Abstracts

Rationale: Sudden unexpected death in epilepsy (SUDEP) is an important cause of mortality for patients with refractory epilepsy, with lifetime SUDEP risk of 35%. It accounts for almost 8-17% of deaths in patients with epilepsy with an annual incidence of 1.2 per 1000 person in adults. SUDEP is known to be associated with a history of convulsive seizures. Other markers identified in SUDEP patients include postictal electroencephalographic suppression (PGES), reduced interictal heart rate variability (HRV, or RMSSD, root mean square of successive differences between RR-intervals), and QT-prolongation (QTcB, or corrected QT-interval, Bazett formula). The objective of our retrospective case-control study is to analyze the subsequent EEG & ECG changes in people with SUDEP. Assuming that SUDEP is due to progressive seizure-induced brainstem injury due to recurrent convulsive seizures, we expect PGES to increase in duration, interictal HRV to decrease, and interictal heart rate (HR) and QTc intervals to stay the same.  Methods: Four cases of SUDEP (mean age at death 45 years) were identified with more than one EMU admission, at least 4 years apart. Duration of the convulsions, PGES duration, as well as sleep-related interictal QTc-intervals, HR, and HRV were compared between video-EEG evaluations in the SUDEP cases to two epileptic, non-SUDEP, age- and gender-matched controls. Results: During serial EEG comparison, we have found an average mean duration of convulsive period 104.2 sec in SUDEP group compared to 62 sec and the duration of GPES is 49.6 sec compared to 10 sec in control group. Also, in SUDEP group the duration of the convulsive period (48%) compared to control where the GPES is shorter (16%). Also, serial EEG analysis showed prolonged convulsive periods in SUDEP patients from 90 seconds to 114 seconds. Postictally, we observed abnormalities in ECG morphology, including PVCs, mild-T inversion, irregularly irregular HR and periods of asystole in 3 of 4 SUDEP cases, and none in the control group. While HR and QTc intervals were similar between SUDEP and non-SUDEP cases, HRV was decreased in 3 of 4 SUDEP cases at baseline but did not decrease progressively over time. Conclusions: While seizures are associated with autonomic and respiratory dysfunction, HRV did not appear to track the duration of the convulsions or PGES, which seem to increase over time. Nonetheless, HRV was lower in the SUDEP group but did not seem to progress, reflecting autonomic changes related to chronic brainstem dysfunction. Larger patient samples need to be studied, with a more rigorous evaluation of interictal HRV in both awake and sleep states. Funding: No funding