Characteristics of Telemetry Interference with Pacemakers Caused by Digital Media Players

Abstract

Contemporary implantable heart rhythm devices communicate multiple complex data simultaneously using radiofrequency telemetry. Interference in communication can expose them to the risk of potential corruption, leading to adverse clinical consequences. We studied the characteristics of interference with uplink (real time intracardiac electrograms, marker channel, and stored histograms) and downlink (attempt to program a change in the lower rate limit, the pacing mode, and the ventricular lead configuration) data transmission between the wand and the pacemaker caused by digital media players (iPods--Photo and 3G) in 50 patients. We also measured and characterized worst-case magnetic field emissions (MFE) from the wand (<or=0.4 microT), pacemaker (<or=0.004 microT), and iPod (<or=0.05 microT) during telemetry to understand the modulation techniques and safety protocols employed during data transmission. Telemetry interference (TI) manifested as high-frequency spikes (24.4%), blanking (17.7%) and interruption (22.2%), or delay (17.6%) in transmission with warning on programmer's screen. TI occurred in 25.6% of patients when the iPod was "on" and in 13% even with the iPod turned "off." There were no inaccuracies in downlinked data when the downlink communication was successful. Wanded telemetry utilizes low-frequency (30-300 kHz) radiowaves and simple digital modulation techniques at relatively slow rates for "sequential" data transmission protected by a continuous "handshake." Emissions from iPods in that range interrupt the telemetry link but are too weak to cause pacemaker malfunction through corruption of vital data. Low-power MFE from iPods can produce interference with establishment and maintenance of a telemetry link and can cause TI with transmission of real time data, but because of continuous check protocols, do not corrupt the stored and vital downlink data.