Abstracts

Rationale: Rationale-Sudden unexpected death in epilepsy (SUDEP) affects 0.35 cases/1,000 person-years and is the most common epilepsy-related cause of death. As far as we know, there is no single risk factor common to all SUDEP, suggesting multiple mechanisms. Animal studies indicate that interictal discharges can affect the cardiac rate but this is not fully established in humans. If human interictal spikes are proven to affect heart rate variability, this may in turn provide further insight into the underlying mechanism in SUDEP. Methods: Methods-We reviewed 15 consecutive EEG's of adult patients with focal spike discharges (IEDs) electively admitted for prolonged video EEG monitoring from May 2008 to May 2010 using Nihon Kohden recording systems. Patients with known cardiac or pulmonary problems, or taking medications which control heart rate, were excluded. Patients with generalized epilepsy or below 18 years were also excluded. We looked at 20 epileptiform focal single spikes per patient and measured the RR intervals 4 seconds before, during, and 4 seconds after and compared them to the RR intervals similarly obtained in a control group. The control epoch always ended or began within 10 seconds before or after, respectively, the interictal spike epoch. This helped to select interictal and control epochs occurring in similar states. Results: RR intervals corresponding to the Interictal spike waves were found to be longer than the control group (p value=0.01), and heart rate variation before and after spikes was greater than in controls. These findings were not spike localization dependent. Conclusions: Conclusions- Interictal epileptiform activity is associated with heart rate variability. Although it is possible that an independent mechanism produces both the RR variability and interictal spikes, we believe RR variability results from direct cortical neural stimulation.