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Gentler method of restoring normal heart rhythm.

High-frequency, alternating current could replace painful defibrillator shocks.

There's no question that cardiac defibrillators save lives. In patients whose heart rhythm becomes dangerously disorganized--a condition called ventricular fibrillation--an implanted defibrillator will automatically shock their heart back into normal rhythm. And while patients may be grateful that the device saves their life, the high-voltage shocks are painful, can cause serious mental stress and may damage the heart itself.

But there's better news on the horizon. Scientists have discovered that using a sustained high-frequency alternating current corrects the arrhythmia in a gentler way. As explained in the September 28, 2011 issue of Science Translational Medicine, their research has been done on cardiac cells in a laboratory dish and animal models. They are optimistic their finding will pave the way for a less painful way to deliver lifesaving defibrillator shocks to humans whose lives depend on them.

HOW IT WORKS. Just like external shock paddles, implanted defibrillators use high-voltage shocks to restore normal heart rhythm and get the heart pumping properly again. The researchers found that applying a high-frequency alternating current for about one-third of a second stops the disorganized cells in their tracks and puts them briefly in a state of suspended animation. When they are released, they behave appropriately.

The concept could be compared to a room full of people who panic to reach an exit when someone calls "Fire!" Applying the current would freeze their motion. When the current is turned off, they would line up and file out the door in an orderly fashion.

THE NEXT STEP. Although it will take time to move the concept from the laboratory to human clinical studies, the researchers are confident their work will result in a more patient-friendly way of restoring a normal heart rhythm.

"We are ultimately hoping to develop a device that, instead of delivering a painful, high-voltage shock when it detects a life-threatening arrhythmia, applies a more gentle alternating current for the right amount of time to stop the dangerous rhythm. We think that would be a great benefit to the millions of people worldwide who have a defibrillator to prevent sudden death," said senior study author Ronald Berger, MD, PhD, a cardiac electrophysiologist at Johns Hopkins University School of Medicine in Baltimore, in a written statement,


RELATED ARTICLE: What YOU SHOULD KNOW about ventricular fibrillation

* Most dangerous type of arrhythmia

* Often caused by heart attack

* Causes muscle fibers in the lower chambers of the heart to quiver

* Heart cannot contract to pump blood

* Patient suffers sudden cardiac death unless revived with CPR or a defibrillator

* About 200,000 defibrillators are implanted in the U.S. every year.


Study Results Are Very Promising

"The study in Science Translation Medicine is a game-changer in the field of heart rhythm medicine. While implantable cardioverter defibrillators save lives every day, they often do so through the use of painful direct current shocks. Not only are these shocks painful, they can also negatively-affect the heart tissue. In this study from Johns Hopkins, heart rhythm physicians discovered that high-frequency alternating current can stop disorderly electrical waves in the heart and restore normal heart rhythm. The physicians tested their new technique in preparations of cells in laboratory dishes and animal models. While much work remains to be done to determine if these techniques will work in humans with heart rhythm disorders, these results are very promising. In the future, stopping a life-threatening heart rhythm may be gentler, with less pain for the patient, the heart (and the mind)."

JONATHAN P. PICCINISR., MD, MHSc, Department of Medicine, Division of Cardiology; Duke Clinical Research Center, Duke
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Author:Piccini, Jonathan
Publication:Duke Medicine Health News
Date:Jan 1, 2012
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