Effects of seizure repetition on postictal and interictal neurocardiac regulation in the rat
Naritoku DK, Casebeer DJ, and Darbin O (2003) Effects of seizure repetition on postictal and interictal neurocardiac regulation in the rat. Epilepsia 44:7 912–6.
Abstract: PURPOSE: Human epilepsy is associated with abnormalities in cardiac regulation, as measured by reductions of heart rate variability (HRV) and approximate entropy (ApEn), but it is not known how these abnormalities are related to seizure experience. METHODS: Baseline electrocardiogram (ECG) was recorded from seizure-naive rats. They were subjected daily to maximal electroshock (MES), which induced tonic seizures with hindlimb extension, for a total of 10 days. ECG was obtained for 30 min before and after the first and last seizure. R-R variability, spectral variability, and ApEn were calculated to determine changes in pre- and postictal cardiac regulation. Before the last seizure, interictal parameters were compared with baseline values to determine changes in interictal HRV as a consequence of seizure repetition. Postictal values obtained after the last seizure were compared with the initial postictal data to look for changes in postictal cardiac regulation. RESULTS: During the postictal state, a mild, but significant, loss of ApEn was present after either the first or last seizure. Seizure repetition induced loss of R-R variability and high-frequency spectral band, which was present both interictally and postictally. CONCLUSIONS: The results suggest that convulsive seizures are associated with an immediate reduction of the complexity of cardiac rhythm regulation, as reflected by reductions of ApEn. Seizure repetition may induce long-term neural abnormalities in neurocardiac regulatory systems, especially parasympathetic, which limit appropriate autonomic responses. These acquired abnormalities may, in turn, predispose individuals to cardiac arrhythmia and sudden unexpected death in epilepsy.
Keywords: Epilepsy, Seizures, Maximal electroshock, Heart rate variability, Approximate entropy, Cardiac arrhythmia, Sudden unexpected death in epilepsy (SUDEP)
- Animal study of heart-rate variability over time in rats that exposed to induced seizures over 10 days, with EKG recorded before and after the first and last seizures. After multiple sizures R- R variability decreased and parasympathetic input as assessed spectrally declined.