What is the clinical evidence from this study?

Study design: Cohort. Population: Long QT Syndrome (LQTS) (n=202). Intervention: LQT2 genotype vs. LQT1 genotype. Primary outcome: lifetime life-threatening arrhythmic events (LAEs) (HR 5.5, 95% CI 2.08-14.68).

August 10, 2026Sunhwan'gi0 citations

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

MSMi Kyoung SongElectrophysiology SJSo Yon JunPediatric / Congenital Cardiology JKJunghye KwonChungnam National University

Key Result

In pediatric LQTS, LQT2 and LQT3 genotypes were associated with a higher risk of lifetime life-threatening arrhythmic events compared to LQT1 (HR 5.5, 95% CI 2.08-14.68 and HR 8.38, 95% CI 2.79-25.19).

Key Points

This study investigates the clinical characteristics and outcomes of pediatric patients with long QT syndrome in Korea, focusing on risk factors for arrhythmic events.
Conducted a retrospective multicenter cohort study involving 202 pediatric patients with LQTS.
Analyzed risk factors for life-threatening arrhythmic events and breakthrough cardiac events through genetic testing in 179 patients.
Examined the impact of variables such as QTc duration and sex on arrhythmic outcomes.
72% of patients undergoing genetic testing had pathogenic variants, with LQT1 being the most common.
Independent risk factors for lifetime arrhythmias included LQT2 (HR 5.5), LQT3 (HR 8.38), fetal arrhythmia (HR 14.8), and QTc ≥500 ms (HR 2.6).
Breakthrough cardiac events occurred in 29% of patients with identified risk factors including female sex and prior arrhythmic syncope.

Study Design

Type

Cohort (n=202)

Multicenter

Yes

Structured PICO

Population

202 Korean pediatric patients with long QT syndrome, with a mean age at diagnosis of 8.2 years.

Outcome

Life-threatening arrhythmic events (LAEs) defined as cardiac arrest, ventricular tachycardia/fibrillation, appropriate ICD shock, or sudden cardiac deathhard clinical

In Korean pediatric patients with LQTS, LQT2/3 genotypes, fetal arrhythmia, and QTc ≥500 ms are independent risk factors for life-threatening arrhythmic events, while nadolol or propranolol therapy is protective.

Main Result

Hazard Ratio: 5.5 (95% CI 2.08–14.68)

Abstract

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. 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. 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). 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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