Effect of Defibrillation on the Performance of an Implantable Vagus Nerve Stimulation System

Abstract

Background Vagus Nerve Stimulation delivers Autonomic Regulation Therapy (ART) for heart failure (HF), and in a pilot study has been associated with improvement in heart rate, heart rate variability, left ventricular function, 6-minute walk distance, NYHA class, and quality of life. VNS is delivered using an implantable pulse generator (IPG) and a lead placed around the cervical vagus nerve. Because patients with HF may receive concomitant cardiac defibrillation therapy, testing was conducted to determine the effect of defibrillation (DF) upon the VNS system. Methods DF testing was conducted on three Model 103 IPGs, which have identical hardware to the VITARIA™ system used to deliver ART for HF. DF testing evaluated whether DF had any permanent effects on the VNS system, and that programmed software settings and data capture were recoverable through reprogramming. Testing was conducted according to the methodology specified in the international standard ISO 14708-1 for active implantable medical devices. All of the testing equipment was verified to be in proper working order with current calibration. Each IPG was connected to a defibrillation pulse generator (MegaPulse Defib) and subjected to a series of voltage spikes, monophasic pulses, and biphasic pulses. The pulse amplitude was 140 V, and was connected to the device through a 300 Ω resistor. For each application of energy, three positive-polarity pulses were delivered 20 seconds apart, followed by a 60-second pause, and three negative-polarity pulses 20 seconds apart (Figure). Results The specified series of high-energy pulses were successfully delivered to each of the three devices. All three IPGs passed the electrical tests, and interrogation confirmed that software and data were unchanged from the pre-programmed values. No shifts in parameters or failures were observed. Conclusions Implantable VNS systems equivalent to VITARIA were tested for immunity to defibrillation, and were found to be unaffected by a series of high-energy defibrillation pulses. These results suggest that this VNS system can be used safely and continue to function after patients have been defibrillated.