title: Evolution of an active fixation atrial pacing lead.
abstract: Three bipolar atrial pacing leads from one manufacturer differing in a single electrode design characteristic were compared. Each lead had nonretractable screw and a microporous electrode tip made of activated carbon. Model S84F had a tip surface area of 8 mm2. In model S44F, the tip surface area was reduced to 4 mm2 by insulation of the screw, and in model BS45D, steroid elution was added to the 4 mm2 tip. Ten patients in each group received identical pulse generators. During implantation, atrial potentials (5.4 +/- 2.0, 4.2 +/- 2.0, 4.6 +/- 2.1 mV), pacing thresholds at 0.5 ms (0.47 +/- 0.14, 0.41 +/- 0.15, 0.55 +/- 0.33 V) and lead impedance at 2.5 V/0.5 ms (515 +/- 80, 575 +/- 152, 546 +/- 131 omega) were comparable among groups. The early postoperative threshold peak was significantly lower with the BS45D than with the S84F and S44F lead models. One year after implantation, charge threshold was significantly lower with the BS45D lead than with the S84F and the S44F model (0.34 +/- 0.11 vs. 0.68 +/- 0.20 and 0.56 +/- 0.21 microC; P < 0.05). Lead impedance at 2.5 V/0.5 ms (557 +/- 90, 549 +/- 36, 524 +/- 72 omega) and atrial sensing (4.3 +/- 2.1, 4.7 +/- 1.9, 4.7 +/- 0.9 mV) were not significantly different. One year postimplant, current drain of the pacing system was measured by pacemaker telemetry at chronic output settings in AAI mode/70 beats/min. Battery current measured among the three atrial lead models did not differ significantly (S84F: 11.9 +/- 0.90, S44F: 12.2 +/- 1.8, BS45D: 11.5 +/- 0.26 microA).
  
  
  CONCLUSIONS
  reduction of the tip surface area by insulation of the screw did not improve pacing performance. Addition of steroid elution to the 4 mm2 tip significantly lowered the early threshold peak and the long-term pacing threshold. Lowering of the pacing threshold, however, did not lower the current drain of the pacing system.
authors.affiliation: Universitätskliniken, Innere Medizin III, 66421 Homburg/Saar, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schwaab
authors.forename: M
authors.initials: M
authors.lastname: Kindermann
authors.forename: G
authors.initials: G
authors.lastname: Frohlig
authors.forename: O
authors.initials: O
authors.lastname: Kusch
authors.forename: H
authors.initials: H
authors.lastname: Schieffer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000628:therapy*; D003907:Dexamethasone / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004343:Drug Implants; D011211:Electric Power Supplies / Q000706:statistics & numerical data; D004567:Electrodes, Implanted / Q000592:standards*; D022062:Electrophysiologic Techniques, Cardiac; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial / Q000592:standards* / Q000706:statistics & numerical data; D012684:Sensory Thresholds
chemical_list: D004343:Drug Implants; C004180:dexamethasone 21-phosphate; D003907:Dexamethasone