title: Benefit of millisecond waveform durations for patients with high defibrillation thresholds.
abstract: BACKGROUND
  Patients with a high defibrillation threshold (DFT) present an atypical but vexing problem with regard to implantable cardioverter-defibrillator (ICD) therapy. Their implant procedures are lengthy and involve more risk of complications. These patients often sustain a reduced safety margin that may compromise their survival.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the use of fixed millisecond duration model-optimized biphasic waveforms compared with conventional tilt-based waveforms in patients having a high DFT.
  
  
  METHODS
  We compared a 65%/65% tilt biphasic waveform to a millisecond duration biphasic waveform based on the biphasic burping theory using a 90-microF shock capacitor.
  
  
  RESULTS
  Fifty-four patients were evaluated. Mean DFT with tilt was reduced from 11.0 +/- 5.5 J to 8.8 +/- 4.1 J, for a mean reduction of 20% (P < .0001). For the 13 patients with tilt-based DFTs > or = 15 J, DFT was reduced from 18.7 +/- 4.1 J to 13.4 +/- 3.5 J, for a mean DFT reduction of 28% (P = .009). The population peak DFT was reduced from 29.0 J to 17.5 J, for a 41% reduction (P = .03).
  
  
  CONCLUSIONS
  Use of simple millisecond biphasic waveforms instead of conventional tilt-based waveforms can lead to substantial reductions in DFT, especially in patients with high DFT.
authors.affiliation: Department of Cardiology, The Prince Charles Hospital, Brisbane, Australia.
authors.forename: Russell A
authors.initials: RA
authors.lastname: Denman
authors.forename: Chirammal
authors.initials: C
authors.lastname: Umesan
authors.forename: Paul T
authors.initials: PT
authors.lastname: Martin
authors.forename: Ross N
authors.initials: RN
authors.lastname: Forbes
authors.forename: Mark W
authors.initials: MW
authors.lastname: Kroll
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Anskey
authors.forename: Helen E
authors.initials: HE
authors.lastname: Burnett
mesh_terms: D000328:Adult; D000368:Aged; D017147:Defibrillators, Implantable / Q000009:adverse effects; D004554:Electric Countershock / Q000009:adverse effects / Q000379:methods*; D017097:Electric Impedance; D004867:Equipment Design; D005260:Female; D019220:High-Energy Shock Waves; D006801:Humans; D008297:Male; D008875:Middle Aged; D012107:Research Design; D018570:Risk Assessment; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy