From CNN Food & Health Correspondent Linda Ciampa

ATLANTA (CNN) -- A Florida doctor is convinced some anti-theft devices, such as those found in retail stores, are interfering with pacemakers, causing people to become dizzy, feel sick or possibly pass out.

Dr. Michael McIvor of The Heart Institute in St. Petersburg said the problem is caused by the electromagnetic signals emitted by some, but not all, security systems.

"The circuit in the pacemaker can also be affected by these magnetic waves of radiation and when that happens, the pacemaker gets confused," he said. "It may think there was a heartbeat where there wasn't; it may think there was a cardiac arrest where there wasn't."

The Food and Drug Administration was to hold an advisory committee meeting on Thursday to listen to testimony about whether these security devices are endangering the health of those who wear pacemakers to regulate their heartbeats.

Pacemaker circuits can be interrupted by electromagnetic signals emitted by some security devices.

McIvor studied 50 volunteers with implantable pacemakers. Each was exposed to the most commonly-used anti-theft devices used in the United States.

His study found pacemakers in 48 of the patients detected the energy generated by the security devices. In some cases, pacemakers speed up heart rates.

While McIvor said he didn't want to panic those with pacemakers, he does want to raise awareness.

"If you went to a store and you pass out and they say it may be your pacemaker -- when you go to the doctor's office to get checked, they say your pacemaker is fine," he said. "Well, yeah, because you're not in the field now."

McIvor said he would like the FDA to require warning signs on the anti-theft devices that may interfere with pacemakers.

He also wants makers of pacemakers to begin talking with makers of anti-theft devices so their signals don't cross.

If you have pacemaker, McIvor recommends walking quickly through anti-theft systems without pausing between the columns.

Also, don't linger near retail store entrances or exits since some security devices may be hidden behind walls.