title: Impedance compensated biphasic waveforms for transthoracic cardioversion of atrial fibrillation: a multi-centre comparison of antero-apical and antero-posterior pad positions.
abstract: OBJECTIVE
  To compare the success rate for transthoracic direct current cardioversion (DCC) of atrial fibrillation (AF) with antero-posterior (AP) and antero-apical (AA) electrode positions using an impedance compensated biphasic (ICB) waveform.
  
  
  RESULTS
  Three-hundred and seven patients [mean age 66 (SD+/-13), 195 male] with AF were recruited in three centres. Patients were randomized to an AA (n=150) or AP (n=144) pad position. Thirteen patients with implanted pacemakers were defaulted to the AP pad position. Cardioversion was performed using an ICB waveform with a 70, 100, 150, and 200 J energy selection protocol. If the fourth shock was unsuccessful, the pads were crossed over to the alternative position for a final 200 J shock. Shock 1 was successful in 54/150 (36%) AA and 45/144 (31%) AP patients, whereas success was achieved by shock 2 in 99/150 (66%) AA and 74/144 (51%) AP, by shock 3 in 123/150 (82%) AA and 109/144 (76%) AP, and by shock 4 in 143/150 (95%) AA and 127/144 (88%) AP and after cross-over in 144/150 (96%) AA and 135/144 (94%) AP. Overall success rate was higher than expected at 95%. Pad position was not associated significantly with success. There was a trend towards an improved outcome with the AA configuration (P=0.05).
  
  
  CONCLUSIONS
  The influence of pad position for DCC of AF may be less pertinent with ICB waveforms than with monophasic waveforms.
authors.affiliation: Regional Medical Cardiology Centre, Royal Victoria Hospital, Grosvenor Road, Belfast BT12 6BA, Northern Ireland, UK.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Walsh
authors.forename: David
authors.initials: D
authors.lastname: McCarty
authors.forename: Anthony J J
authors.initials: AJ
authors.lastname: McClelland
authors.forename: Colum G
authors.initials: CG
authors.lastname: Owens
authors.forename: Tom G
authors.initials: TG
authors.lastname: Trouton
authors.forename: Mark T
authors.initials: MT
authors.lastname: Harbinson
authors.forename: Siobhan
authors.initials: S
authors.lastname: O'Mullan
authors.forename: Andrew
authors.initials: A
authors.lastname: McAllister
authors.forename: Brian M
authors.initials: BM
authors.lastname: McClements
authors.forename: Mike
authors.initials: M
authors.lastname: Stevenson
authors.forename: Gavin W N
authors.initials: GW
authors.lastname: Dalzell
authors.forename: A A Jennifer
authors.initials: AA
authors.lastname: Adgey
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000628:therapy*; D002307:Cardiography, Impedance; D004554:Electric Countershock / Q000295:instrumentation* / Q000379:methods; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D016896:Treatment Outcome