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Echocardiographic Evaluation of a Taser-x26 Application in the Ideal Human Cardiac Axis Jeffrey Ho Et Al 2008.pdf

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BASIC INVESTIGATION

Echocardiographic Evaluation of a
TASER-X26 Application in the Ideal Human
Cardiac Axis
Jeffrey D. Ho, MD, Donald M. Dawes, MD, Robert F. Reardon, MD, Anne L. Lapine, MD,
Benjamin J. Dolan, BS, Erik J. Lundin, BS, James R. Miner, MD

Abstract
Objectives: TASER electronic control devices (ECDs) are used by law enforcement to subdue aggressive
persons. Some deaths temporally proximate to their use have occurred. There is speculation that these
devices can cause dangerous cardiac rhythms. Swine research supports this hypothesis and has
reported significant tachyarrhythmias. It is not known if this occurs in humans. The objective of this
study was to determine the occurrence of tachyarrhythmias in human subjects subjected to an ECD
application.
Methods: This was a prospective, nonblinded study. Human volunteers underwent limited echocardiography before, during, and after a 10-second TASER X26 ECD application with preplaced thoracic electrodes positioned in the upper right sternal border and the cardiac apex. Images were analyzed using
M-mode through the anterior leaflet of the mitral valve for evidence of arrhythmia. Heart rate (HR) and
the presence of sinus rhythm were determined. Data were analyzed using descriptive statistics.
Results: A total of 34 subjects were enrolled. There were no adverse events reported. The mean HR
prior to starting the event was 108.7 beats ⁄ min (range 65 to 146 beats ⁄ min, 95% CI = 101.0 to
116.4 beats ⁄ min). During the ECD exposure, the mean HR was 120.1 beats ⁄ min (range 70 to 158 beats ⁄ min, 95% CI = 112.2 to 128.0 beats ⁄ min) and a mean of 94.1 beats ⁄ min (range 55 to 121 beats ⁄ min, 95%
CI = 88.4 to 99.7 beats ⁄ min) at 1 minute after ECD exposure. Sinus rhythm was clearly demonstrated in
21 (61.7%) subjects during ECD exposure (mean HR 121.4 beats ⁄ min; range 75 to 158 beats ⁄ min, 95%
CI = 111.5 to 131.4). Sinus rhythm was not clearly demonstrated in 12 subjects due to movement artifact
(mean HR 117.8 beats ⁄ min, range 70 to 152 beats ⁄ min, 95% CI = 102.8 to 132.8 beats ⁄ min).
Conclusions: A 10-second ECD exposure in an ideal cardiac axis application did not demonstrate concerning tachyarrhythmias using human models. The swine model may have limitations when evaluating
ECD technology.
ACADEMIC EMERGENCY MEDICINE 2008; 15:838–844 ª 2008 by the Society for Academic Emergency
Medicine
Keywords: TASER, conducted electrical weapon, electronic control device

T

ASER electronic control devices (ECDs) are primarily used by law enforcement officials to subdue or repel aggressive and potentially violent

From the Department of Emergency Medicine, Hennepin
County Medical Center (JDH, RFR, ALL, BJD, JRM), Minneapolis, MN; the Department of Emergency Medicine, Lompoc
Valley Medical Center (DMD), Lompoc, CA; and Western
Kentucky University (EJL), Bowling Green, KY.
Received March 8, 2008; revisions received April 24 and April
26, 2008; accepted April 26, 2008.
Presented at the 2008 Heart Rhythm Society Annual Meeting,
San Francisco, CA, May 2008; and at the 2008 CARDIOSTIM
Annual Meeting, Nice, France, June 2008.
Address for correspondence and reprints: Jeffrey D. Ho, MD;
e-mail: Hoxxx010@umn.edu

838

ISSN 1069-6563
PII ISSN 1069-6563583

persons. Some deaths have occurred temporally proximate to ECD use. Human research has not demonstrated
a connection between these two events to date, but there
has been speculation that these devices could cause
death by induction of dangerous cardiac rhythms, such
as ventricular capture with resultant tachycardia or
ventricular fibrillation (VF).1
Previous studies in this subject area have not demonstrated a dangerous effect on human volunteers.2–5
However, some recent swine model research supports
the hypothesis that ECD application can cause or contribute to sudden death and has demonstrated cardiac
capture rates of 300 beats ⁄ min as well as induced VF,
especially when the ECD probes or electrodes are
placed in specific locations that appear to mimic an
ideal cardiac conduction pathway along the cardiac

ª 2008 by the Society for Academic Emergency Medicine
doi: 10.1111/j.1553-2712.2008.00201.x

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axis.6–8 This pathway is defined by the American Heart
Association as the recommended path for electrical discharge during emergency defibrillation techniques and
was used to create a discharge vector with a higher
likelihood of producing cardiac capture. We conducted
this study to re-create the animal research with human
subjects to examine this possibility.
METHODS
Study Design
This was a prospective, nonblinded study of adult
human volunteers recruited at several TASER International training courses in 2007. The institutional review
board of Hennepin County Medical Center approved
the study. All subjects provided informed consent
before enrollment.
Study Setting and Population
This study was performed at TASER ECD training
courses using volunteer human subjects attending the
training courses. As a voluntary part of their training,
they were to receive an ECD exposure from a TASER
X26 device. All adult subjects (age > 18 years) who
were going to receive this exposure were eligible for
enrollment in the study. All volunteers were personnel
involved in various aspects of law enforcement. They
did not have to participate in the study as a requirement for successful course completion, but declining to
participate in the study did not necessarily absolve
them from receiving an ECD application as part of the
training course. The exclusion criteria were known
pregnancy and persons with a known mental illness.
Study volunteers were given a TASER X26 ECD on successful completion of the study protocol. The TASERs
were donated by TASER International.
Study Protocol
All volunteers completed a medical questionnaire for
the purpose of gathering additional medical information for descriptive reporting. The descriptive data
points gathered for all subjects included age, gender,
body mass index (BMI) parameters, medical history,
and current medication use. After completion of the
study questionnaire, all volunteers underwent limited
echocardiography before, during, and after a 10-second
TASER X26 ECD application with preplaced thoracic
electrodes. The electrodes were placed in the optimal
cardiac axis position per American Heart Association
guidelines for emergency transcutaneous cardiac defibrillation or pacing.9 This position was at the upper
right sternum and the cardiac apex as estimated by the
palpated point of maximal impulse. Ultrasound images
were analyzed using M-mode through the anterior leaflet of the mitral valve for evidence of arrhythmia by a
trained ultrasonographic emergency physician (EP).
Heart rate (HR) and the presence of sinus rhythm were
determined.
The ECD application consisted of a 10-second continuous application (standard application is 5 seconds
with each trigger pull) with manually applied skin surface electrodes powered by a factory standard TASER
X26 model ECD (Figure 1; TASER International,

Figure 1. TASERX26 electronic control device (ECD; cutaway
view).

Scottsdale, AZ). The exposure consisted of manually
applying electrodes to the volunteer while they were
lying on a padded mat in a supine position. The electrodes were manually placed instead of fired from
the ECD, to assure exact placement position on each
volunteer.
A programmable logic controller (PLC) was used to
accurately control the duration of current delivered
(Allen-Bradley MicroLogix 1500, Maple Systems, Inc.,
Everett, WA). The PLC is not a standard part of an
ECD, but the use of it during this study did not change
the characteristic of the electrical waveform. The purpose of the PLC was to enable the ECD current application to be delivered in an objective, reproducible, and
controlled fashion. With the exception of this PLC, the
ECD was not altered from the factory standard. The
PLC was programmed to deliver the ECD discharge for
a total of 10 continuous seconds. Upon completion of
the application protocol, the electrodes were removed,
the attachment points were disinfected, and adhesive
bandages were applied if needed.
Echocardiography was used for continuous cardiac
monitoring before, during, and after the ECD exposure,
so that HR and rhythm could be determined without
interruption. A parasternal long-axis view of the heart
was obtained by an unblinded, trained EP sonographer,
and M-mode was used to record a continuous tracing
of the mitral valve (Figure 2). A Sonosite Micromaxx
(SonoSite, Inc., Bothell, WA) with a P17 tranducer (5–1
MHz 17-mm broadband phased array) was used to
obtain echocardiographic images. An obstetrical preset
(machine imaging mode allowing for computer calculated HR) was used, so that HR could be accurately
determined by measuring the distance between E and
A peaks on the M-mode tracing. Echocardiograms
were continuously recorded, for later review, as
MPEG-4 videos using Security Spy software (http://
www.securityspy.com/) with a direct feed into a MacBook computer. Each M-mode tracing was immediately
measured to accurately determine HR before, during,
and after ECD exposure. Captured video was later
reviewed by the ultrasound physician to determine if
sinus rhythm could be demonstrated during ECD

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HUMAN CARDIAC AXIS TASER APPLICATION

Figure 2. Echocardiographic M-mode image of E-A wave peaks of mitral valve and long-axis parasternal view of the heart.

exposure by the presence of an E ⁄ A pattern on Mmode tracing.
Data Analysis
All data were recorded in a spreadsheet format and
underwent descriptive statistical analysis.
RESULTS
A total of 33 subjects were enrolled, 100% were male,
mean (±standard deviation [SD]) BMI 29.8 (±4.8), mean
age 40.5 (±10.5) years, range 28 to 59 years. There were
no adverse events reported. The mean HR prior to
starting the event was 108.7 beats ⁄ min (range 65 to
146 beats ⁄ min, 95% CI = 101.0 to 116.4 beats ⁄ min).
During the ECD exposure, the mean HR was
120.1 beats ⁄ min (range 70 to 158 beats ⁄ min, 95%
CI = 112.2 to 128.0 beats ⁄ min) and a mean of
94.1 beats ⁄ min (range 55 to 121 beats ⁄ min, 95%
CI = 88.4 to 99.7 beats ⁄ min) at 1 minute after ECD
exposure. Sinus rhythm was clearly demonstrated in
21 (61.7%) subjects during ECD exposure (mean HR
121.4 beats ⁄ min; range 75 to 158 beats ⁄ min, 95%
CI = 111.5 to 131.4 beats ⁄ min). Sinus rhythm was not
clearly demonstrated in 12 subjects due to movement
artifact (mean HR 117.8 beats ⁄ min, range 70 to
152 beats ⁄ min, 95% CI = 102.8 to 132.8 beats ⁄ min).
There were no episodes of ventricular tachyarrhythmias
noted in 33 ⁄ 33 cases (100%, 95% CI = 89.6% to 100%).
There were 11 volunteers with significant past medical problems requiring controlling medications. There
were 6 subjects with hypercholesterolemia on statins,
2 subjects with hypertension on ACE inhibitors, two
subjects with diabetes on oral hypoglycemics, and one
subject with hypothyroidism on synthroid.

DISCUSSION
TASER is a brand name (acronym for Thomas A. Swift
Electric Rifle) of ECD and is manufactured by TASER
International, Inc. (Scottsdale, AZ). The terms TASER
and ECD are often used interchangeably because, at
the time of this writing, the TASER brand of ECD has
market product dominance. Currently, TASER International manufactures two law enforcement models (X26
and M26) and four civilian models (C2, X26c, M18, and
M18L). The X26 is the latest generation and the most
popular model currently in use and was the model used
in this study. It is considered to be a nonlethal weapon
under the definition set forth by the United States
Department of Defense,10 and it is generally considered
to be an intermediate weapon by most law enforcement
agencies.
Intermediate weapons (those devices that generally
can induce subject compliance due to pain or incapacitation and are a level above empty hand control techniques but less than deadly force) are available for law
enforcement, military, and civilian applications. Examples of intermediate weapons include devices such as
aerosolized chemical irritants, impact batons, projectile
beanbags, and ECDs. The ECD has received some favor
by law enforcement officials because it appears to offer
a force alternative that effectively decreases suspect
and officer injuries.11,12
The TASER X26 ECD is programmed to deliver a
roughly rectangular pulse of approximately 100 lsec
duration with about 100 lC of charge at 19 pulses per
second for 5 seconds.13 The peak voltage across the
body is approximately 1200 Volts, but the weapon also
develops an open circuit arc of 50,000 Volts to traverse
clothing in cases where no direct contact is made. The

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average current is approximately 2.1 milliamperes. It
uses compressed nitrogen to fire two metallic darts up
to a maximum of 35 feet with a predetermined angled
rate of spread. It is capable of transmitting an electrical
impulse through two cumulative inches of clothing.
When it makes adequate contact and the darts are
of adequate separation (approximately 4 inches or
greater), it causes involuntary contractions of the regional skeletal muscles that render the subject incapable of
voluntary movement. If the darts are fired at very close
range and do not achieve adequate separation, full
muscular incapacitation may not be achieved, and the
device is then used to encourage certain behavior
through pain compliance. Additionally, the TASER
device has electrical contact points at its tip that are
approximately 1.5 inches apart. These contact points
may be touched to a subject during discharge of the
weapon and are also considered a pain compliance
technique, as the separation is not adequate to cause a
full, involuntary contraction of muscles.
A prior human study has utilized a 5-second ECD
exposure time that is generally accepted as equivalent
to a single ECD exposure.3 In this current study, we
extended the single ECD application time from 5 seconds to 10 continuous seconds. We believe that this
prolonged time may more accurately reflect some fieldusage patterns, since some agitated subjects require
more than a single ECD application. A single ECD
application is considered to be a single depression of
the trigger that would result in a 5-second discharge
from the device. Alternatively, the ECD trigger could
be depressed continuously, resulting in a ECD discharge for as long as the trigger is depressed. Current
information from the manufacturer suggests that the
majority of ECD exposures in the field are for 5 seconds or less (S. Tuttle, personal communication, April
17, 2007). Another reason that we studied prolonged
application times was to increase the chance of uncovering an adverse effect, if one were to be found.
The placement of the electrodes in our study
deserves some discussion. The American Heart Association guidelines for emergency transcutaneous cardiac
pacing ⁄ defibrillation electrode placement recommend
either sternal–apical, biaxillary, or apical-back positioning as optimal (class IIa: therapeutic option for which
the weight of evidence is in favor of its usefulness and
efficacy) for delivery of electrical current to the myocardium.9 Each of these positions has been evaluated and
found to have equivalent ability to deliver myocardial
current as measured by transthoracic impedance.14
We elected to use only the sternal–apical positioning
(Figure 3); the other two positions described cannot be
achieved during realistic field use of an ECD, since
deployed ECD probes (fired simultaneously) can only
contact a subject on the same side of the body.
Our sternal–apical positioning is similar to the electrode placement used by Dennis et al.7 and Walter et
al.8 in their recent swine studies of ECDs. In their studies, descriptions of tachyarrhythmias to 300 beats ⁄ min
with each exposure and some cases of VF are
described. We have conducted multiple human ECD
research trials with well over 400 subjects to date with
probe positions in numerous configurations on the tho-

841

Figure 3. Sternal–apical electrode positioning.

rax and had never experienced any findings concerning
for tachyarrhythmia induction (such as syncope, palpitations, electrocardiogram changes, etc.). We were
therefore curious to examine the differences between
human and swine modeling in ECD research. In the
current study, we were unable to reproduce in humans
the findings of Dennis et al.7 and Walter et al.8
There are several possible explanations for these differences. Animal models for this type of study are
always artificially manipulated as a result of sedation
and anesthesia required by ethical research boundaries.
It is not known what cardiac effect could result from
the introduction of exogenous medications prior to
ECD exposure. It is likely that sedation, anesthesia, and
supine positioning of a quadruped may affect the
response to an applied ECD. This has been suggested
by previous ECD studies. For example, Jauchem et al.15
showed that a swine model fails to breathe during ECD
application. A study by Ho et al. in 200716 demonstrated
that this does not occur when nonsedated, unanesthetized human subjects are used. The study by Jauchem
et al. initially led many to believe that ECDs might be
causally linked to induction of sudden death due to
asphyxia. However, other studies have failed to demonstrate this.
Animal size may also account for differences in our
findings. Dennis et al.7 used animals between 22 and
46 kilograms, and Walter et al.8 used animals between
25 and 71 kilograms. The Centers for Disease Control
and Prevention reported that the average weight for an
adult male in the United States is 86.5 kilograms.17
Since human males are the usual intended ECD targets,
it is likely to be more valid to use an adult human male
model for this type of research than a swine model. In
our study, the mean weight of our subjects was 96.0
(±14.6) kilograms, which is at least on par with the average American male adult. Additionally, there have been
instances when persons of small stature have experienced a ECD deployment without evidence of sudden
death or disability.18,19 Collectively, this human data do
not support the theory of an ECD-induced fatal
arrhythmia.
It is also possible that the swine model may simply
be a poor model for simulating human exposure to

842

ECDs. In 2007, Ideker and Dosdall20 reviewed animal
data to make assumptions about the ability of the TASER X26 to induce cardiac arrythmias in humans. They
determined that less than 0.4% of adults would have an
ectopic beat induced by a TASER, even when the electrodes were placed in a worst-case scenario location
for pacing. The stimulus required to cause VF is higher
than that needed to cause an ectopic beat, and again
using animal data, they concluded that the pulse needed
to induce VF would have to be 30 times greater than
the TASER X26 pulse. These results are in agreement
with our findings in the human model. However, several investigators using swine models have found that
tachyarrhythmias, and in certain cases, VF can be
induced.6–8 These concerning findings using swine
models are not consistent with the data reported from
human study and experience, where there have been
no reports of collapse, syncope, or death that would be
expected with high capture rates during discharge.2,3,5
Also, the findings of previous studies using a swine
model are not supported by our current findings from
humans.
In our study, 12 subjects had movement artifact, and
the ultrasonic view of the mitral valve was not maintained during the full ECD exposure; however, visualization of the posterior wall of the left ventricle was.
Because the mitral valve view was lost, sinus rhythm
could not be assured with complete certainty in this
group. However, the posterior ventricular wall view
allowed for accurate measurement of the rate of cardiac contraction and this did not rise greater than
152 beats ⁄ min in any of these subjects. This data are in
contradistinction to a previous animal model findings of
cardiac capture reporting rates of 300 beats ⁄ min.7
Although some sudden, unexpected, custodial deaths
have occurred temporally proximate to an ECD application, a causal link between the two has not been established. Critics of ECD technology believe that animal
research findings, as described above, may point in the
direction of potential causation. However, these types
of sudden custodial deaths have been documented well
before the invention of this technology.21 A similar theory of causal relationships occurred when oleoresin
capsicum irritant spray was first introduced into the
law enforcement market.22 Eventually, it was determined that this irritant spray was not the cause of
custodial deaths.23,24 It appears that ECD technology
may now also be going through this type of societal
scrutiny.
Although the possibility of ECD-induced arrhythmias
has been examined previously,2,3 it had not been done
in human subjects using an ideal cardiac axis electrode
placement. Additionally, prior cardiac evaluation studies in humans have always used a before ⁄ after methodology with electrocardiography. The electrical artifact
generated by the ECD application made real-time electrocardiography impossible. Our use of real-time echocardiography has allowed simultaneous delivery of
ECD current and monitoring of HR and rhythm, which
eliminates any uncertainty of arrhythmia induction at
the time of exposure.
If an ECD is capable of causing an arrhythmic death
in humans, one would expect that nearly any induction

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HUMAN CARDIAC AXIS TASER APPLICATION

of arrhythmia would be immediate and result in instantaneous collapse. We acknowledge that the possibility
of electrically induced ventricular tachycardia that
degenerates to VF could occur over several seconds,
but this is rare and is almost never seen in humans
without significant underlying heart disease.20,25,26 In a
surveillance of 8 months of sudden and unexpected custodial death events in the United States, only 27% of
these events were associated with occurrence proximal
to application of a ECD, and none of the subjects collapsed immediately after the application.27 In addition,
an even more compelling set of data comes from the
training classes conducted by the ECD manufacturer
TASER International. These classes have delivered over
700,000 ECD applications to participants with no
reported collapses, cardiac arrests, or fatalities.28 When
these data sets are both considered, the possibility of
an ECD induced arrhythmia seems extremely unlikely.
There has been a single report in a letter to the editor
of a case of VF found after exposure to a ECD that
merits some mention.29 The paramedic field report for
this case (that was not part of the letter) indicated that
the subject received an ECD application because of
apparent threatening behavior toward a police officer
during a prolonged, agitated state. The subject was successfully subdued, but found to be in cardiorespiratory
arrest approximately 15 minutes after the ECD application. We believe that this case is very similar to every
other described in the literature in which the cardiopulmonary arrest event occurs proximal to ECD exposure,
but collapse is not instantaneous. We also believe that
the facts of this case report do not support an electrically induced arrhythmic event.
LIMITATIONS
A potential limitation of our study is the duration of
time that the ECD was applied. The studies by Dennis
et al.7 and Walter et al.8 both used two 40-second ECD
applications. It is possible that if we had used similar
time applications, we may have seen similar results,
although Nanthakumar et al.6 demonstrated ventricular
capture and inducement of VF in swine with single 5to 15-second ECD exposures. We elected to study 10second exposures because of the discomfort involved
with the ECD application, and the fact that two continuous 40-second exposures is an extremely atypical, and
likely unrealistic, application of an ECD under normal
field-use conditions. We believe that a 10-second continuous application more closely approximates the way
that ECDs might typically be used in the field.
We recognize that our small sample size of 33 limits
our ability to detect all concerning events. Also, it is
possible that the study subjects we enrolled may have
body habitus characteristics that could raise their transthoracic impedance above that of a typical American
adult. Our study subjects were exclusively male law
enforcement officers. Had they been asthenic females
with little breast tissue, we may have found a different
result. However, previous research indicates that our
study population closely mimics the population at highest risk for sudden custodial death when gender, age,
and BMI are taken into account.30,31

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Although there is a perception that using law
enforcement personnel as our test population might
introduce a ‘‘healthy’’ population bias, we believe this
to be of minimal influence. Our mean volunteer age
was 40.5 years, with a mean BMI of 29.8. This indicates
that our typical volunteer is not a young academy
recruit and has borderline obesity by federal standards.
In addition, 11 ⁄ 33 (33.3%) of our volunteers had significant health problems requiring controlling medication.
Based on these findings, we believe that our volunteer
population likely reflects an average American citizen
and not necessarily a person of exceptional fitness.
Finally, we recognize that we are not fully simulating
real-world field conditions of ECD exposure. Because
ECDs are often used on subjects with illegal drug intoxication, heightened sympathetic tone, and underlying
heart diseases in the field, it is possible that our study
conclusions are limited by the absence of these factors.
Because of the illegal and unethical nature of performing a human study that would fully explore this, we
realize that this question may not be able to be
answered by an experimental model.
CONCLUSIONS
A 10-second ECD exposure in volunteer human subjects, applied in an ideal cardiac axis application, did
not induce any concerning tachyarrhythmias. This finding supports prior human research. Our study suggests
that a swine model has limitations in the study of ECD
technology that may lead to inaccurate conclusions. We
recommend further human study in this area to validate
our findings, as well as further comparative studies
involving swine models to determine which aspect of
the established swine experimental technique is leading
to the observed differences.
The authors acknowledge the valuable assistance of Mr. Mark
Johnson, Mr. Andrew Hinz, and Mr. Matthew Carver with this
project. Without their help, this study would not have been able to
be completed.

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