Abstracts

Rationale: Over half of VNS Therapy^® patients report benefit from magnet activation (Morris, 2003), however, not all can use the magnet to deliver on-demand stimulation during a seizure due to cognitive impairment, sleep, lack of an aura, or the disabling effects of the seizure itself. AspireSR^TM VNS Therapy System can be programmed to activate stimulation upon detecting a predetermined pattern and magnitude of heart rate increase. Heart rate changes associated with seizures (ictal tachycardia) occurs in about two-thirds of seizures (Eggleston et al., 2014). The AspireSR™ VNS Therapy System received CE mark approval in February 2014 based on performance results from the E36 clinical trial (NCT01325623). Methods: In order to evaluate the performance and clinical outcomes for the Automatic Stimulation feature, Protocol E-37 (NCT01846741) is a prospective, unblinded, US multi-site pilot study designed to collect data on up to 20 implanted patients 12 years or older with a clinical diagnosis of drug-resistant epilepsy with partial onset seizures and a history of ictal tachycardia who were implanted with the AspireSR^TM VNS Therapy System and followed for up to 2 years. The seizure detection algorithm threshold for the Automatic Stimulation feature was programmed for each patient based on historical levels of ictal tachycardia ranging from 20-70% increase in heart rate over baseline. Ictal and non-ictal events were recorded during an Epilepsy Monitoring Unit (EMU) stay to evaluate algorithm performance including sensitivity, potential false positive rate per hour, and latency of detection. Clinical outcomes consistent with the benefits reported for magnet mode activation including seizure severity, duration, intensity and post-ictal duration were also assessed using video-EEG as well as validated physician questionnaires (NHS3; National Hospital Seizure Severity Scale) and patient reported scales (SSQ; Seizure Severity Questionnaire). Results: As of June 2014, 20 patients (ages 21-69) were implanted with the AspireSR^TM VNS Therapy system. The seizure detection algorithm threshold for the Automatic Stimulation feature was set to 70% in 6, 60% in 4, 50% in 7, 40% in 2, and 30% in 1 patient. During the EMU stay, a total of 83 seizures were recorded using concurrent vEEG and ECG: 54 simple partial, 15 complex partial, 8 subclinical, 4 other (e.g., unknown), 1 secondarily generalized, 1 non-epileptic. Typical VNS adverse events were reported, including dysphonia, sore throat, incision pain, GI symptoms. Conclusions: Long term follow-up for all subjects is underway. Algorithm performance, clinical outcome data and final safety data will be available at the time of the AES conference.