title: A randomized controlled trial of efficacy and ST change following use of the Welch-Allyn MRL PIC biphasic waveform versus damped sine monophasic waveform for external DC cardioversion.
abstract: OBJECTIVE
  Biphasic waveforms have similar or greater efficacy at cardioverting atrial and ventricular arrhythmias at lower energy levels than monophasic waveforms, and cause less ST depression following defibrillation of ventricular fibrillation. No studies have investigated this effect on ST change with atrial arrhythmias. We studied the efficacy of the Welch Allyn-MRL PIC biphasic defibrillator.
  
  
  METHODS
  One hundred and thirty-nine patients undergoing elective DC cardioversion for atrial arrhythmias were randomised to cardioversion by monophasic (Hewlett Packard Codemaster XL; 100, 200, 300, 360 and 360J) or biphasic (Welch Allyn-MRL PIC; 70, 100, 150, 200 and 300J) defibrillator. We analysed success of cardioversion after 0 and 30min, cumulative energy, number of shocks and energy at successful cardioversion. The ST change in the recorded electrocardiogram was measured at 15s after all shocks using electronic callipers.
  
  
  RESULTS
  Immediately after cardioversion 59/68 (86.8%) of the monophasic group versus 56/60 (93.3%) of the biphasic group were in sinus rhythm. Of the monophasic group, 55/67 (82.1%) remained in sinus rhythm at 30min versus 53/58 (91.4%) of the biphasic group. These differences were not significant at 0min (P=0.35) or 30min (P=0.21). The biphasic group required significantly fewer shocks (P=0.006), less cumulative energy (P<0.0001) and required lower total energy for successful cardioversion (P<0.0001). Of the 102 patients with electrocardiogram recordings suitable for analysis, ST segment change was greater in the monophasic group (P=0.037).
  
  
  CONCLUSIONS
  The Welch Allyn-MRL biphasic waveform for DC cardioversion results in fewer shocks, with less cumulative energy delivered and less post shock ST change than with a Hewlett Packard Codemaster XL damped sine wave monophasic waveform.
authors.affiliation: Shackleton Department of Anaesthetics, Southampton University Hospitals NHS Trust, Southampton SO16 6YD, UK. jjsa@amblers.org
authors.forename: Jonathan J S
authors.initials: JJ
authors.lastname: Ambler
authors.forename: Charles D
authors.initials: CD
authors.lastname: Deakin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000628:therapy*; D004311:Double-Blind Method; D004554:Electric Countershock / Q000295:instrumentation* / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies