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 mm 2 vitreous carbon tip, coaxial multifilar coils, silicons). 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 (δQmin), 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 Ω vs 576 Ω, mean values, 436–10 vs S44F) and at each follow-up (317–126 Ω vs 492–613 Ω). Five of nine patients with the 438–10 lead had Z values < 300 Ω during follow-up (minimum 234 Ω). 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), ±Qmin (0.19–1.23 μC vs 0.18–1.35 μC) 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.