Are biphasic defibrillators superior to monophasic defibrillators for the emergency cardioversion of acute atrial fibrillation?
Date First Published:
January 10, 2004
Last Updated:
January 10, 2006
Report by:
Dr Fiona Saunders, Consultant in Emergency Medicine (Consultant in Emergency Medicine, South Manchester University Hospital Trust)
Search checked by:
Dr KaKatherine Potier, Consultant in Emergency Medicine, South Manchester University Hospital Trust
Three-Part Question:
In [a patient presenting with acute atrial fibrillation] do [biphasic rather than monophasic waveform shocks] result in [better cardioversion rates]?
Clinical Scenario:
A 44 year old man presents to the Emergency Department with a six hour history of palpitations. His ECG confirms that he is in atrial fibrillation and a detailed history suggests that this is acute atrial fibrillation of less than 48 hours duration. It is decided that cardioversion is the treatment of choice, but which waveform is likely to be more effective? Monophasic or biphasic?
Search Strategy:
Medline1966 –08/04 using the OVID interface. Cochrane database.
Search Details:
[exp Atrial Fibrillation/ or atrial fibrillation.mp] AND [Electric Countershock/ or cardioversion.mp OR electroversion.mp] AND biphasic.mp LIMIT to human
Outcome:
The search identified 107 papers, of which four are relevant.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Transthoracic cardioversion of atrial fibrillation: comparison of rectilinear biphasic versus damped sine wave monophasic shocks. Mittal S, Ayati S, Stein KM et al. 2000, USA | 165 adults in AF (30 < 48hours) | Prospective randomised trial | Conversion of AF to sinus rhythm | Efficacy of first shock significantly greater for biphasic than monophasic (p<0.0001) | Small sub group of patients with acute AF |
| Biphasic versus monophasic shock waveform for conversion of atrial fibrillation: the results of an international randomized, double-blind multicenter trial. Page RL, Kerber RE, Russell JK et al. 2002, USA | 203 haemodynamicaly stable adults in AF. (21 with AF < 48hours duration) |
Randomised triple blind trial | Successful cardioversion | Significantly greater number of shocks and total energy delivered to patients randomised to monophasic shocks (p<0.0001) | Small sub group of patients with acute AF |
| Comparison of the rectilinear biphasic waveform with the monophasic damped sine waveform for external cardioversion of atrial fibrillation and flutter. Niebauer MJ, Brewer JE, Chung MK, Tchou PJ. 2004, USA | 3703 cardioversion procedures for AF. 1503 biphasic (195 acute) 2200 monophasic (363 acute) |
Retrospective Review | Cardioversion success | Overall success rate for biphasic 99.1%, for monophasic 92.4%. Difference significant in all subgroup comparisons including duration of AF | Retrospective |
| A randomized trial comparing monophasic and biphasic waveform shocks for external cardioversion of atrial fibrillation. Koster RW, Dorian P, Chapman FW. 2004, Canada | 73 adults in AF (6 < 48hrs duration) |
Single blind randomised trial | Shock success | Cumulative success rates significantly higher in patients randomised to biphasic shock (97% vs. 38% p<0.0001) | Very small sub-group of patients with acute AF |
Author Commentary:
There is a wealth of evidence in the published literature that biphasic waveforms are more effective than monophasic waveforms at cardioversion of atrial fibrillation. The vast majority of this work however pertains to patients with chronic atrial fibrillation i.e. present for more than 48 hours. The four studies in the table above include subgroups of patients with AF of < 48 hours duration. Only Niebauers large retrospective study performs a subgroup analysis, which concludes that the superior effectiveness of the biphasic waveform can be extrapolated to the acute group.
Bottom Line:
It is likely that biphasic cardioversion is more effective than monophasic cardioversion in patients with acute atrial fibrillation.
References:
- Mittal S, Ayati S, Stein KM et al.. Transthoracic cardioversion of atrial fibrillation: comparison of rectilinear biphasic versus damped sine wave monophasic shocks.
- Page RL, Kerber RE, Russell JK et al.. Biphasic versus monophasic shock waveform for conversion of atrial fibrillation: the results of an international randomized, double-blind multicenter trial.
- Niebauer MJ, Brewer JE, Chung MK, Tchou PJ.. Comparison of the rectilinear biphasic waveform with the monophasic damped sine waveform for external cardioversion of atrial fibrillation and flutter.
- Koster RW, Dorian P, Chapman FW.. A randomized trial comparing monophasic and biphasic waveform shocks for external cardioversion of atrial fibrillation.