Cardiac Autonomic Modulation in Seizure Disorders With and Without Interictal Epileptiform Discharges: A Retrospective Heart Rate Variability Analysis Using Archived Digital EEG Recordings

Background Cardiac autonomic dysfunction is increasingly recognized in epilepsy and has been implicated in cardiovascular complications and sudden unexpected death in epilepsy (SUDEP). Heart rate variability (HRV) provides a non-invasive measure of cardiac autonomic modulation; however, the influence of interictal epileptiform discharges (IEDs) on resting HRV remains uncertain. This study compared HRV among patients with seizure disorders with and without IEDs and a non-seizure neurological comparison group using ECG signals extracted from archived routine electroencephalography (EEG) recordings. Methods This retrospective observational study included 45 adults (15 per group): seizure disorder with IEDs, seizure disorder without IEDs, and non-seizure neurological complaints. A stable, artifact-free five-minute lead II ECG segment was extracted from archived digital EEG recordings after completion of activation procedures. Short-term HRV analysis was performed using LabChart Pro (ADInstruments, Dunedin, New Zealand) and included time-domain, frequency-domain, and nonlinear parameters. Groups were compared using one-way ANOVA or the Kruskal-Wallis test, with appropriate post hoc analyses. Results Demographic characteristics were comparable across the three groups. pNN50 differed significantly among the groups (F(2,42) = 5.127, p = 0.010), with higher values in the non-seizure group than in both seizure groups. Total power (F(2,42) = 3.353, p = 0.045) and high-frequency (HF) power (F(2,42) = 3.905, p = 0.028) also differed significantly, with post hoc differences observed between the non-seizure comparison group and the seizure without IED and seizure with IED groups, respectively. No significant differences were observed in LF power, LF/HF ratio, or nonlinear HRV indices. No HRV parameter differed significantly between the two seizure groups. Conclusions Patients with seizure disorders demonstrated lower vagally mediated HRV than the non-seizure neurological comparison group, whereas the presence of IEDs was not associated with measurable additional alterations in resting cardiac autonomic modulation.