Introduction: Impedance changes over time, or “impedance drift”, in neuromodulation can influence the need for device reprogramming, lead revision, and battery replacement. Abnormal electrical impedance (AEI) has been understudied with respect to impact on sacral neuromodulation (SNM). This study assessed SNM longevity in individuals with and without AEI and its impact on revisions.
Methods: Patients with one or more SNM interrogations in the office were identified. Those implanted from 2003 to present were included. Follow-up within the first 10 years of device implantation was analyzed. Patients with AEI were identified as cases and the remaining patients who underwent device interrogation were controls. Time intervals collected included: implant to device interrogation encounter, device interrogation to revision, and original implant to revision. Revision included surgical interventions for the lead and/or pulse generator. Device longevity, or time from original implant to revision, was analyzed by Kaplan-Meier analysis.
Results: Of 710 patients with device interrogations, 132 (18.6%) were ‘cases’ and had an AEI within the first 10 years of follow-up (Figure 1A). Of these, 11 (1.5%) were short circuits (<50O) and 121 (17%) were open circuits (>4,000O). The remaining 578 patients were ‘controls’ and had normal impedances. Amongst patients with AEI, 41% (N=50/121) underwent revision, 58% (N=70/121) received device reprogramming, and 0.8% (N=1/121) pursued removal. Operative intervention was avoided in 54% (N=38/70) of the patients undergoing reprogramming. A 21% (N=121/578) revision rate was noted in the control group. Device longevity did not differ between cases and controls with regard to time from implant to revision (p=0.24, Figure 1 B). Interval from implant to device interrogation (AEI: 27.6 vs control: 23.3 months, p=0.16) nor interval from SNM interrogation to revision (AEI: 7.6 vs control: 9.8 months, p=0.24) differed between cases and controls. Cases with AEI that underwent reprogramming achieved a mean additional 17.3 months of device longevity prior to revision.
Conclusions: The prevalence of AEI in SNM increases with duration of follow-up, however device reprogramming can avoid surgical revision in many cases. Source of