Ripple mapping demonstrates putative signals identifying the right inferior nodal extension to the lower nodal bundle during AVNRT

BACKGROUND: Mapping wavefronts within the triangle of Koch is challenging owing to multiple small and large amplitude signals within a short time interval. Ripple mapping was designed to overcome these limitations. OBJECTIVE: We tested the feasibility of delineating wavefronts within the triangle of Koch during slow-fast atrioventricular nodal reentrant tachycardia (AVNRT). METHODS: Patients undergoing electrophysiological studies were recruited. Right atrial CARTO maps were collected during atrial pacing, ventricular pacing, and typical AVNRT. Using ripple mapping, we marked His activation during atrial pacing, the earliest retrograde atrial activation during ventricular pacing, the earliest signal during AVNRT (E-AVNRT), and the earliest retrograde right atrial activation during AVNRT. RESULTS: 72 patients were recruited, with typical AVNRT in 40 patients and a full mapping protocol in 30 patients (6327 ± 948 points collected). The E-AVNRT was 14.7 ± 5.3 mm inferior to the earliest His identified during atrial pacing. A wavefront consistent with slow pathway activation started at E-AVNRT taking 22.2 ± 4.8 ms to reach the His cloud with a line of block demarcating the atrial side. This same line formed the ventricular border of atrial activation during atrial pacing, consistent with slow pathway activation over the right inferior nodal extension. These wavefront signals became sharper approaching His but consistently activated a region inferior to the His cloud, consistent with the right inferior nodal extension activating the lower nodal bundle. Earliest retrograde fast pathway-mediated right atrial activation during AVNRT was 57.3 ± 27.1 ms later and 11.7 ± 6.0 mm from E-AVNRT and distinct from the earliest atrial activation during ventricular pacing (7.0 ± 3.2 mm). Successful ablation sites were closer to E-AVNRT than unsuccessful sites (6.4 ± 3.0 vs 14.8 ± 5.6 mm; 95% confidence interval 5.2-7.6 vs 12.2-17.4 mm; P < .01). CONCLUSION: Ripple mapping can delineate slow and fast pathway activation during AVNRT. Lower nodal bundle signals "lead" during AVNRT, inferior to the conventional His cloud. Ripple mapping-guided AVNRT ablation may be feasible.