Disclosure Statement
Researchers have only recently conducted
out-of-hospital human studies that document outcomes of
transthoracic defibrillation using a low-energy biphasic
waveform shock. The American Heart Association Committee on Emergency
Cardiovascular Care (ECC) and its subcommittees
included prepublication reports of these studies in this review of
transthoracic biphasic waveform defibrillation. The writing
group and a panel of invited experts have diligently attempted to
assess the quality of the studies reviewed here by using a formal
evidence-based template, which is summarized in this statement.
The experts most familiar with defibrillation technology and
assessment are often recipients of research support from manufacturers
of automated external defibrillators (AEDs). Several of the authors and
expert reviewers of this report have signed disclosure statements
acknowledging training or research support from one or more AED
manufacturers. However, in every case, support was administered through
the academic institutions employing those individuals. No one has
disclosed receiving personal salary support or consultant's
fees from any AED manufacturer, nor has anyone disclosed that they are
or were a shareholder, paid advisor, or member of an advisory board of
an AED manufacturer. The same is true of ECC Committee members with one
exception, an employee of an AED manufacturer who abstained from
discussions of the reviewed material and this statement.
The final statement was reviewed and approved by the AHA Science
Advisory and Coordinating Committee, 2 ECC science advisors, and 2 AHA
vice presidents. These reviewers were familiar with the comments and
recommendations of the expert reviewers and their disclosure
statements. It was the opinion of the final reviewers that statements
by the writing group and reviewers were objective, balanced, and based
on known scientific facts and did not appear influenced by the
disclosed possible conflicts of interest.
Purpose
This report addresses important clinical questions regarding newly
developed AEDs that deliver impedance-compensating, fixed, low-energy
biphasic waveform shocks.
The ECC Committee and subcommittees recognize generic questions that
should be addressed as new information, therapy, or technology becomes
available. What criteria are required to initiate a review of new
technologies or interventions? How is such a review conducted? Will
this evidence-based process apply to all future discussions of the
guidelines? This report addresses immediate clinical questions
regarding biphasic waveform defibrillators and describes the process to
apply to new guideline questions in the future.
Review Triggers
New interventions, devices, or approaches can trigger a review by
the ECC Committee when all or most of the following criteria are
met:
Review Process
The ECC Committee and subcommittees are dedicated to developing
evidence-based guidelines and have prepared a new document on
developing such guidelines in emergency cardiovascular
care.2 This document presents in detail the
ECC evidence-based review process. The clinical questions regarding
biphasic defibrillation offered the first opportunity to use this
process. Fig 1
Step 1: Refine the Question and Gather Relevant
Evidence
At the time this review began, results of studies of
out-of-hospital biphasic defibrillation had not been published in
peer-reviewed journals. For this statement, a panel of 14 expert
reviewers examined 3 manuscripts in the prepublication stage that
reported data on out-of-hospital biphasic
defibrillation.18 19 20 During preparation of this
statement for publication, however, 2 of the 3 articles were
published.
Several disadvantages are associated with any review of
manuscripts or abstracts in preparation, review, prepublication, or
press. Such reviews lack reactions and critique from the broad range of
readers who review and comment on published articles. When possible,
the ECC Committee will base all future guideline revisions on the
results of published studies. However, circumstances may arise when
prepublished materials are acceptable for review, as in this case. As a
precedent, the ECC Committee reviewed data before publication when
revising the 1992 guidelines on high-dose
epinephrine.21
Step 2: Assess the Quality of Evidence
Step 2b: Critically Evaluate the Evidence (Execution of
Methodology)
Step 3: Determine the Class of Recommendation
The AHA Commitment to Early Defibrillation and the Chain
of Survival
Since 1986,22 the AHA has firmly supported
the concept of a strong Chain of Survival,23 with
early defibrillation as the most important
link.24 This support has been expressed
through
Public Access Defibrillation: A Stimulus to New
Technology
The AHA Task Force on Automatic External Defibrillation included a
wide range of representatives from the scientific and
clinical community. The task force promulgated the concept of public
access defibrillation as an innovative means of achieving early
defibrillation for adults in sudden out-of-hospital cardiac
arrest.26 Public access defibrillation
means witness defibrillation: defibrillation shocks
delivered by the person—most often a layperson—who witnesses the
collapse. This concept represents the development of ideas
generated by the Task Force on the Future of
CPR,27 which affirmed that "the future of CPR
lies with the future of defibrillation."
Public access defibrillation can succeed only if lay rescuers and
nontraditional responders are trained and equipped to use AEDs.
However, widespread dissemination of AED training and equipment
requires devices that are small, light, modestly priced, durable,
low-maintenance, almost intuitively obvious to operate, and
capable of being stored for long periods without
recharging.30
The goal of developing AEDs for public access has driven manufacturers
to investigate design improvements, battery enhancements, and
alternative waveforms. Alternative waveforms include multiple types of
biphasic and monophasic waveforms as well as impedance-compensating or
voltage-adjusting waveforms.30 More effective
waveforms mean decreased defibrillator energy requirements because
equal effectiveness can be achieved at lower energy levels. A decrease
in energy requirements confers advantages in size, weight, and cost.
The Second Public Access Defibrillation Conference in 1997 provided a
forum for a number of scientific reports and abstracts on alternative
waveforms.31 36
In 1995 the AED Task Force formed a subcommittee on AED safety and
efficacy that included representatives from the FDA and
AED manufacturers.34 The group was charged with
making recommendations for specifying arrhythmia
analysis and algorithm performance and incorporating
new defibrillator waveforms. The task force stated that alternative
waveforms for transthoracic defibrillation "should be
provisionally approved for use in AEDs" if they are "convincingly
demonstrated to be equivalent or superior to standard waveforms in the
electrophysiology laboratory... . Performance of waveforms
incorporated into AEDs should be monitored as part of a postmarket
surveillance program... . "34
The steps recommended by the AED Task Force are outlined schematically
in Fig 2
Monophasic Versus Biphasic Waveform Defibrillation
Defibrillation waveforms are a complex intervention. Monophasic
waveforms vary in the speed with which the waveform returns to the zero
voltage point—either gradually (damped sinusoidal) or instantaneously
(truncated exponential). Biphasic waveforms deliver current that first
flows in a positive direction for a specified duration. In the second
phase the device reverses the direction of current so that it flows in
a negative direction. Many features of defibrillation waveforms can be
changed and shaped by researchers and manufacturers to develop new
waveforms.37 38 39 40
Over the past 2 decades, biphasic waveform defibrillation has attracted
clinical and commercial attention in a variety of research models and
settings.3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 In these studies biphasic shocks
appear to achieve the same defibrillation success rates (most often
defined as termination of ventricular fibrillation [VF]
for at least 3 to 5 seconds) as monophasic waveforms but at
significantly lower energy levels.36
Defibrillator manufacturers can use lower-energy waveforms to achieve a
number of technical advantages. Lower-energy devices can be smaller,
lighter, less expensive, and less demanding of batteries, with fewer
maintenance requirements. These technical advantages help
fulfill the AED design features needed for public access
defibrillation.27 30
Researchers and manufacturers of implantable
cardioverter-defibrillators (ICDs) have noted the advantages of
biphasic waveforms for more than a decade.10 11 12
Human studies in EPS laboratories13 14 have
confirmed the advantages of intracardiac and transvenous biphasic
defibrillation noted in animals. By the early 1990s all implantable
defibrillator manufacturers had switched to biphasic waveforms.
Monophasic shocks are no longer used in newly implanted ICDs.
Commercially Available Biphasic Waveform AEDs
The first biphasic AED cleared by the FDA for commercial sale
(ForeRunner(TM), HeartStream Corporation) became available in September
1996. The device adjusts the amount and duration of current delivered
based on impedance measurements performed twice during every shock.
Some research has confirmed the value of impedance-based adjustments to
current and voltage.41 42 The manufacturer states
that this unique combination of features—biphasic waveform shocks
combined with impedance adjustment or compensation—provides equivalent
defibrillation success at lower energy levels than those of monophasic
shocks and eliminates the need to increase the energy for persistent
VF.
The evidence regarding the efficacy and effectiveness of the
biphasic AED has accumulated in the rationally sound sequence of animal
studies,9 pilot human feasibility
studies,15 and a prospective, randomized,
controlled trial.16 These data, which were
gathered under controlled and rigorous conditions, fit the category of
"efficacy" data (see footnote, Table 2
After the device was cleared by the FDA for commercial sale,
researchers and clinicians collected out-of-hospital data that fit
Level 4 evidence (nonrandomized observational study with some
historical control group)20 and Level 5 evidence
(case series).18 Fig 3
Human Studies: Biphasic Waveform Defibrillation for In-Hospital
Transthoracic Rescue Shocks
The efficacy of different waveforms for human
ventricular fibrillation (VF) has been measured by success
at transthoracic "rescue" defibrillations delivered in
EPS laboratories. Cardiologists delivered these
transthoracic shocks during threshold determinations for
ICDs. In this situation, VF is induced by an electric stimulus and
allowed to persist for only 20 to 30 seconds before the rescue shock.
Defibrillation success is defined as the termination of VF for 5 to 30
seconds, depending on the researchers. A successful postshock rhythm
can therefore be any non-VF electrical activity, including
asystole.
Three in-hospital studies are summarized in Table 3
Refine the Question: Biphasic Waveform Defibrillation for
Out-of-Hospital Cardiac Arrest
The first biphasic AED is being marketed for use in the clinical
setting of adult out-of-hospital sudden cardiac arrest. Intuitively the
same high level of success associated with transthoracic
shocks in EPS laboratories should occur with transthoracic
shocks delivered in out-of-hospital VF arrest. The out-of-hospital
scenario, however, is unquestionably different from the EPS laboratory.
Out-of-hospital VF is most often due to myocardial ischemia,
frequently in the absence of cardiopulmonary resuscitation
(CPR), within a hypoxic and acidotic substrate.
Furthermore, the transthoracic "rescue" shock in
the out-of-hospital scenario arrives late, minutes rather than seconds
after onset of VF. Clinical evidence suggests that VF of long duration
is much harder to defibrillate than VF of short
duration.46 Some research has compared the
efficacy rates of defibrillation in short- versus long-duration VF
using monophasic and biphasic transthoracic shocks.
Biphasic shocks perform better in both animals5
and humans.47 In the recent human study, the
biphasic shock defibrillation rate for long-duration VF was 82%
(55/67), which was significantly higher than the monophasic shock
defibrillation rate of 66% (108/164).47
Therefore, for humans in out-of-hospital cardiac arrest from VF, the
clinical questions can best be refined as follows:
Are 150-J first defibrillation shocks using an
impedance-compensated biphasic waveform clinically equivalent to 200-J
first defibrillation shocks using a monophasic waveform? (First shock:
150 J biphasic versus 200 J monophasic.)
For people in refractory or recurrent VF (following an initial
biphasic shock of 150 J), are subsequent impedance-compensated biphasic
shocks of 150 J clinically equivalent to monophasic defibrillation
shocks delivered in a progressive energy sequence of 300 J to 360 J?
(First 3 shocks: 150 J-150 J-150 J biphasic versus 200 J-300 J-360 J
monophasic.)
Attempts to answer these clinical questions have led to a sobering
observation: research has not clearly established an expected success
rate for out-of-hospital monophasic defibrillation using either
truncated exponential or damped sinusoidal waveforms. Some measure of
the success of defibrillation can be derived by reviewing published
out-of-hospital research. In some studies, reviewers can relate
defibrillation outcome to the type and energy of waveform. However,
noncomparability of patients and inconsistent nomenclature for
"success" render detailed comparisons difficult if not invalid.
The problem of imprecise nomenclature and noncomparability of
out-of-hospital patients has challenged researchers for years. To
resolve this situation, the AHA and other international resuscitation
organizations conducted 4 Utstein Style symposia to address (1)
out-of-hospital cardiac arrest,48 (2) in-hospital
arrest,49 (3) pediatric
resuscitation,50 and (4) laboratory-based
resuscitation research.51 Fully 12 years ago 2
expert reviewers of this statement published an article titled "What
Is a `Save'? Outcome Measures in Clinical Evaluations of Automatic
External Defibrillators."52 This same question
applies to the current problem of selecting outcome measures for
comparison of alternative defibrillation waveforms and energy
levels.
Biphasic waveform defibrillators became clinically available so
recently that no published report of out-of-hospital experience existed
at the time of this review: 2 reports were in press, and a third had
been submitted for publication.18 19 20 Table 3
There are important limitations in the data in Table 3
Another important limitation of this review must be understood:
The definitions of defibrillation and resuscitation success are
inconsistent. Table 4
To a large extent, these variations reflect the realities of data
collection in the prehospital setting. Resuscitations are dynamic
events with multiple rescuers and interventions and intermediate
outcomes. Defibrillation has several outcomes: persistent VF or
conversion to a perfusing rhythm, asystole, or pulseless electrical
activity. Furthermore, patients who have had defibrillation may later
refibrillate and require more shocks. Shock delivery and outcome occur
in combination with many other interventions, such as CPR and the
arrival of ACLS personnel who provide endotracheal intubation and
intravenous medications. Clinical treatment data are
difficult to correlate with data recorded by the event
documentation components of the AED. Claims that one definition of
"shock success" is more meaningful or commonly accepted than
another are insupportable.
The Need for an Energy Reserve: Persistent Low-Energy Biphasic
Shocks Versus Progressive-Energy Monophasic Shocks
It could be argued that the outcome "all shocks success,"
"
Table 5
The return of either organized electrical activity or a
pulse at the time of transport was also higher for the biphasic
waveform: 77% of 44 patients had organized rhythm at transport, and
57% of 34 had a pulse. This compares with 48% of 85 patients treated
with the monophasic truncated exponential AED, who had a return of
organized electrical activity at the time of transport to the
hospital.45 Although statistical comparisons are
inappropriate here, the trend toward better outcome rates for
low-energy biphasic shocks is reassuring and should reduce concerns
that withholding progressive energy shocks does harm or is a disservice
to patients.
Limitations of Data and Reviewers' Critique
"Doing Versus Studying": Moving From the Laboratory to the
Field
No clear conclusions could be reached on the precise implications
of these data for patients during out-of-hospital VF arrest.
Out-of-hospital VF is induced by ischemia and occurs most often
in hypoxic, acidotic hearts with chronic, fixed coronary artery
disease. Treatment of VF with an AED occurs in the late
shock-refractory stages of the arrest. The marked differences in the
mechanism of VF induction and its duration prevent direct comparison
between in-hospital and out-of-hospital patients. Some reviewers
considered these data sufficient evidence to support endorsement of
out-of-hospital biphasic defibrillation. For others, however, these
data only provided support for studying out-of-hospital biphasic
defibrillation.
Small Numbers of Patients
Unavailable and Nontraditional Outcomes
The intermediate outcome of defibrillation success, defined simply as
removal or termination of VF for >5 seconds, was considered
unsatisfactory, especially when asystole and pulseless electrical
activity were classified as "success." Although it is preferable to
report the effects of biphasic defibrillation based on the return of
spontaneous circulation, hospital admission rates, and survival rates
for this evidence-based guideline review, this information was not
available in the Level 4 and Level 5
data supplied in these reports.
Inadequate Data for Comparisons
The redundancy of case reporting noted above prevented meaningful
combinations of the 3 articles. In the absence of the recommended
clinical variables, evaluations of defibrillation success, however
defined, become extremely difficult. The problem of noncomparability
arose in the Poole manuscript in the authors' efforts to construct at
least a "historical" control group derived from previously
published studies. Although the reviewers recognized the conscientious
effort to provide some type of control comparison, most reviewers
considered this compilation inadequate and invalid.
Lack of Definitive Level 1 Evidence
Lack of Comparative Data Regarding MonophasicWaveform Success
FDA Clearance for Commercial Sale Versus AHA Class of
Recommendation
The safety and efficacy data that led to FDA clearance of the biphasic
defibrillator came largely from laboratory animal projects and
human EPS data on transthoracic rescue
shocks.16 For several reviewers, FDA clearance of
a device proposed under the 510-K regulations should have led to
prospective, randomized clinical trials (as outlined in Fig 3
Some questions have arisen over whether there is a need for AHA ECC
recommendations when the FDA has cleared a device for commercial sale.
There must be no confusion or misunderstanding on this point: the FDA
evaluation and clearance process and the ECC evidence-based guideline
recommendations are at this time separate, independent processes.
Manufacturers of ECC-related products, medical devices, or
pharmaceutical agents must not assume that FDA clearance for commercial
sale automatically conveys a high-level recommendation by the AHA ECC
Committee.
Lack of Energy Reserve: Possibility of Harm?
ECC providers who select a device that lacks the reserve to provide
higher-energy shocks are in a sense depriving an unknown proportion of
VF patients of this reserve. Although higher-energy shocks may improve
outcomes in these situations, this is unlikely, given the long time
intervals and physiological deterioration that
occur in out-of-hospital cardiac arrest. The small amount of clinical
data on the expected success rate of any type of defibrillation
waveform makes it impossible to estimate the size or even the validity
of this energy reserve problem. The comparative results from the first
44 instances of clinical use of the low-energy biphasic AED appear
positive; if such success continues, this concern will be
eliminated.
Summary: Applying the Evidence-Based Template to Evaluation of
Biphasic Defibrillation
The AHA ECC Committee and the International Liaison Committee on
Resuscitation (ILCOR)54 will revise the AHA
guidelines for CPR and ECC in the year 2000. The commitment to
evidence-based guidelines requires an explicit template for guideline
review and revision.
Review Triggers
Step 1: Refine the Question and Gather Relevant
Evidence
Step 2a: Determine the Level of Evidence
Table 3
In the out-of-hospital setting, however, the level and quality of
evidence drops precipitously due to the intrinsic difficulties of
conducting controlled prospective studies in this
setting.55 Table 3
Step 3: Determine the Class of Recommendation
Another mismatch factor that played a role in this review was the
decision-making principles of expert reviewers and the differing
weights they gave the same scientific evidence. For some reviewers,
experience with ICDs and the numerous studies on biphasic
defibrillation conducted in animal and EPS laboratories provided
compelling support for a Class I recommendation. For other experts, the
same evidence only provided justification for a prospective, randomized
clinical trial.
Conclusions
The AHA ECC Committee and subcommittees reviewed this statement
and have endorsed the following conclusions:
Recently other manufacturers began marketing smaller, lightweight,
less expensive monophasic defibrillators that require only low
maintenance, have long shelf and battery life, and allow for
administration of progressive energy (200 J-300 J-360 J) shocks. These
include LifePak 500(TM) (Physio-Control Corporation), Laerdal 911(TM)
(Laerdal Manufacturing Company), and First Save(TM) (SurvivaLink
Company). These general characteristics should translate into increased
availability of AEDs in the community and reduced time to
defibrillation for the cardiac arrest victim.
Future Research
AHA guidelines and recommendations for different defibrillation
waveforms delivered at different energy levels have not yet been
formulated. Prospective, randomized clinical trials must be conducted
to confirm any advantage of one waveform over another. Some studies are
in progress and will be carefully evaluated at the AHA Guidelines 2000
International Conference.
The AHA commends defibrillator manufacturers who are engaged in
intensive efforts to develop better, more effective devices for use in
a variety of clinical and community settings. Their efforts, coupled
with those of scientists who evaluate the devices, will further the AHA
mission to reduce disability and death from
cardiovascular diseases and stroke.
Acknowledgments
Carole Carey, senior reviewer, and Dan Spyker, medical
officer of the Center for Devices and Radiological Health of
the Food and Drug Administration, provided technical assistance. Janice
Jones, PhD, and Charles Babbs, MD, also reviewed the manuscript and
provided comments.
Footnotes
"Low-Energy Biphasic Waveform Defibrillation: Evidence-Based Review Applied to Emergency Cardiovascular Care Guidelines" was approved by the American Heart Association Science Advisory and Coordinating Committee in February 1998.
A single reprint is available by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Avenue, Dallas, TX 75231-4596. Ask for reprint No. 71-0138. To purchase additional reprints: up to 999 copies, call 800-611-6083 (US only) or fax 413-665-2671; 1000 or more copies, call 214-706-1466, fax 214-691-6342, or E-mail pubauth@amhrt.org. To make photocopies for personal or educational use, call the Copyright Clearance Center, 508-750-8400.
1 These reviewers have indicated a relationship involving previous or current research support that may be perceived as a conflict of interest.
2 As of December 1997, only 1 FDA-cleared defibrillator uses biphasic waveform defibrillation shocks. Unless otherwise stated, the term biphasic defibrillator, as used in this statement, refers only to ForeRunner(TM) (HeartStream Corporation), an impedance-compensated, fixed 150-J, biphasic waveform AED.
References
1.
Emergency Cardiac Care Committee and Subcommittees,
American Heart Association. Guidelines for cardiopulmonary
resuscitation and emergency cardiac care. JAMA.. 1992;268:2172–2295.
2.
Cummins RO, Billi JE, Hazinski MF, Idris A, Ornato J,
et al. New perspectives on developing evidence-based guidelines in ECC
and CPR: levels of evidence and classes of recommendations.
Circulation. 1998. In preparation.
3.
Jones JL, Jones RE, Balasky G. Improved cardiac cell
excitation with symmetrical biphasic defibrillator waveforms.
Am J Physiol. 1987;253:H1418–H1424.
4.
Jones JL, Tovar OH. Threshold reduction with biphasic
defibrillator waveforms: role of charge balance. J
Electrocardiol. 1995;28(suppl):25–30.
5.
Jones JL, Swartz JF, Jones RE, Fletcher R. Increasing
fibrillation duration enhances relative asymmetrical biphasic versus
monophasic defibrillator waveform efficacy. Circ Res.. 1990;67:376–384.
6.
Schuder JC, Gold JH, Stoeckle H, McDaniel WC, Cheung
KN. Transthoracic ventricular defibrillation in
the 100 kg calf with symmetrical one-cycle bidirectional rectangular
wave stimuli. IEEE Trans Biomed Eng. 1983;30:415–422.[Medline]
[Order article via Infotrieve]
7.
Schuder JC, McDaniel WC, Stoeckle H.
Transthoracic defibrillation of 100 kg calves with
bidirectional truncated exponential shocks. Trans Am Soc Artif
Intern Organs.. 1984;30:520–525.[Medline]
[Order article via Infotrieve]
8.
Schuder JC, McDaniel WC, Stoeckle H. Defibrillation of
100 kg calves with asymmetrical, bidirectional, rectangular pulses.
Cardiovasc Res. 1984;18:419–426.[Medline]
[Order article via Infotrieve]
9.
Gliner BE, Lyster TE, Dillion SM, Bardy GH.
Transthoracic defibrillation of swine with monophasic and
biphasic waveforms. Circulation. 1995;92:1634–1643.
10.
Chapman PD, Vetter JW, Souza JJ, Wetherbee JN, Troup
PJ. Comparison of monophasic with single and dual capacitor
biphasic waveforms for nonthoracotomy canine internal defibrillation.
J Am Coll Cardiol.. 1989;14:242–245.[Abstract]
11.
Fain ES, Sweeney MB, Franz MR. Improved internal
defibrillation efficacy with a biphasic waveform. Am Heart
J.. 1989;117:358–364.[Medline]
[Order article via Infotrieve]
12.
Wyse DG, Kavanagh KM, Gillis AM, Mitchell LB, Duff HJ,
Sheldon RS, Kieser TM, Maitland A, Flanagan P, Rothschild J, et al.
Comparison of biphasic and monophasic shocks for defibrillation using a
nonthoracotomy system. Am J Cardiol. 1993;71:197–202.[Medline]
[Order article via Infotrieve]
13.
Winkle RA, Mead RH, Ruder MA, Gaudiani V, Buch WS,
Pless B, Sweeney M, Schmidt P. Improved low energy defibrillation
efficacy in man with the use of a biphasic truncated exponential
waveform. Am Heart J. 1989;117:122–127.[Medline]
[Order article via Infotrieve]
14.
Bardy GH, Ivey TD, Allen MD, Johnson G, Mehra R, Greene
HL. A prospective randomized evaluation of biphasic versus monophasic
waveform pulses on defibrillation efficacy in humans. J Am
Coll Cardiol.. 1989;14:728–733.[Abstract]
15.
Bardy GH, Gliner BE, Kudenchuk PJ, Poole JE, Dolack GL,
Jones GK, Anderson J, Troutman C, Johnson G. Truncated biphasic pulses
for transthoracic defibrillation. Circulation.. 1995;91:1768–1774.
16.
Bardy GH, Marchlinski FE, Sharma AD, Worley SJ, Luceri
RM, Yee R, Halperin BD, Fellows CL, Ahern TS, Chilson DA, Packer DL,
Wilber DJ, Mattioni TA, Reddy R, Kronmal RA, Lazzara R, for the
Transthoracic Investigators. Multicenter comparison of truncated
biphasic shocks and standard damped sine wave monophasic shocks for
transthoracic ventricular defibrillation.
Circulation. 1996;94:2507–2514.
17.
Greene HL, DiMarco JP, Kudenchuk PJ, Scheinman MM, Tang
AS, Reiter MJ, Echt DS, Chapman PD, Jazayeri MR, Chapman FW, et al.
Comparison of monophasic and biphasic defibrillating pulse waveforms
for transthoracic cardioversion. Biphasic Waveform
Defibrillation Investigators. Am J Cardiol.. 1995;75:1135–1139.[Medline]
[Order article via Infotrieve]
18.
White R. Early out-of-hospital experience with an
impedance-compensating low-energy biphasic waveform automatic external
defibrillator. J Intervent Card Electrophysiol. 1997;1:203–208.[Medline]
[Order article via Infotrieve]
19.
Poole JE, White RD, Kanz KG, Hengstenberg F, Jarrard
GT, Robinson JC, Santana V, McKenas DK, Rich N, Rosas S, Merritt S,
Magnotto L, Gallagher JV III, Gliner BE, Jorgenson DB, Morgan CB,
Dillon SM, Kronmal RA, Bardy GH. Low-energy impedance-compensating
biphasic waveforms terminate ventricular fibrillation at
high rates in victims of out-of-hospital cardiac arrest. LIFE
Investigators. J Cardiovasc Electrophysiol.. 1997;8:1373–1385.[Medline]
[Order article via Infotrieve]
20.
Gliner B, White R. A low-energy, impedance-compensating
biphasic waveform defibrillates at high rates compared with a
high-energy monophasic waveform in victims of out-of-hospital cardiac
arrest. 1998. In review.
21.
Emergency Cardiac Care Committee and Subcommittees,
American Heart Association. Guidelines for cardiopulmonary
resuscitation and emergency cardiac care, III: adult advanced cardiac
life support. JAMA. 1992;268:2208–2209.
22.
Emergency Cardiac Care Committee and Subcommittees,
American Heart Association. Guidelines for cardiopulmonary
resuscitation (CPR) and emergency cardiac care (ECC), III: adult
advanced cardiac life support. JAMA. 1986;255:2945–2946.
23.
Cummins RO, Ornato JP, Thies W, Pepe PE. Improving
survival from sudden cardiac arrest: the `chain of survival' concept:
a statement for health professionals from the Advanced Cardiac Life
Support Subcommittee and the Emergency Cardiac Care Committee, American
Heart Association. Circulation. 1991;83:1832–1847.
24.
Emergency Cardiac Care Committee and Subcommittees,
American Heart Association. Guidelines for cardiopulmonary
resuscitation and emergency cardiac care, IX: ensuring effectiveness of
communitywide emergency cardiac care. JAMA.. 1992;268:2289–2295.
25.
Kerber RE. Statement on early defibrillation from the
Emergency Cardiac Care Committee, American Heart Association.
Circulation. 1991;83:2233.
26.
Weisfeldt ML, Kerber RE, McGoldrick RP, Moss AJ, Nichol
G, Ornato JP, Palmer DG, Riegel B, Smith SC Jr. Public access
defibrillation: a statement for healthcare professionals from the
American Heart Association Task Force on Automatic External
Defibrillation. Circulation.. 1995;92:2763.
27.
Cobb LA, Eliastam M, Kerber RE, Melker R, Moss AJ,
Newell L, Paraskos JA, Weaver WD, Weil M, Weisfeldt ML. Report of the
American Heart Association Task Force on the Future of
Cardiopulmonary Resuscitation. Circulation.. 1992;85:2346–2355.
28.
Stapleton EM, Aufderheide TP, Hazinski MF, et al.
Heartsaver AED. Dallas, Tex: American Heart Association;
1998. In press.
29.
AHA Subcommittee on Advanced Cardiac Life Support.
Cummins RO, Billi JE, eds. Instructor's Manual for Advanced
Cardiac Life Support. Dallas, Tex: American Heart Association;
1994.
30.
Weisfeldt ML, Kerber RE, McGoldrick RP, Moss AJ, Nichol
G, Ornato JP, Palmer DG, Riegel B, Smith SC Jr. American Heart
Association report on the Public Access Defibrillation Conference,
December 8–10, 1994. Automatic External Defibrillation Task Force.
Circulation. 1995;92:2740–2747.
31.
Nichol G, Hallstrom A, Kerber R, et al. Report on the
Second American Heart Association Public Access Defibrillation
Conference, April 17–19, 1997. Circulation. 1998. In press.
32.
When Every Second Counts: Cardiac Arrest and the
Need for Early Defibrillation. Dallas, Tex: American Heart
Association; 1995.
33.
Hazinski MF, Cummins RO, Bowser P, and the Emergency
Cardiovascular Care Committee. Recommended elements to
include in legislation to support public access defibrillation.
Circulation. 1998. In press.
34.
Kerber RE, Becker LB, Bourland JD, Cummins RO,
Hallstrom AP, Michos MB, Nichol G, Ornato JP, Thies WH, White RD,
Zuckerman BD. Automatic external defibrillators for public access
defibrillation: recommendations for specifying and reporting
arrhythmia analysis algorithm performance,
incorporating new waveforms, and enhancing safety: a statement for
health professionals from the AHA Task Force on Automatic External
Defibrillation, Subcommittee on AED Safety and Efficacy.
Circulation. 1997;95:1677–1682.
35.
Riegel B. Training the public to use external
defibrillators: principles of adult learning and review of the
literature. Ann Emerg Med. 1998. In review.
36.
Ideker RE, Charbonnier F. Established and alternative
waveforms. Workshop report presented at the Second American
Heart Association Public Access Defibrillation Conference; April 19,
1997; Washington, DC.
37.
Scott BD, Kallok MJ, Birkett C, Keiso R, Kerber RE.
Transthoracic defibrillation: effect of dual-pathway
sequential pulse shocks and single pathway biphasic pulse shocks in a
canine model. Am Heart J.. 1993;125:99–109.[Medline]
[Order article via Infotrieve]
38.
Tang AS, Yabe S, Wharton JM, Dolker M, Smith WM, Ideker
RE. Ventricular defibrillation using biphasic waveforms:
the importance of phasic duration. J Am Coll Cardiol.
1989:207–214.
39.
Feeser SA, Tang AS, Kavanagh KM, Rollins DL, Smith WM,
Wolf PD, Ideker RE. Strength-duration and probability of success curves
for defibrillation with biphasic waveforms. Circulation. 1990;82:2128–2141.
40.
Bardy GH, Dolack GL, Poole JE, Kudenchuk PJ, Johnson G,
Raitt MH, Mehra R, DeGroot P, Hofer BO. A prospective randomized
comparison in humans of 50% vs 65% tilt biphasic pulse defibrillation
using the unipolar pectoral transvenous defibrillation system.
Circulation. 1993;88(suppl I):I-113. Abstract.
41.
Kerber RE, Martins JB, Kienzle MG, Constantin L,
Olshansky B, Hopson R, Charbonnier F. Energy, current, and success in
defibrillation and cardioversion: clinical studies using an automated
impedance-based method of energy adjustment. Circulation. 1988;77:1038–1046.
42.
Kerber RE. Electrical treatment of cardiac
arrhythmias: defibrillation and cardioversion. Ann Emerg
Med. 1993;22:296–301.[Medline]
[Order article via Infotrieve]
43.
Behr JC, Hartley LL, York DK, Brown DD, Kerber RE.
Truncated exponential versus damped sinusoidal waveform shocks for
transthoracic defibrillation. Am J Cardiol. 1996;78:1242–1245.[Medline]
[Order article via Infotrieve]
44.
Weaver W, Cobb L, Copass M, et al.
Ventricular defibrillation: a comparative trial using 175-J
and 320-J shocks. N Engl J Med. 1982;307:1101–1106.[Abstract]
45.
Brewer JE, Lilja GP, Tay S-W, Mason J. Automated
external defibrillators using truncated exponential waveforms have good
field performance. Prehosp Emerg Care. 1997;1:190.
Abstract.
46.
Yakatis RW, Ewy GA, Otto CW, Taren DL, Moon TE.
Influence of time and therapy on ventricular defibrillation
in dogs. Crit Care Med.. 1980;8:157–163.[Medline]
[Order article via Infotrieve]
47.
Bardy GH, Gliner BE, White RD. Comparison of human
defibrillation efficacy rates in short-duration and long-duration
ventricular fibrillation using monophasic and biphasic
transthoracic shocks. Circulation.
1997;96(suppl):I-560. Abstract.
48.
Cummins RO, Chamberlain DA, Abramson NS, Allen M,
Baskett PJ, Becker L, Bossaert L, Delooz HH, Dick WF, Eisenberg MS, et
al. Recommended guidelines for uniform reporting of data from
out-of-hospital cardiac arrest: the Utstein Style. A statement for
health professionals from a task force of the American Heart
Association, the European Resuscitation Council, the Heart and Stroke
Foundation of Canada, and the Australian Resuscitation Council.
Circulation. 1991;84:960–975.
49.
Cummins RO, Chamberlain D, Hazinski MF, Nadkarni V,
Kloeck W, Kramer E, Becker L, Robertson C, Koster R, Zaritsky A,
Bossaert L, Ornato JP, Callanan V, Allen M, Steen P, Connolly B,
Sanders A, Idris A, Cobbe S. Recommended guidelines for reviewing,
reporting, and conducting research on in-hospital resuscitation: the
in-hospital `Utstein Style.' A statement for healthcare professionals
from the American Heart Association, the European Resuscitation
Council, the Heart and Stroke Foundation of Canada, the Australian
Resuscitation Council, and the Resuscitation Councils of Southern
Africa. Circulation. 1997;95:2213–2239.
50.
Zaritsky A, Nadkarni V, Hazinski MF, Foltin G, Quan L,
Wright J, Fiser D, Zideman D, O'Malley P, Chameides L, et al.
Recommended guidelines for uniform reporting of pediatric advanced life
support: the pediatric Utstein Style. A statement for healthcare
professionals from a task force of the American Academy of Pediatrics,
the American Heart Association, and the European Resuscitation Council.
Circulation. 1995;92:2006–2020.
51.
Idris AH, Becker LB, Ornato JP, Hedges JR, Bircher NG,
Chandra NC, Cummins RO, Dick W, Ebmeyer U, Halperin HR, Hazinski MF,
Kerber RE, Kern KB, Safar P, Steen PA, Swindle MM, Tsitlik JE, von
Planta I, von Planta M, Wears RL, Weil MH. Utstein-style guidelines for
uniform reporting of laboratory CPR research: a statement for
healthcare professionals from a task force of the American Heart
Association, the American College of Emergency Physicians, the American
College of Cardiologists, the European Resuscitation Council, the Heart
and Stroke Foundation of Canada, the Institute of Critical Care
Medicine, the Safar Center for Resuscitation Research, and the Society
for Academic Emergency Medicine. Writing group. Circulation. 1996;94:2324–2336.
52.
Cummins RO, Eisenberg MS, Hallstrom AP, Hearne TR,
Graves JR, Litwin PE. What is a `save'? Outcome measures in clinical
evaluations of automatic external defibrillators. Am Heart
J. 1985;110:1133–1138.[Medline]
[Order article via Infotrieve]
53.
Jones JL, Jones RE. Improved defibrillator waveform
safety factor with biphasic waveforms. Am J Physiol.. 1983;245:H60–H65.
54.
Cummins RO, Chamberlain DA. Advisory statements of the
International Liaison Committee on Resuscitation.
Circulation.. 1997;95:2172–2173.
55.
Cummins RO. Human research on cardiopulmonary
resuscitation: current constraints on implementation. New
Horiz. 1997;5:120–127.[Medline]
[Order article via Infotrieve]
56.
Reddy RK, Gleva MJ, Gliner BE, Dolack GL, Kudenchuk PJ,
Poole JE, Bardy GH. Biphasic transthoracic defibrillation
causes fewer ECG ST-segment changes after shock. Ann Emerg
Med.. 1997;30:127–134.[Medline]
[Order article via Infotrieve]
57.
Ujhelyi MR, Schur M, Frede T, Gabel M, Markel ML.
Differential effects of lidocaine on defibrillation threshold with
monophasic versus biphasic shock waveforms. Circulation.. 1995;92:1644–1650.
58.
Kerber R. Early out-of-hospital experience with an
impedance-compensating low-energy biphasic waveform automatic external
defibrillator. J Intervent Card Electrophysiol.. 1997;1:209–211. Editorial comment.
59.
Jones JL, Milne KB. Dysfunction and safety factor
strength-duration curves for biphasic defibrillator waveforms.
Am J Physiol. 1994;266:H263–H271.
© 1998 American Heart Association, Inc.
AHA Scientific Statement
Low-Energy Biphasic Waveform Defibrillation: Evidence-Based Review Applied to Emergency Cardiovascular Care Guidelines
A Statement for Healthcare Professionals From the American Heart Association Committee on Emergency Cardiovascular Care and the Subcommittees on Basic Life Support, Advanced Cardiac Life Support, and Pediatric Resuscitation
Key Words: AHA Medical/Scientific Statements • defibrillation • sudden death • cardiopulmonary resuscitation
Clinicians
and responsible medical directors have phrased these questions in the
context of the 1992 AHA Guidelines for Cardiopulmonary
Resuscitation and Emergency Cardiac Care.1 The
guidelines did not address defibrillation waveforms because AEDs using
biphasic waveforms were not commercially available until 1996 (1
biphasic AED, which is no longer available, existed before the 1976
Food and Drug Administration [FDA] amendment). 
displays the AHA template
for evidence-based review of ECC guidelines. A brief summary of these
steps applied to the clinical question of biphasic defibrillation
follows.
View larger version (38K):
[in a new window]
Figure 1. AHA template for evidence-based evaluations of
emergency cardiovascular care guideline recommendations.
Reviewers must gather evidence in the context of a specific,
refined clinical question. The questions regarding biphasic
defibrillators, which are discussed below, are specifically related to
the use of these devices in humans in the out-of-hospital setting.
Numerous studies of biphasic waveform defibrillation have been
published, including
Step 2a: Determine the Level of Evidence (Power of
Methodology)
This step requires identification of methods used in the research
projects. Some study designs and methods are intrinsically more
powerful than others. The ECC Committee uses 8 levels of evidence,
which are listed and defined in Table 1.
View this table:
[in a new window]
Table 1. AHA Emergency Cardiovascular Care
Levels of Evidence
In this step the study is critiqued, and reviewers determine how
well the researchers executed their design: "This was a randomized,
controlled trial, but was it a good randomized, controlled
trial?"
To determine the final class of recommendation, experts must
integrate a heterogeneous collection of research, which is
sorted by level of evidence and quality of execution. This is not an
explicit step. Valid methods are lacking to weigh and sum multiple
studies in which different methods were used and executed with varying
degrees of success. In the final analysis, guideline developers
as well as expert reviewers must make a form of global subjective
judgment that integrates the evidence review with personal experience
and existing expertise. Table 2
summarizes and defines the 1998 classes of recommendation used to
qualify the ECC guidelines. Note that the ECC Committee and
subcommittees have revised the language describing these classes of
recommendations since publication of the 1992
guidelines.1 Previously the 4-point scale used
the terms definitely useful, probably useful, possibly
useful, and harmful. The improved scale defines the
strength of evidence as excellent, very good, fair to good,
and harmful.
View this table:
[in a new window]
Table 2. 1998 Classes of Recommendations for Therapeutic
Interventions in Cardiopulmonary Resuscitation and Emergency
Cardiovascular Care along with a level-of-evidence
notation as defined in Table 1
.
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[in a new window]
Figure 2. Recommended steps to validate alternative
defibrillation waveforms. Each of these steps was followed by the
manufacturer of the AED reviewed in this report. FDA indicates Food and
Drug Administration. From the AHA Task Force on Automated External
Defibrillation, Subcommittee on AED Safety and
Efficacy.34 ). illustrates the sequence of direct
evidence related to biphasic waveform defibrillation.
View larger version (27K):
[in a new window]
Figure 3. Sequence of research and levels of evidence
related to biphasic waveform defibrillation. EPS indicates
electrophysiological study, and FDA, Food
and Drug Administration. .15 16 17 This data
demonstrates that
View this table:
[in a new window]
Table 3. In-Hospital and Out-of-Hospital Clinical Evidence on
Alternative Waveform and Energy Level Defibrillation
summarizes results from 2 of the 3 articles.19 20
The third article discusses the work of Roger D. White and colleagues
in Rochester, Minn.18 Although Dr. White's
article is the first report on out-of-hospital use of a low-energy
biphasic defibrillator, the 10 patients described are also discussed in
the 2 later reports that review a larger experience. Table 3 also
summarizes 3 other studies (1 unpublished) that provide comparative
data on alternative waveforms and energy levels in the out-of-hospital
setting.43 44 45 . This
table is not a meta-analysis based on a comprehensive
literature review using prescribed criteria to determine study
eligibility. Therefore, any pooling of data or detailed cross-study
comparisons would be invalid. These studies simply provide a
broad-stroke framework for the question, "Do these various waveforms
appear to have clinical equivalence?" lists
the variations in definition that occurred or were
mentioned.15 16 19 20 43 44 45
View this table:
[in a new window]
Table 4. Variations in Shock "Success" or Outcome
Nomenclature and Definitions 
3 shocks success," or "return of an organized rhythm" for
the 2 monophasic waveforms reflects progressive shock energies
delivered to VF patients during resuscitation. These patients averaged
3 to 4 shocks during resuscitation. The standard protocols call for an
increase in energy levels after the first shock. A rough comparison
becomes available when the outcomes for multiple monophasic shocks are
compared with outcomes for multiple biphasic shocks. Such a comparison
provides a simple test of the sequence 150 J-150 J-150 J
biphasic shocks versus 200 J-300 J-360 J
monophasic shocks. If there is a clinical disadvantage for
persistent low-energy biphasic shocks compared with progressive-energy
monophasic shocks, the disadvantage should appear in these data. , however, demonstrates that the
"all shocks or 3 shocks success" rate was higher for the biphasic
AED than for the monophasic damped sinusoidal AED and
truncated exponential AED:
View this table:
[in a new window]
Table 5. Outcomes of Out-of-Hospital Defibrillation With AEDs
Using Three Different Waveforms
The numerous preliminary laboratory,3 4 5 53
animal,6 7 8 and pilot human
studies13 14 15 40 provided compelling support for
performing multicenter studies in EPS laboratories. Subsequently the 2
multicenter studies of transthoracic biphasic rescue shocks
delivered in the EPS laboratory provided definitive Level 1 evidence to
confirm the efficacy of biphasic shocks in very short–duration,
witnessed VF arrest induced by an electric
stimulus.16 17
At the start of this review, only 3 articles in the prepublication
stage addressed the question of biphasic waveform defibrillation for
out-of-hospital cardiac arrest.18 19 20 Data from
all 3 studies was considered only Level 4 or Level 5 evidence because
of the simple case-series design and the small numbers of VF patients
treated with the biphasic defibrillator: 10 patients were listed in the
original report from Rochester,18 18 in the
Gliner paper20 (including the 10 from the White
paper), and 44 in the Poole paper19 (including
the 18 from the Gliner paper). As of October 1, 1997, only 44 VF
patients provided the total clinical out-of-hospital experience with
biphasic defibrillation. Two of the 14 reviewers considered these
numbers unacceptably small and the data insufficient evidence on which
to base any statement.
The success of defibrillation waveforms should be reported in
terms of the most widely accepted definition of resuscitation
success—survival-to–hospital discharge.48 This
primary outcome, however, was not available in the case series reported
by Poole et al19 because of the intrinsic
limitations of postmarket surveillance data. In most cases, researchers
had only intermediate outcome information downloaded from the AED
event-documentation PCMCIA card. Although clinical data were supplied
for some patients, often outcome determination ended when the patients
were transported to the emergency department. Neither the Gliner nor
the Poole study provided the recommended outcome of
survival-to–hospital discharge. In the White study, only 1 of 10
patients survived to hospital discharge.
The 3 unpublished studies supplied few of the variables in
patients, emergency medical services, treatment, and outcome
recommended in the Utstein guidelines for reporting outcome of
out-of-hospital cardiac arrest.48 For example,
the variables related to witnessed arrest, bystander CPR, and
collapse-to–treatment intervals are largely lacking. The more
comprehensive articles with respect to clinical variables (the
original articles by White18 and
Gliner20 ) report on only 10 and 18 patients,
respectively.
For this report, evidence existed only at Level 4
(historically controlled, retrospective cohort studies) and Level
5 (a case series with a historical control group assembled
from published articles). There is no definitive Level 1 evidence
regarding performance of low-energy biphasic defibrillators in
the out-of-hospital setting. No randomized, controlled prospective
clinical trial discusses either of the 2 clinical questions: 150 J
biphasic versus 200 J monophasic for first shock success or a sequence
of 150 J-150 J-150 J biphasic shocks versus 200 J-300 J-360 J
monophasic shocks for persistent shock-refractory VF.
There are simply no out-of-hospital prospective studies of
defibrillation waveforms, either monophasic or biphasic. Consequently
it becomes impossible to define an expected performance level
for a new alternative waveform such as a low-energy,
impedance-compensated biphasic shock. Because clinical outcomes, such
as survival-to–hospital discharge, are multifactorial in nature, the
incremental value of a single intervention, such as a different
defibrillation waveform, cannot be determined. A review of previous AHA
guidelines for the energy sequence 200 J-300 J-360 J reveals that the
evidence supporting this reputed "gold standard" is largely
speculative and based on common-sense extrapolations from animal data
and human case series.
More than 1 year after the FDA cleared the first biphasic
defibrillator for commercial sale, the AHA ECC Committee has determined
a class of recommendation for the device. For medical devices, the FDA
must determine whether a device is safe and effective when
used as intended. Safety means that the probable benefits of
a device to health outweigh any probable risks when used in the manner
for which it was intended and when accompanied by adequate warnings and
directions for use. "Effectiveness," from the FDA perspective,
means that in a significant portion of the target population the use of
a device for its intended purpose will provide clinically significant
benefit. The device is not required to work for every patient. ) rather
than commercial distribution. The manufacturer of this biphasic AED
followed the sequence noted in Fig 3, including FDA review and
postmarketing studies.
Although 150-J impedance-based biphasic AEDs may perform
effectively for a large percentage of out-of-hospital VF arrest
patients, an unidentified proportion of patients will still need a
higher energy shock. This energy reserve is lacking in the current
biphasic device. In the 44 VF patients reported thus far, the
all-shocks defibrillation success rate was 80% in 1
study19 and 91% in the
other.20 It would be a misinterpretation,
however, to argue that the remaining patients simply needed higher
energy levels. Multiple high-energy shocks could easily result in more
harm than good. A current perspective, as yet unproved, is that
multiple low-energy shocks may be superior to a few high-energy
shocks.
Low-energy, biphasic waveform defibrillation met the stated
criteria for guideline review:
The clinical questions are related to initial shocks delivered at
150 J (rather than the traditional 200 J) and all subsequent shocks
delivered at 150 J (rather than the traditional progressive energy
shocks of 300 J to 360 J). The refined guideline questions
were phrased in terms of out-of-hospital human cardiac
arrest, a situation for which results of published studies were not
available. Therefore, the process of gathering evidence included not
only bibliography reviews and database searches but also a request for
any unpublished or prepublication research data related to
out-of-hospital VF cardiac arrest in humans treated with biphasic
waveform defibrillators. Two articles scheduled for publication and one
in preparation were identified18 19 20 as well as
an unpublished case series originally presented at a conference
as an abstract and poster.45
Step 2b: Critically Evaluate the Evidence summarizes 3 studies from an in-hospital setting: a
moderate-sized multicenter Level 1B study with 47
patients,17 a moderate-sized Level 1B
study with 30 patients,15 and a large multicenter
Level 1B study with 294 patients.16
These studies, in the rigorously controlled setting of in-hospital EPS
laboratories with witnessed, stimulus-induced VF of short duration,
were considered to be of high quality, exact execution, and powerful
design. summarizes a Level 5 case
series reporting on the first 44 VF patients treated with the biphasic
AED18 and a Level 4 series reporting on 18
patients treated with the biphasic AED.20 Lacking
a contemporaneous control group, instead the authors constructed a
control group by examining published studies of monophasic
defibrillation. For purposes of comparison, 3 of these "control
group" studies are summarized in Table 3.43 44 45
The quality of these data was considered modest.
Evidence-based guidelines should display a close match between the
level and quality of evidence and the final class of recommendation.
Table 2 describes Classes I, IIa, and IIb as acceptable,
differing in the strength of the supporting evidence. A number of
"mismatch" factors may come into play in the integration of
evidence into a final class of recommendation,2
including cost, practicality, ease of teaching and learning, and
comparisons with "standard" practices that have arisen from
common-sense extrapolations rather than compelling evidence. 
The human
out-of-hospital studies that currently exist, however, are only
fair-to-good observational studies (Level 4) and case series (Level 5);
definitive Level 1 evidence is not yet available.
This is
consistent with a Class IIb recommendation:
acceptable and useful; fair-to-good evidence provides support.
Low-energy,
nonprogressive biphasic waveform defibrillators may be used for both
out-of-hospital and in-hospital VF arrest, including persistent or
recurrent VF that does not respond to the initial low-energy shock.
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