ADJUNCTIVE INTRACARDIAC ECHOCARDIOGRAPHY TO GUIDE SLOW PATHWAY ABLATION IN HUMAN ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA - ANATOMIC INSIGHTS

Background Because of the inability of fluoroscopy to image intracardi ac structures, the precise anatomic location of successful slow pathwa y (SP) ablation is controversial. We hypothesized that adjunctive intr acardiac echocardiography (ICE) in concert With conventional fluorosco py and electrogram guidance could identify the anatomic site of succes sful SP ablation. Methods and Results In 25 patients, radiofrequency a blation was performed in the triangle of Koch directed by biplane fluo roscopy and a 6.2F, 12.5-MHz ICE catheter positioned adjacent to the t riangle of Koch. Persistent SP conduction, number of radiofrequency ap plications, presence of junctional tachycardia, and fluoroscopy times were evaluated. As demonstrated by ICE, anterograde SP ablation was ac hieved between 2 and 7 mm from the tricuspid valve in imaging planes c ontaining the AV muscular septum in all cases. Radiofrequency energy a pplications applied at other sites within the triangle of Koch failed to interrupt SP conduction. A mean of three radiofrequency energy appl ications (3+/-2; range, 1 to 12) successfully ablated all evidence of anterograde SP conduction in all patients studied. Junctional tachycar dia was seen in 96% (71/74) of the radiofrequency energy applications. Conclusions Radiofrequency ablation at the tricuspid valve's insertio n into the AV muscular septum as identified by ICE reliably terminates anterograde SP conduction, supporting the hypothesis that the SP cons istently traverses this anatomic location.