title: Successful implantation of cardioverter-defibrillator systems in patients with elevated defibrillation thresholds.
abstract: OBJECTIVE
  . The purpose of this study was to conduct a retrospective analysis of 16 patients with high initial defibrillation thresholds in whom a three-electrode system was used to lower defibrillation thresholds and permit implantation of a cardioverter-defibrillator system.
  
  
  BACKGROUND
  Patients with high defibrillation thresholds (> 25 J) are uncommon but may be problematic to physicians implanting cardioverter-defibrillator systems. Most conventional systems use two defibrillating electrodes, most commonly two epicardial patches. When defibrillation thresholds remain elevated despite extensive testing of a two-electrode system, a third electrode can be incorporated and tested. However, few published data exist on the use of a three-electrode system in patients with high defibrillation thresholds.
  
  
  METHODS
  After failure to achieve satisfactory defibrillation thresholds < 25 J with a two-patch electrode system, a third electrode was incorporated and tested. In all cases, two electrodes were joined to form a common cathode or anode, while a single electrode was used as the opposite polarity electrode. Various three-electrode configurations were then tested.
  
  
  RESULTS
  In all 16 patients, satisfactory defibrillation thresholds were achieved and a cardioverter-defibrillator was implanted (95% confidence interval [CI] = 0% to 21%). The mean final defibrillation threshold using the revised three-electrode system was 19.5 +/- 3.7 J (p < 0.0001). A mean of 6 +/- 3 electrode configurations/patient were tested before the final configuration was selected. A total of nine different electrode configurations were used in the 16 study patients; the most common of these incorporated left and right ventricular patches as combined cathode and a superior vena cava coil (n = 5) or right atrial patch electrode (n = 3) as single anode.
  
  
  CONCLUSIONS
  Patients with high initial defibrillation thresholds can generally undergo successful cardioverter-defibrillator implantation with a three-electrode system if enough electrode configurations are tested after a third electrode is incorporated.
authors.affiliation: Harvard Medical School, Cardiac Unit, Massachusetts General Hospital, Boston 02114.
authors.forename: R
authors.initials: R
authors.lastname: Brooks
authors.forename: D
authors.initials: D
authors.lastname: Torchiana
authors.forename: G J
authors.initials: GJ
authors.lastname: Vlahakes
authors.forename: J N
authors.initials: JN
authors.lastname: Ruskin
authors.forename: B A
authors.initials: BA
authors.lastname: McGovern
authors.forename: H
authors.initials: H
authors.lastname: Garan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017147:Defibrillators, Implantable; D004554:Electric Countershock; D004562:Electrocardiography; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*