Evaluation of the skin-to-heart distance in the standing adult by two-dimensional echocardiography

Background: An electromuscular incapacitating device (EMD) delivers pulses of high-voltage electricity, causing strong muscle contraction. Data from a pig model suggest that an EMD dart tip placed within 17 mm of the epicardial surface can cause ventricular fibrillation. The current study estimates minimum skin-to-heart distance in the adult, to determine whether individuals might be at risk for ventricular fibrillation from an EMD. Methods: We performed 2-dimensional echocardiograms in 150 standing adults in the parasternal, apical, and subcostal views. From each view, the shortest linear skin-to-heart distance was measured. Results: Average skin-to-heart distances were: parasternal 32.1 +/- 7.9 mm; apical 31.3 +/- 11.3 mm; and subcostal 70.8 +/- 22.3 mm. There were 9 (6%) individuals with a skin-to-heart distance less than or equal to 17 mm. The skin-to-heart distance was significantly correlated with body mass index: parasternal r = 0.57, apical r = 0.55 (P < .0001). Conclusions: An EMD dart penetrating the skin directly over the heart might put individuals at risk for ventricular fibrillation.