title: Effects of high energy shocks on pacing impedance during transvenous ICD implantation.
abstract: The purpose of the current study was to characterize the effects of transvenous ICD shocks on myocardial impedance. Rather than recording impedance during shocks, it was measured during continuous pacing in order to minimize confounding effects such as electrode polarization. Pacing impedance (reflecting the combined impedances of the electrode-tissue interface, myocardium, and blood pool) was measured every 5 seconds before and after 58 single shocks in 22 patients undergoing ICD implantation with a Transvene (n = 14) or Endotak (n = 8) lead. There was a progressive and long-lasting decrease in impedance after shocks. The magnitude of this change was similar for 0.6-J test shocks and shocks > or = 5 J (28 +/- 32 omega vs 23 +/- 16 omega; P = 0.8). However, the drop in impedance was more abrupt after high energy shocks. Because impedance continued to decline throughout the 5-minute interval between shocks, successive shocks had a cumulative effect, with a decrease of 46 +/- 42 omega after four discharges. In conclusion, a progressive decline in pacing impedance is a characteristic response to transvenous ICD discharges.
authors: Cardiology Division, Emory University Hospital, Atlanta, Georgia 30322, USA.
authors: F
authors: F
authors: Hidden-Lucet
authors: W M
authors: WM
authors: Hartung
authors: K K
authors: KK
authors: McTeague
authors: P F
authors: PF
authors: Walter
authors: J J
authors: JJ
authors: Langberg
mesh_terms: D000328:Adult; D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001769:Blood; D002304:Cardiac Pacing, Artificial; D015986:Confounding Factors, Epidemiologic; D017147:Defibrillators, Implantable; D004553:Electric Conductivity; D017097:Electric Impedance; D004567:Electrodes, Implanted; D004867:Equipment Design; D005260:Female; D006321:Heart / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D000889:Anti-Arrhythmia Agents