Identification and Characterization of Sites Where Persistent Atrial Fibrillation Is Terminated by Localized Ablation

Abstract

BACKGROUND:The mechanisms by which persistent atrial fibrillation (AF) terminates via localized ablation are not well understood. To address the hypothesis that sites where localized ablation terminates persistent AF have characteristics identifiable with activation mapping during AF, we systematically examined activation patterns acquired only in cases of unequivocal termination by ablation. METHODS AND RESULTS:We recruited 57 patients with persistent AF undergoing ablation, in whom localized ablation terminated AF to sinus rhythm or organized tachycardia. For each site, we performed an offline analysis of unprocessed unipolar electrograms collected during AF from multipolar basket catheters using the maximum -dV/dt assignment to construct isochronal activation maps for multiple cycles. Additional computational modeling and phase analysis were used to study mechanisms of map variability. At all sites of AF termination, localized repetitive activation patterns were observed. Partial rotational circuits were observed in 26 of 57 (46%) cases, focal patterns in 19 of 57 (33%), and complete rotational activity in 12 of 57 (21%) cases. In computer simulations, incomplete segments of partial rotations coincided with areas of slow conduction characterized by complex, multicomponent electrograms, and variations in assigning activation times at such sites substantially altered mapped mechanisms. CONCLUSIONS:Local activation mapping at sites of termination of persistent AF showed repetitive patterns of rotational or focal activity. In computer simulations, complete rotational activation sequence was observed but was sensitive to assignment of activation timing particularly in segments of slow conduction. The observed phenomena of repetitive localized activation and the mechanism by which local ablation terminates putative AF drivers require further investigation.

Impact of pulmonary vein isolation on mechanisms sustaining persistent atrial fibrillation: Predicting the acute response

“…Baseline maps showed that all patients had both rotational and focal PDs which were intermittent and repetitive in localized regions. This is in keeping with prior studies with this noninvasive mapping system, 7,8 and is also compatible with studies using basket catheters for contact mapping 3,4,9,10,16 . Studies utilizing the ECGI system have described a greater number of drivers per patient than studies using analysis of contact electrograms from basket catheters.…”

“…Mapping data suggest that mechanisms supporting AF are patient specific in terms of the location and characteristics of drivers and that these mechanisms evolve over time with remodeling in terms of the number and distribution of drivers 3,4,6‐10 . Despite this, for reasons that remain unclear, PVI remains a relatively effective treatment for persistent AF, particularly when AF terminates during PVI 1,2,11 …”

Another method that shows organization in persistent AF? That's a RAAP

“…Similar to this study, we identified repetitive activation patterns in all patients with persistent AF at sites where AF terminated with limited ablation, using electrograms obtained from basket catheters, highly suggestive of mechanistic importance of these sites (Figure ) . The validity of these approaches is further supported by other mapping methods that show repetitive patterns using noncontact methods or using the same mapping catheter and show stability of spatiotemporal dispersion .…”

“…Of note, the smaller area of the Pentaray (cartoon in blue) and necessary overlapping of these in Wolf et al may be responsible for the higher number of focal activations. Adapted with permission from Zaman et al…”

The interconnected atrium: Acute impact of pulmonary vein isolation on remote atrial tissue

“…Better understanding of how PVI affects persistent AF may offer insight to improve technique, guide patient selection, or target alternative mechanisms. Complexity in AF likely reflects a network of competing mechanisms including multiple spatially non‐localized wavelets, 4,5 spatially localized fibrillatory drivers, 6,7 or ganglionated plexuses (GPs) 8 . PVI acts locally by electrically isolating the PVs but may also lead to spatially distributed effects by disarticulating nonlocal mechanisms such as autonomic activity driven by GPs 9 .…”