Go ahead and make that cell phone call

But playing your CD player might make Grandma go all funny:

WASHINGTON -- Calls made on cellphones do not affect hospital medical devices, US researchers said yesterday, but store antitheft alarms may make implanted heart devices misfire.

Tests at the Mayo Clinic in Rochester, Minn., showed that normal use of cellphones caused no noticeable interference with patient care equipment, researchers said.

But a portable CD player caused an abnormal electrocardiographic reading when a patient used it near the device, according to one report in the March issue of Mayo Clinic Proceedings.

At least two reports suggest that anti theft devices set up near the doors of retail stores can cause implantable rhythm devices such as pacemakers and defibrillators to malfunction.

Most hospitals forbid the use of cellphones. But Dr. David Hayes and colleagues said their tests suggest the ban is unmerited. They tested cellphones using two different technologies from different carriers, switching them on near 192 different medical devices.