Doctors must warn patients with pacemakers that their devices may be disrupted by anti-theft devices used in shops, experts have said.
Many patients are unaware that electronic anti-theft systems, also known as electronic article surveillance (EAS) systems, can pose a threat to people using cardiac devices, they said.
Prolonged exposure to the in-store devices can cause pacing therapy to drop beats and cause implantable defibrillators (ICDs) to deliver inappropriate shocks, experts told the Cardiostim EHRA Europace 2016 conference in Nice, France.
While previous warnings have been issued, many patients are unaware of the problem, they said.
Some of the anti-theft devices are hidden under floors, in walls and in doors, while traditional pedestal systems in doorways are often covered by advertising sleeves.
A new study, presented by Professor Robert Stevenson, senior scientist at Greatbatch Medical in Santa Clarita, California, US, examined pacemakers against an array of anti-theft devices.
Traditional pedestal systems interfered with cardiac device functioning, especially when the devices were in prolonged close proximity, they found.
In particular, they raised concerns about patients standing in close to EAS pedestals and toddlers with pacemakers crawling over sub-floor systems.
Professor Stevenson added: "Doctors must educate patients about the potential dangers of EAS systems as many have never been warned not to lean or linger in retail store entrances. It is particularly important that patients do not sit or slouch in a chair or couch in store entry areas.
"Electronic anti-theft systems are a part of everyday life, with more than 800,000 pedestals alone installed worldwide.
"Patients are safe if they walk at a constant pace through the system.
"EAS gates that are obscured with advertising or goods for sale, or hidden in the floor with couches or chairs adjacent, are a serious concern and EAS manufacturers have a responsibility to ensure that retailers install them in such a way that they are visible and well marked."
Co-author Dr Rod Gimbel, an electrophysiologist at Case Western Reserve University in Cleveland, Ohio, US, said: "Cardiac implantable electronic devices (CIEDs) are critical to patients' health.
"Pacemakers provide pacing support, without which there would be no heartbeat at all for a pacemaker-dependent patient. ICDs deliver pacing or shocks to rescue patients from potentially life-threatening arrhythmias.
"We tell patients 'Don't linger, don't lean' but that advice is hard to follow when systems are invisible. To make matters worse, advertising draws patients closer to the pedestals. Some shops have placed camouflaged pedestals next to a chair or in a checkout line, so patients may be next to them for some time, and sofas are put on top of under-floor systems, encouraging patients to sit for long periods."