title: Marked reduction in internal atrial defibrillation thresholds with dual-current pathways and sequential shocks in humans.
abstract: BACKGROUND
  This study tested the ability of sequential shocks delivered through dual-current pathways to lower the atrial defibrillation threshold (ADFT) compared with a biphasic shock through a standard single-current pathway.
  
  
  RESULTS
  Electrodes were positioned in the right atrial appendage (RA), left subclavian vein (LSV), proximal coronary sinus (CSos), and distal coronary sinus (DCS) in 14 patients with chronic atrial fibrillation (170+/-185 days). Using a step-up protocol, we compared ADFTs for a single-current pathway (RA-->DCS) that used a single 7.5/2.5-ms biphasic shock from a 150-microF capacitor with those for a dual-current pathway system (RA-->DCS followed by CSos-->LSV) using sequential 7.5/2.5-ms biphasic shocks with capacitor discharge waveforms for 150-microF and 600-microF capacitors. Both dual-current pathway configurations (2.0+/-0.4 J for 150-microF capacitance, 2.4+/-0.5 J for 600-microF capacitance) had a significantly lower ADFT than the single-current pathway (5.1+/-1.8 J). Whereas the dual-current pathway with 150-microF capacitor shocks had a significantly lower energy threshold, there was no statistical difference in terms of leading-edge voltage compared with the dual-current pathway with 600-microF capacitance shocks. There were no ventricular arrhythmias induced with appropriately synchronized shocks.
  
  
  CONCLUSIONS
  For internal atrial defibrillation in humans, sequential biphasic waveforms delivered over dual-current pathways resulted in a markedly reduced (>50% reduction) ADFT compared with a single shock over a single-current pathway.
authors.affiliation: Department of Medicine, The University of Alabama at Birmingham Medical Center, USA. rac@crml.uab.edu
authors.forename: R A
authors.initials: RA
authors.lastname: Cooper
authors.forename: V J
authors.initials: VJ
authors.lastname: Plumb
authors.forename: A E
authors.initials: AE
authors.lastname: Epstein
authors.forename: G N
authors.initials: GN
authors.lastname: Kay
authors.forename: R E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome