Stun guns used by law enforcement officers may rarely cause lethal heart rhythm disturbances, what doctors call cardiac arrhythmia, investigators in Canada report, based on animal experiments.

Dr. Kumaraswamy Nanthakumar and colleagues at the University of Toronto used pigs to more thoroughly evaluate the risks associated with stun guns. They implanted heart catheters and blood pressure devices into the animals.

During 150 stun gun discharges, 74 resulted in abnormal stimulation of the heart muscle. The danger was apparent only for thoracic discharges (administered parallel to the long axis of the heart on the chest wall) as opposed to nonthoracic (away from the chest, across the abdomen).

When epinephrine was administered to the animals, to simulate the stress that targeted individuals may face during the incident, one out of 16 discharges induced ventricular fibrillation - a condition in which the heart muscle quivers instead of contracting normally - and one caused ventricular tachycardia - a rapid, abnormal heart rhythm.

These findings, the authors say, suggest that there “exists the possibility of serious” heart rhythm disturbances during stun gun device discharges in structurally normal hearts under intense stress. Moreover, they add, there is heightened risk for individuals with pre-existing structural heart disease.

A related study suggests that cocaine use may attenuate that risk. Dr. Patrick Tchou at the Cleveland Clinic Foundation, Ohio, and associates again used a pig model, and observed that cocaine appears to increase the ability of the heart to withstand the effects of the stun gun.

SOURCE: Journal of the American College of Cardiology August 2006.