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Three Part Question

In [an adult in ventricular fibrillation] is [external biphasic shock better than monophasic shock] at [achieving defibrillation]?

Clinical Scenario

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.

Search Strategy

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.

Search Outcome

Altogether 337 papers were found of which 7 related to out of hospital studies relevant to the original question.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
White RD et al, 1997, USA	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, 1997, 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, 1998, 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, 1999, USA	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, 2000, 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 2001 USA	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, 2001, 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

Comment(s)

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.

References

1. 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.
2. 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.
3. 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.
4. Gliner BE, White RD. Electrocardiographic evaluation of defibrillation shocks delivered to out-of-hospital sudden cardiac arrest patients. Resuscitation 1999;41(2):133-44.
5. 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.
6. 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.
7. Martens PR, Russell JK, Wolcke B, et al. Optimal Response to Cardiac Arrest Study: Defibrillation Waveform Effect. Resuscitation 2001;49(3):233-243.