title: A pilot study of a low-tilt biphasic waveform for transvenous cardioversion of atrial fibrillation: improved efficacy compared with conventional capacitor-based waveforms in patients.
abstract: BACKGROUND
  The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms.
  
  
  METHODS
  We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for >/=30 seconds.
  
  
  RESULTS
  The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008).
  
  
  CONCLUSIONS
  The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage).
authors.affiliation: Regional Medical Cardiology Center, Royal Victoria Hospital, Belfast, Northern Ireland. ben.glover@hotmail.com
authors.forename: Benedict M
authors.initials: BM
authors.lastname: Glover
authors.forename: Conor J
authors.initials: CJ
authors.lastname: McCann
authors.forename: Ganesh
authors.initials: G
authors.lastname: Manoharan
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Walsh
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Moore
authors.forename: James D
authors.initials: JD
authors.lastname: Allen
authors.forename: Omar
authors.initials: O
authors.lastname: Escalona
authors.forename: John McC
authors.initials: JM
authors.lastname: Anderson
authors.forename: Tom G
authors.initials: TG
authors.lastname: Trouton
authors.forename: Mike
authors.initials: M
authors.lastname: Stevenson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Roberts
authors.forename: Jennifer Aa
authors.initials: JA
authors.lastname: Adgey
mesh_terms: D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000628:therapy*; D004554:Electric Countershock / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D016896:Treatment Outcome