Design and clinical application of a low-pass input filter for the evaluation of intracardiac electrograms during radiofrequency catheter ablation

Successful ablation of an accessory pathway using radiofrequency current may be defined by the elimination of ventricular preexcitation or the loss of eccentric retrograde atrial activation.1 Because of the low voltages of intracardiac electrograms (0.1 to 5.0 mV) compared with the high voltages applied during radiofrequency ablation (30 to 50 V), monitoring of local electrograms during ablation may not be feasible with conventional biopotential amplification and filtering systems2. However, given the fundamental differences in signal frequencies between intracardiac electrograms (10 to 230 Hz) and radiofrequency current (550 to 750 KHz), selective attenuation of high-frequency radiofrequency signals and amplification of the lower frequency intracardiac electrograms may allow continuous monitoring of intracardiac electrograms during ablation.3 The purpose of this study was to evaluate the feasibility and clinical use of an input bandpass filter, selective for frequencies < 1 KHz, which allowed continuous monitoring of intracardiac electrograms in patients undergoing radiofrequency catheter ablation of accessory pathways.