# Holter study of heart rate variability in children and adolescents with long QT syndrome

## TL;DR

This study found that children with long QT syndrome have reduced heart rate variability at higher heart rates, suggesting abnormal autonomic responses that may increase arrhythmia risk during physical activity.

## Contribution

The study provides new insights into autonomic dysfunction in LQTS patients by analyzing heart rate variability across age groups and heart rate ranges.

## Key findings

- LQTS patients showed significantly lower low and high frequency HRV values at higher heart rates compared to healthy controls.
- Symptomatic LQTS patients aged 10–15 had lower total power at specific heart rate ranges than asymptomatic patients.
- LQT1 girls aged 10–18 had lower total power compared to boys in the same age groups.

## Abstract

This study aimed to retrospectively assess cardiac autonomic activity in children with LQTS, considering genotype, symptoms, sex, age, and beta‐blocker therapy (BB) and compare it to healthy controls.

Heart rate variability (HRV), using power spectrum analysis, was analyzed in 575 Holter recordings from 116 children with LQTS and in 69 healthy children. The data were categorized into four age‐groups and four heart rate (HR) ranges.

In LQT1 and LQT2, increasing HR corresponded to significantly lower low (LF) and high frequency (HF) compared to controls. Total power (PTOT) was lower in all LQT1 age‐groups compared to controls at HR 120–140 bpm (1–15 years: p < .01; 15–18 years: p = .03). At HR 80–100, LQT1 patients aged 1–10 years had lower HF than LQT2 patients (1–5 years: p = .05; 5–10 years: p = .02), and LQT2 patients aged 15–18 years had lower HF than LQT1 patients (p < .01). Symptomatic patients aged 10–15 years had lower PTOT at HR 100–120 bpm than asymptomatic patients (p = .04). LQT1 girls aged 10–15 and 15–18 years had a lower PTOT (10–15 years: p = .04; 15–18 years: p = .02) than boys.

This study shows a correlation between HR and changes in HRV parameters. At higher HRs, LQTS patients generally had lower HRV values than controls, suggesting an abnormal autonomic response. These results may strengthen the link between physical activity and arrhythmias in LQTS.

This study compared cardiac autonomic activity in 116 LQTS children to 69 healthy controls using 24‐h ECG recordings. Lower heart rate variability (HRV) values in LQTS patients were found at higher heart rates (HRs), indicating an abnormal autonomic response. This may strengthen the link between LQTS, physical activity, and arrhythmias.