Regulatory bodies recommend keeping a certain distance between wireless devices and medical equipment in order to avoid interference, but these guidelines are based on research from ten years ago. The Food and Drug Administration (FDA) says that patients with pacemakers or implantable cardioverter defibrillators (ICDs) should hold smartphones at least six inches away from the implanted devices. Researchers from Germany recently conducted a study to see if this standard still makes sense for cardiac devices and phones that were introduced in the last decade, especially since mobile network standards have changed from GSM to UMTS and LTE.
Dr. Carsten Lennerz said, “Pacemakers can mistakenly detect electromagnetic interference (EMI) from smartphones as a cardiac signal, causing them to briefly stop working. This leads to a pause in the cardiac rhythm of the pacing dependent patient and may result in [fainting]. For ICDs, the external signal mimics a life threatening ventricular tachyarrhythmia, leading the ICD to deliver a painful shock.” The conclusion is that interference is rare, but the consequences can be quite serious, so patients should continue to follow the FDA’s current recommendations: hold your smart phone on the opposite side of the body as the device and avoid putting your phone in a shirt pocket directly over a cardiac implant.
The research was presented on June 22 at the joint meeting of the European Society of Cardiology’s European Heart Rhythm Association and Cardiostim. In the study, smartphones were placed on patients’ skin directly above implanted devices. The smartphones were connected to a radio communication tester and more than 3,400 tests were conducted at the maximum transmission power and at 50 Hz, a frequency that has been known to affect medical devices. Electrocardiograms continuously monitored interference. Of the 308 patients who participated in the study, one (0.3 percent) was affected by EMI, when the ICD mistakenly detected electromagnetic waves from smartphones as cardiac signals. The ICD was MRI-compatible, so it is worth noting that those devices are not immune from cell phone radiation. “Interference between smartphones and cardiac devices is uncommon but can occur,” said Lennerz, “So the current recommendations on keeping a safe distance should be upheld.”
Another study presented at the same conference cautioned patients with cardiac devices to avoid exposure to high voltage power lines (230 kV and up). Dr. Katia Dyrda, a cardiologist from the University of Montreal, said that high electric fields can cause implanted devices to stop working or deliver inappropriate shocks. She said that despite the risks, “there are no recommendations from device manufacturers about power lines or higher electric fields.” The study exposed 40 cardiac devices to 20 kV/m in a high voltage laboratory. The researchers found no problems for pacemakers that were programmed in typical configurations, but when the devices were set to higher sensitivity levels or unusual modes, the EMI threshold decreased. Dyrda said that patients with standard pacemakers or ICDs do not need to avoid crossing under high voltage power lines, but they should avoid staying underneath them for longer periods of time. She also added that driving below high voltage power lines is fine, saying, “If you’re in a vehicle you are always protected because your car acts as a Faraday cage and shields you automatically.”
