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Metal detector security screening appears safe for people with pacemakers or implantable cardioverter-defibrillators (ICDs), researchers found.

In a simulation of airport screening, even prolonged swipes with hand-held metal detectors resulted in no device function abnormalities among the 388 patients tested by Clemens Jilek, MD, of the German Heart Center in Munich, and colleagues.

The office-based experiment needs further confirmation in real-world screening settings, the group cautioned in the Nov. 1 issue of the Annals of Internal Medicine.

But the results should be reassuring, Jilek and colleagues suggested, calling such security screening "probably safe for patients with pacemakers and ICDs."

Metal detector gates, which generate much stronger electromagnetic fields, also appeared safe for cardiac rhythm device patients in a prior study by the same research group.

Because of concerns over interference, the U.S. Transportation Security Administration (TSA) recommends that travelers request a pat-down instead at the airport if they have a pacemaker or ICD.

The FDA had reported 44 cases in which hand-held metal detectors or anti-theft devices had possibly interfered with cardiac rhythm devices from 1988 to 1998.

However, those reports involved older screening technologies and older pacemakers, whereas there have been no recent reports of problems during airport screening, a patient summary page in the Annals noted.

So, Jilek's group bought two of the most commonly used metal detector wands and tested them on patients who came in for routine follow-up of their pacemaker or ICD at two German centers from September 2009 to December 2010.

After checking that each rhythm device was working normally and with the patient lying down under continuous electrocardiogram monitoring, they swiped the detector over the pacemaker or ICD and leads for at least 30 seconds.

When the researchers interrogated the rhythm devices for any abnormalities, they found no pacing or sensing problems or device reprogramming during or after metal detector exposure.

Nor were there any ECG abnormalities.

The researchers noted that their experiment was under exaggerated conditions -- with the metal detectors at their highest settings over the device and leads for 10 times longer than typical for security screening -- to maximize the chances of interference.

Clinically-significant interference is unlikely in real-world settings, they pointed out.

Pacemaker-dependent patients wouldn't be likely to lose consciousness unless oversensing of the signal inhibits device function for more than six seconds, but device exposure to a metal detector in routine screening is at most three seconds.

For ICD patients, inappropriate shocks would require repeated oversensing during the six seconds the device takes to charge up for a shock, which is also longer than its expected exposure to the metal detector's electromagnetic field, the group argued.

The results are likely generalizable, they added.

The 209 pacemaker patients had 81 different devices across 37 different model "families" from 11 different manufacturers, which altogether covered 73% of those available over the past decade.

Likewise, the 179 ICD patients had 61 different devices that covered 76% of the ICD families available over the prior 10 years.

"Nevertheless, our negative findings cannot be considered definitive because the study used a convenience sample of patients and devices; the number of each model device tested was small and often consisted of a single device in a single patient," Jilek's group wrote.

Device manufacturers and other research groups should test a broader array of devices in real-world security screening settings, they suggested.

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