Some Cell Phones Called a Hazard to Pacemakers

SEATTLE — People fitted with pacemakers should be aware that carrying a digital cellular phone could cause the heart-regulating devices to slow down, shut off or even speed up the heart rate, a researcher says.

The first large-scale study on the subject, released Thursday, found the digital cellular phones caused interference with heart pacemakers in more than half of the 975 patients tested.

Dr. David Hayes, a co-author of the study, said interference occurred most often when a phone’s antenna rested directly over the pacemaker, and rarely when a phone was held at the ear.

“I would tell patients that analog phones are certainly the safest,” said Hayes, director of pacemaker services at the Mayo Clinic in Rochester, Minn. “Whatever kind of phone you’re using, it’s best to avoid carrying it around turned on in your breast pocket.”

Analog phones, the most common type of wireless phone available in the United States, caused interference in just 3.1% of the tests. The results, which were similar to those of earlier investigations, were presented at the annual meeting of the North American Society of Pacing and Electrophysiology.

Tim Ayers, a spokesman for the Cellular Telecommunications Industry Assn., said the study contained no surprises. He said new methods to shield medical devices and cell phones are helping to lessen the problems.