title: Atrial defibrillation thresholds of electrode configurations available to an atrioventricular defibrillator.
abstract: BACKGROUND
  Little investigation has been conducted to assess the atrial defibrillation thresholds of electrode configurations using electrodes designed for internal ventricular defibrillation (right ventricle [RV], superior vena cava [SVC], and pulse generator housing [Can]) combined with coronary sinus (CS) electrodes. We hypothesized that a CS-->SVC+Can electrode configuration would have a lower atrial defibrillation threshold than a standard configuration for defibrillation, RV-->SVC+Can. We also tested the atrial defibrillation thresholds of five other configurations.
  
  
  RESULTS
  In 12 closed chest sheep, we situated a two-coil (RV, SVC) defibrillation catheter, a left-pectoral subcutaneous Can, and a CS lead. Atrial fibrillation was burst induced and maintained with continuous infusion of intrapericardial acetyl-beta-methylcholine chloride. Using fixed-tilt biphasic shocks, we determined the atrial defibrillation thresholds of seven test configurations in random order according to a multiple-reversal protocol. The peak voltage and delivered energy atrial defibrillation thresholds of CS-->SVC+Can (168+/-67 V, 2.68+/-2.40 J) were significantly lower than those of RV-->SVC+Can (215+/-88 V, 4.46+/-3.40 J). The atrial defibrillation thresholds of the other test configurations were RV+CS-->SVC+Can: 146+/-59 V, 1.92+/-1.45 J; RV-->CS+SVC+Can: 191+/-89 V, 3.53+/-3.19 J; CS-->SVC: 188+/-98 V, 3.77+/-4.14 J; SVC-->CS+ Can: 265+/-145 V, 7.37+/-9.12 J; and SVC-->Can: 516+/-209 V, 24.5+/-15.0 J.
  
  
  CONCLUSIONS
  The atrial defibrillation threshold of CS-->SVC+Can is significantly lower than that of RV-->SVC+Can. In addition, the low atrial defibrillation threshold of RV+CS-->SVC+Can merits further investigation. Based on corroboration of low atrial defibrillation thresholds of CS-based configurations in humans, physicians might consider using CS leads with atrioventricular defibrillators.
authors.affiliation: Cardiac Rhythm Management Laboratory, Guidant Corporation, St. Paul, Minnesota, USA. meb@crml.uab.edu
authors.forename: M E
authors.initials: ME
authors.lastname: Benser
authors.forename: G P
authors.initials: GP
authors.lastname: Walcott
authors.forename: C R
authors.initials: CR
authors.lastname: Killingsworth
authors.forename: S D
authors.initials: SD
authors.lastname: Girouard
authors.forename: M M
authors.initials: MM
authors.lastname: Morris
authors.forename: R E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000407:Alabama; D000818:Animals; D001281:Atrial Fibrillation / Q000139:chemically induced / Q000503:physiopathology* / Q000628:therapy*; D016275:Atrial Function; D017147:Defibrillators, Implantable; D004056:Differential Threshold / Q000187:drug effects / Q000502:physiology; D004554:Electric Countershock / Q000295:instrumentation*; D004566:Electrodes; D022062:Electrophysiologic Techniques, Cardiac; D004867:Equipment Design; D016210:Methacholine Chloride / Q000008:administration & dosage; D008955:Models, Cardiovascular; D012756:Sheep; D014683:Vena Cava, Superior / Q000502:physiology; D016276:Ventricular Function
chemical_list: D016210:Methacholine Chloride