title: Coronary sinus electrode does not reduce atrial defibrillation thresholds.
abstract: BACKGROUND
  Atrial defibrillation can be achieved with a conventional dual-coil, active pectoral implantable cardioverter-defibrillator (ICD) lead system. Shocking vectors that incorporate an additional electrode in the CS have been used, but it is unclear if they improve atrial DFTs.
  
  
  OBJECTIVE
  The objective of this prospective, randomized study was to determine if a coronary sinus (CS) electrode reduces atrial defibrillation thresholds (DFTs).
  
  
  METHODS
  This was a prospective study of 36 patients undergoing initial ICD implant for standard indications. A defibrillation lead with superior vena cava (SVC) and right ventricular (RV) shocking coils was implanted in the RV. An active can emulator (Can) was placed in a pre-pectoral pocket. A lead with a 4 cm long shocking coil was placed in the CS. Atrial DFTs were determined in the following 3 shocking configurations in each patient, with the order of testing randomized: RV --> SVC + Can (Ventricular Triad), distal CS --> SVC + Can (Distal Atrial Triad), and proximal CS --> SVC + Can (Proximal Atrial Triad).
  
  
  RESULTS
  The Proximal and Distal Atrial Triad configurations were both associated with significant reductions in peak current (p < 0.01), but this effect was offset by significant increases in shock impedance (p < 0.01), resulting in no net change in the peak voltage or DFT energy in comparison to the Ventricular Triad configuration (Ventricular Triad: 4.9 +/- 6.6 J, Proximal Atrial Triad: 3.3 +/- 4.1J, Distal Atrial Triad: 4.4 +/- 6.7 J, p > 0.2).
  
  
  CONCLUSIONS
  Shocking vectors that incorporate a CS coil do not significantly improve atrial defibrillation efficacy. Since the Ventricular Triad shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.
authors.affiliation: Division of Cardiology, University of Maryland School of Medicine, Baltimore, 21201, USA. erashba@medicine.umaryland.edu
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Rashba
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Shorofsky
authors.forename: Avram
authors.initials: A
authors.lastname: Scheiner
authors.forename: Robert W
authors.initials: RW
authors.lastname: Peters
authors.forename: Carol
authors.initials: C
authors.lastname: Ma
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
mesh_terms: D001281:Atrial Fibrillation / Q000628:therapy*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation*; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies