title: Implantation of additional subcutaneous array electrode reduces defibrillation threshold in ICD patients - preliminary results.
abstract: BACKGROUND
  Among the recipients of implantable cardioverter-defibrillators (ICDs), there is a group of patients in whom the defibrillation threshold (DFT) is too high to enable a sufficient safety margin between the DFT and the maximal available output of the device. The aim of the study was to investigate the ability of an additionally implanted single-coil subcutaneous array electrode to reduce the DFT in such patients.
  
  
  METHODS
  Medtronic 6996SQ electrode was implanted in 15 patients selected from our follow-up group of 741 ICD patients: 10 of them had insufficient post-implant DFT safety margin, and 5 had ineffective first maximal energy shock as recorded by the device. In 6 cases the patients had CRT-D devices, in 5 cases - dual-chamber ICDs, and in 4 cases - single-chamber ICDs. In all patients but one the defibrillating electrode was single-coil. In one patient it was dual-coil. The underlying disease was coronary artery disease in 10 patients, dilated cardiomyopathy in 4 patients and hypertrophic cardiomyopathy in 1 patient.
  
  
  RESULTS
  The subcutaneous electrode was successfully implanted in all the patients qualified for the procedure. No technical issues or perioperative complications were observed. Mean DFT was reduced from 33.3 ±4.1 J before the procedure to 25.3 ±4.4 J after the implantation procedure (p < 0.01).
  
  
  CONCLUSIONS
  Our results show that the use of a single-coil subcutaneous electrode to reduce the DFT is a safe and effective procedure. Further studies are necessary to confirm these results.
authors.affiliation: Department of Cardiology and Electrotherapy, Medical University of Gdansk, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Kempa
authors.forename: Szymon
authors.initials: S
authors.lastname: Budrejko
authors.forename: Lukasz
authors.initials: L
authors.lastname: Drelich
authors.forename: Tomasz
authors.initials: T
authors.lastname: Królak
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Raczak
authors.forename: Dariusz
authors.initials: D
authors.lastname: Kozłowski
keywords: defibrillation threshold; implantable cardioverter-defibrillator; subcutaneous electrode