DO PERMANENT PACEMAKERS NEED AN INSULATIVE COATING - RESULTS OF A PROSPECTIVE RANDOMIZED DOUBLE-BLIND-STUDY

During conventional manufacturing of implanted pulse generators (IPGs) , an insulative coating is often applied to prevent local muscle stimu lation and myopotential sensing in unipolar pacing. This can limit the orientation of the IPG into ifs pocket, be a potential source of musc le stimulation via coating scratches, and result in an increase in IPG production costs. We hypothesized that advances in the design and con struction of current IPGs and leads obviates the need for an insulativ e coating of the IPG. Using a double-blind prospective randomized desi gn, 39 patients were implanted with either coated or uncoated otherwis e identical IPGs (19 dual, 20 single chamber). All testing wets done i n unipolar and bipolar mode in both channels. A strength-duration curv e for muscle stimulation was constructed for all patients with muscle stimulation. Myopotential sensing was established during isometric exe rcise. At 6-month follow-up when tested in unipolar mode, 3 of 15 (20% ) patients with coated IPGs and 3 of 20 (15%) with uncoated IPGs had m uscle stimulation at 5.0 V/1.5 ms or lower (P = NS). No patients in ei ther population had muscle stimulation at their normally programmed ou tput. Myopotential sensing occurred in all patients in unipolar mode a t a mean of 2.29 +/- 1.3 mV and 2.73 +/- 1.14 mV for coated versus unc oated, respectively (P = NS). The statistical power of these negative observations wets 80%. An insulative coating for pacemakers does not a ppear to alter sensing performance or cause a significant difference i n the occurrence or characteristics of muscle stimulation.