Physiologic effects of a new-generation conducted electrical weapon on human volunteers.

BACKGROUND: Conducted electrical weapons (CEWs) are used by law enforcement to restrain or repel potentially violent persons. The TASER X2 CEW is a next-generation device with new technology, including new electrical waveform and output specifications. It has not previously been studied in humans. OBJECTIVE: The objective of this study was to evaluate the human physiologic effect of a new-generation CEW. METHODS: This was a prospective, observational human study. Volunteers received a 10-s exposure via deployed probes from an X2 CEW in the abdomen and upper thigh. Measured data included vital signs; 12-lead electrocardiograms; and blood serum biomarkers before, immediately after, and 24 h post exposure. Biomarkers measured included pH, lactate, potassium, creatine kinase (CK), and troponin-I. Real-time spirometry and echocardiography were performed before, during, and after the exposure. RESULTS: Ten volunteers completed the study. There were no important changes in vital signs or potassium. Median increase in lactate as a consequence of the exposure was 1.2 mg/dL (range 0.6-2.8 mg/dL). Median change in pH was -0.031 (range -0.011 to -0.067). No subject had a positive troponin. Median change in CK at 24 h was 313 ng/mL (range -40 to 3418 ng/mL). There was no evidence of respiratory impairment. Baseline median minute ventilation was 14.2 L/min, increased to 21.6 L/min intra-exposure (p = 0.05), and remained elevated at 21.6 L/min post exposure (p = 0.01). CONCLUSIONS: There was no evidence of dangerous physiology found in the measured parameters. The physiologic effects of the X2 CEW are similar to older-generation CEWs. We encourage further study to validate these results.

Electrocardiographic differentiation of early repolarization from subtle anterior ST-segment elevation myocardial infarction.

STUDY OBJECTIVE: Anterior ST-segment elevation myocardial infarction (STEMI) can be difficult to differentiate from early repolarization on the ECG. We hypothesize that, in addition to ST-segment elevation, T-wave amplitude to R-wave amplitude ratio (T-wave amplitude(avg)/R-wave amplitude(avg)), and R-wave amplitude in leads V2 to V4, computerized corrected QT interval (QTc) and upward concavity would help to differentiate the 2. We seek to determine which ECG measurements best distinguish STEMI versus early repolarization. METHODS: This was a retrospective study of patients with anterior STEMI (2003 to 2009) and early repolarization (2003 to 2005) at 2 urban hospitals, one of which (Minneapolis Heart Institute) receives 500 STEMI patients per year. We compared the ECGs of nonobvious ("subtle") anterior STEMI with emergency department noncardiac chest pain patients with early repolarization. ST-segment elevation at the J point and 60 ms after the J point, T-wave amplitude, R-wave amplitude, QTc, upward concavity, J-wave notching, and T waves in V1 and V6 were measured. Multivariate logistic regression modeling was used to identify ECG measurements independently predictive of STEMI versus early repolarization in a derivation group and was subsequently validated in a separate group. RESULTS: Of 355 anterior STEMIs identified, 143 were nonobvious, or subtle, compared with 171 early repolarization ECGs. ST-segment elevation was greater, R-wave amplitude lower, and T-wave amplitude(avg)/R-wave amplitude(avg) higher in leads V2 to V4 with STEMI versus early repolarization. Computerized QTc was also significantly longer with STEMI versus early repolarization. T-wave amplitude did not differ significantly between the groups, such that the T-wave amplitude(avg)/R-wave amplitude(avg) difference was entirely due to the difference in R-wave amplitude. An ECG criterion based on 3 measurements (R-wave amplitude in lead V4, ST-segment elevation 60 ms after J-point in lead V3, and QTc) was derived and validated for differentiating STEMI versus early repolarization, such that if the value of the equation ([1.196 x ST-segment elevation 60 ms after the J point in lead V3 in mm]+[0.059 x QTc in ms]-[0.326 x R-wave amplitude in lead V4 in mm]) is greater than 23.4 predicted STEMI and if less than or equal to 23.4, it predicted early repolarization in both groups, with overall sensitivity, specificity, and accuracy of 86% (95% confidence interval [CI] 79, 91), 91% (95% CI 85, 95), and 88% (95% CI 84, 92), respectively, with positive likelihood ratio 9.2 (95% CI 8.5 to 10) and negative likelihood ratio 0.1 (95% CI 0.08 to 0.3). Upward concavity, upright T wave in V1 or T wave, in V1 greater than T wave in V6, and J-wave notching did not provide important information. CONCLUSION: R-wave amplitude is lower, ST-segment elevation greater, and QTc longer for subtle anterior STEMI versus early repolarization. In combination with other clinical data, this derived and validated ECG equation could be an important adjunct in the diagnosis of anterior STEMI.