Effects of posture on ventricular repolarization parameters in children with Long QT Syndrome and syncope history

INTRODUCTION: Syncope is a common benign symptom in childhood. Some life-threatening diseases may present with syncope in childhood. In children with syncope, it is critical to exclude a cause associated with ventricular arrhythmias or sudden death, such as long QT syndrome. Studies providing information about ventricular repolarization on ECG (QTc, QTd, QTcd, Tpe, Tpe/QT, Tpe/QTc) as a result of changes in body posture in children are limited. In our study, we aimed to investigate the effects of body posture on ventricular repolarization. MATERIALS/METHODS: Our study consisted of two volunteer study groups and one healthy control group. The study group included 37 patients with long QT syndrome aged 3-18 years who were admitted to Manisa Celal Bayar University Hafsa Sultan Hospital Pediatric Cardiology Polyclinic and İzmir Tepecik Training and Research Hospital Pediatric Cardiology Polyclinic between March 2023 and December 2023. The study group included 51 patients aged 3-18 years with syncope who were admitted to Manisa Celal Bayar University Hafsa Sultan Hospital Pediatric Cardiology Polyclinic between March 2023 and December 2023 and 51 healthy children aged 3-18 years as the control group. All patients included in the study underwent 12-lead ECG in three positions in the ECG room in the lying position, sitting position and standing position, respectively. Kta, PR, QRS, QT, QT, QTc, QTd, QTcd, Tpe, Tpe/QT, and Tpe/QTc were calculated. SPSS 21.0 program was used for statistical data analysis. RESULTS: Of the 37 patients with LQTS, 18 (48.6%) were male and 19 (51.4%) were female; of the 51 patients in the syncope group, 20 (39.2%) were male and 31 (60.8%) were female; and of the 51 patients in the control group, 25 (49.0%) were male and 26 (51.0%) were female. In our study, 29 (20.86%) of the LQTS patients were on beta blockers and there was no history of drug use in the other groups. When ECG parameters of LQTS, syncope and healthy control group patients in lying, sitting and standing positions were compared, an increase was observed in kta, QTc, Tpe, Tpe/QT, Tpe/QT, Tpe/QTc values with position in all groups. Statistically significant differences were found in QTc, Tpe/QT in both lying, sitting and standing ECGs in LQTS children compared to controls. No statistically significant difference was found in Tpe, Tpe/QTc between the groups. In the other parameters QTd, QTcd, the increase with positional change was not significant in all groups and there was no statistically significant difference. There was a shortening in the QT interval from lying to sitting and standing positions in all groups. CONCLUSION: There is an increase with position in kta, QTc, Tpe, Tpe/QT, Tpe/QTc values, which give us information about ventricular repolarization measured on the ECG during changes in body posture. This increase is more pronounced especially in LQTS patients. Therefore, analyzes of outpatient testing with other assessments may be valuable in diagnosing patients who may benefit from genetic screening by offering practical and accessible treatment through clinical methods. This study emphasizes the importance of ECG evaluation in different body positions for a comprehensive evaluation of LQTS in pediatric syncope cases. KEY WORDS: Long QT syndrome, syncope, body posture, standing test, electrocardiography, ventricular repolarization, QTc