Cardiac effects of electrical stun guns: does position of barbs contact make a difference?

BACKGROUND: The use of electrical stun guns has been rising among law enforcement authorities for subduing violent subjects. Multiple reports have raised concerns over their safety. The cardiovascular safety profile of these devices in relationship to the position of delivery on the torso has not been well studied. METHODS: We tested 13 adult pigs using a custom device built to deliver neuromuscular incapacitating (NMI) discharge of increasing intensity that matched the waveform of a commercially available stun gun (TASER(R) X-26, TASER International, Scottsdale, AZ, USA). Discharges with increasing multiples of output capacitances were applied in a step-up and step-down fashion, using two-tethered barbs at five locations: (1) Sternal notch to cardiac apex (position-1), (2) sternal notch to supraumbilical area (position-2), (3) sternal notch to infraumbilical area (position-3), (4) side to side on the chest (position-4), and (5) upper to lower mid-posterior torso (position-5). Endpoints included determination of maximum safe multiple (MaxSM), ventricular fibrillation threshold (VFT), and minimum ventricular fibrillation induction multiple (MinVFIM). RESULTS: Standard TASER discharges repeated three times did not cause ventricular fibrillation (VF) at any of the five locations. When the barbs were applied in the axis of the heart (position-1), MaxSM and MinVFIM were significantly lower than when applied away from the heart, on the dorsum (position-5) (4.31 +/- 1.11 vs 40.77 +/- 9.54, P< 0.001 and 8.31 +/- 2.69 vs 50.77 +/- 9.54, P< 0.001, respectively). The values of these endpoints at position-2, position-3, and position-4 were progressively higher and ranged in between those of position-1 and position-5. Presence of ventricular capture at a 2:1 ratio to the delivered TASER impulses correlated with induction of VF. No significant metabolic changes were seen after standard NMI TASER discharge. There was no evidence of myocardial damage based on serum cardiac markers, electrocardiography, echocardiography, and histopathologic findings confirming the absence of significant cardiac effects. CONCLUSIONS: Standard TASER discharges did not cause VF at any of the positions. Induction of VF at higher output multiples appear to be sensitive to electrode distance from the heart, giving highest ventricular fibrillation safety margin when the electrodes are placed on the dorsum. Rapid ventricular capture appears to be a likely mechanism of VF induction by higher output TASER discharges.

Do electrical stun guns (TASER-X26) affect the functional integrity of implantable pacemakers and defibrillators?

AIMS: High voltage electric current can adversely affect pacemakers (PM) and implantable cardioverter-defibrillator (ICD). The standard shock from an electrical stun gun (TASER- X26, TASER International, Scottsdale, AZ) consists of a 5-s long application of high voltage, low current pulses at 19 pulses per second. Its effect on the functional integrity of PM and ICDs is unknown. METHODS AND RESULTS: We tested the functional integrity of nine PMs and seven ICDs in a swine model after a standard stun gun shock. A transvenous, dual coil, bi-polar ICD lead (St Jude-SP01) and a PM lead were placed in the right ventricular (RV) apex and connected to pulse generators buried in the pre-pectoral pocket. The two darts were placed at the sternal notch (SN) and apex of the heart bracketing the device pocket. Standard neuromuscular incapacitating (NMI) discharges were delivered. Functional parameters of the devices and leads were checked before and after the shocks. The mean pacing thresholds, sensing thresholds, pacing impedances, and defibrillation coil impedances of the ICD lead were similar before and after the shocks. Similarly, pacing thresholds, sensing thresholds, and impedances of the PM lead were not significantly different before and after the shocks. No significant change was noted in battery voltage and projected longevity. Implantable cardioverter-defibrillator generators detected the NMI impulses at a mean cycle length of 176 +/- 20 ms with detection to charge time of 5.9 +/- 1.5 s. Shock delivery was aborted in all tests as tachycardia detection abruptly terminated at the end of the 5 s NMI application. None of the devices exhibited power on reset (POR), elective replacement indicator (ERI), or noise mode behaviour after the shock. CONCLUSION: Pacemakers and ICD generators and leads functions were not affected by the tested standard 5 s stun gun shocks.

Effects of cocaine intoxication on the threshold for stun gun induction of ventricular fibrillation.

OBJECTIVES: This study sought to assess cocaine's effects on Taser-induced ventricular fibrillation (VF) threshold in a pig model. BACKGROUND: Stun guns are increasingly used by law enforcement officials to restrain violent subjects, who are frequently intoxicated with cocaine and other drugs of abuse. The interaction of cocaine and the stun gun on VF induction is unknown. METHODS: We tested five adult pigs using a custom device built to deliver multiples of standard neuromuscular incapacitating (NMI) discharge that matched the waveform of a commercially available electrical stun gun (Taser X-26, Taser International, Scottsdale, Arizona). The NMI discharges were applied in a step-up and step-down fashion at 5 body locations. End points included determination of maximum safe multiple, minimum VF-inducing multiple, and ventricular fibrillation threshold (VFT) before and after cocaine infusion. RESULTS: Standard NMI discharges (x1) did not cause VF at any of the 5 locations before or after cocaine infusion. The maximum safe multiple, minimum VF-inducing multiple, and VFT of NMI application increased with increasing electrode distance from the heart. There was a 1.5- to 2-fold increase in these values at each position after cocaine infusion, suggesting decreased cardiac vulnerability for VF. Cocaine increased the required strength of NMI discharge that caused 2:1 or 3:1 ventricular capture ratios at all of the positions. No significant changes in creatine kinase-MB and troponin-I were seen. CONCLUSIONS: Cocaine increased the VFT of NMI discharges at all dart locations tested and reduced cardiac vulnerability to VF. The application of cocaine increased the safety margin by 50% to 100% above the baseline safety margin.