Implantable Cardioverter Defibrillators Study

[Order Report]       [Executive Summary]

        The EMC Center presented the findings of the Implantable Cardioverter Defibrillator (ICD) - Wireless Phone Study at the Fourth Annual EMC Forum in Dallas, Texas and at the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology Society in Chicago, Illinois in October of 1997. The in vitro laboratory tests were designed to determine the critical factors influencing the interaction between wireless digital phones and implantable cardioverter defibrillators (ICDs), and to investigate the extent of the interaction. ICDs are electronic devices that are implanted within the body to monitor and correct abnormal heart rhythms. Like a pacemaker, the ICD can compensate when the heart beat is too slow, but the ICD can additionally correct rhythms that are too fast. Interaction with wireless phones could occur if the RF from a pulsing phone signal is misinterpreted as an abnormal heart rhythm, and might cause the ICD to deliver an unnecessary therapy. Alternatively, the ICD could be blinded by the phone signal and fail to deliver a needed therapy.

        Ten ICDs were tested against nine phone technologies currently employed in the United States and Europe. These technologies transmit in either the "low" frequency bands, at 800 MHz (AMPS, CDMA, TDMA-50 Hz, TDMA-11 Hz) and 900 MHz (TDMA-217 Hz), or in the "up-bands" of 1800 MHz (TDMA-217 Hz) and 1900 MHz (CDMA, TDMA-50 Hz, TDMA-217 Hz). All tests were conducted under worst-case conditions, with phones operating at their highest power levels and the ICDs programmed to their maximum sensitivity. The phones were tested in close proximity to the ICD to represent the phone being carried in a pocket or being held adjacent to the user's chest.

        Only four of the ten tested ICDs exhibited interaction, and only two of these interacted with more than one phone technology. The largest number of interactions were noted with the TDMA-11 Hz phones. No permanent reprogramming of the ICDs occurred during testing. The maximum coplanar separation distance between the ICD and the phone at which interactions were noted was 7.4 inches (6.2 inches for the majority of phone-ICD interactions). Relative orientation of the phone with respect to the ICD significantly affected the amount of interaction. No interactions were noted for phones in the 1.8 to 1.9 GHz region.

        Based on the findings of the study, the researchers suggest that the HIMA-recommended minimum separation distance of six inches between pacemakers and wireless phones is also applicable for ICDs. Injection of an ECG trigger signal was shown to increase the opportunity to observe the interaction, and is therefore recommended for inclusion in future test protocols.

[Order Report]       [Executive Summary]

For more information, please contact Wireless EMC Center, The University of Oklahoma, Office phone number: 405-325-2429, Internet email address: emc@ou.edu