Radiofrequency catheter ablation of atrial fibrillation: A review of techniques

Ablation of atrial fibrillation is a key area of current research. A multitude of techniques have been tested, some of which are poorly evidenced and not recommended in routine clinical practice whilst others are more promising. Additionally, a plethora of issues exist when researching ablation techniques, from control arm ablation strategy to the relevance of outcome measures. In this review article, we discuss these issues in the context of the current evidence base.

High-density characterization of the sinus rhythm: a new functional substrate map of scar-related atrial tachycardia

BACKGROUND

Reentrant atrial tachycardias (ATs) utilize critical isthmus (CI) for the maintenance of the circuit. The electrophysiological characteristics and clinical implications of the targeted CI regions of reentrant ATs during sinus rhythm (SR) were not clear. Therefore, our research aims at studying the electrical properties of the CI sites for scar-related reentrant ATs and the functional substrate mapping identified during SR.

METHODS

Patients mapped with high-density catheters during SR and reentrant ATs were retrospectively analyzed. The CI regions of the reentrant ATs were confirmed by the combination of the activation map and the entrainment. The substrate mapping was analyzed for wavefront propagation, conduction velocity, and electrogram patterns.

RESULTS

Twenty patients with 22 reentrant ATs that underwent high-density maps were analyzed at 2 hospitals. Mapping performed during SR identified a scar region of 23.0 ± 13.6% of the left atrium. Regions of the CI in SR were characterized by low voltage (0.3 ± 0.2 mV), conduction slowing (0.4 ± 0.2 m/s), and fractionated electrogram (duration 62.5 ± 13.9 ms). Substrate mapping during SR showed that the regions of the CI located with the low-voltage zone in 16 out of 22 CI (72.7%), the deceleration zone in 15 out of 22 CI (68.2%), and late atrial activation in 12 out of 22 CI (54.5%). Targeting regions of CI achieve 94% of termination or change of the reentrant circuit. At 6.2 ± 7.1 months, there was 75% freedom from atrial arrhythmia.

CONCLUSIONS

Novel high-density mapping can identify the functional substrates during SR and guide ablation. Low-voltage areas with conduction slowing are putative predictors of the CI for the maintenance of the reentrant ATs.

Deep Sedation with Intravenous Anesthesia Is Associated with Outcome in Patients Undergoing Cryoablation for Paroxysmal Atrial Fibrillation

Whether deep sedation with intravenous anesthesia will affect the recurrence after cryoballoon ablation (CBA) of paroxysmal atrial fibrillation (AF) is yet to be examined. Thus, in this study, we hypothesize that there is difference in terms of the recurrence between local anesthesia and deep sedation with intravenous anesthesia after an index ablation procedure.In total, 109 patients were enrolled and received CBA, of which 68 (58.2 years) patients underwent pulmonary vein (PV) isolation with a local anesthesia (group 1) and 41 patients (63.2 years) underwent PV isolation with deep sedation using intravenous anesthesia (group 2).During the index procedure, isolation of all major PVs was achieved in 66 patients in group 1 and in 41 patients in group 2. There was no difference in non-PV triggers between the two groups. The periprocedural complication was found to be similar between the two groups (2.9% in group 1 and 4.9% in group 2). Further, 17 patients in group 1 and 4 patients in group 2 experienced recurrences after a follow-up of 19.3 months (P = 0.019). Repeat procedures revealed similar PV reconnection rates between the two groups. It has also been noted that the number of reconnected PV and incidence of atypical flutter seem to increase in group 1.Deep sedation with intravenous anesthesia during CBA for paroxysmal AF is safe and had a better long-term outcome than those with local anesthesia.

Biparietal bidirectional bipolar radiofrequency in hybrid cardiac ablation: an in vitro evaluation

 

OBJECTIVES

The aim of this study was to evaluate the lesion size and depth of radiofrequency (RF) ablation in a simultaneous biparietal bidirectional bipolar (SBB) approach, compared to a simultaneous and staged unipolar and uniparietal bipolar setup [simultaneous uniparietal bipolar (SiUB) and staged uniparietal bipolar (StUB), respectively].

METHODS

Fresh left atrial porcine tissue was mounted into the ABLA-BOX simulator. Different ablation approaches were tested: (i) SBB: a concept consisting of SBB endo-epicardial ablation, (ii) SiUB: simultaneous epicardial uniparietal bipolar and endocardial unipolar ablation and (iii) StUB: staged epicardial uniparietal bipolar and endocardial unipolar ablation. In the StUB setup, a 1-h interval between the epi-endo ablation was respected.

RESULTS

Transmural lesions were present in 90% of the bipolar biparietal ablations, yet no full transmurality was observed in the simultaneous nor in the staged unipolar with uniparietal bipolar ablation group. In SBB, the area and volume of the ablation lesions were smaller (523.33 mm2/mm and 52.33 mm3/mm, respectively) than in SiUB (588.17 mm2/mm and 58.81 mm3/mm, respectively) and StUB (583.76 mm2/mm and 58.37 mm3/mm, P = 0.044). Also, in SBB, the overall, epicardial and endocardial maximum diameters of the lesions (1.59, 1.57 and 1.52 mm; respectively) were smaller than in SiUB (2.38, 2.26 and 2.33 mm; respectively) and in StUB (2.36, 2.28 and 2.14 mm; respectively, all P < 0.001).

CONCLUSIONS

Although bipolar biparietal bidirectional RF ablation results in smaller lesions than uniparietal bipolar and unipolar ablation, their capacity to penetrate the tissue is much higher. Moreover, in uniparietal RF applications, the energy spreads in the superficial layers of the tissue but fails to penetrate. Therefore, the degree of transmurality is much higher when using such a 'truly bipolar' ablation approach.

The importance of extrapulmonary vein triggers and atypical atrial flutter in atrial fibrillation recurrence after cryoablation: Insights from repeat ablation procedures

INTRODUCTION

It has not been previously investigated whether the recurrence mechanism after cryoballoon ablation (CBA) of paroxysmal atrial fibrillation (AF) is similar to that of radiofrequency catheter ablation (RFCA). We aimed to evaluate the differences of recurrence characteristics between RFCA and CBA after the index procedure.

METHODS

A total of 210 patients were enrolled in the study, and 69 patients underwent pulmonary vein (PV) isolation using a 28-mm second-generation CBA. The control group comprising 140 patients underwent PV isolation using an open-irrigated radiofrequency ablation catheter. A total of 69 patients in the CBA group and 69 patients in the RFCA group were investigated after propensity score matching. Recurrence patterns of AF were studied in the repeated procedure.

RESULTS

During the index procedure, there was no difference in PV or non-PV triggers between the two groups. Nineteen (27.5%) patients in the CBA group and 19 (27.5%) patients in the RFCA group had recurrence after a follow-up of 11.3 ± 7 months. The Kaplan-Meier curve did not reveal significant difference in recurrence (log-rank, P = 0.364) between the two groups. In the second procedure, the CBA group had more non-PV triggers (63.6%, P = 0.009) and left atrial (LA) flutters (54.5%, P = 0.027) compared with the RFCA group (12.5% and 12.5%, respectively). The PV reconnection rates were similar between both groups.

CONCLUSIONS

There was no difference in AF recurrence after catheter ablation between CBA and RFCA, but significant increases of non-PV triggers and LA flutter during the second procedure suggest the importance of the atrial substrate in maintaining AF during the second procedure after previous CBA.

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.

Adenosine Testing After Atrial Fibrillation Ablation: Systematic Review and Meta-Analysis

BACKGROUND

Adenosine can be used to reveal dormant pulmonary vein (PV) conduction after pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF). We performed a systematic review and meta-analysis to assess the impact of adenosine administration in patients undergoing PVI for AF.

METHODS

Meta-analysis of 22 studies was performed to assess the rates of freedom from AF in 1) patients with dormant PV conduction versus patients without dormant PV conduction, and 2) patients given routine adenosine post PVI versus patients not given adenosine. Relative-risks (RR) were calculated using random effects modelling.

RESULTS

In 18 studies, 3038 patients received adenosine and freedom from AF in those patients with dormant PV reconnection was significantly lower (62.9%) compared to patients without PV reconnection (67.2%) (RR 0.87; 95% CI: 0.78-0.98). In seven studies with 3049 patients, the freedom from AF was significantly higher in patients who received adenosine (67%) versus those patients who did not receive adenosine (63%) (RR: 1.11; 95% CI: 1.01-1.22).

CONCLUSIONS

The present study showed clear benefits of adenosine testing for freedom from AF recurrence. Adenosine-guided dormant conduction is associated with higher AF recurrence despite further ablation. Future studies should investigate the optimal methodology, including dosage and waiting time between PVI and adenosine administration.