Congenital Long QT Syndrome in Children Identified by Family Screening

The diagnosis of congenital long-QT syndrome (LQTS) in the relatives (nonprobands) of index patients (probands) is increasing because of screening. This report documents the clinical courses and outcomes of nonproband pediatric patients with LQTS. All patients aged <18 years with LQTS were identified at 3 pediatric centers. Demographic data, personal and family histories, electrocardiographic data, and genetic diagnoses (if available) were obtained. Probands were defined as the first patients in their families diagnosed with LQTS and nonprobands as those diagnosed by screening. Of 144 patients with LQTS, 84 (58%) were nonprobands aged 6.5 ± 5.4 years with QTc intervals of 479 ± 34 ms. No nonproband presented with resuscitated sudden death, atrioventricular block, or ventricular arrhythmia, but 7 (8.3%) had histories of syncope at presentation. All nonproband patients were treated. During a follow-up period of 4.7 ± 3.9 years, there were no deaths in the nonproband group, but device implantation was performed in 13 (15%), 4 of whom had appropriate shocks. As expected, compared with probands, nonprobands were less symptomatic. Additionally, nonprobands were younger and had shorter QTc intervals. Although device implantation was more common in probands, there was no difference in appropriate implantable cardioverter-defibrillator shocks or mortality between the probands and their affected relatives. In conclusion, children are increasingly identified with LQTS as a result of family screening. Although phenotypic differences exist between probands and nonprobands, survival is excellent in the 2 groups with therapy. Appropriate implantable cardioverter-defibrillator discharges in the nonproband group underscore the importance of follow-up in this relatively asymptomatic population.