iPods can cause heart pacemakers to malfunction

In only six years, the small, plastic device that can hold your entire record collection has revolutionised the way we listen to music, changed society and turned the ailing Apple computer company into the dominant force in the download music industry. But researchers are so concerned about new evidence of potential effects of MP3 players on heart pacemakers that a major clinical investigation is to start this month.

The trial comes in the wake of a report earlier this year that iPods may cause pacemaker interference in up to half of patients. A study in Michigan in the US found that when an iPod was held 2 inches from a patient's chest for five to 10 seconds it interfered with pacemakers in half the 100 patients, whose average age was 77.

Now researchers want to test the possible dangers with other types of player and different ages of patients. "Our hypothesis is that the close approximation of portable MP3 players interfere with the appropriate sensing and recording of pacemakers," said researchers at the Children's Hospital in Boston, Massachusetts.

There have been concerns about the possible interference of other gadgets with pacemakers, and mobile phones are among those that have been investigated. One study showed that a phone being used at the ear was sufficiently far away to prevent a health risk, but recommended that phones not be put in shirt pockets or used near the implanted device.

The Boston researchers point out that, unlike phones, which are usually held to the ear, portable MP3 players can be held almost anywhere, including positions close to the site of the implanted device.

They cite the research showing that the players caused pacemaker interference in half of patients tested; with over-sensing – where the pacemaker misreads the heart's functioning – in 20 per cent; interference in 29 per cent; and pacemaker inhibition – where the pacemaker stopped functioning properly for a time – in 1.2 per cent. In some cases, interference was detected when the players were held 18 inches from the chest.

Those researchers said that while older people with pacemakers may not use MP3 players, they may well come close to them through contact with grandchildren. As the baby-boomer generation grows older, with many rock musicians in their 60s and 70s, the potential for older people to use MP3 players is growing.

In the Boston trial, four different brands of MP3 players will be tested at three distances from the implanted medical device in children and adults aged four to 55 with congenital heart disease. At each distance the pacemaker will be checked for changes in sensing and pacing. The whole process takes around 10 minutes.

The trial is expected to be completed in September next year.