title: Transvenous-subcutaneous defibrillation leads: effect of transvenous electrode polarity on defibrillation threshold.
abstract: BACKGROUND
  The defibrillation threshold (DFT) of a transvenous-subcutaneous electrode configuration is sometimes unacceptably high. To obtain a DFT with a sufficient safety margin, the defibrillation field can be modified by repositioning the electrodes or more easily by a change of electrode polarity. In a prospective randomized cross-over study, the effect of transvenous electrode polarity on DFT was evaluated.
  
  
  RESULTS
  In 21 patients receiving transvenous-subcutaneous defibrillation leads, the DFT was determined intraoperatively for two electrode configurations. Two monophasic defibrillation pulses were delivered in sequential mode between either the right ventricular (RV) electrode as common cathode and the superior vena cava (SVC) and subcutaneous electrodes as anodes (configuration I) or the SVC electrode as common cathode and the RV and subcutaneous electrodes as anodes (configuration II). In each patient, both electrode configurations were used alternately with declining energies (25, 15, 10, 5, 2 J) until failure of defibrillation occurred. The DFT did not differ between both configurations (18.3 +/- 8.2 J vs 18.9 +/- 8.9 J; P = 0.72). Eleven patients had the same DFT with both electrode configurations, 5 patients a lower DFT with the RV electrode as cathode, and 5 patients a lower DFT with the SVC as cathode. Four patients had a sufficiently low DFT (< or = 25 J) with only 1 of the 2 configurations.
  
  
  CONCLUSIONS
  A change of electrode polarity of transvenous-subcutaneous defibrillation electrodes may result in effective defibrillation if the first electrode polarity tested fails to defibrillate. In general, neither the RV electrode nor the SVC electrode is superior if used as a common cathode in combination with a subcutaneous anodal chest patch.
authors.affiliation: Medizinische Klinik und Poliklinik, Westfälische-Wilhelms-Universität, Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Block
authors.forename: D
authors.initials: D
authors.lastname: Hammel
authors.forename: D
authors.initials: D
authors.lastname: Böcker
authors.forename: M
authors.initials: M
authors.lastname: Borggrefe
authors.forename: T
authors.initials: T
authors.lastname: Budde
authors.forename: F
authors.initials: F
authors.lastname: Isbruch
authors.forename: H H
authors.initials: HH
authors.lastname: Scheld
authors.forename: G
authors.initials: G
authors.lastname: Breithardt
mesh_terms: D000328:Adult; D000368:Aged; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology / Q000628:therapy*; D003327:Coronary Disease / Q000503:physiopathology / Q000628:therapy*; D018592:Cross-Over Studies; D017147:Defibrillators, Implantable; D005260:Female; D006329:Heart Conduction System / Q000502:physiology; D006801:Humans; D008297:Male; D008839:Microelectrodes; D008875:Middle Aged; D011446:Prospective Studies; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy