CMAJ • September 23, 2008; 179 (7). doi:10.1503/cmaj.1080080.
© 2008 Canadian Medical Association or its licensors
All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association.
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Letters

TASER safety

Mark W. Kroll, PhD*, Hugh Calkins, MD{dagger}, Richard M. Luceri, MD{ddagger}, Michael A. Graham, MD§ and William G. Heegaard, MD MPH

*Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minn.; {dagger}Electrophysiology and Arrhythmia Service, Johns Hopkins University and Hospital, Baltimore, Md.; {ddagger}Interventional Arrhythmia Center, Holy Cross Hospital, Fort Lauderdale, Fla.; §Department of Pathology, St. Louis University, St. Louis, Mo.; ¶Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minn.

We are members of the TASER International Scientific and Medical Advisory Board and would like to comment on the review by Nanthakumar and colleagues.1 This review focused on porcine studies; it ignored the 30 papers and abstracts that have provided data on the application of electronic control devices to humans. In addition, there are 4 implications in the review that we believe are erroneous.

The first is that the induction of ventricular fibrillation is relevant to the problem of arrest-related deaths. There are over 700 arrest-related deaths per year in 47 of the 50 United States.2 TASER electronic control devices have been applied to over 1.3 million people. In about 95% of the arrest-related deaths in which an electronic control device was used, the initial rhythm (established by paramedics on the scene) was asystole or pulseless electrical activity.3 These patients typically responded rapidly to atropine and epinephrine, which further differentiates these cases from cases of asystole arising from long-term ventricular fibrillation (lasting about 15 minutes).

The second erroneous implication is that small swine provide a reasonable model with which to measure the risk of electrical induction of ventricular fibrillation in humans. Swine, especially small ones, are extremely sensitive to the electrical induction of ventricular fibrillation.4 In pigs, the Purkinje fibers cross the entire ventricular wall whereas in dogs and humans they are confined to a very thin endocardial layer.5 Activation in swine proceeds from the epicardium to the endocardium, whereas it occurs in the reverse direction in dogs and humans.6 Thus, swine are much more sensitive to external electrical currents. Radiofrequency ablation is routinely done in humans but it will typically produce ventricular fibrillation in swine because they are sensitive to higher frequencies than humans. In addition, the threshold for ventricular fibrillation is directly related to body weight for both utility waveforms and electronic control device waveforms.4,7 In humans, even if the barbs of an electronic control device are placed directly on the cardiac axis, no effect is captured with echocardiographic monitoring.8

Third, it is erroneous to imply that electronic control devices can cause dangerous acidosis. Reports of acidosis induced by the use of an electronic control device come from studies of anesthetized pigs in which the ventilators were turned off.

A final erroneous statement is that the presence of cocaine makes an electronic control device more dangerous. Cocaine is a strong sodium-channel blocker and this effect trumps its adrenergic effects.9,10 The net effect is to increase the threshold for ventricular fibrillation by at least 50%, not lower it.

The authors asked how we can resolve the conflicting experimental findings.1 The answer has been known since 1936: it is far easier to cause ventricular fibrillation in a small swine than in a human.4 There is no conflict within the larger body of clinical literature, which consistently shows no problems with the use of electronic control devices in humans.

Footnotes

Competing Interests: Mark Kroll, Richard Luceri and William Heegaard hold stock in TASER International. Mark Kroll and Michael Graham have served as consultants for TASER International. Mark Kroll has received travel assistance from TASER International for attending medical conferences. Hugh Calkins is a paid consultant for TASER International. Richard Luceri is a paid board member of TASER International and has received travel assistance for attending board meetings. William Heegaard has received travel assistance to attend a scientific medical advisory board meeting and has been paid for medical advice about conducted electrical devices.


REFERENCES

  1. Nanthakumar K, Masse S, Umapathy K, et al. Cardiac stimulation with high voltage discharge from stun guns. CMAJ 2008;178:1451-7.[Abstract/Free Full Text]
  2. Mumola C. Arrest-related deaths in the United States, 2003–2005. Bureau of Justice Statistics special report no. NCJ 219534. Washington: US Department of Justice; 2007.
  3. Swerdlow C, Kroll M, Williams H, et al. Presenting rhythm in sudden custodial deaths after use of TASER(r) electronic control device. Heart Rhythm 2008;5:S44.
  4. Ferris LP, King BG, Spence PW, et al. Effect of electric shock on the heart. Electr Eng 1936;55: 498-515.
  5. Howe BB, Fehn PA, Pensinger RR. Comparative anatomical studies of the coronary arteries of canine and porcine hearts. I. Free ventricular walls. Acta Anat (Basel) 1968;71:13-21.
  6. Allison JS, Qin H, Dosdall DJ, et al. The transmural activation sequence in porcine and canine left ventricle is markedly different during long- duration ventricular fibrillation. J Cardiovasc Electrophysiol 2007;18:1306-12.[CrossRef][Medline]
  7. McDaniel WC, Stratbucker RA, Nerheim M, et al. Cardiac safety of neuromuscular incapacitating defensive devices. Pacing Clin Electrophysiol 2005;28(1 Suppl):S284-7.[CrossRef][Medline]
  8. Ho J, Dawes D, Reardon R, et al. Echocardiographic evaluation of human transcutaneous TASER(r) application along the cardiac axis. Heart Rhythm 2008;5:S97.
  9. Tisdale JE, Shimoyama H, Sabbah HN, et al. The effect of cocaine on ventricular fibrillation threshold in the normal canine heart. Pharmacotherapy 1996;16:429-37.[Medline]
  10. Lakkireddy D, Wallick D, Ryschon K, et al. Effects of cocaine intoxication on the threshold for stun gun induction of ventricular fibrillation. J Am Coll Cardiol 2006;48:805-11.[Abstract/Free Full Text]



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Was the Toronto Police Services Board misled into approving taser use?
Patrick Bolland
CMAJ, 2 Oct 2008 [Full text]
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