QT Variability Index is Correlated with Autonomic Nerve Activity in Healthy Children

Hirofumi Kusuki,Shota Oikawa,Hidetoshi Uchida,Yumi Kiriyanagi,Tadayoshi Hata,Miki Nishio,Tsuneaki Sadanaga,Yuka Tsuchiya,Arisa Kojima,Kazuyoshi Saito,Rina Nagata,Namiko Kojima,Yuri Mizutani,Kayo Horio

doi:10.1007/s00246-020-02399-8

Abstract

The QT variability index (QTVI), which measures the instability of myocardial repolarization, is usually calculated from a single electrocardiogram (ECG) recording and can be easily applied in children. It is well known that frequency analysis of heart rate variability (HRV) can detect autonomic balance, but it is not clear whether QTVI is correlated with autonomic tone. Therefore, we evaluated the association between QTVI and HRV to elucidate whether QTVI is correlated with autonomic nerve activity. Apparently, healthy 320 children aged 0–7 years who visited Fujita Health University Hospital for heart checkup examinations were included. The RR and QT intervals of 60 continuous heart beats were measured, and the QTVI was calculated using the formula of Berger et al. Frequency analysis of HRV, including the QTVI analysis region, was conducted for 2 min and the ratio of low-frequency (LF) components to high-frequency (HF) components (LF/HF) and HF/(LF + HF) ratio was calculated as indicators of autonomic nerve activity. Then, the correlations between QTVI and these parameters were assessed. QTVI showed a significant positive correlation with LF/HF ratio (r = 0.45, p < 0.001) and negative correlation with HF/(LF + HF) ratio (r = −0.429, p < 0.001). These correlations remained after adjustment for sex and age. QTVI, which is calculated from non-invasive ECG and can detect abnormal myocardial repolarization, is significantly correlated with frequency analysis of HRV parameters. QTVI reflects autonomic nerve balance in children.

Highlights

Instability of myocardial repolarization detected by the QT interval variability indicates a substrate that can induce lethal arrhythmias [1]
Adult patients with myocardial dysfunction exhibit high QT interval variability following the preceding cardiac cycle, and such increased QT variability may be an ominous sign of cardiac death [2]
The QT Variability Index (QTVI) is a non-invasive measure to assess repolarization liability that has been applied to a wide variety of subjects with cardiovascular disease [6]

Summary

Introduction

Instability of myocardial repolarization detected by the QT interval variability indicates a substrate that can induce lethal arrhythmias [1]. Adult patients with myocardial dysfunction exhibit high QT interval variability following the preceding cardiac cycle, and such increased QT variability may be an ominous sign of cardiac death [2]. Heart rate variability (HRV) calculated from the variations in the RR interval reflects autonomic nerve balance. Reduced HRV can predict the poor prognosis in patients with heart diseases [3, 4]. There were limited studies assessing the myocardial repolarization in children, and sufficient clinical applications have not been achieved. The QT Variability Index (QTVI) is a non-invasive measure to assess repolarization liability that has been applied to a wide variety of subjects with cardiovascular disease [6].

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Results

Conclusion