Abstracts

Rationale: Sudden unexpected death in epilepsy (SUDEP) is a major cause of premature death with an incidence of 1 in 100 patient years in a population with intractable epilepsy. The underlying etiology of SUDEP is unknown and includes a cascade of events eventually leading to cardio-respiratory failure often in the context of a preceding generalized convulsion. Postictal generalized EEG suppression (PGES) > 50s after generalized convulsions has been recently described as a neurophysiologic marker of SUDEP. It is however unclear how the postictal suppression of brain activity affects cardiorespiratory function. In this study, we compare pre- to post-ictal heart rate (HR)variability after a generalized convulsion in patients with and without PGES of >50s to determine the impact of PGES on post-ictal autonomic function.Methods: We reviewed video EEG and EKG data from patients admitted to the Epilepsy Monitoring Unit at Northwestern Memorial Hospital for long term monitoring between January 2010 and April 2011, in whom generalized convulsions were recorded. Those with PGES >50s (N=8) were compared to a control group of those without PGES (N=8). Seizures with PGES <50s were excluded. Baseline demographic data were compared as well as baseline and post-ictal HR and seizure duration. The first recorded generalized seizure from each patient was included. HR variability was assessed using MATLAB software to analyze time and frequency domain EKG data from 2 minute periods of pre- and post-ictal recordings. Absolute and relative differences between the PGES and non-PGES populations were compared via unpaired 2 tailed t-tests.Results: There were no statistically significant differences in demographics, baseline HR or seizure duration between the populations. Patients with >50s of PGES were observed to have statistically significant increases in post-ictal HR (p=0.02), decreased mean RR interval (p=0.03), and decreased LF/HF ratio (p=0.02) when compared to generalized seizures without PGES. Data for post-ictal HR and LF/HF ratios are shown in figures 1 and 2, respectively.Conclusions: An increased postictal tachycardia has been previously described in patients who had died of SUDEP compared to controls. The similar finding in our study further supports the role of PGES as a marker of SUDEP. The reduced LF/HF ratio suggests that there is relative post-ictal loss of sympathetic input and/or increased parasympathetic drive. The latter is more likely given the sympathetic activation during a generalized convulsion. It is therefore conceivable that post-ictal suppression of brain activity leads to parasympathetic disinhibition which then contributes to cardiorespiratory instability.