Smartphones harmful for people with pacemakers, says study

Pacemakers can mistakenly detect electromagnetic interference from smartphones as a cardiac signal, causing them to briefly stop working

People with pacemaker should keep a safe distance from smartphones to avoid unwanted painful shocks or pauses in function, a new study has warned.

"Pacemakers can mistakenly detect electromagnetic interference (EMI) from smartphones as a cardiac signal, causing them to briefly stop working," said Dr Carsten Lennerz, first author and cardiology resident in the Clinic for Heart and Circulatory Diseases, from the German Heart Centre.

"This leads to a pause in the cardiac rhythm of the pacing dependent patient and may result in syncope. For implantable cardioverter defibrillators (ICDs) the external signal mimics a life threatening ventricular tachyarrhythmia, leading the ICD to deliver a painful shock," said Lennerz.

Device manufacturers and regulatory institutions including the US Food and Drug Administration (FDA) recommend a safety distance of 15 to 20 cm between pacemakers or ICDs and mobile phones. The advice is based on studies performed primarily in pacemakers 10 years ago.

New cardiac devices are now in use including ICDs, cardiac resynchronisation therapy (CRT) and MRI compatible devices.

The current study evaluated whether the recommended safety distance was still relevant with the new smartphones, networks and cardiac devices.

A total of 308 patients (147 pacemakers and 161 ICDs, including 65 CRT) were exposed to the electromagnetic field of three common smartphones which were placed on the skin directly above the cardiac device.

The smartphones were connected to a radio communication tester, which works like a mobile network station.

The investigators put the smartphones through a standardised protocol of the calling process which included connecting, ringing, talking and disconnecting.

Electrocardiograms (ECGs) were recorded continuously and checked for interference.

More than 3,400 tests on EMI were performed. One out of 308 patients (0.3 per cent) was affected by EMI caused by smartphones.

"Interference between smartphones and cardiac devices is uncommon but can occur so the current recommendations on keeping a safe distance should be upheld.

"Interestingly, the device influenced by EMI in our study was MRI compatible which shows that these devices are also susceptible," said Lennerz.