Abstract 631: The Effect of Step-Wise Atrial Ablation on the Substrate for Persistent Atrial Fibrillation
Introduction: The step-wise approach to ablation of persistent AF involves LA linear lesions to organize the atrial substrate. This strategy is monitored by assessing the AF electrogram (EGM) CL at a discrete sites such as the coronary sinus. However, the global effect on the overall LA substrate is unknown.
Methods: In 11 patients with persistent AF, the NavX system was used to repetitively obtain high-density maps of the LA-PVs during stepwise ablation. Using multipolar (circular and penta-array) catheters, EGM recordings (2– 8 secs in duration) were obtained throughout the LA. The degree of EGM complexity and fractionation was assessed by mean CL at each site and displayed in a color-coded map (Figure⇓). The degree of EGM organization was determined at baseline, post-PVI and post-PVI+LA roof line.
Results: A total of 319±91, 274±67 and 260±91 discrete EGMs were analyzed at baseline, post-PVI and post-Roof. EGM disorganization was greater in the LA body than the PVs. Ablation caused progressive coalescence of the disorganized EGMs. Paired EGMs (mean 156±44, range 111–239) were compared across the 3 maps (Graph). From baseline to post-PVI, there was a significant increase in the mean CL: from 134.8±28.4 to 156±28.4 ms (p=0.04). The LA roof line did not significantly increase the mean CL (159.9±19.1 ms) beyond PVI alone (p=NS).
Conclusions: In conclusion, PVI changes the global LA substrate and as such mean CL mapping to target areas of disorganized EGMs may best be performed post-PVI. In addition, while PVI organized the global LA substrate, the LA roof line did not – raising doubt as to the prudence of routinely ablating the LA roof.