Abstracts

Rationale: The AspireSR® Vagal Nerve Stimulator (VNS) provides responsive neurostimulation based on detection of heart rate increases that may be associated with seizures. A published review of early experience with the device reported that 41% of seizures were stimulated within ± 2 minutes of seizure onset. This device has been in use at UT Southwestern Medical Center, in the Comprehensive Epilepsy Center at Children’s Medical Center Dallas, since 2015. The center’s clinical experience was reviewed to determine how often the VNS detected heart rate change and delivered an autostimulation at the time of a clinical seizures Methods: Patients with pharmacoresistant epilepsy treated with VNS devices at the Comprehensive Epilepsy Center at Children’s Medical Center Dallas have their VNS interrogated routinely at each outpatient clinic visit. For those with VNS AspireSR® with activated autostimulation settings, this interrogation includes downloading and reviewing data for recent magnet activations. Caregivers are counseled to use the magnet for each seizure when possible so that events can be reviewed to determine if there was an associated autostimulation. Downloaded data from patients were reviewed to determine the frequency with which the device appeared to detect and respond to clinical seizures in this population of pediatric patients. Results: Data was reviewed for 8 patients treated with VNS AspireSR® with activated autostimulation settings. A total of 93 seizures, identified by magnet activation, had available data downloaded for review at the time of the office visit. 36/93 seizures had evidence of an autostimulation delivered during the 4 minute interval beginning 2 minutes preceding the magnet activation and ending 2 minutes after activation. Of these seizures, 25/93 had autostimulation prior to magnet activation and 11/93 following activation. In one patient there was a consistent pattern of autostimulation following magnet swipe in 6/13 seizures, accounting for many of the late activations. This raises the possibility that for this child, the heart rate increase could have been provoked by the magnet activation. Patients with a higher average number of autostimulations per day tended to have a higher percentage of seizures associated with autostimulation, suggesting that greater sensitivity to tachycardia at baseline increases the likelihood of autostimulation with seizure. In patients where complete data was available, the percentage of seizures with associated autostimulation was significantly higher (p < 0.001) than would be expected by chance based on the average number of autostimulations delivered per day. Conclusions: Retrospective review of experience with the AspireSR® Vagal Nerve Stimulator in an outpatient pediatric epilepsy clinic shows a significant association between autostimulation delivery and clinical seizures. In routine clinical use, the device appears to detect and respond to 39% of clinical seizures, consistent with results from an earlier prospective study. In most patients the autostimulation preceded the magnet activation, indicating that even if the seizure had gone unrecognized by the caregiver, the VNS would have provided an autostimulation. The results of this clinical review cannot determine the percentage of seizures without magnet activation which are associated with autostimulation. Further investigation is ongoing to evaluate the association between seizure type and likelihood of tachycardia detection, and the impact of this heart-rate responsive VNS therapy on clinical seizure frequency and severity. Funding: None