PO 168 Exploring the central autonomic network: effects of anterior cingulate stimulation on heart rate variability

Abstract

Introduction/Background: Drug-resistant epilepsy (DRE) is frequently associated with autonomic dysregulation. Heart rate variability (HRV), which reflects the balance between sympathetic and parasympathetic activity in the heart, is often decreased and therefore shifted towards sympathetic dominance. One of the key parts of the central autonomic network is the anterior cingulum, but its role is not fully understood. This study aims to elucidate the physiological effects of direct electrical cortical stimulation (CS) of the anterior cingulum on HRV in people with epilepsy (PWE) undergoing intracranial EEG to determine surgical candidacy. Method(s): We conducted a retrospective analysis of HRV in 44 PWE undergoing CS of the anterior cingulum, with stimulation of other brain regions not involved in the autonomic network serving as controls. CS was performed using bipolar stimulation with up to 5-s trains of 50 Hz biphasic square wave pulses (500 ms width), starting at 0.5 mA and increasing stepwise to a maximum of 7 mA. HRV parameters clearly associated with parasympathetic tone (RMSSD, HF) and others (LF, LF/HF) were measured at baseline (before any cortical stimulation), during anterior cingulum stimulation, and in its immediate pre- and post-stimulation periods. The Wilcoxon signed-rank test was used to assess changes in HRV parameters between conditions. Result(s): Data from 38 patients were analyzed. Significant increases during stimulation compared to pre-stimulation period were observed in RMSSD from 3.00 ms [IQR 2.72-3.23] to 3.42 ms [IQR 2.89-4.37], (p = 0.001), HF power from 4.37 ms² [IQR 3.41-5.10] to 4.97 ms² [IQR 3.90-6.52], (p = 0.003), and LF power from 5.24 ms² [IQR 4.16-5.98] to 6.10 ms² [IQR 4.89-6.95] (p < 0.001), with all values returning to baseline post-stimulation. When comparing baseline to stimulation periods, only HF showed a significant increase (p = 0.045), while other parameters remained unchanged (see image 1). Heart rate mean remained stable from baseline to post-stimulation. Conclusion(s): Cortical stimulation of the anterior cingulum induces a transient shift towards parasympathetic dominance, as evidenced by increased HRV, but without sustained changes. This highlights its role in modulating cardiac dynamics. Limitations include the brief stimulation periods and potential influence from prior stimulation of other regions. Future studies will be needed to confirm these findings. Copyright © 2025