Abstracts

Rationale: Vagus nerve stimulation was approved in 1997 for medically refractory focal epilepsy in patients aged >12 years old. Potential side effects include dysphonia (voice alteration), sore throat, headache, dyspnea, dyspnea on exertion, dysphagia, infection, nerve injury, or arrhythmia. Bradyarrhythmias and even asystole have been reported in adults, but not in children. Methods: Pediatric case analysis was performed with concomitant literature review. Results: A 13 year old female with mitochondrial disease due to respiratory chain complex I deficiency developed medically refractory focal epilepsy. She was seen as a second opinion after failing multiple anti-seizure medications, hemispherectomy (suspected Rasmussen's), and ketogenic diet all at an outside institution. Concomitant anti-seizure medications included Levetiracetam, Clobazam, Zonisamide, and intermittent IVIG infusions. VNS (model type 105) was placed (05/2014) with settings optimized over 16 months: normal mode current 2.25mA, signal frequency 30Hz, pulse width 250usec, On time 30sec, Off time 0.8min, Magnet Current 2.50mA, Magnet on time 60sec, and Magnet pulse width 500usec. There was no history of arrhythmia prior to insertion of VNS or in the immediate post-operative period. Pediatric Cardiology confirmed sinus bradycardia without any conduction blocks via Holter monitor (02/2015). This evolved to second degree heart block ( < 6 seconds of non-conducted P waves after an episode of Wenckebach phenomenon, 09/2015) and later first degree heart block was observed (11/2015). As a result, VNS was turned off. Her ECG and intervals normalized on follow-up 30 day event recorder (12/2015). Whether the VNS exacerbated underlying, primary bradycardia/heart block due to mitochondrial disease progression or if the heart block was only secondary to VNS stimulation is unclear. In 6 months follow-up, she had increased seizures and worsened mental status since the VNS was turned off suggesting VNS was an effective therapy for the epilepsy. However, the improved cardiac rhythm suggests VNS stimulation at the minimum potentiated underlying mitochondrial cardiac dysfunction and resulted in heart block, rather than heart block developed simply due to isolated mitochondrial cardiac disease progression. Late onset asystole (12 months post-VNS placement) has been reported (Iriarte et al., 2009). It was previously reported that restarting VNS at baseline current, after a six week off period after AV block was detected, did not eliminate the recurrence of AV block (Shankar et al., 2012). Vagally induced bradyarrhythmia has been reported to correlate with vagus nerve stimulation periods in adults over 2 years after VNS implantation (Amark et al., 2007). Conclusions: Patient populations, especially those in pediatrics, who are high-risk for heart block, should understand this risk before VNS insertion, especially regarding potential cardiac manifestations. We recommend regular EKG screening intervals, annually or as clinically indicated, in such high risk patients. Funding: N/a