To catch a thief may stop a heart
Devices to nab shoplifters can interfere with the functioning of pacemakers and implantable cardioverter-defibrillators.
The exits of most stores these days are guarded even when there's no security guard in sight. Doors are monitored by "electronic article surveillance" systems that use radio or electromagnetic waves to detect whether tiny sensors affixed to the merchandise have been deactivated. If they haven't, an alarm goes off. Often these systems are in plain view: two pedestals — one serving as a transmitter, the other as the receiver — form a little checkpoint that you walk through as you leave the store. They're so common now that we hardly notice them.
People with pacemakers and implantable cardioverter-defibrillators (ICDs) — which shock the heart back into a regular rhythm if it starts to beat erratically — are warned not to lean on, or linger near, the pedestals because they could interfere with the electronics of the cardiac devices. Metal detectors at airports pose a similar risk, which is why people with cardiac devices are usually excused from going through them and searched with a handheld wand instead.