title: Serial defibrillation lead impedance in patients with epicardial and nonthoracotomy lead systems.
abstract: BACKGROUND
  The stability of implantable cardiac defibrillation lead impedance subsequent to implantation has not been reported and may have important clinical implications. The objective was to characterize the incidence and degree of impedance changes occurring after implantation of defibrillation lead systems.
  
  
  RESULTS
  The study cohort consisted of patients who received epicardial or nonthoracotomy lead systems. Defibrillation impedance was recorded at implantation, prior to hospital discharge (predischarge), and during follow-up. For each individual the magnitude of the impedance change relative to implantation was characterized. Among patients with an epicardial system, a significant decrease in impedance was observed at predischarge (mean 9.3 omega). The magnitude of the decrease was large in 39% and moderate in 31% of individuals. Subsequently, a gradual rise in mean impedance was apparent. At 18-21 months postimplantation, impedance was significantly increased relative to implantation (mean 6.8 omega). At this time, the magnitude of the increase was large in 46% and moderate in 23% of patients. Among patients with a nonthoracotomy lead system including a subcutaneous patch, a significant decrease in mean impedance was observed at predischarge (mean 3.5 omega). The magnitude of the decrease was large in 8% and moderate in 50% of individuals. Subsequently, a gradual rise in impedance was apparent. At 5-6 months, it was significantly increased relative to implantation (mean 2.3 omega). The magnitude of the increase was large in 10% and moderate in 33% of patients. Among the group of patients whose nonthoracotomy lead system did not include a subcutaneous patch, there was no significant change in mean impedance at predischarge relative to implantation. In subsequent intervals, a gradual rise was apparent. At 5-6 months, impedance was significantly increased relative to implantation (mean 4.3 omega). The magnitude of the increase was large in 16% and moderate in 47% of individuals.
  
  
  CONCLUSIONS
  Significant changes in defibrillation lead impedance occur after implantation of epicardial and nonthoracotomy defibrillation lead systems. These data may serve as a standard for identifying the anticipated maximum change in lead impedance and thus may be useful as a tool for recognizing problems with defibrillation lead integrity.
authors.affiliation: Clinical Electrophysiology Section, Medical College of Pennsylvania-Hahneman University School of Medicine, Philadelphia, USA.
authors.forename: D
authors.initials: D
authors.lastname: Schwartzman
authors.forename: M L
authors.initials: ML
authors.lastname: Hull
authors.forename: D J
authors.initials: DJ
authors.lastname: Callans
authors.forename: C D
authors.initials: CD
authors.lastname: Gottlieb
authors.forename: F E
authors.initials: FE
authors.lastname: Marchlinski
mesh_terms: D017147:Defibrillators, Implantable; D017097:Electric Impedance; D006801:Humans; D007854:Lead
chemical_list: D007854:Lead