Cardiologists are concerned that Tasers might interrupt the
rhythm of the human heart, throwing it into a potentially fatal chaotic
state known as ventricular fibrillation. When 50,000 volts of electricity
from a Taser surge across the body, it can instantly incapacitate a person
-- more safely than a blow from a police baton or a blast of pepper spray,
its manufacturer contends.
But cardiologists are concerned that, in certain cases, the
device might also interrupt the rhythm of the human heart, throwing it into
a potentially fatal chaotic state known as ventricular fibrillation. Rather
than pump blood in sequence through its four chambers, a heart in ventricular
fibrillation writhes uncontrollably. It is a common cause of sudden death.
Dr. Zian Tseng, a cardiologist at the University of California,
believes Tasers are potentially dangerous because a jolt of electricity,
at just the right moment in the heartbeat cycle, can trigger ventricular
He ought to know. He uses a precisely timed jolt to throw
the hearts of his patients into ventricular fibrillation on a regular basis.
Tseng installs implantable electric defibrillators into the
chests of heart patients who are at risk of sudden cardiac arrest. The devices
are miniature versions of the electric paddles used to jolt a stalled heart
back into its proper rhythm. Vice President Dick Cheney is the most prominent
American with such a device implanted in his chest.
Before Tseng can wheel a patient out of the operating room,
he must test the new defibrillator by stopping the heart, and watching to
see if the life-saving implant does its job.
"There are vulnerable periods in the cardiac
cycle, when shocks can cause dangerous arrhythmias,"
Known as a T-wave on the heart monitor, the brief pause in
pumping takes up about 3 percent of a heartbeat's cycle. Tseng times his
jolt of electricity for that moment, to stop a heart, so the defibrillator
can automatically start it again.
People using Tasers, he said, risk jolting a person at precisely
the wrong instant. "I think they are dangerous," he said. "If
you are shocking someone repeatedly, it becomes a bit like Russian roulette.
At some point, you may hit that vulnerable period."
Cardiologists also know that the window in which a jolt of
electricity can halt a heart expands significantly when a patient is treated
with certain drugs, or when the body is flooded with the fear hormone, adrenaline.
Patients with heart problems are also more vulnerable to the condition.
Executives at Taser International are aware
of the heart's vulnerability to ventricular fibrillation, but they insist
their device is safe. The electrical current used in an operating room to
stop a heart is 30 times higher than that produced by a Taser, said Mark
Kroll, an electrical engineer and board member of the Scottsdale,
Ariz., firm. Medically induced fibrillation involves applying a current
directly to the inside of the heart, he added, while a Taser's current is
applied to the clothing and skin.
"The current delivered by a Taser is too weak to induce
ventricular fibrillation," he said.
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