Intracardiac echocardiography guided radiofrequency catheter ablation of the slow pathway in atrioventricular nodal reentrant tachycardia

ICE has demonstrated its utility in imaging right atrial structures but its utility in slow pathway (SP) ablation has not been documented in a randomized trial. The feasibility of using ICE as a imaging modality to identify the effective site of SP ablation was done in part one of the study comprising 10 patients of typical AVNRT. Subsequently, a prospective randomized study was done comparing the conventional (group A) and ICE guided (group B) ablation of the SP. Each group had 20 patients of typical AVNRT. Ablation in the conventional arm was guided by intracardiac electrograms and fluoroscopy. Group B patients underwent SP ablation guided primarily by ICE imaging; fluoroscopy was used mainly for initial placement of catheters. Reliable & stable ICE images were obtained in all patients. Part I of the study showed that RF pulses given when the ablation catheter was seen to cross the atrioventricular muscular septum (AVMS), always resulted in junctional rhythm. In Group B, RF pulse was delivered only when the ablation catheter was at the AVMS making an obtuse angle with the image of the His-bundle catheter. Consistent junctional rhythm and abolition of SP resulted at this site. Compared to group A, patients in group B required fewer pulses (mean 1.4 +/- 0.6 vs. 4.4 +/- 3.0; p < 0.05, median 1 vs. 5; p < 0.01), achieved a higher temperature (56 +/- 4 degrees C vs. 50 +/- 6 degrees C) and had more frequent junctional rhythm (100% vs. 70%) during RF pulse. A critical portion of SP exists adjacent to Tricuspid valve overlying the AVMS. ICE imaging consistently and reliably localizes this site and RF applications here result in interruption of antegrade SP conduction.