title: Novel rectangular biphasic and monophasic waveforms delivered by a radiofrequency-powered defibrillator compared with conventional capacitor-based waveforms in transvenous cardioversion of atrial fibrillation.
abstract: OBJECTIVE
  To investigate the feasibility and efficacy of novel low-tilt biphasic waveforms in transvenous cardioversion of atrial fibrillation (AF), delivered by a radiofrequency-powered defibrillator.
  
  
  RESULTS
  The investigation was performed in three phases in an animal model of AF: a feasibility and efficacy study (in 10 adult Large White Landrace swine), comparison with low-tilt monophasic and standard capacitor-based waveforms, and an assessment of sequential shocks delivered over several pathways (in 15 adult Suffolk sheep). Defibrillation electrodes were positioned transvenously under fluoroscopic control in the high lateral right atrium and distal coronary sinus. When multiple defibrillation pathways were tested, a third electrode was also attached to the lower interatrial septum. The electrodes were then connected to a radiofrequency (RF)-powered defibrillator or a standard defibrillator. After confirmation of successful induction of sustained AF, defibrillation was attempted. Percentage success was calculated from the effects of all shocks delivered to all the animals within each set of experiments. Of the low-tilt (RF) biphasic waveforms delivered during internal atrial cardioversion, 100% success was achieved with a 6/6 ms 100/-50 V waveform (1.45+/-0.01 J). This waveform was similar in efficacy to low-tilt (RF) monophasic waveforms (88 vs. 92% success, 1.58+/-0.01 vs. 2.67+/-0.03 J; P=NS; delivered energy 41% lower) and superior to equivalent voltage standard monophasic (50% success, 0.67+/-0.00 J; P<0.001) and biphasic waveforms (72% success, 0.69+/-0.00 J; P=0.03). Sequential shocks delivered over dual pathways did not improve the efficacy of low-tilt biphasic waveforms.
  
  
  CONCLUSIONS
  A low-tilt biphasic waveform from a RF-powered defibrillator (6/6 ms 100/-50 V) is more efficacious than standard monophasic or biphasic waveforms (equivalent voltage) and is similar in efficacy to low-tilt 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: Ganesh
authors.initials: G
authors.lastname: Manoharan
authors.forename: Omar J
authors.initials: OJ
authors.lastname: Escalona
authors.forename: Jose
authors.initials: J
authors.lastname: Santos
authors.forename: Noel
authors.initials: N
authors.lastname: Evans
authors.forename: John McC
authors.initials: JM
authors.lastname: Anderson
authors.forename: Mike
authors.initials: M
authors.lastname: Stevenson
authors.forename: J Desmond
authors.initials: JD
authors.lastname: Allen
authors.forename: A A Jennifer
authors.initials: AA
authors.lastname: Adgey
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000628:therapy*; D047548:Defibrillators; D004867:Equipment Design; D013552:Swine