PREDICTORS OF SUCCESSFUL RADIOFREQUENCY ABLATION OF EXTRANODAL SLOW PATHWAYS

Catheter positioning for radiofrequency ablation of extranodal slow pa thways is often guided by local electrogram recordings. To determine t he predictors of successful ablation sites, we reviewed data from 32 s uccessful and 104 unsuccessful sites. Univariate predictors of a succe ssful site included the occurrence of junctional rhythm during ablatio n (P < 0.001), shorter time to onset of junctional rhythm (P = 0.05), the presence of a discrete slow pathway potential (P < 0.001), a small er ratio of the amplitude of the atrial:ventricular electrogram (P = 0 .04), later timing (P = 0.001) and longer duration (P < 0.001) of the atrial slow pathway electrogram, and the duration of (P < 0.001), and maximal voltage used during ablation (P < 0.001). By multivariate anal ysis junctional rhythm (P < 0.001), a discrete slow pathway potential (P = 0.003), a longer duration of the atrial slow pathway electrogram (P = 0.01) and the duration of ablation (P = 0.02) were predictors of success. Because ablations at unsuccessful sites were often aborted at 10-30 seconds, a separate analysis was performed using only the 41 un successful sites where the duration of ablation was greater-than-or-eq ual-to 30 seconds. The results were nearly identical. Thus, the occurr ence of junctional rhythm during ablation and the morphology and durat ion of the atrial slow pathway electrogram may serve as guides for slo w pathway ablation site selection.