Anti-theft systems seem safe for people with implanted defibrillators
August 2, 1999
Web posted at: 1:07 PM EDT (1707 GMT)
By Kathleen Doheny
The estimated 400,000 people worldwide who are fitted with implanted defibrillators may no longer have to worry about walking through electronic anti-theft systems, researchers have found.
In response to a rapid heartbeat, defibrillators emit a shock to restore the heart's normal rhythm, according to the American Heart Association. Without a defibrillator, people who develop a rapid heartbeat could collapse and die or suffer a stroke.
However, problems can result when the defibrillator misinterprets the electronic beam of anti-theft systems, which are made to detect security-tagged goods. Instead, the defibrillator mistakes the beam for a rapid heartbeat and fires a shock, which is so intense that it feels like "a giant mule kick in the chest," said Dr. Douglas Zipes, one of the authors of the study and Distinguished Professor of Medicine and Pharmacology at the Indiana University School of Medicine, Indianapolis.
The current study shows that defibrillator-wearers should no longer be concerned, he said. However, people with defibrillators should avoid touching the anti-theft systems. Loitering in or near the systems may also cause problems. "Don't lean, don't linger, don't worry," said Zipes, whose study was published in a recent issue of the journal Circulation. He added that the results of his study also apply to people who are fitted with heart pacemakers, which also help the heart to maintain a normal heartbeat rhythm.
Researchers from the Methodist Hospital in Indianapolis and the Southwest Florida Heart Group in Fort Myers, Florida, were also involved in the study.
Walk through, but don't linger
During the study, researchers monitored the defibrillators of 169 people, in whom the devices were reprogrammed not to deliver a shock while continuing to record heartbeats as usual. None of the defibrillator-wearers reported any problems after walking through an anti-theft system in 15 seconds or less. However, when the study participants stood within six inches of the system for two minutes, researchers observed an interference in the defibrillators of 19 people.
Of the 19 incidents of interference, 12 were minor and unlikely to result in any problems. The remaining seven had interference so great that the defibrillator could have fired a shock under normal conditions. The researchers also found that people who had a defibrillator fitted to their abdomen, which are now rarely prescribed, were more likely to have interference problems.
Mishaps possible but defibrillators generally safe
Defibrillator-wearers became concerned after an issue of the New England Journal of Medicine late last year published a brief report describing the plight of a 72-year-old man with a defibrillator. While standing just one foot from a bookstore's anti-theft system, he received four consecutive shocks. Another customer, a registered nurse, pulled him away from the security system and he recovered.
But people with implanted defibrillators should have nothing to fear, said Dr. Cynthia Tracy, director of the cardiac arrhythmia service at Georgetown University Hospital and a spokeswoman for the American Heart Association.
The results of the study "should put to rest any concerns people have," she said. "Yes, it is safe for a person with an implantable cardioverter-defibrillator to walk through these electronic security devices," Tracy said.
That's good news for study participant Scott Rodgers, who has used an implantable defibrillator for almost two years. The 46-year-old Indianapolis resident said that anti-theft systems have never bothered him and that the study confirmed his attitude.
In the past 10 years, the Food and Drug Administration (FDA) has received 44 reports on adverse interactions between electronic anti-theft systems and defibrillators and similar devices. This prompted the FDA to issue an informational letter to physicians late last year advising them to educate patients about the potential hazards of anti-theft systems.
Anti-theft systems used worldwide
Anti-theft systems, such as those tested in the study, have grown in popularity since they were introduced 30 years ago, said Lee Pernice, a spokeswoman for Boca-Raton, Florida-based Sensormatic Electronics Corporation. The company partially funded the study, but was not allowed to influence the results, study author Zipes said.
Pernice said that about 10 companies now produce the estimated 800,00 systems in place worldwide. And most companies usually offer its customers signs to place on the systems to alert people. According to Sensormatic estimates, only 1 percent of the systems in use are hidden or camouflaged.
Copyright 1999 WebMD, Inc. All rights reserved.
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