SIGNAL-AVERAGED INTRACARDIAC ELECTROGRAMS - A NEW METHOD TO DETECT KENT POTENTIALS

Introduction: In patients with manifest accessory pathways, Kent poten tials are often difficult to identify even at sites of successful cath eter ablation, due largely to signal noise and catheter instability. W e hypothesized that signal averaging the intracardiac electrogram reco rded from the ablation catheter over a number of beats would improve t he signal-to-noise ratio of the electrogram and aid in the detection o f Kent potentials at accessory pathway locations. Methods and Results: We retrospectively analyzed distal-pair electrograms recorded from 9 successful, 6 transiently successful, and 10 failed ablation sites in 10 patients with manifest accessory pathways who underwent catheter ab lation. We developed custom software to finely align 20 to 30 consecut ive sinus beats and compute the signal average of the electrogram (SAE ) for each site. Kent potentials were classified as probable, possible , or absent in the raw ablation site electrogram and the SAE base on m orphologic criteria. A measure of beat-to-beat signal instability, the variability quotient (VQ), was also computed for each site. Probable Kent potentials were found in the raw ablation site electrogram at onl y 2 of the 15 successful and transiently successful sites, but were fo und in the SAE at 10 of these sites (P = 0.008). Eight of the 9 succes sful sites had VQ < 0.2, suggesting stable catheter-tissue contact, wh ile 3 of the 6 transiently successful sites had VQ > 0.2, indicating u nstable contact. Conclusions: Signal averaging the intracardiac ablati on site electrogram enhances detection of Kent potentials at accessory pathway locations. Catheter instability can be quantified by signal v ariability analysis and, when high, may predict lack of successful abl ation even at sites where Kent potentials are present.