The Journal of Emergency Medicine, Vol. 43, No. 6, pp. 970–975, 2012Copyright � 2012 Elsevier Inc.

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doi:10.1016/j.jemermed.2012.03.022

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TRANSCARDIAC CONDUCTED ELECTRICAL WEAPON (TASER) PROBEDEPLOYMENTS: INCIDENCE AND OUTCOMES

William P. Bozeman, MD,* Eric Teacher, MD,† and James E. Winslow, MD, MPH*

*Department of Emergency Medicine, Wake Forest University School of Medicine, Winston Salem, North Carolinaand †Department of Emergency Medicine, Loma Linda University Medical Center, Loma Linda, California

Reprint Address: William P. Bozeman, MD, Department of Emergency Medicine, Wake Forest University School of Medicine,1 Medical Center Drive, Winston Salem, NC 27106

, Abstract—Background: TASER (TASER International,Scottsdale, AZ) conducted electrical weapons (CEWs) arecommonly used by law enforcement officers. Although ani-mal studies have suggested that transcardiac CEW dis-charges may produce direct cardiac effects, this has notbeen demonstrated in human studies. Objectives: This studysought to determine the incidence and outcomes of transcar-diac CEW probe impact locations in a large series of actualCEW deployments. Methods: A multi-center database ofconsecutive CEW uses by law enforcement officers was ret-rospectively reviewed. Case report forms were indepen-dently reviewed by three investigators to identify caseswith paired probe configurations potentially producinga transcardiac discharge vector. Descriptive analysis wasperformed and inter-rater reliability was assessed. Results:Among 1201 total CEW uses, 813 included probe deploy-ments and 178 cases had paired anterior probe impacts po-tentially capable of producing a transcardiac dischargevector. This represents 14.8% of all CEW uses (95% confi-dence interval [CI] 12.9–16.9%) and 21.9% of CEW usesin probe mode (95%CI 19.1–24.9%). Inter-rater agreementwas very good, with kappa = 0.82. There were no immediatedeaths in any cases (97.5%CI 0.0–0.3%) to suggest a cardiacdysrhythmia, including those with transcardiac dischargevector. Conclusion: CEW deployments with probe impactconfigurations capable of producing a transcardiac dis-charge occur in a minority of cases in field use conditions.None of these cases, transcardiac or otherwise, produced im-mediately fatal dysrhythmias. These data support the over-all safety of CEWs and provide a benchmark estimate of the

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likelihood of transcardiac discharge vectors occurring infield use of CEWs. � 2012 Elsevier Inc.

, Keywords—TASER; conducted electrical weapon;conducted energy weapon; conducted electrical device;conducted energy device; injuries; cardiac; dysrhythmia

INTRODUCTION

Conducted electrical weapons (CEWs) are commonlyused by law enforcement personnel worldwide as an in-termediate force option to subdue and apprehend poten-tially dangerous or combative suspects, and the TASERcompany (TASER International, Scottsdale, AZ) is thedominant manufacturer of these devices. CEWs functionby delivering a series of very brief (125 ms) high-voltage,low-current electric pulses of 0.36 joules that result inpain, muscle contraction, and inhibition of voluntarymovement (1–3).

Although not risk free, CEWs have been associatedwith lower rates of injuries to suspects and officers thanother traditional intermediate police force options suchas physical force, pepper spray, and handheld impactweapons (4). Field studies have shown an overall risk ofsignificant injury to suspects after CEWuse of 0.25%, pri-marily due to blunt trauma from falls, and the risk of death

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after CEW use has been estimated to be < 0.09% (5–8).However, the safety of CEWs has been questioned due toa number of unexplained deaths that have occurred inpolice custody after CEW use (9–11). A commonconcern in the ongoing debate is that the CEW’selectrical discharge may, in rare cases, interfere withnormal cardiac conduction and induce fatal cardiacdysrhythmias (10). This has been observed in anesthetizedanimal models, but to date, has not been replicated in hu-man studies, evenwith intentional ‘‘worst case’’ precordialplacement of CEW probes in human volunteers (12–15).

Animal studies have demonstrated that probe place-ment is critically important in whether cardiac effectsmay occur; anterior probe placement with a transcardiacdischarge vector is necessary for CEWs to affect cardiacconduction in these experimental models at normal CEWoutput levels (16). It is currently unknown how often thisconfiguration occurs in field uses of CEWs by law en-forcement officers, and outcomes have not been reportedin this potentially higher-risk subgroup. We sought to de-termine the incidence and outcomes of transcardiacTASER probe deployments in actual field conditions.This important information can aid in making informed,evidence-based decisions regarding the safety and usageof CEWs in the field.

MATERIALS AND METHODS

CEW Modes and Cardiac Risks

CEWs can be used in two modes. One is ‘‘drive stun’’mode with the front of the weapon applied directly tothe subject. In this mode, the electrical contacts are inclose proximity to each other, resulting in a short dischargevector that has not been associated with direct cardiac ef-fects in animals or humans (17). The secondmode ofCEWuse is ‘‘probemode’’ with a pair ofmetal probes fired fromthe weapon. These travel some distance to imbed in a sus-pect’s skinor clothing.Theprobes leave theweaponat a di-verging angle, making the probe separation as they reachthe subject a function of the distance traveled and positionof the suspect at time of impact. Animal studies have indi-cated that transcardiac discharge vectors with probe loca-tions across the anterior torso are at risk of producingdirect cardiac effects, whereas dorsal locations and broadprobe placements outside the torso did not result in cardiaceffects (16,18,19). Thus, paired anterior thoracic probeimpacts are of interest when considering transcardiacdischarges that might result in cardiac effects.

Study Design

A retrospective review was conducted of a multicenterdatabase of consecutive CEW deployments by law en-

forcement officers against criminal suspects. The studyprotocol was reviewed and approved by the authors’ Insti-tutional Review Board.

Case Reports and Database

A research network of United States law enforcementagencies in six geographic areas contributed to the data-base; each subject in the database received an electricalimpulse from a CEW during the course of apprehensionby police. All CEW uses within the participating agencywere reviewed and submitted to the database. This data-base has been previously described (5). Briefly, manda-tory Use of Force investigation documents, includingpolice reports and medical records, were reviewed bya physician investigator at each study site and a de-identified Case Report Form (CRF) was completed andsubmitted to the study coordinating center. Data collectedon the CRF included incident information, suspect demo-graphics, CEW deployment details, a body diagram indi-cating probe or drive stun impact locations, injuriesrelated or potentially related to CEW use, and outcomes.An a priori injury stratification matrix was used to rate in-juries as mild, moderate, or severe based on need for hos-pitalization and risk of long-term disability or threat tolife. Locations of probe impacts and injuries were re-corded in the database by anatomic region (head/neck,chest, abdomen, back, upper extremities, and buttocks/lower extremities). These data were exported to a spread-sheet (Excel 2007; Microsoft Corporation, Redmond,WA) for analysis.

Transcardiac Vector Identification

A two-stage review was conducted to identify cases withtranscardiac discharge vectors. In the first stage, the data-base was filtered to identify cases with two or more ante-rior thoracic (chest and abdomen) probe impacts. Caseswith drive stun use only, with single probe contact, orwith probe contacts outside the anterior thorax wereexcluded.

In the second stage, CRFs with paired anterior thoracicprobe impacts were individually reviewed independentlyby each of three investigators to assess specific probe lo-cations as indicated on the CRF body diagram. A body di-agram indicating the anatomic location of the humanheart was used for reference (Figure 1) and comparedto the CRF diagram indicating probe impact locations.Any case with a probe placement configuration that re-sulted in a discharge vector that traversed or touchedthe outside border of the designated heart region was des-ignated as transcardiac. In cases with more than twoCEW probe impact locations, an a priori decision wasmade to presume the worst case scenario in terms of

Figure 1. Body diagram indicating the approximate anatomicposition of the heart.

972 W. P. Bozeman et al.

assessing potential transcardiac vectors. In cases withdiscordant designations, the determination of 2 of the 3investigators was used.

Analysis

Demographic and injury information were recorded anddescriptive analysis was performed using commercialstatistical software (InStat version 3.10; GraphPad Soft-ware Inc., La Jolla, CA). Inter-rater agreement was as-sessed using Fleiss’ method for use with multiple raters(20). This results in an aggregate kappa statistic forinter-rater agreement. Kappa values of 0.80–1.00 indicatevery good inter-rater agreement, whereas values of 0.60–0.80 correspond to good, values of 0.40–0.60 correspondto moderate, values of 0.20–0.40 correspond to fair, andvalues of < 0.20 correspond to poor inter-rater agreement.

RESULTS

There were 1201 consecutive CEW uses reviewed; 94%of the suspects were male; the mean age was 32 years(range 13–80 years; SD 10.7). Overall, 99.75% of sus-pects sustained no or mild injuries, whereas 0.25% sus-tained significant (moderate or severe) injuries relatedto CEW use. These included two head injuries from fallsand one case of rhabdomyolysis. Two deaths occurred;medical examiner investigations determined that neitherwas related to CEW use. As previously described, thesedeaths had features including prolonged combative be-havior, cocaine use, cardiac abnormalities, and possibleolanzapine toxicity (5).

Incidence of Transcardiac Discharge

Of the 1201 cases, 388 involved CEW use in drive stunmode only and were excluded (Figure 2). An additional67 cases indicated single-probe contact only, leaving746 cases with paired probe impacts. Four hundred ninety

of these cases had extra-thoracic or back impact areas,leaving 256 cases with paired anterior thoracic probesin a chest/chest or chest/abdomen configuration. Of these,178 cases resulted in a transcardiac discharge vector and78 cases resulted in noncardiac discharge vectors. Thesetranscardiac discharge vectors represent 14.8% of all1201 CEW uses (95% confidence interval [CI]12.9–17.0%) and 21.9% of the 813 CEW uses in probemode (95% CI 19.1–24.9%). The kappa statistic for mul-tiple reviewers was 0.82, indicating very good inter-raterreliability.

Outcomes after Transcardiac Discharge

No sudden death events suggestive of cardiac dysrhyth-mias occurred in the 178 cases with transcardiac dis-charge (0% observed proportion, 97.5% CI 0.0–2.1%)or in the group as a whole (0% observed proportion,97.5% CI 0.0–0.3%). Significant injuries were rare over-all (0.25%) and did not occur more frequently in thegroup with transcardiac CEW discharge.

DISCUSSION

This epidemiologic study describes the incidence andoutcomes of transcardiac CEWdischargevectors in a fielduse setting. Using the largest existing multicenter data-base of such uses, these data provide an observational es-timate that potentially transcardiac discharge vectorsoccur in approximately 15% of all CEW uses and 22%of CEW uses in probe mode. In the group of 178 subjectswith potentially transcardiac discharge vectors, therewas no increased risk of significant injury, and none sus-tained an immediate sudden death event suggestive ofCEW-induced cardiac dysrhythmias. This informationis important to clinicians, law enforcement personnel,policymakers, and others interested in the safety ofCEW devices.

The possible relationship of CEW use and unexpecteddeaths in police custody remains controversial (21).Death in custody has been described in the literaturelong before implementation of CEWs, and much researchhas been dedicated to this phenomenon. CEWs are uti-lized in only a minority (approximately 30%) of in-custody death cases, and the role of CEWs in many ofthese deaths remains inconclusive (21,22).

Animal studies in anesthetized swine models have hadvariable results in regards to a CEW’s capability to inducepotentially fatal ventricular dysrhythmias. Althoughsome animal studies have noted no cardiac conduction ef-fects of any kind, several investigators have observedmyocardial capture, ventricular tachycardia, or ventricu-lar fibrillation in these swine models using standard CEWoutput levels (12,18,23). Cocaine and methamphetamine

Figure 2. Cases with and without transcardiac dischargevectors. CEW = conducted electrical weapon.

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have been administered in animal models without anyobserved episodes of induced ventricular dysrhythmiasand a suggestion of protective effects; and epinephrinehas also been used, with observation of two episodes ofventricular dysrhythmias (18,23,24). Studies comparinganterior thoracic discharges to dorsal or extra-thoracicdischarges have determined that the latter are not atrisk of producing cardiac dysrhythmias at normal out-puts (16,18,19). Unfortunately, extrapolation of theseanimal studies is problematic, and it is unclear howwell these findings translate from animals to humanpopulations.

Numerous studies in healthy human volunteers havealso examined the potential cardiac effects of CEW dis-charges (1,25). Using combined electrocardiographicand echocardiographic monitoring, these studies havenot documented any unstable dysrhythmias in humansand have failed to reproduce the cardiac conductioneffects found in animal models, even when dischargesare intentionally produced in a transcardiac vector. Onecase report documented myocardial capture in a patientwith an implanted cardiac pacer/defibrillator, withreturn of normal cardiac rhythm after completion of theCEW discharge. It remains unclear whether thepresence of an intracardiac pacing wire played any role

(26). Ho et al. and Dawes et al. have performed testingof CEW along the cardiac axis in human volunteerswith echocardiographic recordings using intentional‘‘worst case’’ transcardiac probe placement across theprecordium, without detection of any cardiac dysrhy-thmias (14,15). This is consistent with our data, andtheir conclusion that there may be limitations inreplicating human physiology in swine models forCEW discharges seems plausible.

Our study reports 178 cases with probable transcardiacCEW discharges, with no evidence of dysrhythmia gener-ation. Whereas animal and controlled human studiesremain critical, the importance of also performing real-world epidemiologic surveillance of field use cannot beoverstated. Studies of this type incorporate numerousconfounding factors that cannot be replicated in animalmodels or volunteer studies, such as preexisting cardiacand other diseases, the presence of prescribed and illegalsubstances, and a variety of heightened sympathetic stim-ulation and metabolic states due to pursuits and arreststruggles. These findings do not exclude the possibilityof CEW-induced dysrhythmias in humans. They do, how-ever, indicate that the risk of such dysrhythmias, even inthe presence of a transcardiac CEW discharge, is low, andsuggest that policies restricting anterior thoracic dis-charges of CEWs based on cardiac safety concerns areunnecessary.

Previous estimates of the potential for mortalityafter CEW use have combined the several studies thattracked outcomes in all patients exposed to a CEWdischarge (5–8). Applying the proportions of potentialtranscardiac discharges seen in our study (i.e.,approximately 15% of all CEW uses have a potentiallytranscardiac discharge vector), this information can beextrapolated to the several studies that report outcomesin 4058 consecutively monitored CEW uses with anelectrical shock delivered. An estimated 609 of these(15%) may have had a transcardiac discharge; with nosudden deaths suggestive of cardiac dysrhythmiaobserved, the 97.5% confidence interval for an observedproportion of zero deaths in 609 criminal suspects withpotential transcardiac CEW discharge is 0.0–0.6.

Limitations

Aswith any retrospective review of records, these data aresubject to recall bias and recording errors. The case re-ports were completed by physician investigators basedon police reports; photographs and medical records werealso reviewed when available, and all effort was made toinsure accuracy, but errors are still possible. When identi-fying transcardiac cases, we used a reference diagram ofthe chest to define potential transcardiac cases. Our pur-pose was to identify as many probable transcardiac cases

974 W. P. Bozeman et al.

as possible and identify any adverse outcomes as a resultof those discharges; thus, a relatively generous representa-tion of the cardiac silhouette was used, and an a priori de-cision was made to presume the worst case scenario incases with more than two probe impacts. This may resultin an overestimation of the instances of actual transcardiaccases. It remains possible that subjectswith cardiomegaly,dextrocardia, or other conditions could have a cardiac sil-houette that falls outside the borders used, resulting in anunderestimation of transcardiac cases. However, the pop-ulation against whom CEWs are used is one of relativelyyoung males (mean age 32 years, 94% male gender), inwhom many of these conditions are unlikely. In addition,not all CEW probes embed themselves in the skin. Probesthat embed in the clothing are subject tomotion in relationto the chest during CEW discharge, and it is difficult to re-liably determine discharge vectors in these subjects.Lastly, different raters may categorize borderline casesdifferently during review. We attempted to account forthis with inter-rater reliability assessment; with a kappastatistic of 0.82, inter-rater reliability was very good.

CONCLUSIONS

The incidence of probable transcardiac CEW probe con-figuration in field deployments is approximately 15% ofall cases of CEW use and 22% of cases when used inprobe mode. There were no adverse outcomes suggestiveof fatal cardiac dysrhythmia in either the transcardiaccases or the extra-cardiac cases. These findings basedon actual field data confirm that fatal cardiac dysrhyth-mias are unlikely to occur when CEWs are deployed onhuman subjects in real-life situations, even with transcar-diac placement of CEW probes.

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ARTICLE SUMMARY

1. Why is this topic important?TASER conducted electrical weapons (CEWs) are

commonly used by law enforcement, but may be associ-ated with direct cardiac events if probes result in a trans-cardiac discharge.2. What does this study attempt to show?

This study sought to determine the incidence and out-comes of transcardiac CEW probe impact locations ina large series of actual CEW deployments.3. What are the key findings?

In 1201 total CEWuses, 14.8% of paired anterior probeimpacts were potentially capable of producing a transcar-diac discharge vector, however, there were no immediatedeaths in any cases or any evidence of cardiac dysrhyth-mia.4. How is patient care impacted?

These data support the overall safety of CEWs and pro-vide a benchmark estimate of the likelihood of transcar-diac discharge vectors occurring in field use of CEWs.