Jan 08, 2010A study published this month in a medical journal shows that while interrogators of passive RFID tags do cause some electromagnetic interference to implantable pacemakers and implantable cardioverter-defibrillators (ICDs), the devices pose no urgent health risks. However, the study's authors believe that the "continued proliferation of RFID without taking implantable pacemaker and ICD EMC into consideration could potentially cause clinically significant events for patients."
The research was conducted by the U.S. Food and Drug Administration's (FDA) Center for Devices and Radiological Health, which is responsible for regulating companies that manufacture medical devices sold in the United States, as well as for regulating radiation-emitting electronic products (medical and non-medical) such as lasers, x-ray systems, ultrasound equipment, microwave ovens and color televisions. This research was supported by the Cardiac Rhythm Management Devices (CRMD) Electromagnetic Compatibility (EMC) Task Force of the Association for the Advancement of Medical Instrumentation, a nonprofit organization that works to advance the safety of medical devices through standards development and information-sharing.
The study, conducted in a laboratory, involved exposing 15 implantable pacemakers and 15 ICDs to an interrogation field. Each device manufacturer provided an engineer for testing its own implantable devices. The group employed 13 RFID readers from six different manufacturers in three frequency bands: 134 kHz low-frequency (LF), 13.56 MHz high-frequency (HF) and 915 MHz ultrahigh-frequency (UHF). There were five LF, six HF and two UHF readers. Each device was turned on, and proper operation was verified.
The study's findings were peer-reviewed and published in the January 2010 edition of HeartRhythm Journal, the official journal of the Heart Rhythm Society and the Cardiac Electrophysiology Society The findings show that the readers in the LF band produced the most significant reaction; 67 percent of all pacemakers tested showed EMI interference from these devices at a maximum distance of 60 centimeters (24 inches) between the interrogator and the pacemaker. And 47 percent of all ICDs tested showed interference at a maximum distance of 40 centimeters (16 inches). During HF exposure, an adverse reaction was observed for 6 percent of all pacemaker tests when the maximum distance was 22.5 centimeters (9 inches), and 1 percent of all ICD tests when the maximum distance was 7.5 centimeters (3 inches). But the UHF readers produced no measurable reaction from either the pacemakers or the ICDs. When EMI occurred, the signals emitted by the ICDs and pacemakers were altered, resulting in a variety of reactions from the medical devices, including pacing inhibition, inappropriate pacing, noise reversion mode, changed pacing rates, inappropriate delivery of antitachycardia pacing, inappropriate high-voltage shocks and device programming change.
Seth Seidman, a research electrical engineer for the Center for Devices of Radiological Health, and the report's lead author, notes that while individuals outfitted with pacemakers or ICDs are not commonly exposed to RFID readers in clinical settings, the growing number of medical applications using RFID technology may mean that in the future, such exposure will increase during patient care. To mitigate pacemaker and ICD electromagnetic interference from RFID interrogators, the FDA is working with manufacturers of potentially susceptible devices, in order to test the potential adverse effects of radio frequency identification, and to take those potential effects into account when developing devices.
The report goes on to note that signals from LF readers are a "near-perfect source to cause EMI for implantable pacemakers and ICDs," because the "low carrier frequency allows the signal to enter the implant, bypassing commonly used feed-through filters."
Despite these clinical findings, the FDA indicates it has not received any reports of adverse incidents caused by electromagnetic interference emitted by any RFID system. And while it does not believe that individuals who have an implanted pacemaker or ICD are at significant risk for those devices to malfunction due to interference from RFID readers, the agency does recommend that these individuals not linger near RFID readers, as a precaution.
This newly published study, initiated in 2008, confirms preliminary findings from a 2006 study entitled "Electromagnetic Compatibility of Pacemakers and Implantable Cardiac Defibrillators Exposed to RFID Readers," that Seidman presented at the fifth RFID Academic Convocation, which was held in conjunction with RFID Journal LIVE! 2007. A complete copy of the study can be downloaded from HeartRhythm Journal's Web site.
Recommendations for future testing, the authors say, would include "extending each distance test dwell time from 10 to 20 seconds, creating a more anatomical torso simulator, grading each distance for clinical significance as opposed to each test, modifying the pulse repetition rate of RFID readers outside the physiological band, and modifying the modulation depth of each RFID reader."
