Pausing With the Gauze: Inhibition of Temporary Pacemakers by Radiofrequency Scan During Cardiac Surgery.

BACKGROUND: Radiofrequency identification (RFID) detection systems are used to detect retained surgical sponges and may cause electromagnetic interference (EMI), altering intended function of cardiac pacing systems. Three pediatric patients requiring temporary pacing for postoperative atrioventricular block experienced transient inhibition of ventricular pacing during the use of RFID detection system. Bench testing was performed to evaluate the mechanism of pacemaker inhibition. METHODS: Impedance of temporary pacing wires was obtained using a pacing system analyzer. Temporary pacemakers (Medtronic 5388, Medtronic 5392, and Biotronik Reocor D) at nominal settings (VVI 120 bpm, output 10 mA) were attached at the ventricular terminal to temporary pacing wires and a resistor for sham impedance in physiologic range. An RFID detection system and wand (RF Assure, model 200) or mat was tested over wires. Induced current and voltages were recorded via an oscilloscope attached to lead terminals. Inhibition of pacing was determined for the following variables: distance from wires, sham impedance, and programmed sensitivity. RESULTS: In bench testing, the RFID system induced a stereotyped EMI signal in temporary pacing wires with peak root-mean-square voltage demonstrating an exponential decay relationship with increasing distance from pacing wires. Induced voltages overlapped with normal sensing range of temporary pacemakers, resulting in pacemaker inhibition at nominal settings (ventricular sensitivity 2.0 mV, distance from wand <23 cm). Increasing height, decreasing device sensitivity, or increasing sham impedance (at fixed sensitivity) attenuated EMI and inhibition for all 3 temporary pacemakers used and with the automated RFID detection mat in place of the wand. Programming pacemakers asynchronously prevented inhibition. CONCLUSIONS: Normal operation of RFID detection systems may cause inhibition of temporary pacing systems consistent with oversensing from EMI. Precaution should be taken, including considering pacing asynchronously to avoid effects of inhibition.