Three Part Question
In [an adult in ventricular fibrillation] is [external biphasic shock better than monophasic shock] at [achieving defibrillation]?
An adult is brought into the emergency department following an out of hospital ventricular fibrillatory arrest. Ventricular fibrillation persists despite repeated shocks. You remember reading about biphasic defibrillation and wonder if it offers any advantages.
Medline 1966-06/03 using the OVID interface.
Biphasic.mp AND (defib$.mp OR shock$.mp OR exp electric countershock) LIMIT to human AND English.
Altogether 337 papers were found of which 7 related to out of hospital studies relevant to the original question.
|Author, date and country
||Study type (level of evidence)
|White RD et al,|
|18 SCA patients, 10 VF receiving biphasic shocks||Observational||1st shock efficacy||82% (CI 70-92%)||Small number - an early subset of 2|
|1st shock efficacy for initial VF episode||70%|
|Poole JE et al,|
USA & Germany
|100 consecutive AED uses. 44 patients received biphasic shocks||Observational||1st shock efficacy for initial VF episode compared with pooled and best monophasic data published||89% (CI 75-97%) vs 63% (CI 60-67%) and 77% (CI 70-83%)||Descriptive study - no controls
Inclusion of patient data between this and following studies occurs|
|Gliner BE et al,|
USA, UK, Italy, Germany
|286 consecutive AED uses
100 patients received biphasic shocks||Observational||3 shock efficacy for all VF episodes||97% (CI 91-99%)||Includes patients from reference 2|
|1st shock efficacy for all VF episodes||86% (CI 81-91%)|
|1st shock efficacy for initial VF episode||86% (CI 78-92%)|
|Gliner B & White RD et al,|
|All AED uses - 29 patients treated with biphasic shocks, 87 monophasic
Biphasic vs monophasic||Observational||1st shock efficacy||85% vs 66% p<0.0001||Retrospective comparing data from differing periods
Includes some data from 2, 1 and 6|
|3 shock efficacy||99% vs 85% p<0.0001|
|Schneider T et al,|
Germany, Finland, Belgium
|246 SCA patients, 115 in VF
Biphasic (54) vs monophasic (61)||PRCT||1st shock efficacy for initial VF episode||96% vs 59% p<0.0001||Randomisation of defibrillation waveform by day rather than episode|
|3 shock efficacy for initial VF episode||98% vs 69% p<0.0001 (%s relate to biphasic then monophasic)|
|ROSC during ALS||76% vs 54% p=0.01|
|White RD et al|
|35 witnessed VF arrests receiving biphasic shocks||Descriptive||% discharged home||46% including all who required shocks alone||Excludes unwitnessed arrest
Includes some data from 1 and 4|
|% ROSC during ALS||74%|
|% ROSC with shocks alone||38%|
|Martens PR et al,|
Germany, Finland, Belgium
|246 SCA patients, 115 VF - 54 treated with biphasic, 61 with monophasic shocks - 48 MTE, 13 MDS||Sub group analysis of PRCT||1st shock efficacy for initial VF episode||96% vs 54% p=0.0001 or 77% p=0.047||Subgroup analysis of above so small numbers for MDS|
|3 shock efficacy for initial VF episode||98% vs 67% p<0.0001 or 77% p<0.021 (%s relate to Biphasic vs MTE then MDS)|
|ROSC during ALS||76% vs 54% p=0.024 or 54% p=0.17|
The studies shown in the table represent two independent groups of patients. The first two studies are a prospective randomised controlled trial (PRCT) and subsequent subgroup analysis of data from it. The latter five studies represent ongoing investigation by a group of researchers with some overlap of patient groups between each study due to differing selection criteria and differing dates of study.
The PRCT provides good evidence for the superiority of biphasic defibrillation over monophasic. Analysis of the data from this study gives an NNT of 3 for successful defibrillation with first shock, and an NNT of 4 for successful defibrillation within the first 3 shocks by biphasic vs monophasic waveforms. These out of hospital studies follow on from extensive in hospital and animal studies showing the superiority of biphasic defibrillation.
All the studies reported used the Heartstream Forerunner defibrillator with non-escalating 150 Joule shocks. This device uses an impedance compensating biphasic truncated Exponential waveform. Laboratory and hospital based studies show the superiority of biphasic waveforms to be broadly applicable and not confined to this specific example of a biphasic waveform. Work is ongoing to refine which parameters of the waveform influence effectiveness. Evidence should be appraised for the effectiveness of the specific waveform used when selecting a defibrillator. Local considerations will determine when biphasic devices replace monophasic defibrillators.
Clinical Bottom Line
Biphasic defibrillation is currently the best treatment for adult VF and should be used when available.
Level of Evidence
Level 2 - Studies considered were neither 1 or 3.
- White RD. Early Out-of-Hospital Experience With an Impedance-Compensating Low-Energy Biphasic Waveform Automatic External Defibrillator. J Interv Card Electrophysiol 1997;1(3):203-8.
- Poole JE, White RD, Kanz KG, et al. Low-Energy Impedance-Compensating Biphasic Waveforms Terminate Ventricular Fibrillation at High Rates in Victims of Out-of-Hospital Cardiac Arrest. LIFE Investigators. J Interv Card Electrophysiol 1997;8(12):1373-85.
- Gliner BE, Jorgenson DB, Poole JE, et al. Treatment of Out-of-Hospital Cardiac Arrest With a Low-Energy Impedance-Compensating Biphasic Waveform Automatic External Defibrillator. The LIFE Investigators. Biomed Instrum Technol 1998;32(6):631-44.
- Gliner BE, White RD. Electrocardiographic evaluation of defibrillation shocks delivered to out-of-hospital sudden cardiac arrest patients. Resuscitation 1999;41(2):133-44.
- Schneider T, Martens PR, Paschen H, et al. Multicenter, Randomized, Controlled Trial of 150-J Biphasic Shocks Compared With 200- to 360-J Monophasic Shocks in the Resuscitation of Out-of-Hospital Cardiac Arrest Victims. Circulation 2000;102(15):1780-1787.
- White RD, Hankins DG, Atkinson EJ. Patient Outcomes Following Defibrillation with a low energy Biphasic Truncated Exponential Waveform in Out-of-Hospital Cardiac Arrest. Resuscitation 2001;49(1):9-14.
- Martens PR, Russell JK, Wolcke B, et al. Optimal Response to Cardiac Arrest Study: Defibrillation Waveform Effect. Resuscitation 2001;49(3):233-243.