New research indicates that it is rare for magnetic fields associated with power lines to interfere with cardiac pacemakers. However, there is some evidence that these magnetic fields can cause alterations of devices programmed in the unipolar sensing configuration, according to a new report.

Electromagnetic energy can interfere with function of pacemakers, Dr. Alexandre Trigano, from Centre Hospitalier Universitaire Nord in Marseille, France, and colleagues note. However, no studies have found “specific and relevant information pertaining to magnetic fields near power lines or electrical appliances.”

The findings, which appear in the Journal of the American College of Cardiology, are based on a study of 245 pacemaker recipients who were exposed to magnetic fields while being monitored by ECG.

A switch to the asynchronous mode was observed in three patients with devices set to the unipolar sensing configuration, the investigators report. Moreover, in one patient, symptomatic pacing inhibition occurred after a sustained mode switch.

The test magnetic fields had little or no effect on the function of devices programmed in bipolar sensing, the researchers note.

“Our study shows a low incidence of interference by a high-density magnetic field in patients tested during routine follow-up visits, without changes in the programmed sensitivity settings or other pacing parameters made before the test,” the authors conclude.

SOURCE: Journal of the American College of Cardiology, March 15, 2005.