The Potential of RFID Tag Readers to Interfere with Pacemakers and Defibrillators

RFID tags: they have become ubiquitous additions to our electronic and medical worlds, concealed in automatic automobile tolling systems, key fobs, store and drug packaging, pets and even humans.

No doubt the trend will continue to grow.

Recall that RFID tags are used to locate and tract objects and come in two varieties: passive and active. While active devices contain a small battery, passive devices require no battery since they get their energy from the reader that transmits a signal that is received by the RFID tag's antennae and returns a unique identifier signal to the reader.

Surpisingly, it seems some lower frequency readers have the potential to interfere with implantable pacemakers and cardiac defibrillators (ICDs) when they are held in fairly close proximity to the implanted devices.

Now before you blame and RFID reader for your last defibrillator shock, realize that the FDA has not received any clinical reports of this interference. But researchers from the FDA reported in this month's journal Heart Rhythm that bench testing has demonstrated the potential for interference from certain types of tag readers, particularly those working at the unrestricted lower frequencies (LF) of 125-135 kHz in close proximity to the medical devices. The authors of this bench research concluded:

Although there is in vitro testing evidence for concern for implantable pacemaker and ICD EMI at LF and HF (high frequency - 13.56 MHz), the FDA has not received any incident reports of pacemaker or ICD EMI caused by any RFID system. This could reflect a low clinical risk due to a number of factors: class III (minor) reactions are probably not clinically significant, close patient proximity to RFID readers may not commonly occur, and most reactions observed are transient. This could also be the result of underreporting; EMI issues are difficult to recognize as they are typically transient. If a patient is experiencing symptoms (e.g., lightheadedness) that they believe are the result of EMI effects from an identifiable source, the best advice is to move away from that source.

To effectively mitigate implantable pacemaker and ICD EMI (electromagnetic interference) from RFID readers will require work on the part of both implant manufacturers and the RFID industry. During testing, some implantable pacemakers and ICDs were more susceptible to EMI than others. Active implantable medical device manufacturers are currently working to understand these issues, to develop industry requirements, and to design future devices appropriately.

The RFID industry should also take note with regard to medical device EMC. With so many promising health care applications for RFID, it is inevitable that RFID and medical devices will increasingly function in close proximity. Modulated LF RFID is a near-perfect source to cause EMI for implantable pacemakers and ICDs. The low carrier frequency allows the signal to enter the implant, bypassing commonly used feed-through filters. Once inside the implant, the RFID signal is interpreted as a physiologic signal due to the slow pulse repetition rates. The pulse repetition rate of each RFID reader varies greatly as it is not limited by the Federal Communications Commission or defined by most RFID standards. Limitations for implantable pacemaker and ICD EMC do exist as these devices must sense in the physiological band. If it can be predicted that an RFID system will be near pacemaker or ICD patients, appropriate RFID technology should be selected. The RFID technologies that were most compatible with implantable pacemakers and ICDs in our testing were UHF RFID and continuous-wave RFID readers. Maintaining a reasonable separation distance between RFID readers and implantable pacemakers and ICDs will also help mitigate EMI.

Although this article suggests a particular risk in the use of sample RFID systems, this is not the sole intended message. The potential advantages of RFID in health care seem promising, and the FDA is promoting RFID as a technology to reduce counterfeit drugs in the supply chain. An important message from the results of this study should be that RFID implementation should take implantable pacemaker and ICD EMC into consideration. Additionally, both patients and their cardiologists should be aware of the possibility of adverse reactions from RFID.

We do not believe the current situation reveals an urgent public health risk.

Hey, but it's still good to know.

-Wes


References:

Seidman SJ, Brockman R, Lewis BM, Guag J, Shein MJ, Clement WJ, Kippola J, Digby D, Barber C, Huntwork D; "In vitro tests reveal sample radiofrequency identification readers inducing clinically significant electromagnetic interference to implantable pacemakers and implantable cardioverter-defibrillators," Heart Rhythm Jan 2010, 7(1), 99-107.

Heart Rhythm Society's press release.