Status of Cardiac Autonomic Functions Among Hypertensive Children Identified by Ambulatory Blood Pressure Monitoring (ABPM): A Case-Control Study.

INTRODUCTION: Hypertension is no longer an adult-only disorder; it is increasingly seen in children and adolescents worldwide. Earlier, pediatric hypertension was mainly attributed to secondary causes, but recent evidence shows a rising prevalence of primary hypertension, largely driven by sedentary lifestyle, unhealthy diet, and increased screen time. Hypertension affects not only blood pressure levels but also cardiac autonomic function, disturbing the balance between sympathetic and parasympathetic activity. This study aimed to obtain objective evidence of altered autonomic function in hypertensive children. METHODS: It is a case-control study. Thirty hypertensive children diagnosed by 24-hour ambulatory blood pressure monitoring and 30 age-matched normotensive controls were included after ethical approval and informed consent/assent. Autonomic function was assessed using Ewing's battery tests and a five-minute heart rate variability recording. RESULTS: Hypertensive children had significantly higher BMI (p<0.001), body weight (p<0.001), systolic blood pressure (SBP; p<0.001), and diastolic blood pressure (DBP; p<0.001) compared to controls. They also showed a higher low-frequency/high-frequency (LF/HF) ratio, mean heart rate, and stress index (p<0.001), indicating increased sympathetic activity. In contrast, mean RR interval, total heart rate variability (HRV) power, pNN50, and triangular index (p<0.001) were significantly lower, reflecting reduced parasympathetic activity. A significant positive correlation was observed between BMI and the LF/HF ratio, and linear regression showed that for every 1 kg/m² increase in BMI, the LF/HF ratio increases by approximately 6-7%, suggesting that higher BMI is associated with greater sympathetic activity in hypertensive children. CONCLUSION: The findings indicate an early autonomic imbalance among pediatric hypertensives, which may contribute to future cardiovascular risks. It necessitates early screening of children as a routine for hypertension using ambulatory blood pressure monitoring.