New research suggests that smartphones may be dangerous for cardiac device wearers.

German researchers found that patients with pacemakers and implantable cardioverter defibrillators (ICDs) may experience unwanted painful shocks or pauses in the function of their cardiac devices when they use or carry a smartphone, MedPage Today reported.

"Pacemakers can mistakenly detect electromagnetic interference (EMI) from smartphones as a cardiac signal, causing them to briefly stop working," Dr. Carsten Lennerz, first author of the study, said in a statement. "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."

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 10 years ago, according to Tech Times.

For the study, researchers collected and analyzed data from more than 300 patients. to evaluate whether the recommended safety distance was still relevant with the new smartphones, networks and cardiac devices. These volunteers were exposed to the electromagnetic fields (EMI) from three common smartphones: Samsung Galaxy 3, Nokia Lumia, HTC One XL.

They found that only one of the study participants (0.3 percent)of participants were affected by the EMI from smartphones, Medical News Today reported.

"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, who is also a cardiology resident in the Clinic for Heart and Circulatory Diseases in Germany.

The findings were presented at the at the European Heart Rhythm Association EUROPACE -- CARDIOSTIM 2015.