title: Current density distribution by ring and diagonally arranged half-ring electrodes in bipolar and overlapping biphasic impulse stimulation.
abstract: BACKGROUND
  We have studied the acute and long-term efficacy of overlapping biphasic impulse (OLBI) stimulation for atrial pacing with VDD pacemakers and demonstrated the feasibility of DDD pacing in OLBI with diagonally arranged half-ring (Half-Ring) electrodes. We made two three-dimensional computational analysis models to verify our clinical studies.
  
  
  RESULTS
  Model I was composed of a heart, a pacemaker, and a human body. Model II was a cube with dimensions of 20 by 20 by 20 mm quarried from Model I for the detailed study of current density distributions. Laplace's equation was solved using the finite element method and the current density J was calculated. For Model I, the distal and proximal voltages were -10 V, 0 V in bipolar and -5 V, +5 V in OLBI, using Ring electrodes. In Model II, the actual measurements of electrode impedances obtained from the clinical study (1,180 Ω for Ring and 630 Ω for Half-Ring) were added to the analysis conditions. Model I showed that OLBI produced more concentrated current density distributions than those by bipolar. According to Model II, at the atrial myocardium position current density produced by Half-Ring was larger than that by Ring electrodes, 70 μA/mm(2) versus 30 μA/mm(2) in OLBI configuration. It also indicated that even if electrode impedances were equal between Half-Ring and Ring electrodes, the maximum current density produced by Half-Ring would be greater than that by Ring electrodes.
  
  
  CONCLUSIONS
  It was considered that OLBI configuration with Half-Ring electrodes provides more effective current density distributions.
authors.affiliation: Department of Cardiovascular Surgery, Hiratsuka City Hospital, Hiratsuka, Kanagawa, Japan. sstrjackjo@yahoo.co.jp
authors.forename: Satoru
authors.initials: S
authors.lastname: Suzuki
authors.forename: Norio
authors.initials: N
authors.lastname: Ishikawa
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Inoue
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Cho
authors.forename: Shinya
authors.initials: S
authors.lastname: Inoue
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hashizume
authors.forename: Yuji
authors.initials: Y
authors.lastname: Aoki
mesh_terms: D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017097:Electric Impedance; D006321:Heart / Q000502:physiology*; D018594:Human Body; D006801:Humans; D008955:Models, Cardiovascular; D010138:Pacemaker, Artificial