Impact of atrial fibrillation termination site and termination mode in catheter ablation on arrhythmia recurrence

Beyond Pulmonary Vein Isolation: the Role of Additional Sites in Catheter Ablation of Atrial Fibrillation

PURPOSE OF REVIEW

Pulmonary vein (PV) isolation is the cornerstone of atrial fibrillation (AF) ablation. However, the long-term procedural outcome remains suboptimal and there is a frequent need for repeat ablation procedure, especially in patients with non-paroxysmal AF. The review article summarizes the rationales, recent evidences, and strategies of ablation of extra-PV sites and its clinical outcomes.

RECENT FINDINGS

It is a consensus that durable PV isolations are a definite therapy in patients with paroxysmal AF. In non-paroxysmal AF, many laboratories still believe that adequate substrate ablation outside PVs is definitely required. Empirical linear ablation is not recommended because of difficulty in achieving complete linear block, unless macro-reentry atrial tachycardia developed during procedure. Most of laboratories applied complex fractionated atrial electrogram (CFAE) ablation after PV isolation in non-paroxysmal AF, but the efficacy is limited in the long-term follow-up studies. A combined approach using CFAE, non-linear similarity, and phase mapping strategy to identify rotors or focal sources for substrate modification increases the ablation outcome, when compared to CFAE ablation alone. Provocative test with mapping of non-PV triggers is also recommended in all patients to improve long-term ablation success. Ablation beyond PV isolation is important, especially in non-paroxysmal AF patients, to modify the diseased atrial substrate and eliminate the non-PV triggers, which in turn improve the ablation outcome.

Occurrence of Focal Atrial Tachycardia During the Ablation Procedure Is Associated With Arrhythmia Recurrence After Termination of Persistent Atrial Fibrillation

INTRODUCTION

Catheter ablation can terminate persistent atrial fibrillation (AF). However, atrial tachycardia (AT) often arises after termination of AF.

METHODS AND RESULTS

Of 215 patients who underwent index stepwise ablation for persistent AF, 141 (66%) patients (64 ± 9 years) in whom AF terminated during the ablation procedure were studied. If AF converted into AT, ablation for AT was subsequently performed. ATs were categorized as focal or macroreentrant AT. We assessed whether type of AT occurring after conversion of AF during the ablation procedure was associated with freedom from atrial tachyarrhythmia (AF or AT) during follow-up. Sinus rhythm was directly restored from AF in 37 patients, while 34, 37, and 33 patients had focal AT alone, a mix of focal and macroreentrant AT, and macroreentrant AT alone after termination of AF, respectively. Arrhythmia-free survival rates at 1 year after the index procedure were 30%, 34%, 61%, and 59% in the patients with focal AT alone, a mix of focal AT and macroreentrant AT, macroreentrant AT alone, and direct restoration of sinus rhythm, respectively (P = 0.004). Type of AT occurring during the index procedure was associated with type of recurrent AT (P = 0.03), but the origin of focal AT occurring during the index ablation differed from that of the recurrent AT in 85% of patients.

CONCLUSION

In patients who had AF termination by ablation, occurrence of focal AT during the ablation procedure was associated with worse clinical outcome than occurrence of macroreentrant AT, likely due to ATs arising from other foci during follow-up.

Spatial Relationship of Focal Impulses, Rotors and Low Voltage Zones in Patients With Persistent Atrial Fibrillation

INTRODUCTION

Focal impulses (FI) and rotors are sources associated with the initiation and maintenance of atrial fibrillation (AF). Their ablation results in a lower recurrence rate. The aim of this study was to characterize for the first time the spatial relationship between such sources and atrial low voltage zones (LVZ) representing fibrosis.

METHODS

Twenty-five consecutive patients undergoing their first ablation for persistent AF were included. Voltage mapping of both atria was done during AF. Endocardial mapping of FI and rotors (sources) was performed using a basket catheter and displayed using RhythmView(TM) (Topera Inc.) before ablation. Spatial relationship of LVZ and sources was analyzed.

RESULTS

LVZs covered 13 ± 12% of right atrial (RA) endocardial surface and 33 ± 25% of left atrial (LA) endocardial surface. The median number of sources was 1 [1-3] in RA and 3 [1-4] in LA. Of LA sources, 18 (30%) were definitely not associated with LVZs or pulmonary vein (PV) antra. Of RA sources, 32 (84%) were remote from LVZ. During ablation of such sources substantial cycle length (CL) prolongation or AF conversion occurred in 11/23 patients (48%). Altogether, 8/11 (73%) of these pertinent sources were located remotely from LVZ and PV antra.

CONCLUSIONS

There is a wide discrepancy in distribution of LVZ areas and sites of identified rotors. Site and incidence of FIRM sources appear to be unpredictable with atrial substrate mapping. Further prospective, randomized studies are necessary to elucidate the impact of additional ablation of such sources in patients with persistent or longstanding persistent AF.

Early Recurrence After Pulmonary Vein Isolation of Paroxysmal Atrial Fibrillation With Different Ablation Technologies - Prospective Comparison of Radiofrequency vs. Second-Generation Cryoballoon Ablation

BACKGROUND

Inflammation plays a prominent role in the etiology of the early recurrence of atrial fibrillation (ERAF). We prospectively compared the proportion of ERAF and time-course patterns of biomarkers between radiofrequency (RF) and cryoballoon (CB) ablation.

METHODS AND RESULTS

We enrolled 82 consecutive paroxysmal AF patients undergoing pulmonary vein (PV) isolation, performed with either a 28-mm 2nd-generation CB and 3-min freeze technique or point-by-point RF ablation. Each group had 41 patients. In the RF group, all PVs were successfully isolated with 28.9 ± 6.5 min of RF delivery. In the CB group, a mean of 5.3 ± 1.4 applications/patient was delivered. The proportion of ERAF was similar between the groups. The time-course patterns significantly differed between the groups for high-sensitivity C-reactive protein (hs-CRP) value (P=0.006) and myocardial injury markers (P<0.0001). Greater myocardial injury was observed in the CB than in the RF group (P<0.0001), whereas the peak hs-CRP value was comparable between the groups. The 2-day post-procedure hs-CRP value was the sole factor correlating with ERAF as identified by the multivariable analysis (hazard ratio 1.697; 95% confidence interval, 1.005-2.865; P=0.048) in the RF, but not the CB group.

CONCLUSIONS

The proportion of ERAF was comparable after RF and 2nd-generation CB ablation. Despite CB ablation exhibiting greater myocardial injury than RF ablation, the inflammatory responses were comparable between the groups. The inflammatory response extent predicted ERAF post-RF ablation but not post-CB ablation.

Pre-procedural evaluation of the left atrial anatomy in patients referred for catheter ablation of atrial fibrillation

BACKGROUND

Cardiac computed tomography (CT) provides accurate imaging of the pulmonary vein (PV) and left atrial (LA) anatomy. This study aimed to evaluate the prevalence and morphological characteristics of anatomical variants that could influence atrial fibrillation (AF) ablation procedures.

METHODS AND RESULTS

One thousand forty consecutive patients (62±10 years, 243 female, 644 paroxysmal AF) undergoing pre-procedural imaging with a 320-row CT and their first AF ablation procedure were analyzed. A total of 194 (18.7%) patients had anatomical variants. Left, right, and inferior common PVs were observed in 118, 5, and 6 patients, respectively. Three right and left PVs were observed in 44 and 4 patients, respectively. Three patients had remnants of PVs after lobectomies, and significant PV stenosis was observed in one. Supernumerary PVs that drained into the LA and diverticula were observed in eight patients. One patient had a string-like structure connecting the LA septum and posterior LA, and the others had membranous structures incompletely compartmentalizing the LA. Three patients had persistent left superior vena cavae, two strong deviations of the LA and PVs, and one dexiocardia. All patients underwent successful PV isolation during the index procedure.

CONCLUSIONS

Patients referred for AF ablation often have anatomical variants, which could influence the procedure. This information might aid in planning procedural strategies, and reducing unexpected procedural complications in AF ablation.

Non-Inducibility Or Termination As Endpoints Of Atrial Fibrillation Ablation: What Is The Role?

Catheter ablation is widely used to treat drug-refractory, symptomatic atrial fibrillation (AF). However, beyond pulmonary vein isolation, there remains little consensus on the recommended approach to ablation both in paroxysmal or persistent AF patients. Although ancillary ablation strategies are often used, the lack of a clear endpoint for AF ablation makes it challenging to evaluate their importance. Non-inducibility and termination of AF during AF ablation have been advocated as potential endpoints. Several studies have attempted to assess their role in an AF ablation protocol. However, the data for non-inducibility and termination as endpoints are mixed. Moreover, there are a number of limitations in the studies reported and limitations of the endpoints themselves. It is likely that non-inducibility or termination of AF during AF ablation may be markers of less structural remodeling rather than true endpoints for ablation. Herein, we review the relevant literature on the topic of inducibility and termination with respect to AF ablation and attempt to draw conclusions with guidance to further investigation.

Role of extended external auto-triggered loop recorder monitoring for atrial fibrillation

BACKGROUND

Clinical outcomes after atrial fibrillation (AF) ablation are evaluated using standard 24-h Holter monitoring, and the large spontaneous variability of AF episodes and incidence of silent AF are major limitations. Further, symptoms generally decrease after AF ablation. METHODS AND RESULTS: Newly developed extended external auto-trigger loop recorders (ELR) were used for 14-day consecutive monitoring to detect atrial tachyarrhythmia (ATa). Continuous tracings were stored for the initial 24h. Among 500 examinations after AF ablation in 342 patients, 40 ATa episodes were manually detected in 25 patients during the initial 24h. All episodes including 27 asymptomatic episodes (67.5%) were successfully identified using ELR. Recurrent ATa after AF ablation were detected in 83 patients, and a median monitoring duration of 4.0 days (IQR, 1.0-7.75 days) was required to detect the first episode of recurrence. The sensitivity of 24-h monitoring in detecting arrhythmia recurrence was 27.7% relative to the 14-day monitoring. The diagnostic yield gradually improved with longer monitoring duration regardless of the period after the ablation procedure. Longer follow-up, however, was required to obtain similar diagnostic yield >1 year after as compared to <1 year after the procedure.

CONCLUSIONS

Twenty-four-hour monitoring detected a part of the ATa recurrences after ablation procedures. Extended ELR enabled arrhythmia monitoring for longer, with higher diagnostic yield of recurrence, regardless of patient symptoms.