Reproducible asystole following vagal nerve stimulator lead replacement: a case report

BACKGROUND: Vagal nerve stimulation (VNS) is approved therapy for the treatment of intractable epilepsy. The stimulation of either nerve, left or right, is effective. However, due to the anatomic and physiological effects of cardiac innervation, the right vagus nerve is typically avoided in order to minimize the risk of cardiac bradyarrhythmias. The location of the VNS lead contacts on the nerve can also have an effect, namely, more distally placed contacts have been associated with lower risk of cardiac arrhythmias, presumably by avoiding vagal cervical cardiac branches; however, our case demonstrates reproducible asystole despite left sided, distal VNS lead placement. CASE PRESENTATION: We report a 28-year-old male patient with pharmacoresistant generalized clonic-tonic seizures. The VNS therapy with 1.5 mA output and 16% duty cycle drastically reduced his seizure burden for several years. The breakthrough seizures along with stabbing pain episodes at the implantable pulse generator (IPG) site have prompted the VNS lead revision surgery with new lead contacts placed more caudally than the old contacts. However, the intraoperative device interrogation with 1 mA output resulted in immediate asystole for the duration of stimulation and it was reproducible until the output was decreased to 0.675 mA. CONCLUSIONS: Our case highlights the possibility of new severe cardiac bradyarrhythmias following surgical VNS lead replacements even in patients without preoperatively known clinical side effects. We suggest preoperative electrocardiography and cardiology consultation for detected abnormalities for all patients undergoing new VNS implantations, as well as revision surgeries for VNS malfunctions. Intraoperatively, the surgeon and anesthesia team should be vigilant of cardiac rhythms and prepared for the immediate management.