Estimation of the Very Low Frequency Components in Heart Rate Variability During Hemodiafiltration

Abstract

Heart rate variability (HRV) has been used to indirectly assess and study the autonomic nervous system (ANS). For the analysis of HRV, two different time windows are recommended. For certain physiological conditions, neither of the standard time windows are appropriate for evaluating the very low frequency (VLF) band of HRV. In this work, we evaluate HRV using two different time windows, one of 5 min and the other of 50 min. Analyses were conducted in both the time and frequency domains, with an emphasis on VLF content. Ten patients with chronic kidney disease participated in this study. The electrocardiogram signal was measured during their hemodialysis therapy. Time domain parameters such as the mean heart rate, mean R-R intervals, standard deviation of normal-to-normal intervals (SDNN), and root mean square of standard deviations (RMSSD) are reported, along with frequency domain parameters such as mean power of the very low frequency (VLF), low frequency (LF) and high frequency (HF) bands, as well as the LF/HF ratio. Significant differences were found in the SDNN for 5 min as compared to 50 min (41.13 ± 5.40 ms, 52.85 ± 2.63 ms, p < 0.000), and the VLF power spectra for 5 and 50 min were 1271.54 ± 406.52 ms2 and 1561.99 ± 170.62 ms2 (p = 0.02), respectively.