Smartphones and high voltage power lines can affect functioning of cardiac devices and disrupt the heart rate of their wearers, two studies have revealed.
In a paper presented at a congress of the European Society of Cardiology, German researcher Carsten Lennerz said patients with pacemakers should be advised not to keep their smartphones in pockets close to their hearts and always maintain the devices at a safe distance.
Otherwise, he said they could suffer painful shocks or even faint due to disruptions to the device’s operations by exposure to magnetic fields.
“Pacemakers can mistakenly detect electromagnetic interference from smartphones as a cardiac signal, causing them to briefly stop working,” explained Lennerz, a cardiology resident at the German Heart Centre in Munich, Germany.
“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.”
Interferences between smartphones and cardiac devices were previously evaluated 10 years ago, when regulatory institutions recommended a safety distance between 15 to 20 cm between pacemakers and mobile phones.
However, the technology has changed since then on both sides and the German researchers wanted to see whether the rules may be revised.
During the tests, the researchers repeatedly exposed 308 patients to electromagnetic fields induced by three common smartphones placed directly above the cardiac device.
In about 0.3 per cent of the experiments, the patients experienced disruption of their pacemakers' and ICDs' operations.
“Interference between smartphones and cardiac devices is uncommon but can occur, so the current recommendations on keeping a safe distance should be upheld,” Lennerz said. "Interestingly, the device influenced by EMI in our study was MRI compatible which shows that these devices are also susceptible.”
In a separate study, Canadian researchers have warned that magnetic fields in the vicinity of high-voltage power lines could also have undesirable effects on pacemaker wearers.
“High electric fields may interfere with the normal functioning of cardiac devices, leading to the withholding of appropriate therapy or to the delivery of inappropriate shocks,” said Katia Dyrda, a cardiologist at the University of Montreal, Canada.
The problem, she said, is becoming more prominent as areas under high-voltage power lines are frequently being used to build bicycle routes and walking paths.
These power lines, carrying voltages of more than 230kV, induce magnetic fields strong enough to interfere with cardiac devices. Even higher electric fields could be encountered by workers conducting maintenance in utility substations.
“The International Organization for Standardization says pacemakers and ICDs should give resistance up to 5.4 kV/m (for 60 Hz electric fields) but electric fields can reach 8.5 kV/m under high voltage power lines and 15 kV/m in utility substations.”
Dyrda and her team exposed 40 cardiac devices (21 pacemakers and 19 ICDs) from five manufacturers to electric fields up to 20 kV/m in a high voltage laboratory. The devices were mounted in a saline tank positioned as high above the ground as if being worn by the average person.
The researchers found that while in a nominal and in bipolar mode, the devices were largely immune to the magnetic fields up to 8.6 kV/m, when programmed to higher sensitivity levels or in unipolar mode, they showed signs of interference at as low as 1.5 kV/m.
“There is no need for patients with a pacemaker or ICD to avoid crossing under high voltage power lines (> 230 kV) but patients should avoid staying in a stationary position underneath them,” said Dyrda. “Passing near pylons rather than between two pylons mitigates exposure to the electric field because the wires sag in the middle and the field is higher at this location.”
The researcher said low-voltage power lines delivering electricity to households do not pose any risks for cardiac patients.