Heart Rate Variability in 10 Year Old Children: Normal and Intrauterine Growth Restricted

Heart rate variability (HRV) analysis is a powerful non-invasive tool used to determine the state of the heart and assess the development of the Autonomic Nervous System (ANS). The reduced HRV has been associated with negative outcome of ANS. This work describes the results obtained by HRV analysis of two groups of children, 41 Intrauterine growth retarded (IUGR) and 34 normal for a period of 24 hours. The main objective of this work was to explore the autonomic control in IUGR children by performing HRV analysis and comparing the results with normal children to find differences in HRV at 10 years of age. Barker theory and hypothesis states that the IUGR can be prone to coronary heart diseases or hypertension in their adulthood. Signal processing was performed on the ECG signal (data) provided which included filtering and detecting the QRS to find the RR segments. In the time domain analysis many parameters were calculated for all 75 children. Several comparisons between IUGR and normal children groups using night time and one hour RR data collected at night using several variables were computed. Frequency domain analysis of RR has been performed by autoregressive model (AR) Fast Fourier Transform (FFT) after re-sampling RR data of all 75 children. Calculation of the frequency components, large frequency, high frequency, and ratio of LF/HF, were obtained using FFT, AR and Lomb periodogram. Statistical analyses were performed to compare between IUGR and normal children. Time and frequency analysis comparison between the two groups of children showed no significant statistical differences, but the analysis has shown significant difference when dividing IUGR into IUGR1 (< 2.5 kg) and IUGR2 (≥ 2.5 kg), and highlighted differences in Respiratory Sinus Arrhythmia (RSA) at night time. QT algorithm was developed to measure HR, QRS, ST and QT. It was found that QT for IUGR children is slightly higher than that of normal children. Using Poincaré plots, significant difference was found between female and male children. Females had low long term variability. The 24 hr and 15 min pre-wake HRV time domain and Frequency domain analysis showed that IUGR children have reduced HRV which is a marker of a negative outcome of the ANS.