title: Reduction of the internal atrial defibrillation threshold with balanced orthogonal sequential shocks.
abstract: BACKGROUND
  The aim of this study was to determine the atrial defibrillation threshold (ADFT) of a first shock across the standard right atrium (RA) to distal coronary sinus (dCS) configuration followed by a second shock along the atrial septum with a standard sequential waveform (the second shock leading edge equaled the first shock trailing edge) and a balanced sequential waveform (the leading edges of both shocks were equal).
  
  
  RESULTS
  In nine sheep atrial fibrillation was induced with acetyl-beta-methylcholine and burst pacing. A catheter was placed with electrodes in the dCS, proximal coronary sinus (pCS), and RA. A J-shaped catheter was positioned with an electrode at Bachmann's bundle (BB) while another catheter was positioned with an electrode in the superior vena cava (SVC). The ADFTs of six single- and dual-pathway configurations were determined with single, standard sequential, or balanced sequential shocks. The ADFT of the RA-->dCS configuration (0.86 +/- 0.27 J, 159 +/- 29 V, 2.42 +/- 0.36 A) was significantly reduced when followed by an SVC-->pCS (0.58 +/- 0.17 J, 112 +/- 20 V, 1.64 +/- 0.39 A) or a BB-->pCS shock (0.64 +/- 0.16 J, 119 +/- 18 V, 1.81 +/- 0.38 A) with standard sequential shocks. With balanced sequential shocks, the peak voltage and current ADFTs were further significantly reduced (85 +/- 11 V and 1.24 +/- 0.21 A for second shock SVC-->pCS, and 93 +/- 13 V and 1.38 +/- 0.27 A for second shock BB-->pCS).
  
  
  CONCLUSIONS
  The ADFT of the standard RA-->dCS shock is significantly reduced when followed by a second shock along the atrial septum delivered between electrodes in the pCS and either SVC or BB and ADFT is further reduced with balanced sequential shocks.
authors.forename: Xiangsheng
authors.initials: X
authors.lastname: Zheng
authors.forename: Michael E
authors.initials: ME
authors.lastname: Benser
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Walcott
authors.forename: William M
authors.initials: WM
authors.lastname: Smith
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000139:chemically induced / Q000503:physiopathology / Q000628:therapy; D017147:Defibrillators, Implantable; D004056:Differential Threshold; D004195:Disease Models, Animal; D004554:Electric Countershock; D017097:Electric Impedance; D004567:Electrodes, Implanted; D006325:Heart Atria / Q000503:physiopathology / Q000601:surgery; D006329:Heart Conduction System / Q000503:physiopathology / Q000601:surgery; D016210:Methacholine Chloride / Q000009:adverse effects; D008955:Models, Cardiovascular; D010277:Parasympathomimetics / Q000009:adverse effects; D012756:Sheep; D016896:Treatment Outcome; D014683:Vena Cava, Superior / Q000503:physiopathology / Q000601:surgery
chemical_list: D010277:Parasympathomimetics; D016210:Methacholine Chloride