Keeping pace of mobile phone safety

A new study in the Institute of Physics journal Physics in Medicine and Biology, reveals that the new generation of digital mobile phones can interfere with many types of heart pacemaker. The pacemakers can confuse the signals generated by mobile phones for the heart’’s own electrical signals, causing the pacemaker to malfunction. The authors of the paper, based in the US and Italy, say that newer pacemakers fitted with a ceramic filter are immune and recommend that all manufacturers use these filters.

Electromagnetic interference between mobile phones and cardiac pacemakers has caused concern among physicians since 1994, when it was reported that mobile phones could cause the life-saving implants to malfunction. Early studies found various pacemakers susceptible to interference and the researchers suggested wearers should keep a safe distance from mobile phones. The studies did not look at the cause of the interference, however, so it was not known which pacemaker wearers were most at risk.

Biomedical engineer Giovanni Calcagnini of the Italian Institute of Health in Rome explains that some electrical components of the pacemakers act like an aerial. They can pick up undesirable radio frequency signals and transmit them to the pacemaker’’s sensitive electronic circuits. He and his colleagues at the Center for Devices and Radiological Health of the Food and Drug Administration, in Rockville, Maryland, USA, have investigated exactly how radio frequency signals of the kind used by modern mobile phones are transmitted to the pacemaker’’s internal components.

The researchers tested three versions of the same pacemaker model. The first was equipped with a conventional filter, used to block high-frequency radio signals. The second used the newer ceramic filters connected directly to the internal circuits. The third pacemaker was fitted with both devices.

For each pacemaker, the researchers monitored the pacemaker’’s output signal, which usually helps control the patient’’s heart beat, while exposing the device to the radio signals from mobile phones, including the GSM (Global System for Mobile) phones used throughout Europe.

They report in Physics in Medicine and Biology that the radio frequency signals from GSM phones passed straight through the standard filter device. “This phenomenon could pose a critical problem for people wearing pacemakers because digital mobile phones use extremely low-frequency signals, which can be mistaken for normal heartbeat,” explains Calcagnini. “If a pacemaker detects a normal heartbeat it will not function properly and could be very dangerous for the wearer.” The pacemaker equipped with the ceramic filter, however, was immune to mobile phone radio frequency signals.

“Most manufacturers have started to equip their new models with ceramic filters,” explains Giovanni Calcagnini. “We recommend all new models be equipped with these filters, since it is difficult to change cellphone technology to avoid them producing low-frequency radio frequency signals.”