Which children are at high risk for long QT syndrome?

Long QT syndrome (LQTS) is an electrocardiographic abnormality that causes rapid and chaotic heartbeats, putting patients at risk of syncope, cardiac arrest, or sudden death. It is characterized by a prolonged QT interval on the electrocardiogram.A German cohort study published in the European Heart Journal examined the frequency and risk factors for serious LQTS events in 548 children and adolescents (48.9% boys). The cases considered were diagnosed before the age of 18 and followed in 12 specialized institutions in Germany between 1973 and 2023—but mostly after 2010.The patients, who had a median age of 6.3 years, were diagnosed following incidental findings (26.5%), symptoms (31.3%), and cascade screening (42.2%). Nearly half (44%) of the patients had LQT1, and 26.6% had LQT2. The LQT3 form was diagnosed in 6% of cases, while 4.7% of patients had rare forms of the syndrome. All included patients did not have any structural heart defects. The results were analyzed, for each factor, using Kaplan-Meier survival curves.The majority of children (92.1%) received drug therapy, and an implantable cardioverter-defibrillator (ICD) was inserted in 73 children (13.3%). A major adverse cardiac event (sudden death, resuscitated cardiac arrest, or appropriate shock delivered by an implantable cardioverter-defibrillator) occurred in 58 patients, or 10.6% of the cohort. Of these, 40 patients (7.3%) experienced resuscitated cardiac arrest, 11 received an ICD (2%), and seven (1.3%) died of sudden cardiac death."The most important finding of this study is that, although major adverse cardiac events before the age of 18 years affected a significant proportion of patients, the rate of sudden cardiac death was low," the study authors emphasized.According to the study, the risk of experiencing a serious cardiac event was higher in patients with the LQT3 genetic form (HR 2.5, 95% CI 1.1–5.6), in those with a prior syncope (HR 3.0, 95% CI 1.7–5.5), in those not taking medication (HR 9.5, 95% CI 5.3–17.3), and in those with a very prolonged QT interval of more than 500 ms (HR 2.9, 95% CI 1.4–6.3).In patients with both LQT3 and LQT2 forms, the presence of a genetic mutation in the pore region of the KCNH2 gene and a younger age at diagnosis were risk factors identified in subanalyses. The risk of experiencing a serious cardiac event was virtually zero in patients identified by screening or incidental electrocardiogram.While international registries on LQTS existed, data on patients under 18 years of age remained scarce. The authors hope that the risk factors identified in this study will help optimize individualized clinical management of patients and reduce serious adverse events.Reference: Lea Lippert, Tobias Burkard, Franziska Markel, et al., Long QT syndrome in children and adolescents: risk factors and outcomes in a large German cohort, European Heart Journal, 2025;, ehaf365, https://doi.org/10.1093/eurheartj/ehaf365This article has been translated from its original French and first appeared on our sister site Profession Santé.

Which children are at high risk for long QT syndrome?

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