COMPUTER SOFTWARE HELPS HEART IMPLANTS DIAGNOSE ARRHYTHMIA
COLUMBUS, Ohio -- Researchers at Ohio State University have found a way to improve computerized medical implants that treat cardiac arrhythmia.
With this improvement, the implants -- automatic implantable cardiovertor defibrillators (AICDs) -- will save more lives by properly diagnosing and treating different types of fatal arrhythmias.
The researchers wrote signal-analysis software that helps AICDs tell the difference between two common arrhythmias -- ventricular tachycardia (VT), a very rapid heart beat, and ventricular fibrillation (VF), an irregular heart beat.
AICDs typically aid people whove suffered previous heart attacks, or who experience arrhythmias that doctors cannot correct by drugs alone.
"In a sense, they are a last chance for people who have a history of heart disease and who cant be treated in any other way," said Peter M. Clarkson, research scientist and associate
professor in Ohio States Biomedical Engineering Center and lead author of the study.
VF kills because a fibrillating heart beats wildly but pumps no blood. A heart attack, or death of part of the heart due to lack of oxygen, often causes VF.
Within an AICD, a tiny computer chip monitors the electrical activity that accompanies each heart beat, and notices when something goes wrong. When the device senses an arrhythmia resembling VF, it defibrillates the heart by issuing a single, large shock.
"Its just like what you see in the emergency room when doctors shock someone with paddles, but in this case its done automatically," said Clarkson. As with the paddles, when an AICD shocks a persons heart, the person convulses.
Thousands of people carry AICD implants today, and the devices work, for the most part. But occasionally, AICDs misdiagnose an arrhythmia and shock a person at the wrong time, with potentially fatal consequences. An inappropriate shock may cause a lethal arrhythmia and kill a person experiencing VT.
Clarkson and his colleagues wrote signal analysis software to help AICDs better distinguish between VT and VF and shock people at the right time. A study on the effectiveness of the new programming technique recently appeared in the journal IEEE Transactions on Biomedical Engineering.
The Ohio State researchers tested their new programming algorithms on a database of recorded arrhythmias, and compared the results to the performance of the old technique for distinguishing between VT and VF. The old technique misdiagnosed arrhythmia 16 percent of the time, while the Ohio State technique reduced that figure to 5 percent.
The Food and Drug Administration (FDA) will test the new AICDs further before approving them for medical use. Clarkson said that doctors probably wont have access to the new devices for about 5 years.
In the meantime, Clarkson and his colleagues will continue to find new ways to improve AICDs.
"In practice, a person can develop a wide range of arrhythmias, so we are anxiously trying to come up with methods for identifying and dealing with different arrhythmias."
When a person experiences some forms of VT, for example, todays AICDs dont always provide the proper treatment -- a series of small pacing shocks that manually shift the heart down to a slower rhythm. According to Clarkson, future AICDs will most likely contain more powerful processors that will identify VF, and many separate forms of VT.
Contact: Peter M. Clarkson, (614) 292-5570; Clarkson.9@osu.edu
Written by Pam Frost, (614) 292-9475; Frost.18@osu.edu
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