What does a taser do to the human heart?

By Dayo Olopade | TheRoot.com

August 1, 2008--On January 17, 21-year-old Baron Pikes was stopped by the police. Nearly half a million volts of electricity later, he died on the street. Handcuffed, held down and stunned with a Taser-brand electro-weapon seven times before he died (and then twice more after that), Pikes' heart, the coroner notes, simply gave out. Amnesty International estimates that in the past seven years, 150 people have been killed after being shocked by stun guns like Tasers. But that's still a very small fraction of the population, even that fraction being stunned by police officers or worried civilians. So just how can a Taser—designed to be non-lethal force—kill you?

Tasers, often shaped like pistols, use compressed nitrogen to fire two darts at a target. The darts are connected to the gun by insulated wires that give it a range of up to 21 feet. Once the darts make a connection with a target, the Taser sends 50,000-volt electric pulses into the victim's body, causing intense muscle spasms and sharp pain. Seized, the victim often falls to the ground.

While 50,000 volts sounds like a lot, humans are actually able to conduct electricity—which is why we tend to steer clear of open sockets or stick forks into toasters that could give us a nasty shock. But despite the high voltage of a Taser's current, the relatively low amperage on the device is what allows it to immobilize but not kill you. (Being struck by lightning, by comparison, kills frequently because it sends an exponentially greater amount of voltage and amperage through a victim, at levels that our bodies just can't handle.)

Still, Taser shocks are dangerous in general because they interfere with the most important muscle in the body—the heart. When your heart beats normally, it is, like the rest of the body, already in the process of conducting electricity. The biological process that lets your heart rhythmically contract and pump blood represents "electricity going to the heart in an organized way," says cardiologist Abraham Kocheril, a specialist in electrophysiology at the University of Illinois at Chicago. So if someone gets a mini-jolt of electricity from the outside, be it from a live socket or a hospital defibrillator, they'll probably live.

But the shock had better be at the right place and the right time. Each time the heart beats, it charges and discharges stored electricity. In between contractions, the heart automatically goes into a brief recovery mode called diastole. In that tiny window of recovery time, a sudden jolt of electricity could cause the heart muscle to go into ventricular fibrillation (VF), which is essentially the first stage of a heart attack. The heart begins to pump erratically, if at all, and blood pressure drops to nothing, leaving no oxygen available for brain and body cells.

The effects of any major disruptions during this brief diastolic window can be swift and catastrophic. When young children are hit by a baseball or athletes are struck forcefully in the chest, these blows can be transduced into an electric jolt. If these shocks occur while the victim's heart happens to be vulnerable, the rhythm is disturbed and the body goes into VF, hypertrophic cardiomyopathy or cardiac arrest. This possibility is the most common explanation of sudden, sports-related deaths.

So what about Baron Pikes? Well, if somebody is prone to dying suddenly or has a weak heart, then a 50,000-volt stress would precipitate it. Some prior Taser deaths, such as one in Fayetteville, N.C., occurred because the victim was in an altered state, on drugs. Another death, in Colorado, was chalked up to the vigorous foot chase that preceded the police's use of the Taser. But people at risk of this outcome are typically those who have had heart disease, heart failure or certain congenital abnormalities.

In the case of Pikes, a healthy 21-year-old, the initial six shocks probably got him at a time when his heart was contracting, and he was not adversely affected (beyond the muscle spasms, confusion and immobility). Cuffed on the ground and in the back of a squad car, he would not have been exerting himself—nor were there more than trace amounts of drugs in his system. But that seventh time, the Taser more than likely hit Pikes' heart when it was in diastole, sending him into VF and toward sudden death.

Once a person is in VF, spontaneous recovery is rare. Ironically, the solution to the problem is to administer another electric shock—well-known to provide instant theatrics for so many network hospital dramas. In one reported case, a man was Tased while suffering from atrial fibrillation (which affects the upper chamber of the heart, not the part responsible for pumping blood. The Taser shock turned out to be therapeutic, bringing his heart back into correct rhythm. In Pikes' case, the police did continue to Tase him, without the happy ending. The coroner's report states that the last two shocks were administered after he was dead.

So the Taser, while marketed as an effective way to stop a bad guy cold without killing—and even, at times, as a women's fashion accessory—is actually a form of physiological Russian roulette. The odds of the unthinkable increase the more times one is subjected to the powerful electric current. Cruelly, Pikes made it through six rounds, which would have emptied a gun clip in a real game of chance. Tase me once, shame on me. Tase me nine times—well, the odds aren't good.

Dayo Olopade is a reporter at the New Republic.