Objective: To demonstrate the utility of before and after impedance correlations to determine whether leads have been correctly connected to the left and right ports of the internal pulse generator (IPG).

Background: Frequently, left and right stimulating leads deliver pulses to the neural targets using different parameters. Accidental delivery of incorrect parameters can result in discomfort for the patient. Ideally, one lead at a time is disconnected from the depleted device and then reconnected to the new device. However, across 225 device exchanges, we have documented three instances where determining the lead origin was difficult. These were resolved intraoperatively by correlating the before and after impedances across devices in standard alignment and in swapped alignment.

Method: We analyzed the impedance correlations, along with modelling the mishaps during normal IPG exchanges across Activa PC to PC, PC to Percept^tm, and Infinity7 to Infinity7 samples. In Medtronic devices monopolar impedances are systematically less than bipolar, while for Abbott devices annular impedances are less than segmented impedances. This can both inflate the correlations and ameliorate the differences between swapped lead impedance correlations. Consequently, only Medtronic monopolar impedances and only Abbott segmented impedances were analyzed.

Results: For Activa PC to PC (n=10) the average correctly placed correlation was (r_ave=.949; sem=0.024) compared to the average incorrectly placed correlation (r_ave=.0.095; sem=0.178) with an average difference of (Diff=0.854; sem=0.178; min=0.198). For the Activa PC to Percept^tm (n=10) the average correctly placed correlation was (r_ave=.928; sem=0.044) compared to the average incorrectly placed correlation (r_ave=-.160; sem=0.135) with an average difference of (Diff=1.088; sem=0.162; min=0.301). Finally, for the Infinity7 to Infinity7 (n=4) the average correctly placed correlation was (r_ave=.717; sem=0.154) compared to the average incorrectly placed correlation (r_ave=-.244; sem=0.361) with an average difference of (Diff=.961; sem=0.305; min=0.278).

Conclusion: We have demonstrated the validity of correlating the impedances of the depleted device to that of the new device for determining whether the leads have been placed in the correct ports of the new IPG.  This is a simple solution which can prevent patients leaving the operation with incorrect settings.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/using-impedance-correlations-to-determine-the-leads-hemispheric-origin-during-dual-channel-ipg-exchanges/