Human Electrical Muscular Incapacitation and Effects on QTc Interval

Abstract

Human Electrical Muscular Incapacitation (HEMI) is used to subdue combative individuals. Changes in cardiac electrical activity have been proposed as the cause of death in a small fraction of these individuals. The current study sought to determine whether changes in QTc interval occur after HEMI exposure. Twenty-four participants had EKG readings before a 5-second HEMI exposure and within 30 min after exposure. All subject EKGs were read by a data-blinded cardiac electrophysiologist who calculated a QT corrected (QTc) interval. QTc interval was calculated using Bazett method. QTc prolongation was defined as >430 ms and a threshold of 30 ms for identifying QTc lengthening. Five participants experienced QTc prolongation and six had QTc lengthening. One participant developed QTc prolongation exceeding 500 ms, which carries a risk of developing multifocal ventricular tachycardia. These results suggest that HEMI exposure may cause EKG changes with a risk of ventricular tachycardia.

Keywords: Bazett method; QT interval; QTc interval; electrocardiogram; electromuscular incapacitation; forensic science; human electromuscular incapacitation; ventricular tachycardia.