title: Effect of electrode length on atrial defibrillation thresholds.
abstract: BACKGROUND
  Catheter-based electrodes have been used previously to terminate episodes of atrial fibrillation in animals and man. Typically, these electrodes span 6 to 7 cm, and lowest energy requirements are achieved when these electrodes are positioned in the distal coronary sinus and in the right atrium. The purpose of this study was to evaluate the use of longer electrode lengths for atrial defibrillation.
  
  
  RESULTS
  In 15 patients, two decapolar catheters were inserted, one into the distal coronary sinus and one in the right atrium. To provide longer electrodes lengths, a third catheter was inserted and alternated positioned in the right atrium or coronary sinus. A 6-cm electrode span was obtained by using the distal 8 rings on the coronary sinus catheter or 8 consecutive electrodes on the right atrial catheter and increased from 6 to 11 cm by connecting 5 consecutive, nonoverlapping rings of the third catheter with the 10 rings of the initial right atrial or coronary sinus catheter. Atrial defibrillation thresholds were determined twice, in a randomized order, in each patient for each of the three combinations of electrode lengths. All 15 patients could be successfully converted to sinus rhythm without complications; however, one patient could be converted reproducibly with only 2 of the 3 electrode combinations. Mean thresholds were 306 +/- 102 V, 5.9 +/- 4.0 J for the 6 cm/6 cm electrode length combination with an impedance of 72 +/- 18 omega. For the electrode combination using the 11-cm electrode in the right atrium, the defibrillation threshold was 296 +/- 107 V, 5.8 +/- 3.9 J with an impedance of 61 +/- 17 omega and was 294 +/- 91 V, 5.6 +/- 3.6 J with an impedance of 55 +/- 11 omega for the 11-cm electrode in the coronary sinus. There were no significant differences in defibrillation voltage or energy (P > 0.05) associated with the longer electrode lengths; however, the longer electrode lengths did significantly lower shock impedance (P < 0.05).
  
  
  CONCLUSIONS
  The use of longer electrodes, when using the right atrium to coronary sinus shock vector, does not lower the defibrillation requirements for restoration of sinus rhythm.
authors.affiliation: Department of Cardiology, Academic Hospital Maastricht, The Netherlands. C.Timmermans@cardio.azm.nl
authors.forename: C
authors.initials: C
authors.lastname: Timmermans
authors.forename: L M
authors.initials: LM
authors.lastname: Rodriguez
authors.forename: G M
authors.initials: GM
authors.lastname: Ayers
authors.forename: H
authors.initials: H
authors.lastname: Lambert
authors.forename: J
authors.initials: J
authors.lastname: Smeets
authors.forename: H J
authors.initials: HJ
authors.lastname: Wellens
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000628:therapy*; D004056:Differential Threshold; D004554:Electric Countershock / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged