Abstracts

We studied the changes related to cardiac rhythm in patients with generalized tonic-clonic seizures (GTCS) as it relates to episodes of apnea and during the motor and premotor phase of the seizure. Patients in the epilepsy monitoring unit were recruited if they experienced a GTCS. We assessed the heart rate as well as the oxygen saturation in 24 GTCS experienced in 18 patients (2 bitemporal, 2 right temporal, 5 left temporal, 3 focal epilepsy not otherwise localizable, and 2 left hemisphere, 2 left frontal, and 2 primary generalized epilepsy). One of the 24 seizures was excluded because in this seizure we were unable to define the onset of the motor component. In three seizures the baseline heart rate was already in the tachycardic range (defined as [gt]90 beats/min). A significant heart rate escalation (tachycardic response TR) was defined as an escalation of heart rate response during a seizure that was higher than the baseline variability of the patient[apos]s interictal heart rate by a third (TR[gt] (interictal HR +1/3 interictal HR)). The slope of the tachycardic response was classified as a fast slope if the maximum heart rate value during the premotor component was achieved in less than 90 seconds and as slow slope if the time to get from baseline to peak was greater than this time. The time of peak hypoxemia was also determined for each seizure. A heart rate deceleration was defined as a drop in heart rate of more than 20bpm within the first minute after the peak hypoxemia (sat O2[lt] 80%). Of the 23 seizures analyzed, 18 (78%) showed a TR in the premotor phase. In this phase the maximum heart rate ranged from 62 to 155 beats/min. Sixteen out of 20 (80%) seizures achieved TR in the premotor phase. A fast slope TR was noted in 10 seizures, which include 5 seizures originating from the right temporal lobe, one seizure originating from the left temporal lobe and four extratemporal seizures. A slow slope response was seen in 7 seizures arising from left temporal lobe and three extratemporal seizures. A heart rate deceleration associated with hypoxemia was seen in 18 out of 24 seizures (75%). There was also a statistically higher variability in the heart rate in the postictal phase as compared to the preictal phase in 20 out of 24 seizures (83%). A TR in the premotor phase of GTCS occured frequently. We were able to demonstrate a difference in the morphology of the TR slope as it relates to the lateralization of the seizure focus in temporal lobe epilepsy. Rapid heart rate decelerations following the ictal tachycardia seem associated with the peak hypoxemia. There was a greater heart rate variability in the postical period as compared with the preictal period in GTCS. These findings may be related to central lateralization of autonomic control and might be speculated to contribute to the mechanisms involved in SUDEP.