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 intracardiac structures, the precise anatomic location of successful slow pathway (SP) ablation is controversial. We hypothesized that adjunctive intracardiac echocardiography (ICE) in concert With conventional fluoroscopy and electrogram guidance could identify the anatomic site of successful SP ablation. Methods and Results In 25 patients, radiofrequency ablation was performed in the triangle of Koch directed by biplane fluoroscopy and a 6.2F, 12.5-MHz ICE catheter positioned adjacent to the triangle of Koch. Persistent SP conduction, number of radiofrequency applications, presence of junctional tachycardia, and fluoroscopy times were evaluated. As demonstrated by ICE, anterograde SP ablation was achieved between 2 and 7 mm from the tricuspid valve in imaging planes containing the AV muscular septum in all cases. Radiofrequency energy applications applied at other sites within the triangle of Koch failed to interrupt SP conduction. A mean of three radiofrequency energy applications (3+/-2; range, 1 to 12) successfully ablated all evidence of anterograde SP conduction in all patients studied. Junctional tachycardia was seen in 96% (71/74) of the radiofrequency energy applications. Conclusions Radiofrequency ablation at the tricuspid valve's insertion into the AV muscular septum as identified by ICE reliably terminates anterograde SP conduction, supporting the hypothesis that the SP consistently traverses this anatomic location.