Long-term comparison of the electrical characteristics of polyurethane and polyethylene insulated ventricular leads

Two types of pacing leads with different insulation material, polyurethane, and polyethylene, were followed for 44 months with respect to their electrophysiological characteristics and complications. In 48 patients, 32 polyurethane leads (Lifeline 493-03) and 16 polyethylene leads (EMT 588 D) were implanted and connected in all cases to the same type of programmable ventricular inhibited (VVI) pulse generator (Programalith, Pacesetter). There was a significant fall during the follow-up in lead impedance with the polyurethane leads (495 +/- 62 to 444 +/- 58 ohms, P less than 0.01), whereas the corresponding measurements for the polyethylene leads were essentially unchanged (360 +/- 58 to 378 +/- 71 ohm, ns). The energy of the stimulation threshold tended to increase in the polyurethane group, whereas an opposite tendency was observed in the polyethylene group. Pacing and/or lead failures were not observed in any case. The observed fall in impedance with the polyurethane leads was seemingly of no clinical significance.