Recurrent Post-Ablation Paroxysmal Atrial Fibrillation Shares Substrates With Persistent Atrial Fibrillation : An 11-Center Study

A Randomized Trial of Electrographic Flow-Guided Redo Ablation for Nonparoxysmal Atrial Fibrillation (FLOW-AF)

BACKGROUND

Electrographic flow (EGF) mapping enables full spatiotemporal reconstruction of organized wavefront propagation to identify extrapulmonary vein sources of atrial fibrillation (AF).

OBJECTIVES

FLOW-AF (A Randomized Controlled Study to Evaluate the Reliability of the Ablacon Electrographic FLOW [EGF] Algorithm Technology [Ablamap Software] to Identify AF Sources and Guide Ablation Therapy in Patients With Persistent Atrial Fibrillation) was multicenter, randomized controlled study of EGF mapping to: 1) stratify a nonparoxysmal AF population undergoing redo ablation; 2) guide ablation of these extrapulmonary vein AF sources; and 3) improve AF recurrence outcomes.

METHODS

FLOW-AF enrolled persistent atrial fibrillation (PerAF)/long-standing PerAF patients undergoing redo ablation at 4 centers. One-minute EGF maps were recorded from standardized biatrial basket positions. Patients with source activity ≥26.5% were randomized 1:1 to PVI + EGF-guided ablation vs PVI only; patients without sources ≥26.5% threshold were not randomized. Follow-up and electrocardiographic monitoring occurred at 3, 6, and 12 months.

RESULTS

We enrolled 85 patients (age 65.6 ± 9.3 years, 37% female, 24% long-standing PerAF). Thirty-four (40%) patients had no sources greater than threshold; at least 1 source greater than threshold was present in 46 (60%) (EGF-guided ablation, n = 22; control group, n = 26). Patients with sources were older (68.2 vs 62.6 years; P = 0.005) with higher CHA2DS2-VASc scores (2.8 vs 1.9; P = 0.001). The freedom from safety events was 97.2%, and 95% of EGF-identified sources were successfully ablated. In randomized patients, AF-free survival at 12 months was 68% for EGF-guided ablation vs 17% for the control group (P = 0.042); freedom from AF/atrial tachycardia/atrial flutter at 12 months was 51% vs 14% (P = 0.103), respectively.

CONCLUSIONS

In nonparoxysmal AF patients undergoing redo ablation, EGF mapping identified AF sources in 60% of patients, and could be successfully ablated in 95%. Compared with PVI alone, PVI + source ablation improved AF-free survival by 51% on an absolute basis. (FLOW-AF: A Study to Evaluate the Ablacon Electrographic FLOW EGF Technology [A Randomized Controlled Study to Evaluate the Reliability of the Ablacon Electrographic FLOW (EGF) Algorithm Technology (Ablamap Software) to Identify AF Sources and Guide Ablation Therapy in Patients With Persistent Atrial Fibrillation]; NCT04473963).

Future Directions for Mapping Atrial Fibrillation

Mapping for AF focuses on the identification of regions of interest that may guide management and - in particular - ablation therapy. Mapping may point to specific mechanisms associated with localised scar or fibrosis, or electrical features, such as localised repetitive, rotational or focal activation. In patients in whom AF is caused by disorganised waves with no spatial predilection, as proposed in the multiwavelet theory for AF, mapping would be of less benefit. The role of AF mapping is controversial at the current time in view of the debate over the underlying mechanisms. However, recent clinical expansions of mapping technologies confirm the importance of understanding the state of the art, including limitations of current approaches and potential areas of future development.

Higher reproducibility of phase derived metrics from electrocardiographic imaging during atrial fibrillation in patients remaining in sinus rhythm after pulmonary vein isolation

BACKGROUND

Electrocardiographic imaging (ECGI) allows evaluating the complexity of the reentrant activity of atrial fibrillation (AF) patients. In this study, we evaluated the ability of ECGI metrics to predict the success of pulmonary vein isolation (PVI) to treat AF.

METHODS

ECGI of 24 AF patients (6 males, 13 paroxysmal, 61.8 ± 14 years) was recorded prior to PVI. Patients were distributed into two groups based on their PVI outcome 6 months after ablation (sinus vs. arrhythmia recurrence). Metrics derived from phase analysis of ECGI signals were computed for two different temporal segments before ablation. Correlation analysis and variability over time were studied between the two recorded segments and were compared between patient groups.

RESULTS

Temporal variability of both rotor duration and spatial entropy of the rotor histogram presented statistical differences between groups with different PVI outcome (p < 0.05). The reproducibility of reentrant metrics was higher (R² > 0.8) in patients with good outcome rather than arrhythmia recurrence patients (R² < 0.62). Prediction of PVI success based on ECGI temporal variability metrics allows for an increased specificity over the classification into paroxysmal or persistent (0.85 vs. 0.64).

CONCLUSIONS

Patients with favorable PVI outcome present ECGI metrics more reproducible over time than patients with AF recurrence. These results suggest that ECGI derived metrics may allow selecting which patients would benefit from ablation therapies.

Is There an Association between Epicardial Adipose Tissue and Outcomes after Paroxysmal Atrial Fibrillation Catheter Ablation?

Background: In patients undergoing paroxysmal atrial fibrillation (PAF) ablation, pulmonary vein isolation (PVI) alone fails in maintaining sinus rhythm in up to one third of patients after a first catheter ablation. Epicardial adipose tissue (EAT), as an endocrine-active organ, could play a role in the recurrence of AF after catheter ablation. Objective: To evaluate the predictive value of clinical, echocardiographic, biological parameters and epicardial fat density measured by computed tomography scan (CT-scan) on AF recurrence in PAF patients who underwent a first pulmonary vein isolation procedure using radiofrequency (RF). Methods: This monocentric retrospective study included all patients undergoing first-time RF PAF ablation at the Nancy University Hospital between March 2015 and December 2018 with one-year follow-up. Results: 389 patients were included, of whom 128 (32.9%) had AF recurrence at one-year follow-up. Neither total-EAT volume (88.6 ± 37.2 cm³ vs. 91.4 ± 40.5 cm³, p = 0.519), nor total-EAT radiodensity (−98.8 ± 4.1 HU vs. −98.8 ± 3.8 HU, p = 0.892) and left atrium-EAT radiodensity (−93.7 ± 4.3 HU vs. −93.4 ± 6.0 HU, p = 0.556) were significantly associated with AF recurrence after PAF ablation. In multivariate analysis, previous cavo-tricuspid isthmus (CTI) ablation, ablation procedure duration, BNP and triglyceride levels remained independently associated with AF recurrence after catheter ablation at 12-months follow-up. Conclusion: Contrary to persistent AF, EAT parameters are not associated with AF recurrence after paroxysmal AF ablation. Thus, the role of the metabolic atrial substrate in PAF pathophysiology appears less obvious than in persistent AF.

Retrospective analysis of FIRM-guided ablation in patients with recurrent atrial fibrillation: a single-center study

BACKGROUND

Ablation of recurrent atrial fibrillation (AF) is common. Studies indicate that AF recurrence is primarily due to pulmonary vein (PV) re-conduction. This retrospective analysis characterized and evaluated recurrent AF patients using focal impulse and rotor mapping (FIRM) plus PV re-isolation, with follow up at 3, 6, 12, and 24 months after the repeat ablation.

METHODS AND RESULTS

Patients (consecutive, n = 100) underwent FIRM-guided ablation followed by conventional PV re-isolation for recurrent AF treatment. All FIRM patients had failed one or more conventional ablation procedures (1.4 ± 0.08) for paroxysmal (14%), persistent (15%), and long-standing persistent (71%) AF. Stable rotors were identified in 97/100 patients: 60% in the right atrium (RA) and 82% in left atrium (LA) (mean 1.5 ± 0.8 and 2.1 ± 1.2 per patient, respectively). No correlation was noted between the previous number of ablations, AF duration, or LA diameter to the number of rotors (R² = 0.0039, R² = 0.0017, and R² = 0.006, respectively). In this limited observation, only 22% of identified rotors were associated with proximity to low voltage areas. The 12- and 24-month arrhythmia free rate was 93% (13/14) and 92% (12/13) for paroxysmal AF, 60% (9/15) and 47% (7/15) for persistent AF, and 70% (48/69) and 64% (43/67) for long-standing persistent AF, respectively, after a single FIRM procedure and re-isolation of the veins.

CONCLUSIONS

The data show a benefit for FIRM-guided ablation in recurrent AF at 12 months. No correlation was found between rotors and tissue characterization, AF duration, or previous number of ablations, suggesting that rotors may play an independent role in maintaining recurrent AF after prior failed ablation.

Repeat pulmonary vein isolation with or without FIRM-guided ablation for recurrent atrial fibrillation with pulmonary vein reconnection

INTRODUCTION

Focal impulse and rotor modulation (FIRM) ablation can be used to target nonpulmonary vein (PV) sources of atrial fibrillation (AF). No published studies have compared freedom from atrial fibrillation (FFAF) after pulmonary vein reisolation (PVRI) plus FIRM to PVRI alone in patients with reconnected PVs undergoing repeat ablation.

METHODS

A 3:1 matched retrospective cohort study was performed on 21 patients with recurrent AF and PV reconnection who underwent PVRI plus FIRM-guided ablation and 63 patients with recurrent AF treated with PVRI alone at a single institution. All patients in the PVRI-alone cohort had cryoballoon PVRI at the time of repeat ablation without additional lesion sets for AF. Cases were matched based on the type of AF (paroxysmal vs nonparoxysmal), left atrial diameter (±4 mm), left ventricular ejection fraction (±10%), duration of AF (±18 months), and age (±5 years). The primary endpoint was FFAF after a 3-month blanking period.

RESULTS

Out of 53 total FIRM cases performed at Northwestern Memorial Hospital between 2015 and 2017, 21 patients had PVRI plus FIRM for recurrent AF with PV reconnection. These patients had an average of 3.3 ± 2.1 rotors (60% left atrial) ablated. Over a median follow-up time of 24.7 months (interquartile range, 13-36 months), patients in the PVRI-alone cohort demonstrated a higher rate of FFAF (n = 35; 55.6%) than patients in the PVRI plus FIRM-guided ablation cohort (n = 7; 33.3%) (logrank P = .049).

CONCLUSION

In patients undergoing repeat ablation for AF with PV reconnection, PVRI plus FIRM did not increase FFAF compared to PVRI alone.

Noninvasive Assessment of Complexity of Atrial Fibrillation: Correlation With Contact Mapping and Impact of Ablation

BACKGROUND

It is difficult to noninvasively phenotype atrial fibrillation (AF) in a way that reflects clinical end points such as response to therapy. We set out to map electrical patterns of disorganization and regions of reentrant activity in AF from the body surface using electrocardiographic imaging, calibrated to panoramic intracardiac recordings and referenced to AF termination by ablation.

METHODS

Bi-atrial intracardiac electrograms of 47 patients with AF at ablation (30 persistent, 29 male, 63±9 years) were recorded with 64-pole basket catheters and simultaneous 57-lead body surface ECGs. Atrial epicardial electrical activity was reconstructed and organized sites were invasively and noninvasively tracked in 3-dimension using phase singularity. In a subset of 17 patients, sites of AF organization were targeted for ablation.

RESULTS

Body surface mapping showed greater AF organization near intracardially detected drivers than elsewhere, both in phase singularity density (2.3±2.1 versus 1.9±1.6; P=0.02) and number of drivers (3.2±2.3 versus 2.7±1.7; P=0.02). Complexity, defined as the number of stable AF reentrant sites, was concordant between noninvasive and invasive methods (r²=0.5; CC=0.71). In the subset receiving targeted ablation, AF complexity showed lower values in those in whom AF terminated than those in whom AF did not terminate (P<0.01).

CONCLUSIONS

AF complexity tracked noninvasively correlates well with organized and disorganized regions detected by panoramic intracardiac mapping and correlates with the acute outcome by ablation. This approach may assist in bedside monitoring of therapy or in improving the efficacy of ongoing ablation procedures.

Pre-ablation levels of brain natriuretic peptide are independently associated with the recurrence of atrial fibrillation after radiofrequency catheter ablation in patients with nonvalvular atrial fibrillation

Association between pre-ablation levels of biomarkers of cardiac and endothelial dysfunctions, CHADS2, CHA2DS2-VASc, and APPLE scores and the recurrence of atrial fibrillation (AF) after radiofrequency catheter ablation has not been fully studied. A total of 254 patients with nonvalvular AF were prospectively followed for AF recurrence after a single ablation procedure. During a two-year follow-up period, AF recurred in 65 (25.6%) patients. Patients with AF recurrence had significantly greater baseline ln brain natriuretic peptide (BNP) than those without AF recurrence (P < 0.01), whereas there were no significant differences in the levels of biomarkers of endothelial dysfunction and points of scoring systems. In the Cox regression analyses, the baseline ln BNP was significantly independently associated with AF recurrence (adjusted HR =1.286, 95% CI =1.000–1.655, P < 0.05). The baseline levels of ln BNP were significantly associated with rhythm at blood collection, age, sex, and left atrial diameter, and left ventricular ejection fraction (P < 0.05).The subgroup analysis showed a significant interaction on the risk of AF recurrence between ln BNP, sex difference, and rhythm at blood collection (P for interaction < 0.05). In conclusion, the results suggest that the pre-ablation levels of ln BNP are useful to evaluate the risk of AF recurrence after ablation therapy; however, there is a need to be careful while using BNP as a biomarker for the risk of AF recurrence by taking account of the effects of rhythm status at blood collection and sex difference.

Characterizing Electrogram Signal Fidelity and the Effects of Signal Contamination on Mapping Human Persistent Atrial Fibrillation

Objective: Determining accurate intracardiac maps of atrial fibrillation (AF) in humans can be difficult, owing primarily to various sources of contamination in electrogram signals. The goal of this study is to develop a measure for signal fidelity and to develop methods to quantify robustness of observed rotational activity in phase maps subject to signal contamination.

Methods: We identified rotational activity in phase maps of human persistent AF using the Hilbert transform of sinusoidally recomposed signals, where localized ablation at rotational sites terminated fibrillation. A novel measure of signal fidelity was developed to quantify signal quality. Contamination is then introduced to the underlying electrograms by removing signals at random, adding noise to computations of cycle length, and adding realistic far-field signals. Mean tip number N and tip density δ, defined as the proportion of time a region contains a tip, at the termination site are computed to compare the effects of contamination.

Results: Domains of low signal fidelity correspond to the location of rotational cores. Removing signals and altering cycle length accounted for minor changes in tip density, while targeted removal of low fidelity electrograms can result in a significant increase in tip density and stability. Far-field contamination was found to obscure rotation at the termination site.

Conclusion: Rotational activity in clinical AF can produce domains of low fidelity electrogram recordings at rotational cores. Observed rotational patterns in phase maps appear most sensitive to far-field activation. These results may inform novel methods to map AF in humans which can be tested directly in patients at electrophysiological study and ablation.

High-Normal Thyroid-Stimulating Hormone Shows a Potential Causal Association With Arrhythmia Recurrence After Catheter Ablation of Atrial Fibrillation

Background

Hypothyroidism has been shown to contribute to enhanced atrial arrhythmogenesis, resulting in atrial fibrillation (AF) development in animal models and clinical populations. We aimed to elucidate whether high thyroid‐stimulating hormone (TSH) levels are related to outcomes of catheter ablation of AF.

Methods and Results

Of 477 consecutive patients who underwent first‐time pulmonary vein isolation–based radiofrequency catheter ablation of AF, 456 with TSH above the lower limit of the normal range (age, 65.5±9.9 years; men, 73.9%; paroxysmal AF, 56.8%) were analyzed for this study. Atrial tachyarrhythmia recurrence for 3 years was compared across groups with hypothyroidism (n=23) and TSH quartile groups with euthyroidism (normal‐range TSH levels, n=433). Atrial tachyarrhythmia recurrence occurred in 179 patients (39%) after the first session. Patients with hypothyroidism had increased recurrence compared with patients with normal TSH levels (crude hazard ratio, 3.14 after the last session; P=0.001). When focusing on patients with normal TSH levels, recurrence‐free survivals after both the first and last sessions were significantly reduced in euthyroid patients with the highest quartile of TSH levels (quartile 4) compared with others (quartiles 1–3). Cox regression analysis identified high TSH levels as an independent predictor of atrial tachyarrhythmia recurrence after both the first (adjusted hazard ratio, 1.51; P=0.018) and last (adjusted hazard ratio, 1.86; P=0.023) sessions. The difference was more pronounced in patients with paroxysmal AF than in those with nonparoxysmal AF.

Conclusions

Not only hypothyroidism but also high‐normal TSH levels may be an independent predictor of atrial tachyarrhythmia recurrence after catheter ablation of AF.

The continuous challenge of AF ablation: From foci to rotational activity

Pulmonary vein isolation (PVI) is central to ablation approaches for atrial fibrillation (AF), yet many patients still have arrhythmia recurrence after one or more procedures despite the latest technology for PVI. Ablation of rotational or focal sources for AF, which lie outside the pulmonary veins in many patients, is a practical approach that has been shown to improve success by many groups. Localized sources lie in atrial regions shown mechanistically to sustain AF in optical mapping and clinical studies of human AF, as well as computational and animal studies. Because they arise in localized atrial regions, AF sources may explain central paradoxes in clinical practice - such as how limited ablation in patient specific sites can terminate persistent AF yet extensive anatomical ablation at stereotypical locations, which should extinguish disordered waves, does not improve success in clinical trials. Ongoing studies may help to resolve many controversies in the field of rotational sources for AF. Studies now verify rotational activation by multiple mapping approaches in the same patients, at sites where ablation terminates persistent AF. However, these studies also show that certain mapping methods are less effective for detecting AF sources than others. It is also recognized that the success of AF source ablation is technique dependent. This review article provides a mechanistic and clinical rationale to ablate localized sources (rotational and focal), and describes successful techniques for their ablation as well as pitfalls to avoid. We hope that this review will serve as a platform for future improvements in the patient-tailored ablation for complex arrhythmias.

Spatial relationship of organized rotational and focal sources in human atrial fibrillation to autonomic ganglionated plexi

BACKGROUND

One approach to improve ablation for atrial fibrillation (AF) is to focus on physiological targets including focal or rotational sources or ganglionic plexi (GP). However, the spatial relationship between these potential mechanisms has never been studied. We tested the hypothesis that rotors and focal sources for AF may co-localize with ganglionated plexi (GP).

METHODS

We prospectively identified locations of AF rotors and focal sources, and correlated these to GP sites in 97 consecutive patients (age 59.9±11.4, 73% persistent AF). AF was recorded with 64-pole catheters with activation/phase mapping, and related to anatomic GP sites on electroanatomic maps.

RESULTS

AF sources arose in 96/97 (99%) patients for 2.6±1.4 sources per patient (left atrium: 1.7±0.9 right atrium: 1.1±0.8), each with an area of 2-3cm2. On area analyses, the probability of an AF source randomly overlapping a GP area was 26%. Left atrial sources were seen in 94 (97%) patients, in whom ≥1 source co-localized with GP in 75 patients (80%; p<0.05). AF sources were more likely to colocalize with left vs right GPs (p<0.05), and colocalization was more likely in patients with higher CHADS2VASc scores (age>65, diabetes; p<0.05).

CONCLUSIONS

This is the first study to demonstrate that clinically detected AF focal and rotational sources in the left atrium often colocalize with regions of autonomic innervation. Studies should define if the role of AF sources differs by their anatomical location.

Two Independent Mapping Techniques Identify Rotational Activity Patterns at Sites of Local Termination During Persistent Atrial Fibrillation

Introduction

The mechanisms for atrial fibrillation (AF) are unclear in part because diverse mapping techniques yield diverse maps, ranging from stable organized sources to highly disordered waves. We hypothesized that AF mechanisms may be clarified if mapping techniques were compared in the same patients, and referenced to a clinical endpoint. We compared two independent AF mapping techniques in patients in whom ablation terminated persistent AF before pulmonary vein isolation (PVI).

Methods and Results

We identified 12 patients with persistent AF (61.2 ± 10.8 years, four female) in whom mapping with 64 pole baskets and technique 1 (activation/phase mapping, FIRM) identified rotational activation patterns during at least 50% of the 4‐second mapping interval and targeted ablation at these rotational sites terminated AF to sinus rhythm (n = 10) or atrial tachycardia. We analyzed the unipolar electrograms of these patients to determine phase maps of activation by an independent technique 2 (Kuklik, Schotten et al., IEEE Trans Biomed Eng 2015). Compared to technique 1, technique 2 revealed a source in 12 of 12 (100%) cases with spatial concordance in all cases (P <0.05) and similar rotational characteristics.

Conclusion

At sites where ablation terminated persistent AF, two independent mapping techniques identified stable rotational activation for multiple cycles that drove peripheral disorder. Future comparative studies referenced to a clinical endpoint may help reconcile if discrepancies between AF mapping studies reports represent techniques, patient populations or models of AF, and improve mapping to better guide ablation.