Is Ablation to Termination the Best Strategy for Ablation of Persistent Atrial Fibrillation?

Pulmonary Vein Isolation Followed by Biatrial Ablation of Rotational Activity in Patients with Persistent Atrial Fibrillation: Results of the Cryo-Vest Study

Background and Aims: Noninvasive mapping allows the identification of patient-specific atrial rotational activity (RA) that might play a key role in the perpetuation of persistent atrial fibrillation (PsAF). So far, the impact of pulmonary vein isolation by cryoballoon (Cryo-PVI) on RA is unclear. Moreover, the long-term effect of periprocedural termination of AF during the ablation procedure is controversial. Methods: Noninvasive electrocardiographic mapping with a 252-electrode vest was performed in 42 patients with PsAF. After the first analysis, Cryo-PVI was performed. The RA was analyzed again and then targeted by radiofrequency catheter ablation. The primary clinical endpoint was periprocedural termination of AF. The secondary endpoint was freedom from any atrial arrhythmia >30 s during a 12-month follow-up. Results: In 33 patients (79%), right atrial RA was identified leading to biatrial ablation, and nine patients (21%) had left atrial RA only. Twelve patients (28.6%) converted from AF to sinus rhythm (SR) (Group A). Thirteen patients (30.9%) converted to atrial tachycardia (AT) (Group B). In 17 patients (40.5%), AF was not terminated by ablation (Group C). After a mean follow-up time of 13.8 months, 26 patients were free from AF and AT (61.9%). In terms of rhythm, control Group A (75%) and B (83.3%) showed higher success rates than Group C (33.3%) (p < 0.01). Cryo-PVI had no substantial impact on RA. Conclusions: The RA-based ablation approach showed acceptable success rates. Periprocedural termination of AF had a positive predictive impact on the outcome. No difference was observed between conversion to SR or to AT. Cryo-PVI had no impact on RA.

Pulsed field ablation of spatiotemporal electrogram dispersion following pulmonary vein isolation and left atrial linear lesions for persistent atrial fibrillation: a case report

Background

Ablation of persistent atrial fibrillation (AF) remains challenging, with atrial substrate modification often being performed as an adjunct to pulmonary vein isolation (PVI). Pulsed field ablation (PFA) is a novel ablation modality that carries a favourable safety profile, which could facilitate complex procedures.

Case summary

We present the case of a 60-year-old male undergoing catheter ablation for symptomatic persistent AF. The procedure was performed with the Farapulse™ PFA system in a stepwise manner, including PVI and linear lesions for the isolation of the posterior left atrial wall and the ablation of the mitral isthmus. The final step of the procedure included the ablation of areas exhibiting spatiotemporal electrogram dispersion, identified with the help of artificial intelligence-based software (VX1, Volta Medical) in both atria. Sinus rhythm was restored after the abolition of an electrogram dispersion zone in the right atrium. The procedure was carried out without any complications.

Discussion

Complex ablation procedures for persistent AF can be successfully performed with PFA. In the context of such extensive ablation strategies, PFA is an attractive energy source, given its non-thermal nature that is known to prevent damage to surrounding tissue and result in less chronic fibrosis. However, caution should be exercised to avoid excessive ablation when using the currently available multispline PFA catheter, as it may inadvertently target adjacent areas of healthy myocardium.

A novel approach for quantitative electrogram analysis for driver identification: Implications for ablation in persistent atrial fibrillation

Objective

This study sought to study the feasibility, efficacy, and safety of using multiscale entropy (MSE) analysis to guide catheter ablation for persistent atrial fibrillation (PsAF) and predict ablation outcomes.

Methods

We prospectively enrolled 108 patients undergoing initial ablation for PsAF. MSE was calculated based on bipolar intracardiac electrograms (iEGMs) to measure the dynamical complexity of biological signals. The iEGMs data were exported after pulmonary vein isolation (PVI), then calculated in a customed platform, and finally re-annotated into the CARTO system. After PVI, regions of the highest mean MSE (mMSE) values were ablated in descending order until AF termination, or three areas had been ablated.

Results

Baseline characteristics were evenly distributed between the AF termination (n = 38, 35.19%) and the non-termination group. The RA-to-LA mean MSE (mMSE) gradient demonstrated a positive gradient in the non-termination group and a negative gradient in the termination group (0.105 ± 0.180 vs. −0.235 ± 0.256, P &lt; 0.001). During a 12-month follow-up, 29 patients (26.9%) had arrhythmia recurrence after single ablation, and 18 of them had AF (62.1%). The termination group had lower rates of arrhythmia recurrence (15.79 vs. 32.86%, Log-Rank P = 0.053) and AF recurrence (10.53 vs. 20%, Log-Rank P = 0.173) after single ablation and a lower rate of arrhythmia recurrence (7.89 vs. 27.14%, Log-Rank P = 0.018) after repeated ablation. Correspondingly, subjects with negative RA-to-LA mMSE gradient had lower incidences of arrhythmia (16.67 vs. 35%, Log-Rank P = 0.028) and AF (16.67 vs. 35%, Log-Rank P = 0.032) recurrence after single ablation and arrhythmia recurrence after repeated ablation (12.5 vs. 26.67%, Log-Rank P = 0.062). Marginal peri-procedural safety outcomes were observed.

Conclusion

MSE analysis-guided driver ablation in addition to PVI for PsAF could be feasible, efficient, and safe. An RA &lt; LA mMSE gradient before ablation could predict freedom from arrhythmia. The RA-LA MSE gradient could be useful for guiding ablation strategy selection.

Coronary sinus electrogram characteristics predict termination of AF with ablation and long-term clinical outcome

INTRODUCTION

Markers predicting atrial fibrillation (AF) termination and freedom from AF/atrial tachycardia (AT) has been proposed. This study aimed to evaluate the role of novel coronary sinus (CS) electrogram characteristics in predicting the acute ablation response and freedom from AF/AT during follow-up.

METHODS

Patients undergoing ablation for persistent AF as part of the Stochastic Trajectory Analysis of Ranked signals mapping study were included. Novel CS electrogram characteristics including CS cycle length variability (CLV) and CS activation pattern stability (APS) and proportion of low voltage zones (LVZs) were reviewed as potential predictors for AF termination on ablation and freedom from AF/AT during follow-up. The relationship between localized driver characteristics and CS electrogram characteristics was also assessed.

RESULTS

Sixty-five patients were included. AF termination was achieved in 51 patients and 80% of patients were free from AF/AT during a follow-up of 29.5 ± 3.7 months. CS CLV of <30 ms, CS APS of ≥30% and proportion of LVZ < 30% showed high diagnostic accuracy in predicting AF termination on ablation and freedom from AF/AT during follow-up (CS CLV odds ratio [OR] 25.6, area under the curve [AUC] 0.91; CS APS OR 15.9, AUC 0.94; proportion of LVZs OR 21.4, AUC 0.88). These markers were independent predictors of AF termination on ablation and AF/AT recurrence during follow-up. Ablation of a smaller number of drivers that demonstrate greater dominance strongly correlate with greater CS organization.

CONCLUSION

Novel CS electrogram characteristics were independent predictors of AF termination and AF/AT recurrence during follow-up. These markers can potentially aid in predicting outcomes and guide ablation and follow-up strategies.

Time-Averaged Wavefront Analysis Demonstrates Preferential Pathways of Atrial Fibrillation, Predicting Pulmonary Vein Isolation Acute Response

Electrical activation during atrial fibrillation (AF) appears chaotic and disorganised, which impedes characterisation of the underlying substrate and treatment planning. While globally chaotic, there may be local preferential activation pathways that represent potential ablation targets. This study aimed to identify preferential activation pathways during AF and predict the acute ablation response when these are targeted by pulmonary vein isolation (PVI). In patients with persistent AF (n = 14), simultaneous biatrial contact mapping with basket catheters was performed pre-ablation and following each ablation strategy (PVI, roof, and mitral lines). Unipolar wavefront activation directions were averaged over 10 s to identify preferential activation pathways. Clinical cases were classified as responders or non-responders to PVI during the procedure. Clinical data were augmented with a virtual cohort of 100 models. In AF pre-ablation, pathways originated from the pulmonary vein (PV) antra in PVI responders (7/7) but not in PVI non-responders (6/6). We proposed a novel index that measured activation waves from the PV antra into the atrial body. This index was significantly higher in PVI responders than non-responders (clinical: 16.3 vs. 3.7%, p = 0.04; simulated: 21.1 vs. 14.1%, p = 0.02). Overall, this novel technique and proof of concept study demonstrated that preferential activation pathways exist during AF. Targeting patient-specific activation pathways that flowed from the PV antra to the left atrial body using PVI resulted in AF termination during the procedure. These PV activation flow pathways may correspond to the presence of drivers in the PV regions.

Stepwise endo-/epicardial catheter ablation for atrial fibrillation: The Mediterranea approach

Background

Outcomes of catheter ablation (CA) among patients with nonparoxysmal atrial fibrillation (AF) are largely disappointing.

Objective

We sought to evaluate the feasibility, effectiveness, and safety of a single‐stage stepwise endo‐/epicardial approach in patients with persistent/longstanding‐persistent AF.

Methods

We enrolled 25 consecutive patients with symptomatic persistent (n = 4) or longstanding‐persistent (n = 21) AF and at least one prior endocardial procedure, who underwent CA using an endo‐/epicardial approach. Our anatomical stepwise protocol included multiple endocardial as well as epicardial (Bachmann's bundle [BB] and ligament of Marshall ablations) components, and entailed ablation of atrial tachycardias emerging during the procedure. The primary outcome was freedom from any AF/atrial tachycardia episode after a 3‐month blanking period. The secondary outcome was patients' symptom status during follow‐up.

Results

The stepwise endo‐/epicardial approach allowed sinus rhythm restoration in 72% of patients, either directly (n = 6, 24%) or after AF organization into atrial tachycardia (n = 12, 48%). BB's ablation was commonly implicated in arrhythmia termination. After a median follow‐up of 266 days (interquartile range, 96 days), survival free from AF/atrial tachycardia was 88%. Antiarrhythmic drugs could be discontinued in 22 patients (88%). As compared to baseline, more patients were asymptomatic at 9‐month follow‐up (0% vs. 56%, p = .02). Five patients (20%) developed mild medical complications, whereas one subject (4%) had severe kidney injury requiring dialysis.

Conclusion

A single‐stage endo‐/epicardial CA resulted in favorable rhythm and symptom outcomes in a cohort of patients with symptomatic persistent/longstanding‐persistent AF and one or more prior endocardial procedures. Epicardial ablation of BB was commonly implicated in procedural success.

Optimum lesion set and predictors of outcome in persistent atrial fibrillation ablation: a meta-regression analysis

AIMS

Ablation of persistent atrial fibrillation (PsAF) has been performed by many techniques with varying success rates. This may be due to ablation techniques, patient demographics, comorbidities, and trial design. We conducted a meta-regression of studies of PsAF ablation to elucidate the factors affecting atrial fibrillation (AF) recurrence.

METHODS AND RESULTS 

Databases were searched for prospective studies of PsAF ablation. A meta-regression was performed. Fifty-eight studies (6767 patients) were included. Complex fractionated atrial electrogram (CFAE) ablation reduced freedom from AF by 8.9% [95% confidence interval (CI) -15 to -2.3, P = 0.009). Left atrial appendage [LAA isolation (three study arms)] increased freedom from AF by 39.5% (95% CI 9.1-78.4, P = 0.008). Posterior wall isolation (PWI) (eight study arms) increased freedom from AF by 19.4% (95% CI 3.3-38.1, P = 0.017). Linear ablation or ganglionated plexi ablation resulted in no significant effect on freedom from AF. More extensive ablation increased intraprocedural AF termination; however, intraprocedural AF termination was not associated with improved outcomes. Increased left atrial diameter was associated with a reduction in freedom from AF by 4% (95% CI -6.8% to -1.1%, P = 0.007) for every 1 mm increase in diameter.

CONCLUSION 

Linear ablation, PWI, and CFAE ablation improves intraprocedural AF termination, but such termination does not predict better long-term outcomes. Study arms including PWI or LAA isolation in the lesion set were associated with improved outcomes in terms of freedom from AF; however, further randomized trials are required before these can be routinely recommended. Left atrial size is the most important marker of AF chronicity influencing outcomes.

In silico Comparison of Left Atrial Ablation Techniques That Target the Anatomical, Structural, and Electrical Substrates of Atrial Fibrillation

Catheter ablation therapy for persistent atrial fibrillation (AF) typically includes pulmonary vein isolation (PVI) and may include additional ablation lesions that target patient-specific anatomical, electrical, or structural features. Clinical centers employ different ablation strategies, which use imaging data together with electroanatomic mapping data, depending on data availability. The aim of this study was to compare ablation techniques across a virtual cohort of AF patients. We constructed 20 paroxysmal and 30 persistent AF patient-specific left atrial (LA) bilayer models incorporating fibrotic remodeling from late-gadolinium enhancement (LGE) MRI scans. AF was simulated and post-processed using phase mapping to determine electrical driver locations over 15 s. Six different ablation approaches were tested: (i) PVI alone, modeled as wide-area encirclement of the pulmonary veins; PVI together with: (ii) roof and inferior lines to model posterior wall box isolation; (iii) isolating the largest fibrotic area (identified by LGE-MRI); (iv) isolating all fibrotic areas; (v) isolating the largest driver hotspot region [identified as high simulated phase singularity (PS) density]; and (vi) isolating all driver hotspot regions. Ablation efficacy was assessed to predict optimal ablation therapies for individual patients. We subsequently trained a random forest classifier to predict ablation response using (a) imaging metrics alone, (b) imaging and electrical metrics, or (c) imaging, electrical, and ablation lesion metrics. The optimal ablation approach resulting in termination, or if not possible atrial tachycardia (AT), varied among the virtual patient cohort: (i) 20% PVI alone, (ii) 6% box ablation, (iii) 2% largest fibrosis area, (iv) 4% all fibrosis areas, (v) 2% largest driver hotspot, and (vi) 46% all driver hotspots. Around 20% of cases remained in AF for all ablation strategies. The addition of patient-specific and ablation pattern specific lesion metrics to the trained random forest classifier improved predictive capability from an accuracy of 0.73 to 0.83. The trained classifier results demonstrate that the surface areas of pre-ablation driver regions and of fibrotic tissue not isolated by the proposed ablation strategy are both important for predicting ablation outcome. Overall, our study demonstrates the need to select the optimal ablation strategy for each patient. It suggests that both patient-specific fibrosis properties and driver locations are important for planning ablation approaches, and the distribution of lesions is important for predicting an acute response.

Conversion of atrial fibrillation to sinus rhythm during cryoballoon ablation: A favorable and not unusual phenomenon during second-generation cryoballoon pulmonary vein isolation

BACKGROUND

The prevalence and the clinical impact of conversion of atrial fibrillation (AF) to sinus rhythm (SR) during cryoballoon ablation (CB-A) are unknown.

OBJECTIVE

The purpose of this study was to evaluate the prevalence of restoration of SR during CB-A and the clinical impact of this phenomenon.

METHODS

Between January 2012 and September 2018, all patients who experienced conversion of AF to SR during CB-A were included. This group was subsequently matched for gender, age, type of AF, diagnosis-to-ablation time, and left atrial size with patients who underwent CB-A and did not experienced conversion of AF to SR. After discharge, patients were scheduled for follow-up visits at 1, 3, 6, and 12 months and 24 hours Holter recordings were obtained at each follow-up visit. All documented AF episodes of >30 seconds were considered as recurrence. A 3 month post-procedural blanking period (BP) was applied.

RESULTS

A total of 1559 patients underwent pulmonary veins isolation by CB-A between January 2012 and September 2018; among them, 58 patients (3.7%) experienced restoration of SR during CB-A. In total, 53 patients (41 males [77.3%], mean age 61.4 ± 13.3 years) were included in the case group. During CB-A, restoration of SR occurred more frequently during right-side PVs applications (right inferior pulmonary vein 39.6%, right superior pulmonary vein 30.2%). If considering a BP, at 2 year follow-up, freedom from recurrences was 86.5% in the case group and 68.0% in the control group (P = .036).

CONCLUSION

Conversion of AF to SR is a favorable and relatively frequent phenomenon during cryoballoon pulmonary vein isolation ablation.

Usage of a new mapping algorithm to detect possible critical substrate for continuity of atrial fibrillation: fractionation mapping in preliminary experience

Although treatment of atrial fibrillation (AF) classically focuses on eliminating the pulmonary vein (PV) triggers, isolation of PVs is associated with limited success rates in patients with persistent AF. The role of the left atrial appendage (LAA) as both trigger and driver in arrhythmogenesis of AF was previously demonstrated. In the present case, fractionation mapping software of Ensite system was firstly tested to detect critical substrate during AF. Focusing on the width and continuity of fractionation pattern, the LAA was accepted as main driver for maintenance of AF. Ablation in fractionated electrograms around the LAA caused acute AF termination. After isolation of the LAA, no AF was inducible with atrial stimulation with and without isoproterenol infusion. Fractionation mapping may be used to detect potential importance of the LAA in AF continuity.

Difference in the maintenance mechanism of atrial fibrillation perpetuated after pulmonary vein isolation between paroxysmal and persistent atrial fibrillation: Effects of subsequent stepwise ablation

BACKGROUND

Neither the atrial fibrillation (AF) maintenance mechanism after pulmonary vein isolation (PVI) nor the mechanism of AF termination via stepwise ablation is clearly understood.

METHODS

Among 226 consecutive AF patients (154 paroxysmal (P-AF) and 72 persistent AF (Per-AF) patients), left atrial endocardial non-contact mapping was performed after PVI in the initial 10 P-AF and 16 Per-AF patients to define the AF maintenance mechanism. Subsequently, effect of stepwise catheter ablation (linear roof lesion and complex fractionated atrial electrogram (CFAE) following PVI) was evaluated in all patients.

RESULTS

After PVI, AF was maintained by the activation around isolated PV/mitral annulus, focal discharge and disorganized activations mostly observed over residual CFAE region (pivoting activation, wave break and fusion). CFAE region in P-AF was smaller than Per-AF after PVI (1.6 ± 2.1 vs. 7.7 ± 2.5 cm(2), p<0.0001). The frequency of pivoting activation, wave break and fusion in P-AF were lower than those in Per-AF (1.9 ± 2.0 vs. 11.8 ± 5.0 times/s; p<0.0001, 0.1 ± 0.3 vs. 3.6 ± 2.5 times/s; p<0.001, 5.8 ± 3.6 vs. 9.8 ± 3.2 times/s; p<0.01). AF termination was more frequent in P-AF than Per-AF (94.8% vs 81.9%, p=0.0019). AF termination by PVI alone was more frequent in P-AF than Per-AF (85.6% vs. 18.6%, p<0.0001). However, AF termination via roof line and/or CFAE ablation was less frequent in P-AF than Per-AF (14.4 vs. 81.4%, p<0.0001).

CONCLUSIONS

Disorganized activations after PVI, more prominent in Per-AF, were associated with residual CFAE region. Most P-AF was terminated by PVI alone, however additional roof line lesion and CFAE ablation were necessary to terminate Per-AF, consistent with mapping results.