Heart rate variability in cyclic alternating pattern during sleep in healthy and Nocturnal Front Lobe Epilepsy patients

The aim of this paper is to assess heart rate variability (HRV) during the cyclic alternating pattern, which is a sleep phenomenon, composed by cortical events that interrupt the basal oscillation of the NREM sleep stage. These cortical events are called A-phases and classified into three subtypes: A1, A2, A3. In addition, a comparison between healthy and Nocturnal Front Lobe Epilepsy (NFLE) patients was carried out. HRV was assessed by means of a time-varying autoregressive (TVAR) model with an adaptive filtering prediction scheme and by the time-varying square root of the mean of the sum of the squares of differences (RMSSD) of the RR intervals. For each A-phase, two signal segments were evaluated, the first one before the onset of the A-phase and the second one after the onset of the A-phase. An increase in the sympathetic outflow was suggested by higher values of low-frequency (LF) power in the three A-phases after the onset of A-phases, where A3-phases showed the largest changes. Increases in LF power were related with increases in heart rate in the same signal segments. These differences were found in both healthy and NFLE patients. LF/HF ratio and normalized LF power in A1-phases resulted significantly higher in NFLE patients in comparison with healthy subjects, which could suggest that there is a shift in the sympatho-vagal balance towards a more sympathetically mediated control of heart rate involving A1-phases in NFLE patients.