4102QT interval duration, long QT pattern and changes over time in children practicing sport

Abstract

Abstract Background Twelve-lead electrocardiogram (ECG) is an established tool in the evaluation of adult athletes, providing information about life-threatening cardiovascular diseases such as long-QT syndrome. However, changes induced by development challenge the interpretation of ECG in the paediatric population, particularly for the repolarisation phase. The aim of this prospective, longitudinal study was to determinate the distribution of QT interval in children practicing sport and to evaluate changes in QT duration during preadolescence. Methods A final population of 1473 children practising sport (mean age: 12.0±1.8 years, interval 7–15 years) was analysed. Each athlete was evaluated at baseline, mid-term and end of the study with a mean follow-up of 3±1 years. QT interval was corrected with Bazett (B) and Fridericia (F) formulae. Results At baseline QTcB was 412±25ms and QTcF 387±21ms, with no changes during follow-up. Ten children (0.68%) had an abnormal QTc. In children with QTc ≥480ms confirmed both by Bazett and Fridericia formulae, QT duration persisted abnormal during the follow-up and children were disqualified. Conversely, children with borderline QTc intervals (>460 and <480ms) were not disqualified and we found a normalization of QT interval during the development. Mean difference in the calculation of QT between the two formulae was 25±11ms, p<0.0001. For HR values higher than 80 bpm, the QTcF resulted with low fluctuations around the mean was independent from HR values. Conversely, the QTcB revealed significant growing trend as the HR increased and showed higher variability than Fridericia correction. Dynamic changes in QT interval duration Baseline Mid-term FU Long-term FU p value Intervallo QT 343±25 345±24* 346±25* <0.0001 RR (ms) 599±111 711±111* 721±119*^ <0.0001 QTc Bazett (ms) 412±25 (371–449) 411±25 (367–449) 409±25 (367–446) 0.10 QTc Fredericia (ms) 387±21 (355–418) 387±20 (353–419) 387±20 (353–418) 0.59 FU, follow up; *p<0.0001 vs. baseline; §p<0.0001 vs. mid-term FU; ^p<0.05 vs. mid-term FU. Conclusions QT duration does not change over time in children with normal duration. A minority of children has a QT ≥480ms; in these subjects QT interval remains prolonged during the follow-up. Conversely, in children with borderline QT, mid-term follow-up is useful to identify a normalization during the growth. Clinicians should take into account that the use of Bazett and Fridericia correction formulae is not interchangeable and that Fridericia formula should be preferred when resting HR is higher than 80 bpm.