Implantable defibrillators currently on the market apply between 600 and 900 volts to the heart, almost 10 times the voltage from an electric outlet, says Ajit H. Janardhan, MD, PhD, a cardiac electrophysiology fellow at the Washington University's School of Medicine.
After being shocked, he says, some patients get post-traumatic stress disorder. Patients may even go so far as to ask their physicians to remove the defibrillator, even though they understand that the device has saved their lives.
The huge shocks are not only unbearably painful, they damage the heart muscle and have been shown in many studies to be associated with increased mortality. In an advance online edition of the Journal of American College of Cardiology, Janardhan and Igor Efimov, PhD, professor of biomedical engineering in the School of Engineering & Applied Science, report on a low-energy defibrillation scheme that significantly reduces the energy needed to re-establish a normal rhythm in the heart's main chambers.
They hope this electrotherapy will be much less painful than shocks from existing implantable defibrillators, and may even fall beneath the threshold at which patients begin to perceive pain.
The team has just received a National Institutes of Health grant to develop a prototype low-energy defibrillator for humans and plan to begin clinical trials of the device shortly.
Losing the beat
The lub-dub of the heartbeat begins with an electrical impulse generated by the sinoatrial node, a group of cells on the wall of the right atrium that is the heart's natural pacemaker.
Spreading through conductive pathways in the heart, the electrical signal first causes the two upper chambers of the heart (the atria) to contract, and then, a split second later, the two lower chambers (the ventricles), coordinated motions that efficiently pump blood to the rest of the body.
The synchronized squeezing of a normal h
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Washington University in St. Louis