title: Right atrial septal electrode for reducing the atrial defibrillation threshold.
abstract: BACKGROUND
  The atrial defibrillation threshold (ADFT) energy of the standard lead configuration, right atrial appendage (RAA) to coronary sinus (CS), was reduced by >50% with the addition of a third electrode traversing the atrial septum in a previous study. This study determined whether the ADFT would be lowered by a more clinically practical third electrode placed in the right atrium along the atrial septum (RSP).
  
  
  RESULTS
  Sustained atrial fibrillation was induced in 8 closed-chest sheep with burst pacing and maintained with pericardial infusion of acetyl-beta-methylcholine chloride. A custom-made, dual-defibrillation catheter was placed with electrodes in the lateral RA, CS, and RSP. A separate defibrillation catheter was also placed in the RAA. ADFT characteristics of RAA-->CS and 6 other single- or sequential-shock configurations were determined in random order by using biphasic, truncated-exponential waveforms in a multiple-reversal protocol. The delivered-energy, peak-voltage, and peak-current ADFTs for the sequential-shock configuration CS-->RSP/RA-->RSP (0.53+/-0.31 J, 86+/-22 V, and 1.6+/-0.6 A, respectively) were significantly lower than those of RAA-->CS (1.14+/-0.64 J, 157+/-34 V, and 2.5+/-1.1 A, respectively). The ADFT characteristics of RAA-->CS and RA-->CS were not significantly different, nor were those of CS-->RSP/RA-->RSP and CS-->RSP/RAA--> RSP.
  
  
  CONCLUSIONS
  The ADFT of the standard RAA-->CS configuration may be markedly reduced with an additional electrode situated at the RSP.
authors.affiliation: Division of Cardiovascular Diseases, Department of Medicine, University of Alabama, Birmingham, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zheng
authors.forename: M E
authors.initials: ME
authors.lastname: Benser
authors.forename: G P
authors.initials: GP
authors.lastname: Walcott
authors.forename: R E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000628:therapy*; D017147:Defibrillators, Implantable; D004567:Electrodes, Implanted; D022062:Electrophysiologic Techniques, Cardiac; D006325:Heart Atria / Q000503:physiopathology*; D006346:Heart Septum / Q000503:physiopathology*; D012684:Sensory Thresholds; D012756:Sheep