Clinical research Impedance compensated biphasic waveforms for transthoracic cardioversion of atrial fibrillation: a multi-centre comparison of antero-apical and antero-posterior pad positions Simon J. Walsh 1 , David McCarty 1 , Anthony J.J. McClelland 1 , Colum G. Owens 1 , Tom G. Trouton 2 , Mark T. Harbinson 2 , Siobhan O’Mullan 2 , Andrew McAllister 3 , Brian M. McClements 3 , Mike Stevenson 4 , Gavin W.N. Dalzell 1 , and A.A. Jennifer Adgey 1 * 1 Regional Medical Cardiology Centre, Royal Victoria Hospital, Grosvenor Road, Belfast BT12 6BA, Northern Ireland, UK; 2 Cardiology Department, Antrim Area Hospital, Bush Road, Antrim, Northern Ireland, UK; 3 Cardiology Department, Mater Infirmorum Hospital, Crumlin Road, Belfast, Northern Ireland, UK; and 4 Department of Epidemiology and Public Health, Queen’s University, University Road, Belfast, Northern Ireland, UK Received 16 July 2004; revised 26 January 2005; accepted 3 February 2005; online publish-ahead-of-print 11 April 2005 Aims To compare the success rate for transthoracic direct current cardioversion (DCC) of atrial fibrilla- tion (AF) with antero-posterior (AP) and antero-apical (AA) electrode positions using an impedance com- pensated biphasic (ICB) waveform. Methods and 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 ¼ 150) or AP (n ¼ 144) pad pos- ition. Thirteen patients with implanted pacemakers were defaulted to the AP pad position. Cardiover- sion 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 ¼ 0.05). Conclusion The influence of pad position for DCC of AF may be less pertinent with ICB waveforms than with monophasic waveforms. KEYWORDS Biphasic waveform; Atrial fibrillation; Direct current cardioversion; Pad position Introduction Electrical cardioversion is a commonly performed procedure for the treatment of atrial fibrillation (AF). Direct current cardioversion (DCC) has been successfully performed since the 1960s, mainly using damped sine wave monophasic waveforms. 1 However, advances have occurred in defibrilla- tion over the last two decades. Biphasic waveforms have been shown to be more efficient in terms of peak voltage and delivered energy than monophasic waveforms of equiv- alent duration both for endocardial atrial 2 and for ventricu- lar defibrillation. 3–6 Transthoracic impedance (TTI) has been shown to be a determinant of atrial 7 and ventricular defibril- lation 8 and is now widely accepted as an important predictor of success. 9 The new generation of external defibrillators have therefore been developed to deliver impedance com- pensated biphasic (ICB) waveforms. External defibrillators that deliver biphasic waveforms have recently been shown to be more efficacious for the treatment of AF, where lower energy ICB waveforms are equivalent or superior to their higher energy monophasic counterparts. 10–14 Biphasic waveforms also cause less skin burns during DCC. 11 Biphasic cardioversion is also associated with less skeletal muscle damage 13 and less pain post-cardi- oversion. 14 In addition, fewer shocks are needed with a biphasic device, 11 potentially leading to shorter cardiover- sion procedures. AF is a common arrhythmia that can cause unpleasant symptoms and haemodynamic sequelae. Although the rationale of rhythm control has been challenged by recent studies, 15,16 electrical cardioversion is likely to remain an & The European Society of Cardiology 2005. All rights reserved. For Permissions, please e-mail: journals.permissions@oupjournals.org * Corresponding author. Tel: þ44 28 90240503; fax: þ44 28 90312907. E-mail address: jennifer.adgey@royalhospitals.n-i.nhs.uk European Heart Journal (2005) 26, 1298–1302 doi:10.1093/eurheartj/ehi196 by guest on June 9, 2013 http://eurheartj.oxfordjournals.org/ Downloaded from