Abnormal heart rate variability during non-REM sleep and postictal generalized EEG suppression in focal epilepsy

To identify any relationship between abnormal interictal heart rate variability (HRV) during sleep and the occurrence of postictal generalized EEG suppression (PGES), a potential biomarker of sudden unexpected death in epilepsy (SUDEP), in patients with focal epilepsy.

We retrospectively reviewed 34 consecutive patients with focal epilepsy, who presented with focal to bilateral tonic-clonic seizures (FBTCSs), 19 with PGES (PGES+) and 15 without PGES (PGES-), and 14 patients without epilepsy as controls. HRV spectrum analysis was performed for periods of 10 minutes during wakefulness, non-REM sleep, and REM sleep. HRV spectra consisted of high frequency (HF) and low frequency (LF) regions. Normalized HF representing parasympathetic activities and normalized LF were compared between the PGES+, PGES-, and control groups for each sleep stage.

The PGES+ group showed significantly decreased normalized HF and increased normalized LF during non-REM sleep compared to the PGES- (P < 0.05) and control (P < 0.01) groups, but not during wakefulness or REM sleep.

Abnormal interictal HRV during non-REM sleep, indicating abnormally decreased parasympathetic activities, was associated with PGES in patients with FBTCS.

This study proposes to further investigate the relation between decreased parasympathetic activities and PGES.