We examined dynamic changes in an EKG marker of cardiac electrical instability, T-wave heterogeneity (TWH), prior to generalized tonic-clonic seizures (GTCs) to determine its capacity to act as a potential seizure predictor.  

In 6 patients admitted to the epilepsy monitoring unit for diagnosis, we analyzed dynamic changes in TWH assessed by second central moment analysis, interictally and ictally, in association with GTCS and psychogenic nonepileptic seizures (PNES) with specific focus on the hour just before seizure.

In 3 patients experiencing GTCs, there was a significant increase in TWH (from 1-hour baseline before seizure of 73±6.6 to 114±4.6 µV at 20 min (p<0.05) and to 131±8.0 µV (p<0.03) at 1 min prior to ictus, followed by an ictal peak of 193±6.7 µV (p<0.006).  By comparison, heart rate was not significantly elevated from 1-hour baseline (75±5.0 beats/min) to 20 min (78±5.6 beats/min, p<0.1) until 1 min prior to seizure (105±2.9 beats/min, p<0.04).  During seizure, heart rate increased to 163±9.7 beats/min (p<0.03).  In 3 patients with EEG-proven PNES, neither TWH nor heart rate was significantly elevated from 1-hour baseline prior to seizure, but both were mildly elevated during seizure (TWH: 51±4.0 to 80±0.9 µV, p<0.02; heart rate: 73±4.4 to 132±6.5 beats/min, p<0.03). 

This is the first study to evaluate dynamic changes in EKG heterogeneity in association with GTCs and to demonstrate that abnormalities are detected well before the electrographic onset of seizures.  Acute changes in TWH pre-ictally have the potential to become reliable predictors of impending GTCS in patients with refractory seizures and may play a key role in development of effective seizure warning systems.