Abstracts

Rationale: Disturbances in cardiac rhythm including asystole, QT prolongation, tachyarrhythmias and bradycardia frequently occur in secondarily generalized tonic-clonic seizures. For these reasons, ictal/post-ictal arrhythmia has been proposed as one potential underlying cause of Sudden Unexplained Death in Epilepsy Patients (SUDEP). Despite the demonstrated influence of seizures on the heart, there is a paucity of data regarding mechanisms through which the brain controls heart rhythms and what specific regions of the brain are involved. Prior studies evaluating how these systems interconnected are limited by single ECG leads and scalp EEG recordings only.Methods: We have developed a novel method to perform simultaneous 12-lead ECG recordings and intracraial electrode recordings using the Nihon Kohden JE120A EEG with appropriate filtering (high-pass filter 0.5Hz, low-pass filter 100Hz, notch filter 60Hz), gain (10mm/mV), sweep speed (25mm/sec) and lead positioning. This system has been validated in comparison with General Electric MAC5500 ECGs machine on patients undergoing intracranial electrode monitoring for seizure localization (Figure 1). We placed 12-lead-ECG recording electrodes on five patients undergoing stereoelectroencephalography (sEEG) for seizure monitoring and they were continuously monitored throughout their hospitalization. The ECG data obtained during seizures was then correlated with sEEG electrode placement and anatomic regions of the brain that were found to be within the ictal onset zone or in the region of early spread. Intracranial electrode positioning was determined using postoperative MRI studies and all ECG data was read by an cardiologist trained in electrophysiology. Depth electrodes localization varied depending on the patient's clinical semiology but included insula, orbitofrontal, cingulate and mesial temporal structures.Results: Of the five sEEG patients that underwent continuous 12-lead ECG, one patient was found to have QTc prolongation during a seizure that arose from the right amygdala and right hippocampus (Figure 2). Seizures in the remaining patients did not demonstrate any rate or rhythm changes regardless of ictal onset zone. There were no complications associated with these patients and all five patients had ictal onset zones localized with sEEG implantation.Conclusions: The use of 12-lead ECG recordings combined with intracranial electrode monitoring is a novel and innovative means to evaluate the brain-heart axis and its contribution to SUDEP. Improving our understanding of the underlying mechanisms connecting these two systems is paramount to our ability to diagnose and prevent this fatal disease. Although causes for SUDEP are multifactorial, cardiac arrhythmias are thought to be a major contributor to this process and correlating intracranial monitoring and 12-lead ECG data will assist. Future studies will utilize intracranial stimulation to evaluate minute cardiac changes in other regions of the brain outside ictal onset zone.