title: Lack of benefit of an active pectoral pulse generator on atrial defibrillation thresholds.
abstract: BACKGROUND
  Atrial defibrillation can be achieved with standard implantable cardioverter defibrillator leads, which has led to the development of combined atrial and ventricular devices. For ventricular defibrillation, use of an active pectoral electrode (active can) in the shocking pathway markedly reduces defibrillation thresholds (DFTs). However, the effect of an active pectoral can on atrial defibrillation is unknown.
  
  
  RESULTS
  This study was a prospective, randomized, paired comparison of two shock configurations on atrial DFTs in 33 patients. The lead system evaluated was a dual-coil transvenous defibrillation lead with a left pectoral pulse generator emulator. Shocks were delivered either between the right ventricular coil and proximal atrial coil (lead) or between the right ventricular coil and an active can in common with the atrial coil (active can). Delivered energy at DFT was 4.2 +/- 4.1 J in the lead configuration and 5.0 +/- 3.7 J in the active can configuration (P = NS). Peak current was 32% higher with an active can (P < 0.01), whereas shock impedance was 18% lower (P < 0.001). Moreover, a low threshold (< or = 3 J) was observed in 61% of subjects in the lead configuration but in only 36% in the active can configuration (P < 0.05). There were no clinical predictors of the atrial DFT.
  
  
  CONCLUSIONS
  These results indicate that low atrial DFTs can be achieved using a transvenous ventricular defibrillation lead. Because no benefit was observed with the use of an active pectoral electrode for atrial defibrillation, programmable shock vectors may be useful for dual-chamber implantable cardioverter defibrillators.
authors.affiliation: Division of Cardiology, Medical University of South Carolina, Charleston 29425, USA. Goldmr@musc.edu
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Shorofsky
authors.forename: Rachida
authors.initials: R
authors.lastname: Bouhouch
authors.forename: Robert A
authors.initials: RA
authors.lastname: Joy
authors.forename: D Scott
authors.initials: DS
authors.lastname: Kirby
authors.forename: Ahmed F
authors.initials: AF
authors.lastname: Osman
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Rashba
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D017147:Defibrillators, Implantable; D004056:Differential Threshold; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010369:Pectoralis Muscles; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy