Changes in a measure of cardiac vagal activity before and after epileptic seizures.

In previous studies of the relationship between the cardiac autonomic activity and seizures, assessment of autonomic changes has relied on alterations in heart rate or R-R intervals. We have used a recently developed continuous index of cardiac parasympathetic activity (CIPA) to examine 20 seizures in 10 patients during pre-surgical evaluation in a video-telemetry unit. The patients had localization related seizures due to non-progressive pathology and both complex partial seizures (CPS) and complex partial with secondary generalised tonic clonic seizures (STCS) were examined. Mean CIPA prior to the onset of STCS was elevated above normal values and fell significantly to previously established normal values following the seizure. CPS were not associated with elevated mean CIPA pre- or post-seizure. STCS were associated with a reduction in anti-convulsant dosage and with elevation of pre-ictal CIPA. We propose that elevation of cardiac parasympathetic activity pre-ictally may be a marker for secondary generalisation of seizures.