Evaluation of interaction between a spinal cord stimulator and implanted cardioverter-defibrillator in a swine model

Spinal cord stimulators (SCS) have been used for many years to treat a myriad of chronic pain conditions using electrical signals to diminish the perception of a painful stimulus. Because of the electrical nature of the devices, there is a concern about the potential for electromagnetic interaction between the device and lifesaving cardiac implantable cardioverters-defibrillators (ICVD).

The purpose of this study was to use a swine model to evaluate the potential for interaction between an implanted SCS and ICVD using the closest possible proximity, highest stimulation settings, and most sensitive ICVD settings.

A pig was anesthetized and subsequently an ICVD and ICVD lead (Cogni 100-D and Endotak Reliance®, Boston Scientific, Natick, MA) were placed into the right prepectoral region and the right ventricle, respectively. An SCS (50 cm linear ST Precision Plu octad electrode lead [Boston Scientific, Valencia, CA] with 3 mm wide contacts spaced one mm apart- ) was implanted using fluoroscopic guidance into the posterior epidural space. Remote interrogation and programming of the ICVD were performed while the SCS lead was placed in as close proximity as possible, using fluoroscopy to guide the final position of the SCS electrode. After confirming that both systems were working, appropriately 9 stimulating configurations of varying current, pulse width, and frequency, including maximal settings, were delivered through the SCS. The effects on the ICVD were recorded at 2 sensitivity settings.

None of the tested SCS configurations caused interference with the proper functioning of the ICVD.

The anatomical proximity of the posterior epidural space and right ventricle of the swine is different from humans. While the entire pacer, including generator, was imbedded in a subcutaneous pocket, an implantable pulse generator for the SCS was not implanted, which did not allow us to study if any damage or a resetting of settings had occurred to the generator. Only one manufacturer was used in this study. Also, this study was performed in an anesthetized pig and the anatomical positions remained static. Realistically, changes in position of the devices would occur in patients who perform activities of daily living, and this can potentially shorten the distance between the 2 leads causing adverse interaction.

This study clearly demonstrated the feasibility of the 2 devices coexisting and functioning appropriately in an animal model using an ICVD and SCS donated by Boston Scientific. Further studies are needed to elucidate restrictions, optimal settings and parameters in a human setting.