AAMI News December 2017
Researchers Probe Retail Security Systems’ Effects on Pacemakers
An example of a storefront entrance containing a concealed EAS floor system and seating near the system.
When people with an implanted life-critical medical device, such as a pacemaker, pass through a field produced by electronic surveillance equipment at their favorite store, can they be sure that their medical device will not be adversely affected?
Ralph M. Herkert, director of the Medical Device Test Center at the Georgia Tech Research Institute (GTRI) in Atlanta, is working with manufacturers to help answer that question and improve the design of both the medical devices and the electronic article surveillance (EAS) systems that they pass through. Herkert presented his most recent findings on the interactions between cardiovascular implantable electronic devices (CIEDs) and electronic security gates during a Nov. 9 meeting of AAMI’s Committee on Cardiac Rhythm Management Devices.
Customers pass through EAS systems—often seen as pillars on either side of a store’s entrance—nearly every time they go shopping. For retailers, these systems help ensure that unpurchased merchandise doesn’t leave the store. For people with a CIED, these systems are a potential risk.
“Electromagnetic emissions from technologies that surround us can produce interference and/or compatibility issues with implanted and external medical devices,” Herkert said.
Herkert’s team previously found that pedestal EAS systems can affect the function of cardiac devices, even causing those devices to administer a shock. Since 2000, the Food and Drug Administration (FDA) has advised patients with a CIED to “Don’t Lean—Don’t Linger” around EAS gates. However, only about half of people with pacemakers and implantable defibrillators know that, according to some physicians. Even those who do know about the FDA’s guidance may not be aware that many retail locations are moving toward concealed EAS systems, which are usually hidden underneath the floor. Herkert and his team are working with EAS system and medical device manufacturers to better understand the effects when security systems are concealed.
Previous tests of hidden EAS systems showed no effect on medical device function, in part because the patient is not expected to get very close to an under-the-floor EAS antenna. However, in his lab, Herkert developed new tests to see if concealed EAS systems would affect a medical device when people find themselves in a “worst-case scenario,” where the device is in a maximum sensitivity mode, individuals are extremely close to a concealed system, and the device with its leads is more parallel to the system’s coils.
Although most people would not consider sitting on the ground of a department store lobby, interior designers are often putting seats and couches in just those locations, Herkert explained. That setup brings customers closer to the EAS system’s coils than was intended. There is also the possibility of a child with a CIED crawling across the store’s entrance.
To find the minimum safe distance in these situations, GTRI tested 31 devices provided by their manufacturers, of which about one-third were legacy devices. The team used a setup that suspended the EAS system in the air, and a simulated torso containing the medical device was moved near the system at different distances, angles, and orientations.
All of the devices showed a response to the floor system at some distance. Most current devices showed no effect until they were positioned about a foot away from the system. Some of the legacy devices were affected to a much greater extent, with some effects occurring when the devices were nearly three feet away from the EAS system. The consequences of these effects on the devices are still being analyzed.
“The data from our most recent tests with concealed systems is important for all stakeholders (e.g., patients, device and EAS manufacturers) because they help to determine the degree of risk for CIED patients who find themselves in worst-case scenarios where they may be at close distances to a concealed system and not know it,” Herkert said.
Herkert is continuing his work and is in discussion with representatives of the ISO 14117 working group, which studies the electromagnetic compatibility of CIEDs, to continue improving device designs.