Doctors must warn patients with pacemakers that their devices might be disrupted by anti-theft systems used in shops, experts have said.Many patients are unaware that electronic anti-theft systems can pose a threat to people using cardiac devices, they said.Prolonged exposure to the in-store devices could cause pacing therapy to drop beats and cause implantable defibrillators to deliver shocks, experts told a conference in Nice, France.Many patients were 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 Robert Stevenson, senior scientist at Greatbatch Medical in Santa Clarita, California, US, examined the 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.Stevenson added: "Doctors must educate patients about the potential dangers of [electronic anti-theft] 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." ..