Novel electrogram featurization reveals a spectrum of response to ablation from atrial tachycardia to types of atrial fibrillation

Background

Although atrial tachycardia (AT) may interconvert with fibrillation (AF) in many patients, it is undefined if this represents a pathophysiological spectrum of organization, or whether it indicates that AF will respond better to ablation.

Objective

To test the hypothesis that the spatial area within which electrograms (EGMs) repeat in synchronized fashion over time indicates a spectrum from AT, in which areas span the entire atria, to AF, in which areas are limited. We further hypothesized that repetitive areas would be larger in AF patients with acute termination than in those with poor response to ablation.

Methods

We studied N=234 patients (47% women, 64±10Y), of whom (i) N=10 had AT, (ii) N=120 had AF that terminated with ablation (“Term”), (ii) N=104 had AF that did not terminate (“Non-term”). All patients had global left atrial mapping by 64 pole baskets (Abbott, IL). Spatial areas of repetitive activity (REACT) were calculated by correlating unipolar EGMs in 2x2 grids for 4 sec, repeated for the entire atria (Figure 1A, B). We quantified global organization by averaging the REACT map for each patient.

Results

Figure 1C shows progressively decreasing areas of repetitive EGM from AT to AF Term to AF Non-term (p<0.001, ANOVA). Figure 1D shows a case of AT in a 71 YO male and global REACT >0.90, a case of AF REACT 0.45 in a 65 YO male with termination by ablation, and a case of AF with REACT 0.19 in an 85 YO male that did not terminate. Further, ROC analysis of REACT analysis in AF cases predicted termination with an AUC of 0.71.

Conclusion

Spatial areas of repeating electrogram shapes indicates a spectrum from AT to AF with good and AF with poor acute response to ablation. Future studies should investigate whether REACT areas can be identified non-invasively, such as by body surface ECG, to guide ablation or prognosis.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): US National Institutes of Health

Spatiotemporal signatures of response to atrial fibrillation ablation

Background

Atrial fibrillation (AF) can have organized regions, in the form of consistent dominant frequency sites, focal or reentrant sites, but it is unclear how these overlap with or differ from focal atrial tachycardias (AT) or potential drivers. We set out to develop an intuitive method based on fundamental electrogram shape and timing to separate types of AF.

Objective

To test the hypothesis that spatial regions of electrogram (EGM) in AF that show similar shapes over time based on cross-correlation analysis may separate patients with differing response to ablation.

Methods

We recruited N=133 patients (63.8±12.1 Y, 32% women), (i) N=10 had AT, (ii) N=122 AF that was or was not terminated by ablation, and (iii) N=1 pacing. All patients had left atrial mapping by 64 pole baskets. We applied repetitive activity (REACT) mapping that correlates EGMs in contiguous 2x2 regions (Fig. 1A) over 4sec. To calibrate REACT, we introduced simulated variations in shape (gaussian noise) and timing (gaussian delay) to pacing EGMs and computed nomograph over 100 random trials (Fig. 1C).

Results

Fig. 1B shows that REACT in a 71-year-old man with AT is more organized than in a 65 YO man with AF (100% vs 40% mapped field). Overall, REACT was higher in AT than AF (0.63±0.15 vs 0.36±0.22, p<0.001). There were 24 cases in which global REACT between AF and AT groups had the overlapping range of values, indicating organized “islands” in AF analogous to AT. From nomograph in Fig. 1C we identified that this overlap reflects 15 ms variation in cycle length and 20% variation in EGM shape (labelled “x” in Fig. 1C).

Conclusion

Basic electrogram properties in AF of similar shapes in spatial areas over time can separate response to ablation and may represent “islands” of AT. Future studies should investigate the mechanisms for such islands and whether they may be targeted for therapy.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): US National Institutes of Health

Extent of atrium with 1:1 electrogram activation predicts response to ablation of atrial fibrillation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): US National Institutes of Health

Background

Mechanisms associated with successful termination of persistent atrial fibrillation (AF) are still under debate. We sought to study the association between spatial extent of atrium with organized conduction and AF ablation success. We hypothesized that patients with large areas of atrium having 1:1 electrogram activation akin to ‘atrial tachycardia’ may have a higher likelihood of AF termination by ablation.

Methods

In n = 40 AF patients, n = 20 had termination by ablation ("Term"), and the remaining did not have AF termination by ablation ("Non-term"). Basket catheters (64 poles) were used to record unipolar electrograms (EGMs) in one or both atrium. Ablation targeted localized rotational/focal regions, after which pulmonary vein isolation was performed. Unipolar EGMs of 4sec duration at each 2x2 electrode neighborhood within 8x8 catheter grid were processed using a statistical correlation technique to identify the duration of 1:1 activations. Any EGM activation cycle that had a correlation above 80% was considered to be 1:1. Duration of contiguous 1:1 cycles was determined as percentage of total duration (4 sec).

Results

Spatial area of atrium (percentage of mapping field) and the corresponding 1:1 durations were assessed for patients in Term and Non-term groups. Fig A shows spatial 1:1 maps of a Term and a Non-term patient. Fig B shows examples of 1:1 and non-1:1 EGMs. Patients in Term group had higher average 1:1 atrial area than non-term group for any 1:1 duration (Fig C, 15 ± 22% vs 2 ± 4% with ≥70% 1:1 duration, p = 0.03). Positive and negative predictive values of duration≥70% for AF termination were 64.7%, and 75%, with specificity 60% and sensitivity 78.6%, exceeding clinical risk scores.

Conclusion

Persistent AF atrium shows areas of organized 1:1 conduction. Larger 1:1 atrial areas were identified in patients in whom AF terminated by ablation. Future studies should investigate mechanistic bases of organized conduction in AF. Abstract Figure.

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