Background: Short QT (SQT) syndrome is a novel inherited arrhythmia characterized by a persistently SQT interval in the ECG. Some reports have claimed that a SQT interval in the ECG is associated with an increased risk of dying suddenly. However, little is known of the prevalence of SQT interval and its clinical significance in the general population. Especially, there is no report on this issue in young population. We sought to assess the prevalence and lethal arrhythmic risk of SQT interval in a young general population.
Methods & Results: QT intervals were measured from the ECGs of 29,531 children (15,143 males and 15,144 females) who were in 1st grade (6-7 years old) or 7th grade (12-13 years old) in a school health examination in Niigata city, Japan. Bazett’s method was used to correct the QT interval for heart rate (QTc). Cutoff values for SQT intervals were defined as 350ms (1st screening) and 330ms (further screening). The prevalence of QT interval <350ms was 0.38% (73 males and 38 females), and the prevalence of QTc <330ms was 0.017% (four males and one female). In addition, echocardiography, Holter ECG, treadmill test and face immersion test were performed in children with a QTc <330ms. There were no abnormal findings but persist SQT interval among children with a QTc <330ms.
Conclusion: SQT interval is rare in children, similarly to adults. Children with SQT interval had no abnormal finding but persist SQT interval, suggesting the risk for lethal arrhythmia may be low in children with SQT.