Bipolar active fixation atrial leads: comparison of two new lead models

The purpose of the study was to examine the pacing and sensing characteristics of two bipolar active fixation atrial leads with a coaxial and a coradial conductor design, respectively. One group of ten patients received the ELA model S44F (4 mm2 vitreous carbon tip, coaxial multifilar coils, silicone). Nine other patients received the Intermedics ThinLine EZ 438-10 (8 mm2 iridium oxide-coated titanium tip, parallel-wound bifilar coil, polyurethane). Both lead models had electrically insulated corkscrews. Intraoperatively, pacing threshold (PT) at 0.50 ms, unfiltered atrial potential (AP), slew rate (SR) and pacing impedance (Z) at 2.5 V, 0.50 ms were measured using a Medtronic 5311 PSA. On the day of implant, and 2, 5, 10, 28, 90, 180, and 360 days after implant, minimum charge threshold (delta Qmin), atrial sensing threshold (Asen) and Z were measured via telemetry of the pacemaker (Intermedics 294-03 and 294-09). Z was significantly lower (P < 0.01) in the ThinLine EZ group at implant (419 omega vs 576 omega, mean values, 438-10 vs S44F) and at each follow-up (317-426 omega vs 492-613 omega). Five of nine patients with the 438-10 lead had Z values < 300 omega during follow-up (minimum 234 omega). There was no significant difference between the two leads with respect to PT (0.42 V vs 0.41 V), AP (3.75 mV vs 4.25 mV), SR (0.56 vs 1.06), delta Qmin (0.19-1.23 microC vs 0.18-1.35 microC) and Asen (3.4-4.5 mV vs 2.7-4.7 mV), respectively. Two patients developed pericardial effusions after implantation of a ThinLine EZ lead. One of them, who had a transient drop of blood pressure during implant, subsequently developed acute exsudative pericarditis. Therefore, both leads had acceptable sensing and pacing thresholds, but the 438-10 lead developed unusually low long-term lead impedance values. The high incidence of perforations in our small group of 438-10 patients has not been observed, thus far, in other studies.