Abstracts

Rationale: Autonomic dysfunction with seizures and its role in SUDEP (Sudden Unexpected Death in Epilepsy) is of increasing interest. Heart rate variability (HRV), or fluctuations in the instantaneous heart rate (HR), is a noninvasive measure of the sympathetic-parasympathetic balance of the autonomic nervous system. We studied autonomic changes with focal seizures in children by examining HR and HRV. Methods: An IRB-approved retrospective study was conducted of all patients (≤ 19 years) who were admitted in the Epilepsy Monitoring Unit at Rainbow Babies and Children’s Hospital in Cleveland, OH from January - December 2006. An automated algorithm identified QRS complexes to measure HR from the one-channel ECG accompanying the EEG record. Time and frequency domain spectral analysis was used to generate an image depicting the intensity of High Frequency (HF: 0.15-0.40 Hz) and Low Frequency (LF: 0.04-0.15 Hz) components of HRV. The instantaneous HR vs time time and supporting spectral data was then visually analyzed. Results: Of the 275 pediatric patients with VEEG, 222 were excluded because of normal EEGs, generalized seizures, only interictal or non-epileptiform events, and/or excessive artifact or poor HR detection by original ECG recording. We studied the remaining 53 patients (mean 7 years, 0-19 years old) of whom 26 were males and 27 females. Eleven (21%) had history of prematurity. Mean seizure years was 4.8 (0-17.3).Thirty five (66%) were on seizure medications. A total of 819 seizures were analyzed. The median number of seizures per patient was 9 (1 - 101). 19 (36%) patients had definitive extratemporal lateralization on EEG. The remainder showed seizure onset from either hemisphere. Data is summarized in Table 1 and Figure1. For analysis, the outcome (increase, decrease, no change) for HR and HRV components was converted to an index for all seizures in each patient. Odds ratios were generated using mixed models in order to account for within-patient correlation due to unequal numbers of seizures per patient. If there was an increase in FF, HR decrease was 37 times more likely. If FF decreased, an increase in HR was 22 times more likely and a decrease in HR was 67% less likely. If FF or SF showed no change, HR was also 22 times more likely to show no change. Age, prematurity, number of seizure-years, number of seizure medications, MRI or scalp EEG lateralization did not significantly impact HR or HRV. Conclusions: Consistent with previous publications on adults, our study in children shows a predominance trend of increase in ictal HR implying that seizure involvement on scalp EEG of presumed extra-temporal involvement does not dictate HR change. Though an individual patient may show a particular trend for HR change, some seizures in the same patient may be accompanied by the opposite trend or no change in HR.