title: Effect of insulation material in aging pacing leads: comparison of impedance and other electricals: time-dependent pacemaker insulation changes.
abstract: BACKGROUND
  There has been concern over declining bipolar (BP) impedance (Z) in aging polyurethane (PU) cardiac pacing leads. Subsequently, a prospective study was conducted comparing BP Z, threshold (Th), and R-wave sensing amplitude of 55D PU-insulated (Model 4024, Medtronic, Inc., Minneapolis, MN, USA) and silicone-insulated (Model 5024) leads.
  
  
  METHODS
  This study was initiated by The Iowa Heart Center. Patients with Model 4024 (N = 162) or 5024 (N = 120) pacing leads with at least 6 years implant time were enrolled and followed for an additional 5 years.
  
  
  RESULTS
  There was a significant drop in the mean BP Z for the Model 4024 population, between enrollment (6 years) and the final endpoint (11 years), which was in contrast to the Model 5024 which did not see a significant drop in its mean BP Z for this same period. The trend difference seen in the means between the two models was statistically significant (P < 0.0001). In addition, a statistically significant relationship was found between dropping BP Z and rising Th (P < 0.0001). The analysis showed that if BP Z dropped below 200 ohms, the probability of having a >3X increase over baseline, in Th at 2.5 V, increases from approximately 3-7% to as high as 30%.
  
  
  CONCLUSIONS
  A significant drop in BP Z observed in the PU-insulated Model 4024 lead was not present in the silicone-insulated Model 5024 lead. The statistically significant relationship between dropping BP Z and rising Th helps to understand how to better manage patients with aging leads.
authors.affiliation: Iowa Heart Center, PC, Des Moines, Iowa 50134, USA. wbjohnson@iowaheart.com
authors.forename: W Ben
authors.initials: WB
authors.lastname: Johnson
authors.forename: Alan
authors.initials: A
authors.lastname: Braly
authors.forename: Kenneth
authors.initials: K
authors.lastname: Cobian
authors.forename: Mary B
authors.initials: MB
authors.lastname: Craig
authors.forename: Loline
authors.initials: L
authors.lastname: Voegtlin
authors.forename: Tarek
authors.initials: T
authors.lastname: Haddad
authors.forename: Rick
authors.initials: R
authors.lastname: McVenes
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D017097:Electric Impedance; D004567:Electrodes, Implanted / Q000706:statistics & numerical data*; D004867:Equipment Design; D004868:Equipment Failure / Q000706:statistics & numerical data*; D019544:Equipment Failure Analysis / Q000706:statistics & numerical data*; D010138:Pacemaker, Artificial / Q000706:statistics & numerical data*; D014481:United States
chemical_list: D020099:Coated Materials, Biocompatible