 genotypes (HR, 26.8). CONCLUSIONS: This multicenter Korean cohort demonstrates genotype-phenotype patterns and highlights the contribution of fetal arrhythmia, female sex, QTc, and beta-blocker use to arrhythmic risk stratification in pediatric LQTS. These results support early diagnosis and genotype- and phenotype-guided management and highlight the need for international studies to refine risk stratification in diverse populations.

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