# Silent Signals: Analyzing Repolarization Heterogeneity and Autonomic Modulation in Children With Euthyroid Hashimoto’s Thyroiditis

## TL;DR

This study finds that children with euthyroid Hashimoto’s thyroiditis show signs of heart rhythm irregularities and autonomic imbalance, suggesting a need for closer cardiac monitoring.

## Contribution

The study introduces electrocardiographic markers to detect asymptomatic cardiovascular risks in children with euthyroid Hashimoto’s thyroiditis.

## Key findings

- Children with eHT showed significantly longer P max, Pd, QT intervals, QTd, and Tp-e intervals compared to controls.
- Reduced HRV time-domain parameters in eHT patients indicate autonomic imbalance.
- A Pd of 51 ms predicted eHT with 67% sensitivity and 72% specificity.

## Abstract

Background: Hashimoto's thyroiditis is the most prevalent autoimmune thyroid condition in children, typically appearing in a euthyroid state. The cardiovascular impact of euthyroid Hashimoto’s thyroiditis (eHT) remains poorly understood, especially regarding its connection to arrhythmias and autonomic dysfunction. This study aimed to evaluate electrocardiographic markers of repolarization inhomogeneity (P-wave dispersion (Pd), QT dispersion (QTd), and peak-to-end interval of the T-wave (Tp-e)) as well as heart rate variability (HRV) in children with eHT to assess the asymptomatic cardiovascular effects that may predispose them to future arrhythmias.

Materials and methods: This retrospective analysis involved 67 patients and 50 healthy controls. Patients were evaluated for anthropometric and biochemical parameters, electrocardiogram (ECG) results, echocardiographic findings, and 24-hour Holter monitoring. ECG parameters were measured and analyzed for repolarization indices, while HRV was assessed using time-domain and frequency-domain analyses.

Results: Patients exhibited significantly longer P max, Pd, QT intervals, QTd, and Tp-e intervals than the controls (all p < 0.001). A receiver operating characteristic analysis indicated that a Pd of 51 ms predicted the disease with 67% sensitivity and 72% specificity (area under the curve: 0.733, p = 0.001, 95% CI: 0.643-0.823). Time-domain HRV parameters (SD of all normal-to-normal intervals and SD of all the five-minute normal-to-normal intervals) were significantly lower in eHT patients, indicating an autonomic imbalance. At the same time, frequency-domain analyses revealed no significant differences.

Conclusions: Children with eHT exhibit increased myocardial repolarization heterogeneity and reduced HRV, indicating a potential risk for arrhythmias. These findings highlight the necessity of regular cardiac symptom inquiry and ECG controls in the follow-up of these patients, considering both thyroid function and underlying autoimmune processes. Further research is needed to clarify the long-term cardiovascular risks of eHT in children.