Cardiac Pacemaker Disruption Studied
Cellular telephone companies and the federal government are looking into how some digital cellular telephones can interfere with cardiac pacemakers, cardiac defibrillators and hearing aids.
Investigators in Italy, Switzerland and Australia have found that certain digital cellular phones can disrupt a pacemaker’s signal if held too close to the chest. Last year, the findings were confirmed by doctors in the United States, where 132,000 pacemakers are implanted annually.
In Great Britain, advocates for the deaf have warned that operating digital cellulars within a few feet of someone wearing a hearing aid can produce a loud buzz in both devices, even if the phone is on standby.
Analog signals, which power the majority of U.S. cellular phones, are not in question. The interference arises from pulsed signals of digital phones, which accounted for about 400,000 of the more than 6 million hand-held cellulars sold in this country last year, according to Herschel Shosteck Associates in Wheaton, Md.
A University of Oklahoma research center formed by cellular companies began looking at that problem from an engineering perspective this summer, along with the potential problems with pacemakers and defibrillators, and the Food and Drug Administration is evaluating all three as well. Potential solutions range from design modifications to new labeling.
So far, no reports are known of serious health effects when pacemakers meet digital phones. But the FDA advises that pacemaker wearers avoid bringing a digital cellular telephone within two inches of the chest.
“In the pacemaker-dependent population, it is a potentially dramatic situation if the pacemaker is inhibited and does not produce the shock when the patient requires it,” said Don Witters, an FDA physicist and biomedical engineer.
An FDA laboratory hopes to release its pacemaker findings before year’s end, Witters said.
The lab recently also began investigating interference with hearing aids and implantable defibrillators, which are surgically placed in the abdomen to shock a fluttering, non-pumping heart back into a strong beat.
Parallel to engineering studies are hospital investigations underwritten by Wireless Technology Research, a five-year cellular research program paid for by an industry trust. Cardiologists will observe as patients hold operating cellular phones against their ears and then directly over their chests, WTR chairman George Carlo said. Results are due in January.
In addition, WTR will fund a hospital study of cellphones and defibrillators.
Meanwhile, Medtronic Inc., the world’s largest developer and manufacturer of cardiac pacemakers, has put its engineers to work on better shielding, spokesman Dick Reid said. The suburban Minneapolis firm, which says 2 million of its devices have been implanted worldwide since 1961, has more than 40% of the U.S. market.
The company normally advises a 6-inch separation between portable cellulars and a pacemaker, Reid said.
“In actual practice, we urge people when using the phone to hold it to the ear opposite the side of the body their implantable device is on,” he said. “We also urge that they do not carry the cellular phone in a chest pocket.”
