Body mass index predicts ventricular repolarisation in obese children: differential effects across obesity levels

Childhood obesity is associated with cardiac electrical remodelling, yet the relationship between body mass index (BMI) and ventricular repolarisation (VR) heterogeneity remains incompletely characterised in paediatric obesity.

This prospective observational comparative study enrolled 184 children (112 obese, 72 normal-weight; age 8-17 years). Electrocardiographic analysis included traditional (QT, QTc, JT) and novel VR parameters (Tp-e interval, Tp-e/QT, Tp-e/QTc ratios). Multiple linear regression and receiver operating characteristic (ROC) analyses identified independent predictors and clinically applicable thresholds.

Obese children demonstrated significantly prolonged Tp-e intervals (87.83 ± 12.35 vs. 80.10 ± 16.80 ms, p = 0.002) and elevated Tp-e/QTcB ratios (0.211 ± 0.028 vs. 0.192 ± 0.034, p < 0.001). BMI emerged as the independent predictor of VR heterogeneity (β = 0.308, p < 0.001), after adjustment for insulin resistance, metabolic parameters, and echocardiographic findings. Regression analyses revealed differences in the BMI-repolarisation relationship: strong associations in normal-weight children (β = 0.353, p = 0.003), disappearing in established obesity (β = -0.041, p = 0.699), and a significant BMI × group interaction was observed (β = -2.079, p = 0.001). ROC analysis identified BMI ≥ 23.1 kg/m² as the optimal threshold for abnormal repolarisation (AUC = 0.682, sensitivity 76.1%, specificity 50.0%, p < 0.001).

Childhood obesity is associated with VR abnormalities independently of metabolic dysfunction and structural cardiac changes. This study suggests that repolarisation abnormalities occur in the early stages of obesity and through different pathophysiological mechanisms. The defined BMI threshold provides a clinically applicable tool for early risk stratification, highlighting the critical importance of intervention before obesity becomes established.