title: Does reducing capacitance have potential for further miniaturisation of implantable defibrillators?
abstract: OBJECTIVE
  To determine whether considerably smaller capacitors could replace 125 microF capacitors as the standard for use in implantable defibrillators.
  
  
  METHODS
  Measured energy, impedance, voltage, and current delivered were compared at defibrillation threshold in 10 mongrel dogs for defibrillation using 75 microF and 125 microF capacitors alternated randomly. Defibrillation was attempted with biphasic shocks of comparable tilt between an endocardial lead in the right ventricular apex and a "dummy" active can of an experimental implantable device placed in the subpectoral position.
  
  
  RESULTS
  A reduction of capacitor size of 40% was associated with an increase in voltage of 21% and in current of 22%. With a 65% tilt, no significant differences were found between the two capacitances with respect to the impedance or energy required for defibrillation.
  
  
  CONCLUSIONS
  Multiple advances in electrode material, electrode configuration, shock morphology, and shock polarity have reduced defibrillation energy requirements. Smaller capacitors could be used in implantable cardioverter/defibrillators without a major decrease in effectiveness.
authors.affiliation: 1 Medizinische Klinik, Klinikum rechts der Isar, Universität, Munich, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Alt
authors.forename: F
authors.initials: F
authors.lastname: Evans
authors.forename: P D
authors.initials: PD
authors.lastname: Wolf
authors.forename: J
authors.initials: J
authors.lastname: Pasquantonio
authors.forename: L
authors.initials: L
authors.lastname: Stotts
authors.forename: S
authors.initials: S
authors.lastname: Heinz
authors.forename: A
authors.initials: A
authors.lastname: Schömig
mesh_terms: D000818:Animals; D017147:Defibrillators, Implantable; D004285:Dogs; D004553:Electric Conductivity; D004867:Equipment Design; D006321:Heart / Q000503:physiopathology; D008904:Miniaturization; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy