Abstract
Fundamental to the potential utilisation of heart rate variability (HRV) indices as a prognostic tool is the reproducibility of these measures. The purpose of the present study was therefore to investigate the reproducibility of 24-hour derived HRV indices in a clinical paediatric population. Eighteen children (10 boys; 12.4 ± 2.8 years) with mild to moderate Cystic Fibrosis (CF; FVC: 83 ± 12% predicted; FEV1: 80 ± 9% predicted) and eighteen age- and sex-matched controls (10 boys; 12.5 ± 2.7 years) wore a combined ECG and accelerometer for two consecutive days. Standard time and frequency domain indices of HRV were subsequently derived. Reproducibility was assessed by Bland-Altman plots, 95% limits of agreement and intra-class correlation coefficients (ICC). In both groups, there was no systematic difference between days, with the variables demonstrating a symmetrical, homoscedastic distribution around the zero line. The time domain parameters demonstrated a good to excellent reproducibility irrespective of the population considered (ICC: 0.56 to 0.86). In contrast, whilst the frequency domain parameters similarly showed excellent reproducibility in the healthy children (ICC: 0.70 to 0.96), the majority of the frequency domain parameters illustrated a poor to moderate reproducibility in those with CF (ICC: 0.22 to 0.43). The exceptions to this trend were the normalised LF and HF components which were associated with a good to excellent reproducibility. These findings thereby support the utilisation of time and relative frequency domain HRV indices as a prognostic tool in children with CF. Furthermore, the present results highlight the excellent reproducibility of HRV in healthy children, indicating that this may be a useful tool to assess intervention effectiveness in this population.
Highlights
Cystic fibrosis (CF) is a complex genetic disease, affecting multiple organs through the disruption of the CF transmembrane conductance regulator protein
In both children with and without CF, the time domain parameters of the heart rate variability (HRV) did not demonstrate a skewed distribution according to the Shapiro-Wilks test (P > 0.05), the VLF, Low frequency (LF) and high frequency (HF) indices demonstrated a significantly skewed distribution (P < 0.05)
The primary purpose of the present study was to determine the reproducibility of HRV indices derived from consecutive 24 hour measurement periods in children with CF compared to ageand sex-matched controls
Summary
Cystic fibrosis (CF) is a complex genetic disease, affecting multiple organs through the disruption of the CF transmembrane conductance regulator protein. In addition to its clinical presentation, there is a growing body of evidence of concomitant autonomic neuropathy in CF. Abnormal HRV has been reported in both children [8] and adults [9] with CF, providing further evidence of autonomic neuropathy in this population. A significant correlation was present between HRV and disease severity in the adult study only. Whilst these discrepancies may be largely attributable to the pathological progression of the disease and the desensitisation of the β-adrenergic receptors consequent to chronic β-adrenergic agonist use, methodological explanations cannot be precluded, such as differences in the conditions under which HRV was derived (pre/post exercise vs supine rest). Despite the potential clinical significance, the applicability of such findings to, and the reproducibility of HRV in, children with CF is presently unclear
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