Objectives: Electrocardiography (ECG) with manual measurements of QT intervals for diagnosing long QT syndrome (LQTS), is burdened with inter-and intra-individual variation. Measurement of QT interval in a pediatric population is even more difficult. The aim of this study was to investigate if vectorcardiographic (VCG) recordings could determine the QT interval with high precision and predict LQTS in a pediatric population.
Methods: ECG and VCG were performed in a pediatric population consisting of 24 children with genetically characterized LQTS and 24 children matched for age and gender in pairs. Mean age was 8±4 years (1–15 y). The 12-lead ECG automatic measurement and interpreting of the QT interval corrected for heart rate (QTc) where performed with a Mac®5000 (GE Medical system), the VCG automatic measurement were assessed with Mida®1000 and CoroNet (Ortivus AB). One experienced observer with small intra-observer variability (1.3%) performed the manual measurements of QTc in lead II, V5 and V6. Bazett's formula was used for rate correction. QTc were categorized as normal
<440 ms, borderline 440-460 ms, prolonged >460 ms, QTc values categorized as borderline and prolonged QTc were counted as having LQTS.
Result: The number of diagnosed mutation-carriers and healthy controls with different electrographic methods are shown in the table below.
Conclusion: The VCG measurement of QTc seems to be a better predictor of LQTS in children than manual or automatic measurement and interpreting in scalar ECG. This will be further studied in larger series.