'Pseudodisappearance' of atrial electrogram during orthodromic tachycardia: new criteria for successful ablation of concealed left-sided accessory pathways

Objectives. This study sought to analyze two new criteria along with other known predictors of success of radiofrequency ablation. Background. Although the overall success rate of radiofrequency ablation of accessory pathways is high, the individual predictive value of each of the established criteria is low. Methods. We prospectively studied the local electrograms obtained before the application of radiofrequency energy in 33 patients with a left-sided concealed accessory pathway successfully ablated. Two new criteria (“pseudodisappearance” during tachycardia of a bipolar atrial electrogram visible during sinus rhythm and the presence of an “atrial notch” in the ascending limb of the unipolar ventricular electrogram during tachycardia) were studied along with other known predictors. Electrograms recorded at a total of 157 sites were analyzed (33 successful applications, 124 failures). Results. Electrogram characteristics that were predictive of success during ablation on the basis of univariate analyses were a pseudodisappearance criterion (p < 0.001), the presence of a Kent potential (p < 0.005) and the presence of an “atrial notch” (p < 0.005). After adjustment for between-patient differences, logistic regression analysis showed that only the “pseudodisappearance” criterion (odds ratio [OR] 7.2, 95% confidence interval [CI] 1.2 to 42.5, p < 0.03) and the presence of a Kent potential (OR 2.4, 95% CI 1.01 to 5.79, p < 0.05) had independent predictive value. Conclusions. The pseudodisappearance during tachycardia or ventricular pacing of a bipolar atrial electrogram present during sinus rhythm is associated with a good outcome during radiofrequency ablation of concealed accessory pathways. These observations may help to ablate accessory pathways and to avoid missing appropriate sites for ablation when the atrial activation is not clearly visible at the local electrogram.