London, June 22 (IANS): If you wear a cardiac device such as a pacemaker, better keep away from smartphones, researchers say.

"Pacemakers can mistakenly detect electromagnetic interference (EMI) from smartphones as a cardiac signal, causing them to briefly stop working," said first author Carsten Lennerz from German Heart Centre, Munich.

"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," Lennerz said.

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.

Now, new cardiac devices are 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 smartphones, networks and cardiac devices.

A total of 308 patients (147 pacemakers and 161 ICDs, including 65 CRTs) were exposed to the electromagnetic field of three common smartphones (Samsung Galaxy 3, Nokia Lumia, HTC One XL), which were placed on the skin directly above the cardiac device.

The actions were performed in GSM, LTE and UMTS at the maximum transmission power and at 50 Hz, a frequency known to influence cardiac implantable electronic devices. 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 percent) was affected by EMI caused by smartphones.

This patient's MRI compatible ICD misdetected electromagnetic waves from the Nokia and HTC smartphones operating on GSM or UMTS as intracardiac signals.

"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."

The results were presented at the joint meeting of the European Heart Rhythm Association (EHRA) and Cardiostim, which is in Milan, Italy.