— So many Americans experience dangerous fluctuations in
heartbeat that about 400,000 times a year a device is
implanted in their chests to keep a normal rhythm.
defibrillators that send a life-saving electric buzz through
the heart can be so painful and damaging that scientists have
been looking for a better way. At the Johns Hopkins University
in Baltimore, researchers believe that a mellow ray of light
could someday replace the electricity.
using explosives to open a door for which we have no
key," said Natalia Trayanova, a professor in Hopkins’
department of biomedical engineering. "We’re hoping
this is the key."
goals are still a bit "pie in the sky," said
Trayanova, who directs the Computational Cardiology Lab within
the Institute for Computational Medicine. The research is
relatively new — it melds study of the heart and
optogenetics, or the use of light to control nerve cells, a
science just over a decade old.
next 10 years it could replace conventional therapy that uses
electricity delivered from a small box containing a battery
and a computer chip implanted in the chest.
an implantable cardioverter defibrillator, or ICD, the box
connects to the heart through wires and electrodes. When heart
rhythms become irregular, the computer sends small electrical
pulses. If this fails to regulate the beat, a larger shock
similar to one delivered by the paddles in a hospital attempts
to reset the heart’s rhythms.
say defibrillators are the gold standard for treatment and
highly successful. Though the implantable devices developed in
the 1980s are now the size of a pocket watch, there are
drawbacks. They include pain, damage to heart tissue,
batteries that need replacing, potentially faulty wires and
anxiety about when the big kick will come.
Hopkins research is being done exclusively on a
"virtual" heart generated by a room-size computer
more powerful than 500 of the best commercial laptops.
Building on their own work and that of others, researchers at
the university are figuring out how to develop a device that
is safe and effective long term.
theory, doctors could someday identify the source of heart
trouble and target specific cells by injecting a benign virus
carrying genetic codes for light-sensitive proteins called
opsins, or by implanting opsin-rich cells produced in the lab.
When a heart beats irregularly, called an arrhythmia, a device
would send light over opsins in the modified heart cells,
passing a small electric current and synchronizing the erratic
the most advanced work in optogenetics has been done in the
brain, and studies have shown that rats with modified cells
will turn left, for example, when a light is turned on. That
control could someday be harnessed to control Parkinson’s
tremors or epilepsy seizures, the researchers said.
heart, those at risk for sudden cardiac arrest, one of the
leading causes of death in the United States, could be saved
with a light source tailored to their heart condition, perhaps
in the next decade or so. Even children with conditions or
genetic predispositions could have their cells modified in
preparation for treatment. The opsins would remain dormant
without light, the researchers said.
we can do this in a model, then there are (live) experiments
worth doing. And we’re narrowing what experiments would need
to be done," said Patrick Boyle, a postdoctoral fellow
working with Trayanova on the project. "It’s a steep
hill to climb. If this all works, it will be a
T. Hickey, an assistant professor at the Columbia University
School of Nursing, agrees that replacing current technology
would be beneficial to patients who fear pain and being
unprepared for a large shock. Some worry that their
implantable defibrillators might not function or might go off
unnecessarily while they are exercising and have an elevated
advocates that nurses provide additional counseling before and
after a patient gets a shock. She has been working with her
university and other professionals through the American Heart
found counseling goes a long way in decreasing anxiety,"
she said. "The patients benefit from knowing what the
device will do and won’t do."
a light-based implant could reduce side effects, the stress on
patients and their families, and the amount of anti-arrhythmia
researchers are working on ways to reduce the large jolt of
electricity now used, said Dr. Douglas Zipes, a professor of
medicine at Indiana University ‘s Krannert Institute of
Cardiology and a past president of the American College of
another promising avenue involves small, simultaneous shocks
to various parts of the heart instead of one large shock. But
he said he is excited about Trayanova’s work because it is
potentially transforming in the way it would regulate
been able in the last 30 to 40 years to reduce mortality by 50
percent," he said of past advances in heart care,
including defibrillators. "If we can reduce the amount of
energy and achieve the same end result as this optogenetics
approach may facilitate, it would be very useful."