Determinants of Acute and Late Pulmonary Vein Reconnection in Contact Force–Guided Pulmonary Vein Isolation: Identifying the Weakest Link in the Ablation Chain

Local impedance for the optimization of radiofrequency lesion delivery: A review of bench and clinical data

INTRODUCTION

Radiofrequency catheter ablation is a cornerstone of treatment for many cardiac arrhythmias. Progression in three-dimensional mapping and contact-force sensing technologies have improved our capability to achieve success, but challenges still remain.

METHODS

In this article, we discuss the importance of overall circuit impedance in radiofrequency lesion formation. This is followed by a review of the literature regarding recently developed "local impedance" technology and its current and future potential applications and limitations, in the context of established surrogate markers currently used to infer effective ablation.

RESULTS

We discuss the role of local impedance in assessing myocardial substrate, as well as its role in clinical studies of ablation. We also discuss safety considerations, limitations and ongoing research.

CONCLUSION

Local impedance is a novel tool which has the potential to tailor ablation in a manner distinct from other established metrics.

Quantification of irrigated lesion morphology using near-infrared spectroscopy

There are currently limited means by which lesion formation can be confirmed during radiofrequency ablation procedures. The purpose of this study was to evaluate the use of NIRS-integrated RFA catheters for monitoring irrigated lesion progression, ex vivo and in vivo. Open-irrigated NIRS-ablation catheters with optical fibers were fabricated to sample tissue diffuse reflectance. Spectra from 44 irrigated lesions and 44 non-lesion sites from ex vivo swine hearts (n = 15) were used to train and evaluate a predictive model for lesion dimensions based on key spectral features. Additional studies were performed in diluted blood to assess NIRS signatures of catheter-tissue contact status. Finally, the potential of NIRS-RFA catheters for guiding lesion delivery was evaluated in a set of in vivo pilot studies conducted in healthy pigs (n = 4). Model predictions for lesion depth (R = 0.968), width (R = 0.971), and depth percentage (R = 0.924) correlated well with measured lesion dimensions. In vivo deployment in preliminary trials showed robust translational consistency of contact discrimination (P < 0.0001) and lesion depth parameters (< 3% error). NIRS empowered catheters are well suited for monitoring myocardial response to RF ablation and may provide useful intraprocedural feedback for optimizing treatment efficacy alongside current practices.

Regional differences in the predictors of acute electrical reconnection following high-power pulmonary vein isolation for paroxysmal atrial fibrillation

BACKGROUND

Acute pulmonary vein reconnection (PVR) is associated with long procedure times and large radiofrequency (RF) energy delivery during pulmonary vein isolation (PVI). Although the efficacy of high-power PVI (HP-PVI) has been recently established, the determinants of acute PVR following HP-PVI remain unclear.

METHODS

We evaluated data on 62 patients with paroxysmal atrial fibrillation undergoing unipolar signal modification (USM)-guided HP-PVI. A 50-W RF wave was applied for 3-5 seconds after USM. In the segments adjacent to the esophagus (SAEs), the RF time was limited to 5 seconds. Each circle was subdivided into six regions (segments), and the possible predictors of acute PVR, including minimum contact force (CFmin), minimum force-time integral (FTImin), minimum ablation index (AImin), minimum impedance drop (Imp-min), and maximum inter-lesion distance (ILDmax), were assessed in each segment.

RESULTS

We investigated 1162 ablations in 744 segments (including 124 SAEs). Acute PVR was observed in 21 (17%) SAEs and 43 (7%) other segments (P = .001). The acute PVR segments were characterized by significantly lower CFmin, FTImin, AImin, and Imp-min values in the segments other than the SAEs and larger ILDmax values in the SAEs. Furthermore, lower Imp-min and larger ILDmax values independently predicted acute PVR in the segments other than the SAEs and SAEs (odds ratios 0.90 and 1.39 respectively). Acute PVR was not significantly associated with late atrial fibrillation recurrence.

CONCLUSIONS

Avoiding PVR remains a challenge in HP-PVI cases, but it might be resolved by setting the optimal target impedance drop and lesion distance values.

Acute and long-term efficacy of ablation index-guided higher power shorter duration ablation in patients with atrial fibrillation: A prospective registry

BACKGROUND

Theoretically, targeting the same ablation index (AI) using higher power may achieve the same lesion size with a shorter ablation time. We evaluated the acute and long-term efficacy of higher-powered ablation guided by ablation index (HPAI) compared with conventional-powered ablation guided by AI (CPAI) for pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF).

METHODS

Drug refractory symptomatic AF patients who had been ablated with 40 W on the anterior/roof segments and 30 W on the posterior/inferior/carina segments were enrolled (HPAI group). We compared the HPAI group with the CPAI group who were ablated with 30 W on the anterior/roof segments and 25 W on the posterior/inferior/carina segments. The same AI was targeted (≥450 on the anterior/roof segments and ≥350 on the posterior/inferior/carina segments). We compared ablation time, acute pulmonary vein reconnection (PVR) and 1-year AF recurrence between the two groups.

RESULTS

A total of 118 patients were included (86 in the HPAI group and 32 in the CPAI group, paroxysmal AF, 73%). There was no significant difference in the acute PVR rate between the HPAI and the CPAI groups (3.7% vs. 4.2%, P = .580) with a 41% reduction in ablation time for PVI (38.7 ± 8.3 vs. 65.8 ± 13.7 minutes, P < .001). The 1-year AF recurrence rate was not significantly different between HPAI and CPAI groups (12.8% vs. 21.9%, Log-rank P = .242). There were no major complications in either group.

CONCLUSIONS

Increased power during AF ablation, using the same AI targets, reduced the procedure and ablation times, and showed a comparable acute and long-term outcome without compromising safety.

CLINICAL TRIAL REGISTRATION

https://www.clinicaltrials.gov. Unique identifier: NCT04379557.

How Close Are We toward an Optimal Balance in Safety and Efficacy in Catheter Ablation of Atrial Fibrillation? Lessons from the CLOSE Protocol

Catheter ablation for atrial fibrillation (AF) is a common treatment strategy in patients with drug-resistant, symptomatic AF. In patients with paroxysmal and short-standing persistent AF, pulmonary vein isolation (PVI) is often enough to prevent recurrence of atrial tachyarrhythmia (ATA). Point-by-point encircling of the PVs with radiofrequency (RF) applications, together with cryoballoon ablation, have been the mainstay strategies for the last 10 to 20 years. Each of these strategies, however, suffers from the delicate balance between preventing PV reconnection, on the one hand (toward more energy), and preventing (mainly esophageal) complications (toward less energy), on the other. The CLOSE protocol was developed as an RF ablation strategy that would result in the safe creation of durable isolation leading to improved outcomes. Basically, the aim of the protocol is to enclose the pulmonary veins with stable, contiguous (intertag distance, ITD ≤ 6 mm) and optimized lesions (35 Watts, W, RF applications up to ablation index targets of ≥400 and ≥550 at the posterior and anterior wall). In this review, we describe the background of the CLOSE protocol and the studies from the St Jan Bruges research group on procedural performance, efficacy, and safety of the CLOSE protocol in (a) single-center prospective PILOT study (CLOSE-PILOT), (b) a single-center prospective study with continuous rhythm monitoring (CLOSE to CURE), (c) a database of systematic esophageal endoscopic studies, (d) a multicenter prospective study (VISTAX), and (e) the CLOSE database (comprising > 400 patients). We also discuss the results of the randomized POWER-AF study comparing conventional CLOSE to high power CLOSE (up to 50 W). Finally, we discuss the performance, safety, and efficacy of the CLOSE protocol in light of the emerging changes in the field of catheter ablation being ultra-short high-power ablation and electroporation.

Personalized paroxysmal atrial fibrillation ablation by tailoring ablation index to the left atrial wall thickness: the 'Ablate by-LAW' single-centre study-a pilot study

AIMS

To determine if adapting the ablation index (AI) to the left atrial wall thickness (LAWT), which is a determinant of lesion transmurality, is feasible, effective, and safe during paroxysmal atrial fibrillation (PAF) ablation.

METHODS AND RESULTS

Consecutive patients referred for PAF first ablation. Left atrial wall thickness three-dimensional maps were obtained from multidetector computed tomography and integrated into the CARTO navigation system. Left atrial wall thickness was categorized into 1 mm layers and AI was titrated to the LAWT. The ablation line was personalized to avoid thicker regions. Primary endpoints were acute efficacy and safety, and freedom from atrial fibrillation (AF) recurrences. Follow-up (FU) was scheduled at 1, 3, 6, and every 6 months thereafter. Ninety patients [60 (67%) male, age 58 ± 13 years] were included. Mean LAWT was 1.25 ± 0.62 mm. Mean AI was 366 ± 26 on the right pulmonary veins with a first-pass isolation in 84 (93%) patients and 380 ± 42 on the left pulmonary veins with first-pass in 87 (97%). Procedure time was 59 min (49-66); radiofrequency (RF) time 14 min (12.5-16); and fluoroscopy time 0.7 min (0.5-1.4). No major complication occurred. Eighty-four out of 90 (93.3%) patients were free of recurrence after a mean FU of 16 ± 4 months.

CONCLUSION

Personalized AF ablation, adapting the AI to LAWT allowed pulmonary vein isolation with low RF delivery, fluoroscopy, and procedure time while obtaining a high rate of first-pass isolation, in this patient population. Freedom from AF recurrences was as high as in more demanding ablation protocols. A multicentre trial is ongoing to evaluate reproducibility of these results.

Improved durable pulmonary vein isolation with shorter procedure times and lower energy levels using RF ablation with ablation index and a stringent lesion contiguity

Background

The single procedure success rates of durable pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) varies between 80 and 90%. Ablation index, incorporating contact force, stability, time and power is a more profound parameter of significant lesion size and has been established. Equally important is a stringent contiguity of the lesion set.

Methods and results

A total number of 100 consecutive patients undergoing de-novo catheter ablation for paroxysmal atrial fibrillation (PAF) were analyzed between 2016 and 2019. In the first 50 patients (group A) PVI was performed using a surround flow, contact force catheter (Biosense Webster Thermocool STSF, Biosense Webster, USA) with a drag-and-ablate technique to encircle the PVs. In the following 50 patients (group B), PVI was performed using ablation index and a stringent lesion contiguity with an interlesion distance (ILD) of <5 mm. The baseline characteristics showed no significant differences between both groups. During a mean follow-up of 18 ± 3 months after a single procedure, 36 (72%) patients of group A were free of arrhythmia recurrence versus 43 (86%) patients in group B (p = 0.047). A total of 14 patients (group A: 10 (20%), group B: 4 (8%); underwent a redo-procedure. 7 patients of group A (14%) and 2 patients of group B (4%) showed recovered veins. In 3 patients of group A and 2 patients of group B the PVs were durably isolated. In these patients persistent AF recurrence was caused by extra-PV AF sources. Four patients of group A and three patients of group B had continued paroxysmal or persistent AF but did not undergo redo-procedure. With regard to the procedural data, the procedure time, the total energy and the fluoroscopy time were significantly lower in group B (AI and ILD <5 mm) (128.86 ± 18.19 versus 115.35 ± 15.38; p < 0.05; 1619.16 ± 988.56 versus 1186.26 ± 756.34; p < 0.05; 11.49 ± 3.20 versus 9.66 ± 3.86; p = 0.04). Both procedures were performed with a low number of complications, no pericardial effusion was seen in either group.

Conclusions

PVI using ablation index in combination with a stringent lesion contiguity improves clinical outcome after first-time PVI with lower PVI recovery, shorter procedure times, lower total energy and shorter fluoroscopy times and therefore, is more efficient.

Predictors of recurrence after durable pulmonary vein isolation for paroxysmal atrial fibrillation

AIMS

Catheter ablation of paroxysmal atrial fibrillation (AF) reduces AF recurrence, AF burden, and improves quality of life. Data on clinical and procedural predictors of arrhythmia recurrence are scarce and are flawed by the high rate of pulmonary vein reconnection evidenced during repeat procedures after pulmonary vein isolation (PVI). In this study, we identified clinical and procedural predictors for AF recurrence 1 year after CLOSE-guided PVI, as this strategy has been associated with an increased PVI durability.

METHODS AND RESULTS

Patients with paroxysmal AF, who received CLOSE-guided PVI and who participated in a prospective trial in our centre, were included in this study. Uni- and multivariate models were plotted to find clinical and procedural predictors for AF recurrence within 1 year. Three hundred twenty-five patients with a mean age of 63 years (CHA2DS2VASc 1 [1-3], left atrium diameter 41 ± 6 mm) were included. About 60.9% were male individuals. After 1 year, AF recurrence occurred in 10.5% of patients. In a binary logistic regression analysis, the diagnosis-to-ablation time (DAT) was found to be the strongest predictor of AF recurrence (P = 0.011). Diagnosis-to-ablation time ≥1 year was associated with a nearly two-fold increased risk for developing AF recurrence.

CONCLUSION

The DAT is the most important predictor of arrhythmia recurrence in low-risk patients treated with durable pulmonary vein isolation for paroxysmal AF. Whether reducing the DAT could improve long-term outcomes should be investigated in another trial.

Comparison of lesion characteristics between conventional and high-power short-duration ablation using contact force-sensing catheter in patients with paroxysmal atrial fibrillation

Background

Transmural lesion creation is essential for effective atrial fibrillation (AF) ablation. Lesion characteristics between conventional energy and high-power short-duration (HPSD) setting in contact force-guided (CF) ablation for AF remained unclear.

Methods

Eighty consecutive AF patients who received CF with conventional energy setting (power control: 25–30 W, force–time integral = 400 g s, n = 40) or with HPSD (power control: 40–50 W, 10 s, n = 40) ablation were analyzed. Of them, 15 patients in each conventional and HPSD group were matched by age and gender respectively for ablation lesions analysis. Type A and B lesions were defined as a lesion with and without significant voltage reduction after ablation, respectively. The anatomical distribution of these lesions and ablation outcomes among the 2 groups were analyzed.

Results

1615 and 1724 ablation lesions were analyzed in the conventional and HPSD groups, respectively. HPSD group had a higher proportion of type A lesion compared to conventional group (P < 0.01). In the conventional group, most type A lesions were at the right pulmonary vein (RPV) posterior wall (50.2%) whereas in the HPSD group, most type A lesions were at the RPV anterior wall (44.0%) (P = 0.04). The procedure time and ablation time were significantly shorter in the HPSD group than that in the conventional group (91.0 ± 12.1 vs. 124 ± 14.2 min, P = 0.03; 30.7 ± 19.2 vs. 57.8 ± 21 min, P = 0.02, respectively). At a mean follow-up period of 11 ± 1.4 months, there were 13 and 7 patients with recurrence in conventional and HPSD group respectively (P = 0.03).

Conclusion

Optimal ablation lesion characteristics and distribution after conventional and HPSD ablation differed significantly. HPSD ablation had shorter ablation time and lower recurrence rate than did conventional ablation.

Procedural efficiencies, lesion metrics, and 12-month clinical outcomes for Ablation Index-guided 50 W ablation for atrial fibrillation

AIMS

The safety of Ablation Index (AI)-guided 50 W ablation for atrial fibrillation (AF) remains uncertain, and mid-term clinical outcomes have not been described. The interplay between AI and its components at 50 W has not been reported.

METHODS AND RESULTS

Eighty-eight consecutive AF patients (44% paroxysmal) underwent AI-guided 50 W ablation. Procedural and 12-month clinical outcomes were compared with 93 consecutive controls (65% paroxysmal) who underwent AI-guided ablation using 35-40 W. Posterior wall isolation (PWI) was performed in 44 (50%) and 23 (25%) patients in the 50 and 35-40 W groups, respectively, P < 0.001. The last 10 patients from each group underwent analysis of individual lesions (n = 1230) to explore relationships between different powers and the AI components. Pulmonary vein isolation was successful in all patients. Posterior wall isolation was successful in 41/44 (93.2%) and 22/23 (95.7%) in the 50 and 35-40 W groups, respectively (P = 0.685). Radiofrequency times (20 vs. 26 min, P < 0.001) and total procedure times (130 vs. 156 min, P = 0.002) were significantly lower in the 50 W group. No complication or steam pop was seen in either group. Twelve-month freedom from arrhythmia was similar (80.2% vs. 82.8%, P = 0.918). A higher proportion of lesions in the 50 W group were associated with impedance drop >7 Ω (54.6% vs. 45.5%, P < 0.001). Excessive ablation (AI >600 anteriorly, >500 posteriorly) was more frequent in the 50 W group (9.7% vs. 4.3%, P < 0.001).

CONCLUSION

Ablation Index-guided 50 W AF ablation is as safe and effective as lower powers and results in reduced ablation and procedure times. Radiofrequency lesions are more likely to be therapeutic, but there is a higher risk of delivering excessive ablation.

[Pulmonary vein isolation using radiofrequency ablation]

Catheter ablation represents the primary treatment for most arrhythmias. The effectiveness of catheter ablation for the treatment of atrial fibrillation is superior to drug therapy. Therefore, catheter ablation has been established as an increasingly common procedure in clinical routine. In this context, the electrical isolation of the pulmonary veins (PVI) constitutes the cornerstone of the interventional therapy of paroxysmal and persistent atrial fibrillation. This article describes the procedure of pulmonary vein isolation utilizing radiofrequency point-by-point ablation. It shall be a practical guide for the staff in the electrophysiological laboratory. This article continues a series of manuscripts focusing on interventional electrophysiology topics in the course of EP (electrophysiology) training.This article describes the procedure of pulmonary vein isolation utilizing radiofrequency point-by-point ablation. It shall be a practical guide for the staff in the electrophysiological laboratory. This article continues a series of manuscripts dealing with topics of interventional electrophysiology in the course of EP training.

Effect of the Balloon Size on Lesion Formation During Visually Guided Laser Balloon Ablation in an In Vitro Model

BACKGROUND

It is unclear whether balloon size can influence lesion formation. The aim of this study was to evaluate the impact of balloon size on lesion formation during laser balloon procedures in an in vitro model.

METHODS AND RESULTS

Laser energy was applied to chicken muscle using a first generation laser balloon. Laser ablation was performed with 2 different balloon sizes (18 mm and 32 mm) using 2 different power settings (12 W/20 s and 8.5 W/20 s) on the chicken muscle. The lesion characteristics, including maximum lesion depth, maximum lesion diameter, surface diameter and depth at maximum diameter, were compared between the 18-mm and 32-mm balloon groups at 12 W/20 s and 8.5 W/20 s, respectively. We created 40 lesions using laser energy at 12 W/20 s and 80 lesions at 8.5 W/20 s. At both power settings, the maximum lesion depth and the depth at the maximum diameter were larger in the 18-mm than in the 32-mm balloon group. At both power settings, the maximum lesion diameter and the surface diameter were smaller in the 18-mm than in the 32-mm balloon group.

CONCLUSIONS

The balloon size could affect the lesion formation during laser balloon ablation. The lesion with the larger balloon size was wider and shallower than the lesion with the smaller balloon size.

Standardized pulmonary vein isolation workflow to enclose veins with contiguous lesions: the multicentre VISTAX trial

AIMS

To evaluate the safety and effectiveness of pulmonary vein isolation in paroxysmal atrial fibrillation (PAF) using a standardized workflow aiming to enclose the veins with contiguous and optimized radiofrequency lesions.

METHODS AND RESULTS

This multicentre, prospective, non-randomized study was conducted at 17 European sites. Pulmonary vein isolation was guided by VISITAG SURPOINT (VS target ≥550 on the anterior wall; ≥400 on the posterior wall) and intertag distance (≤6 mm). Atrial arrhythmia recurrence was stringently monitored with weekly and symptom-driven transtelephonic monitoring on top of standard-of-care monitoring (24-h Holter and 12-lead electrocardiogram at 3, 6, and 12 months follow-up). Three hundred and forty participants with drug refractory PAF were enrolled. Acute effectiveness (first-pass isolation proof to a 30-min wait period and adenosine challenge) was 82.4% [95% confidence interval (CI) 77.4-86.7%]. At 12-month follow-up, the rate of freedom from any documented atrial arrhythmia was 78.3% (95% CI 73.8-82.8%), while freedom from atrial arrhythmia by standard-of-care monitoring was 89.4% (95% CI 78.8-87.0%). Freedom fromrepeat ablations by the Kaplan-Meier analysis was 90.4% during 12 months of follow-up. Of the 34 patients with repeat ablations, 14 (41.2%) demonstrated full isolation of all pulmonary vein circles. Primary adverse event (PAE) rate was 3.6% (95% CI 1.9-6.3%).

CONCLUSIONS

The VISTAX trial demonstrated that a standardized PAF ablation workflow aiming for contiguous lesions leads to low rates of PAEs, high acute first-pass isolation rates, and 12-month freedom from arrhythmias approaching 80%. Further research is needed to improve the reproducibility of the outcomes across a wider range of centres.Clinical trial registration: ClinicalTrials.gov, number NCT03062046, https://clinicaltrials.gov/ct2/show/NCT03062046.

The impact of mechanical oesophageal deviation on posterior wall pulmonary vein reconnection

AIMS

During atrial fibrillation ablation, oesophageal heating typically prompts reduction or termination of radiofrequency energy delivery. We previously demonstrated oesophageal temperature rises are associated with posterior left atrial pulmonary vein reconnection (PVR) during redo procedures. In this study, we assessed whether mechanical oesophageal deviation (MED) during an index procedure minimizes posterior wall PVRs during redo procedures.

METHODS AND RESULTS

Patients in whom we performed a first-ever procedure followed by a clinically driven redo procedure were divided based on both the use of MED for oesophageal protection and the ablation catheter employed (force or non-force sensing) in the first procedure. The PVR sites were compared between MED using a force-sensing catheter (MEDForce), or no MED with a non-force (ControlNoForce) or force (ControlForce) sensing catheter. Despite similar clinical characteristics, the MEDForce redo procedure rate (9.2%, 26/282 patients) was significantly less than the ControlNoForce (17.2%, 126/734 patients; P = 0.002) and ControlForce (17.5%, 20/114 patients; P = 0.024) groups. During the redo procedure, the posterior PVR rate with MEDForce (2%, 1/50 PV pairs) was significantly less than with either ControlNoForce (17.7%, 44/249 PV pairs; P = 0.004) or ControlForce (22.5%, 9/40 PV pairs; P = 0.003), or aggregate Controls (18.3%, 53/289 PV pairs; P = 0.006). However, the anterior PVR rate with MEDForce (8%, 4/50 PV pairs) was not significantly different than Controls (aggregate Controls-3.5%, 10/289 PV pairs, P = 0.136; ControlNoForce-2.4%, 6/249 PV pairs, P = 0.067; ControlForce-10%, 4/40 PV pairs, P = 1.0).

CONCLUSION

Oesophageal deviation improves the durability of the posterior wall ablation lesion set during AF ablation.

Impact of a formula combining local impedance and conventional parameters on lesion size prediction

BACKGROUND

Although ablation energy (AE) and force-time integral (FTI) are well-known active predictors of lesion characteristics, these parameters do not reflect passive tissue reactions during ablation, which may instead be represented by drops in local impedance (LI). This study aimed to investigate if additional LI data improves predicting lesion characteristics and steam pops.

METHODS

RF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (8 g, 15 g, 25 g, and 35 g), and durations (10-180 s) using perpendicular/parallel catheter orientations were performed in excised porcine hearts (N = 30). The correlation between AE, FTI, and lesion characteristics was examined, and the impact of LI (%LI drop (%LID) defined by the ΔLI divided by the initial LI) was additionally assessed.

RESULTS

Three hundred seventy-five lesions without steam pops were examined. Ablation energy (W × s) and FTI (g × s) showed a positive correlation with lesion depth (ρ = 0.824:P < 0.0001 and ρ = 0.708:P < 0.0001), surface area (ρ = 0.507:P < 0.0001 and ρ = 0.562:P < 0.0001), and volume (ρ = 0.807:P < 0.0001 and ρ = 0.685:P < 0.0001). %LID also showed a positive correlation individually with lesion depth (ρ = 0.643:P < 0.0001), surface area (ρ = 0.547:P < 0.0001), and volume (ρ = 0.733:P < 0.0001). However, the combined indices of AE × %LID (AE multiplied by %LID) and FTI × %LID (FTI multiplied by %LID) provided significantly stronger correlation with lesion depth (ρ = 0.834:P < 0.0001 and ρ = 0.809:P < 0.0001), surface area (ρ = 0.529:P < 0.0001 and ρ = 0.656:P < 0.0001), and volume (ρ = 0.864:P < 0.0001 and ρ = 0.838:P < 0.0001). This tendency was observed regardless of the catheter placement (parallel/perpendicular). AE (P = 0.02) and %LID (P = 0.002) independently remained as significant predictors to predict steam pops (N = 27). However, the AE × %LID did not increase the predictive power of steam pops compared to the AE alone.

CONCLUSION

LI, when combined with conventional parameters (AE and FTI), may provide stronger correlation with lesion characteristics.

Pulmonary vein isolation guided by moderate ablation index targets combined with strict procedural endpoints for patients with paroxysmal atrial fibrillation

INTRODUCTION

Ablation index (AI)-guided radiofrequency ablation has been increasingly used for the treatment of drug-resistant paroxysmal atrial fibrillation (AF)，but the optimal AI targets remain to be determined. We aimed to examine the efficacy and safety of catheter ablation guided by moderate AI values but more strict procedural endpoints in patients with paroxysmal AF.

METHODS

We conducted a retrospective review of a consecutive series of patients who received their first AI-guided ablation for paroxysmal AF from 2017 to 2018. The standard procedural protocol recommends AI targets as follows: anterior: 400-450; posterior: 280-330; and roof/inferior wall: 380-430. After circumferential pulmonary vein isolation (PVI), we performed bipolar pacing along the ablation line, adenosine triphosphate (ATP)-provocation, and waited for 30 min to verify PVI. The primary clinical outcome was the rate of freedom from AF recurrence at 12 months.

RESULTS

A total of 140 consecutive patients were included. The mean procedure and ablation times were 132.2 ± 30.2 min and 24.2 ± 7.9 min, respectively. The first-pass isolation and final isolation rates were documented in 49.3% and in 100% of the patients, respectively. At 12 months, single-procedure freedom from atrial tachyarrhythmias was observed in 92.1% of patients. No major procedure-related complications were encountered.

CONCLUSIONS

Moderate AI-guided catheter ablation is highly effective for the treatment of drug-refractory paroxysmal AF in real-world settings. Over 90% of patients achieved single-procedure arrhythmia-free survival at 1 year. The outcome was obtained without major complications and the procedure involved relatively short procedure and ablation times.

Optimizing Durability in Radiofrequency Ablation of Atrial Fibrillation

Radiofrequency ablation (RFA) remains a highly effective therapy in the management of paroxysmal atrial fibrillation (PAF) and is an important therapeutic option in the management of persistent atrial fibrillation (PeAF) when clinically indicated. Lesion size is influenced by many parameters, which include those related to energy application (RFA power, temperature, and time), delivery mechanism (electrode size, orientation, and contact force), and the environment (blood flow and local tissue contact, stability, and local impedance). Successful durable RFA is dependent on achieving lesions that are reliably transmural and contiguous, whilst also avoiding injury to the surrounding structures. This review focuses on the variables that can be adjusted in connection with RFA to achieve long-lasting lesions that enable patients to derive the maximum sustained benefit from pulmonary vein isolation and additional lesion sets if utilized.

Pulmonary vein isolation in atrial fibrillation patients guided by a novel local impedance algorithm: 1-year outcome from the CHARISMA study

BACKGROUND

Highly localized impedance (LI) measurements during atrial fibrillation (AF) ablation have recently emerged as a viable real-time indicator of tissue characteristics and durability of the lesions created. We report the outcomes of acute and long-term clinical evaluation of the new DirectSense algorithm in AF ablation.

METHODS

Consecutive patients undergoing AF ablation were included in the CHARISMA registry. RF delivery was guided by the DirectSense algorithm, which records the magnitude and time-course of the impedance drop. The ablation endpoint was pulmonary vein isolation (PVI), as assessed by the entrance and exit block.

RESULTS

3556 point-by-point first-pass RF applications of >10 s duration were analyzed in 153 patients (mean age=59 ± 10 years, 70% men, 61% paroxysmal AF, 39% persistent AF). The mean baseline LI was 105 ± 15 Ω before ablation and 92 ± 12 Ω after ablation (p < .0001). Both absolute drops in LI and the time to LI drop (LI drop/τ) were greater at successful ablation sites (n = 3122, 88%) than at ineffective ablation sites (n = 434, 12%) (14 ± 8 Ω vs 6 ± 4 Ω, p < .0001 for LI; 0.73 [0.41-1.25] Ω/s vs. 0.35[0.22-0.59 Ω/s, p < .0001 for LI drop/τ). No major complications occurred during or after the procedures. All PVs had been successfully isolated. During a mean follow-up of 366 ± 130 days, 18 patients (11.8%) suffered an AF/atrial tachycardia recurrence after the 90-day blanking period.

CONCLUSION

The magnitude and time-course of the LI drop during RF delivery were associated with effective lesion formation. This ablation strategy for PVI guided by LI technology proved safe and effective and resulted in a very low rate of AF recurrence over 1-year follow-up.

Impact of ablation index settings on pulmonary vein reconnection

PURPOSE

Ablation index (AI) is a radiofrequency lesion quality marker. The AI value that allows effective and safe pulmonary vein isolation (PVI) is still debated. We evaluated the incidence of acute and late PV reconnection (PVR) with different AI settings and its predictors.

METHODS

The Ablation Index Registry is a multicenter study that included patients with paroxysmal/persistent atrial fibrillation (AF) who underwent first-time ablation. Each operator performed the ablation using his preferred ablation catheter (ThermoCool® SmartTouch or Surround Flow) and AI setting (380 posterior-500 anterior and 330 posterior-450 anterior). We divided the study population into two groups according to the AI setting used: group 1 (330-450) and group 2 (380-500). Incidence of acute PVR was validated within 30 min after PVI, whereas the incidence of late PVR was evaluated at repeat procedure.

RESULTS

Overall, 490 patients were divided into groups 1 (258) and 2 (232). There was no significant difference in the procedural time, fluoroscopy time, and rate of the first-pass PVI between the two study groups. Acute PVR was observed in 5.6% PVs. The rate of acute PVR was slightly higher in group 2 (64/943, 6.8%, PVs) than in group 1 (48/1045, 4.6% PVs, p = 0.04). Thirty patients (6%) underwent a repeat procedure and late PVR was observed in 57/116 (49%) PVs (number of reconnected PV per patient of 1.9 ± 1.6). A similar rate of late PVR was found in the two study groups. No predictors of acute and late PVR were found.

CONCLUSION

Ablation with a lower range of AI is highly effective and is not associated with a higher rate of acute and late PVR. No predictors of PV reconnection were found.

Radiofrequency ablation lesions in low-, intermediate-, and normal-voltage myocardium: an in vivo study in a porcine heart model

AIMS

Contact force (CF) between radiofrequency (RF) ablation catheter and myocardium and ablation index (AI) correlates with RF lesion depth and width in normal-voltage (>1.5 mV) myocardium (NVM). We investigate the impact of CF on RF lesion depth and width in low (<0.5 mV) (LVM) and intermediate-voltage (0.5-1.5 mV) myocardium (IVM) following myocardial infarction. Correlation between RF lesion depth and width evaluated by native contrast magnetic resonance imaging (ncMRI) and gross anatomical evaluation was investigated.

METHODS AND RESULTS

Twelve weeks after myocardial infarction, 10 pigs underwent electroanatomical mapping and endocardial RF ablations were deployed in NVM, IVM, and LVM myocardium. In vivo ncMRI was performed before the heart was excised and subjected to gross anatomical evaluation. Ninety (82%) RF lesions were evaluated. Radiofrequency lesion depth and width were smaller in IVM and LVM compared with NVM (P < 0.001). Radiofrequency lesion depth and width correlated with CF, AI, and impedance drop in NVM (CF and AI P < 0.001) and IVM (CF and AI depths P < 0.001; CF and AI widths P < 0.05). Native contrast magnetic resonance imaging evaluated RF lesion depth and width correlated with gross anatomical depth and width (NVM and IVM P < 0.001; LVM P < 0.05).

CONCLUSIONS

Radiofrequency lesions deployed by similar duration, power and CF are smaller in IVM and LVM than in NVM. Radiofrequency lesion depth and width correlated with CF, AI, and impedance drop in NVM and IVM but not in LVM. Native contrast magnetic resonance imaging may be useful to assess RF lesion depth and width in NVM, IVM, and LVM.

Tailored ablation index for pulmonary vein isolation according to wall thickness within the ablation circle

BACKGROUND

Ablation index (AI), a novel lesion quality marker, includes contact force, time, and power of radiofrequency (RF) application, but not regional variation in wall thickness within the wide antral catheter ablation (WACA) circle. This study explored the relationships among AI target value, atrial wall thickness, and gap formation within the WACA circle in patients with paroxysmal atrial fibrillation (PAF).

METHODS

We evaluated 102 consecutive patients (mean age, 65 ± 9 years) with PAF who underwent AI-guided WACA for ipsilateral pulmonary vein isolation (PVI). Each WACA circle was subdivided into eight segments, and overall 7143 RF applications were delivered, including 125 gaps in PVI ablation lines. For each RF tag within the ablation circle, we collected data on ablation lesion depth surrogates (time of application, delivery power, impedance drop, average contact force, force-time integral [FTI], and AI) and left atrial wall thickness measured by multidetector computer tomography scanning.

RESULTS

The anterior and roof walls were the thickest segments of the ablation circle, in which 85.8% of gaps concentrated, while the posterior and inferior walls were the thinnest. Gap formation was significantly associated with FTI, AI, wall thickness, FTI/wall thickness, and AI/wall thickness. AI/wall thickness had the highest predictive value for gap formation, with a cutoff of 195.6 au/mm for effective ablation.

CONCLUSIONS

In AI-guided PVI of PAF, AI/wall thickness by normalizing myocardial thickness variation along the WACA circle was a strong predictor of gap formation, with a target of 195.6 au/mm appearing suitable for effective ablation.

Repeat pulmonary vein isolation in patients with atrial fibrillation: low ablation index is associated with increased risk of recurrent arrhythmia

OBJECTIVES

We aimed to investigate the predictors of recurrent arrhythmia after repeated pulmonary vein isolation (PVI) performed in the era of contact force without additional substrate ablation. One of the predictors studied, ablation index (AI), incorporates power, contact force, and time in a weighted formula and is reported to predict lesion size in animals. Design. Consecutive patients (n = 108) undergoing repeat PVI without additional substrate modification using a contact force sensing catheter were included retrospectively at a tertiary center. All ablation points were analyzed offline. A new variable, normalized AI (AI corrected for the location of the lesion-anterior vs. posterior) was calculated. The patients were systematically followed with clinical visit and 12-lead ECG as well as review of the regional electronic patient files at 3 and 12 months after the procedure with 5-day Holter at 12 months. Results. Electrical reconnection to at least one pulmonary vein (PV) was seen in 97% of the patients. The recurrence rate was 35%. There was no recurrence in patients with nAI above 1.15 (n = 26). Patients with electrical reconnection of up to two PVs had a higher risk of recurrence compared with patients having electrical reconnection of three or four PVs (p = .003), and this risk was especially high in patients with persistent atrial fibrillation (69 [39-91]%). Conclusions. The risk of recurrence is higher in patients with ablations performed with low levels of AI and in patients with reconnection to up to two PVs. Our data may indicate the need for higher target levels of AI during repeat PVI than normally used during de-novo PVI.

A circular mapping catheter is not mandatory for isolating pulmonary veins during paroxysmal atrial fibrillation ablation with radiofrequency

PURPOSE

In this study, we evaluated the feasibility, efficacy, and safety of radiofrequency ablation of paroxysmal atrial fibrillation (AF) with the use of an ablation catheter only (non-CMC group) by retrospectively comparing its procedural success and recurrence rates at 1 year to ablation performed with the help of a circular mapping catheter (CMC group).

METHODS

We compared the success and recurrence rates between 226 patients and 251 patients who underwent index ablation with and without the use of CMC, respectively.

RESULTS

Freedom from recurrence was defined as a 1-year absence of AF/atrial tachycardia (AT) episodes > 30 s, beyond the 3-month blanking period. There was no significant difference between the number of pulmonary vein isolations, recurrence rate of AF/AT, and the use of antiarrhythmic drugs after 1 year of ablation. The procedure and fluoroscopy times were lower in the non-CMC group compared with the CMC group (106 ± 33 vs. 125 ± 32 min, p < 0.0001; 2.2 ± 1.9 vs. 2.7 ± 2.3 min, p = 0.0002, respectively).

CONCLUSIONS

Pulmonary vein isolation without the use of a CMC is feasible; moreover, the material costs, procedure time, and radiation exposure were reduced compared with the CMC group. Freedom of recurrence was similar between groups. Optimized use of 3D electro-anatomical mapping systems could reduce the radiation exposure for both the patient and physician.

A Prospective Registry of Atrial Fibrillation Ablation with the Ablation Index Technology: Rationale and Study Design

This is a prospective multicenter registry of atrial fibrillation (AF) ablation with the Ablation Index (AI) technology, which has been introduced as a marker predicting ablation lesion depth. The index incorporates the main parameters of radiofrequency point-by-point ablation: power, contact force, and time of ablation. The AI is calculated for every operator depending on personal skills, and there are no strict indications on the range of the parameter considering its safety and efficacy during pulmonary vein isolation. The registry aims to evaluate AI values used in different centers by different operators and to evaluate the optimal limits associated with better acute and long-term AF ablation results.

Localization of Residual Conduction Gaps After Wide Antral Circumferential Ablation of Pulmonary Veins

Ablation of atrial fibrillation (AF) is the cornerstone therapy for patients with symptomatic AF resistant to anti-arrhythmic drugs or as first-line therapy, and is based on permanent pulmonary vein (PV) isolation. The presence of a conduction gap in a wide antral circumferential ablation lesion around PVs is often sufficient to transform an initially successful ablation into a procedural failure, thus necessitating a redo intervention. The strategy during a redo procedure is based on the detection and ablation of the reconnection gap. Finding gaps is often simple, but also sometimes challenging, because gaps may be difficult to detect, resulting in unnecessary radiofrequency delivery. The present review aimed to describe the various techniques published thus far to detect residual reconnections along the encircling ablation lines around PVs, to help electrophysiologists to detect and ablate reconnection gaps.

Pulmonary vein encirclement using an Ablation Index-guided point-by-point workflow: cardiovascular magnetic resonance assessment of left atrial scar formation

AIMS 

A point-by-point workflow for pulmonary vein isolation (PVI) targeting pre-defined Ablation Index values (a composite of contact force, time, and power) and minimizing interlesion distance may optimize the creation of contiguous ablation lesions whilst minimizing scar formation. We aimed to compare ablation scar formation in patients undergoing PVI using this workflow to patients undergoing a continuous catheter drag workflow.

METHODS AND RESULTS

Post-ablation cardiovascular magnetic resonance imaging was performed in patients undergoing 1st-time PVI using a parameter-guided point-by-point workflow (n = 26). Total left atrial scar burden and the width and continuity of the pulmonary vein encirclement were determined on analysis of atrial late gadolinium enhancement sequences. Comparison was made with a cohort of patients (n = 20) undergoing PVI using continuous drag lesions. Mean post-ablation scar burden and scar width were significantly lower in the point-by-point group than in the control group (6.6 ± 6.8% vs. 9.6 ± 5.0%, P = 0.03 and 7.9 ± 3.6 mm vs. 10.7 ± 2.3 mm, P = 0.003). More complete bilateral pulmonary vein encirclements were seen in the point-by-point group (P = 0.038). All patients achieved acute PVI.

CONCLUSION

Pulmonary vein isolation using a point-by-point workflow is feasible and results in a lower scar burden and scar width with more complete pulmonary vein encirclements than a conventional drag lesion approach.

Regional differences in the effects of the ablation index and interlesion distance on acute electrical reconnections after pulmonary vein isolation

BACKGROUND

In pulmonary vein isolation, the regional differences in the ablation index (AI) and interlesion distance (ILD) remain unclear. This study aimed to evaluate the association between the AI, ILD, and other relevant indices with pulmonary vein reconnections (PVRs) during the surgical intervention with a focus on the heterogeneous regional variability through a retrospective analysis.

METHODS

We divided the wide area circumferential ablation (WACA) region into 12 segments in 32 consecutive patients, which resulted in a 384 segment analysis to evaluate the association of the minimum AI (AI min) and maximum ILD (ILD max) with acute PVRs, which were defined as spontaneous PVRs or dormant conduction after adenosine triphosphate administration.

RESULTS

Acute PVRs were observed in 48 (13%) segments and 40 (63%) WACA regions. The AI min was significantly lower and ILD max greater in segments with PVRs than in those without (372 vs 403 au and 6.5 vs 5.7 mm, respectively). PVRs were more frequent in the left posterior segments, adjacent to the esophagus, than in other segments (23% vs 10%, respectively). Notably, ILD max was significantly greater in the left posterior segments with acute PVRs with AI min < 297 (median; 6.5 vs 5.1 mm); a similar finding was not observed when with AI min ≥ 297.

CONCLUSION

Smaller ILD may prevent acute PVRs when the AI min is low in the left posterior segments.

One-year outcome and durability of pulmonary vein isolation after prospective use of ablation index for catheter ablation in patients with persistent atrial fibrillation

BACKGROUND

Radiofrequency (RF) catheter ablation for persistent atrial fibrillation (peAF) is associated with less favorable outcomes than for paroxysmal AF (PAF). Recent studies have shown improved clinical outcomes with use of ablation index (AI) targets for pulmonary vein isolation (PVI) in PAF. AI is a novel ablation quality marker that incorporates contact force (CF), time, and power in a weighted formula. This is a single-arm registry to investigate the 1-year efficacy of AF ablation guided by the AI in patients with peAF, and further to evaluate pulmonary vein reconduction at repeat electrophysiology study in case of recurrent AF.

METHODS

In total, 55 consecutive patients (69 ± 10 years, 55% male, median time since first AF diagnosis: 31 months (Q1-Q3: 10-70)) with peAF underwent AIguided PVI using a CF surround-flow catheter. AI targets were 600 for anterior and 450 for roof/posterior/inferior antral segments. Patients were monitored for atrial tachyarrhythmia recurrence using 5-day Holter-ECG recordings at 3, 6, and 12 months.

RESULTS

The median procedure time was 173 min (Q1-Q3: 152-204). The median fluoroscopy time was 4 min (Q1-Q3: 3-6) and the median fluoroscopy dose was 2.64 Gy/cm2 (Q1-Q3: 1.04-3.99). The median ablation time was 57 min (Q1-Q3: 47-63). At 12 months, 42% of the patients were in sinus rhythm. AF recurrence was seen in 58% of patients. No major complications occurred.

CONCLUSIONS

RF ablation using AI in peAF is a feasible and safe technique. At 1 year, AI-guided ablation was associated with AF recurrence in 58% of the patients.

Optimal interlesion distance in ablation index-guided pulmonary vein isolation for atrial fibrillation

PURPOSE

Ablation index (AI) is a useful tool of the CARTO® system to make effective lesions during pulmonary vein isolation (PVI) for atrial fibrillation (AF). However, the optimal distance between neighboring ablation points (interlesion distance (ILD)) is still unclear. Here, we evaluated the optimal ILDs in the AI-guided PVI.

METHODS

Forty-nine AF patients who underwent AI-guided PVI in our institute from July 2018 to March 2019 were retrospectively enrolled in this study. Target AI was set at 500 and 400 for anterior and posterior walls, respectively, and we compared the ILDs with and without electrical gaps after a first encircling PVI.

RESULTS

In both PV, the ILDs with electrical gaps were longer than those without electrical gaps. The best cutoff values of ILD to detect the electrical gaps using the ROC curve were 5.4 mm for the RPV anterior wall (AUC, 0.67; sensitivity, 0.42; specificity, 0.84, P < 0.01) and 4.4 mm for the RPV posterior wall (AUC, 0.68; sensitivity, 0.91; specificity, 0.39, P < 0.01). Similarly, the best cutoff values of ILD were 5.5 mm for the LPV anterior wall (AUC, 0.74; sensitivity, 0.65; specificity, 0.82, P < 0.01) and 5.1 mm for the LPV posterior wall (AUC, 0.67; sensitivity, 0.79; specificity, 0.53, P =0.03).

CONCLUSION

The optimal interlesion distances for PVI were different in each PV segment. To achieve the first-pass isolation, less than 5.4/4.4 mm for the RPV anterior/posterior and 5.5/5.1 mm for the LPV anterior/posterior walls of interlesion distances were the best cutoff values in the patients with AF.

Single transseptal puncture technique and contact force catheter: A simplified ablation strategy for paroxysmal atrial fibrillation

The present study aimed to evaluate the safety and efficacy of an optimized single transseptal puncture technique and contact force sensing atrial fibrillation (AF) radiofrequency catheter ablation (RFCA) strategy within a clinical setting. Fast anatomic mapping and contact force sensing ablation was applied to patients with paroxysmal AF (PAF) ablation between September 2014 and December 2016 using a single trans-septal sheath. Pulmonary vein isolation (PVI) and linear ablation were performed in PAF individually with a 10-20 g contact force with minimal fluoroscopy. Stimulation with 10 mA outputs on the lesions without capture was used as endpoint. A total of 419 consecutive patients who underwent first-time RFCA were enrolled in the current study, and acute PVI was achieved in all patients. The average procedure time was 74.5±9.7 min, with an average ablation time of 27.3±7.8 min. The average fluoroscopy time was 4.7±3.3 min and the average radiation dose was 24.3±25.2 mGy. At a mean follow-up time of 14.5 ± 4.1 months, sinus rhythm was maintained at 85.0%. Cardiac tamponade occurred in one case. The results indicated that this simplified technique was a simple, safe and effective approach for PAF ablation therapy.

The feasibility and effectiveness of a streamlined single-catheter approach for radiofrequency atrial fibrillation ablation

BACKGROUND

Catheter ablation for atrial fibrillation (AF) traditionally requires the use of circular mapping catheter (CMC) for pulmonary vein isolation (PVI). This study aimed to assess the feasibility and effectiveness of a CMC-free approach for AF ablation performed by a contiguous optimized (CLOSE) ablation protocol.

METHODS

A CLOSE-guided and CMC-free PVI protocol with a single transseptal puncture was attempted in 67 patients with AF. Left atrial (LA) CARTO voltage mapping was performed with the ablation catheter pre- and postablation to demonstrate entry block into the pulmonary veins, and pacing maneuvers were used to confirm exit block.

RESULTS

The CMC-free approach was successful in achieving PVI in 66 (98.5%) cases, with procedure time of 148 ± 32 minutes, ablation time of 27.5 ± 5.7 minutes, and fluoroscopy time of 7.8 ± 1.0 minutes. First-pass PVI was seen in 58(86.5%) patients, and pacing maneuvers successfully identified the residual gap in eight of the other nine cases. No complication was observed. At 12 months follow-up, 60 (89.6%) patients remained free from AF. The CMC-free approach resulted in a cost saving of £47,190.

CONCLUSION

A CMC-free CLOSE-guided PVI approach is feasible, safe, and cost-saving, and is associated with excellent clinical outcomes at 1 year.

Randomized study defining the optimum target interlesion distance in ablation index-guided atrial fibrillation ablation

Aims

While the CLOSE protocol proposes a maximally tolerable interlesion distance (ILD) of 6 mm for ablation index ablation index-guided atrial fibrillation (AF) ablation, a target ILD has never been defined. This randomized study sought to establish a target ILD for ablation index-guided AF ablation.

Methods and results

Consecutive patients scheduled for first-time pulmonary vein (PV) isolation (PVI) were randomly assigned to ablation protocols with a target ILD of 5.0–6.0 mm or 3.0–4.0 mm, with the primary endpoint of first-pass PVI. In compliance with the CLOSE protocol, the maximum tolerated ILD was 6.0 mm in both study protocols. A target ablation index of ≥550 (anterior) or ≥400 (posterior) was defined for the ‘5–6 mm’ protocol and ≥500 (anterior) or ≥350 (posterior) for the ‘3–4 mm’ protocol. The study was terminated early for superiority of the ‘3–4 mm’ protocol. Forty-two consecutive patients were randomized and 84 ipsilateral PV pairs encircled according to the study protocol. First-pass PVI was accomplished in 35.0% of the ‘5–6 mm’ group and 90.9% of the ‘3–4 mm’ group (P &lt; 0.0001). Median ILD was 5.2 mm in the ‘5–6 mm’ group and 3.6 mm in the ‘3–4 mm’ group (P &lt; 0.0001). In line with the distinct ablation index targets, median ablation index was lower in the ‘3–4 mm’ group (416 vs. 452, P &lt; 0.0001). While mean procedure time was shorter in the ‘3–4 mm’ group (149 ± 27 vs. 167 ± 33min, P = 0.004), fluoroscopy times did not differ significantly (4.7 ± 2.2 vs. 5.1 ± 1.8 min, P = 0.565).

Conclusion

In ablation index-guided AF ablation, an ILD of 3.0–4.0 mm should be targeted rather than 5.0–6.0 mm. Moreover, the lower target ILD may allow for less extensive ablation at each given point.

Impact of local left atrial wall thickness on the incidence of acute pulmonary vein reconnection after Ablation Index-guided atrial fibrillation ablation

•

Ablation Index-guided ablation allows for ablation lesions of consistent depth.

•

Ablation Index-guided ablation is limited by ignoring local wall thickness.

•

Local atrial wall thickness is associated with acute pulmonary vein reconnection.

•

Wall thickness adjusted Ablation Index targets may improve ablation outcomes.

Background

Although Ablation Index (AI)-guided ablation facilitates creation of lesions of consistent depth, pulmonary vein (PV) reconnection is still commonly observed after AI-guided pulmonary vein isolation (PVI). The present study aimed to investigate the impact of local left atrial wall thickness on the incidence of acute PV reconnection after AI-guided atrial fibrillation (AF) ablation.

Methods and results

Seventy patients (63% paroxysmal AF, 67% male, mean age 63 ± 8 years) who underwent preprocedural CT imaging and AI-guided AF ablation were studied. Occurrence of acute PV reconnection after initial PVI was assessed after a 30-minute waiting period. Ablation procedures were retrospectively analyzed and each ablation circle was subdivided into 8 segments. Minimum AI, force-time integral, contact force, ablation duration, power, impedance drop and maximum interlesion distance were determined for each segment. PV antrum wall thickness was assessed for each segment on reconstructed CT images based on patient-specific thresholds in Hounsfield Units. Acute reconnection occurred in 27/1120 segments (2%, 15 anterior/roof, 12 posterior/inferior) in 19/140 ablation circles (14%). Reconnected segments were characterized by a greater local atrial wall thickness, both in anterior/roof (1.87 ± 0.42 vs. 1.54 ± 0.42 mm; p < 0.01) and posterior/inferior (1.43 ± 0.20 vs. 1.16 ± 0.22 mm; p < 0.01) segments. Minimum AI, force-time integral, contact force, ablation duration, power, impedance drop and maximum interlesion distance were not associated with acute reconnection.

Conclusions

Local atrial wall thickness is associated with acute pulmonary vein reconnection after AI-guided PVI. Individualized AI targets based on local wall thickness may be of use to create transmural ablation lesions and prevent PV reconnection after PVI.

Differences between gap-related persistent conduction and carina-related persistent conduction during radiofrequency pulmonary vein isolation

BACKGROUND

During pulmonary vein isolation (PVI), nonisolation after initial encircling of the pulmonary veins (PVs) may be due to gaps in the initial ablation line, or alternatively, earliest PV activation may occur on the intervenous carina and ablation within the wide-area circumferential ablation (WACA) circle is needed to eliminate residual conduction. This study investigated prognostic implications and predictors of gap-related persistent conduction (gap-RPC) and carina-related persistent conduction (carina-RPC) during PVI.

METHODS AND RESULTS

Two hundred fourteen atrial fibrillation (AF) patients (57% paroxysmal, 61% male, mean age 62 ± 9 years) undergoing first contact force-guided radiofrequency PVI were studied. Preprocedural cardiac computed tomography imaging was used to assess left atrial and PV anatomy. PVI was assessed directly after initial WACA circle creation, after a minimum waiting period of 30 minutes, and after adenosine infusion. Persistent conduction was targeted for additional ablation and classified as gap-RPC or carina-RPC, depending on the earliest activation site. The 1-year AF recurrence rate was higher in patients with gap-RPC (47%) compared to patients without gap-RPC (28%; P = .003). No significant difference in 1-year recurrence rate was found between patients with carina-RPC (37%) and patients without carina-RPC (31%; P = .379). Multivariate analyses identified paroxysmal AF and WACA circumference as independent predictors of gap-RPC, whereas carina width and WACA circumference correlated with carina-RPC.

CONCLUSIONS

Gap-RPC is associated with increased AF recurrence risk after PVI, whereas carina-RPC does not predict AF recurrence. Moreover, gap-RPC and carina-RPC have different correlates and may thus have different underlying mechanisms.

Risk of esophageal thermal injury during catheter ablation for atrial fibrillation guided by different ablation index

BACKGROUND

During ablation for atrial fibrillation (AF), energy delivery toward the left atrial posterior wall may cause esophageal injury (EI). Ablation index (AI) was introduced to estimate ablation lesion size, however, the impact of AI technology on the risk of EI has not been explored.

METHOD

From March 2019 to December 2019, 60 patients with paroxysmal AF undergoing first-time ablation were prospectively enrolled. The first 30 consecutive patients were ablated with the AI target value of 400 (AI-400 group), and the later 30 consecutive patients were ablated with the AI target value of 350 at the posterior wall (AI-350 group). Endoscopic ultrasonography was used to evaluate EI postablation. EI was classified as a category 1 (erythema or erosion) or a category 2 (hematoma or ulceration).

RESULTS

Compared with the AI-400 group (59.9 ± 8.4 years; male, 60%), the AI-350 group (59.1 ± 9.9 years; male, 50%) had a lower incidence of EI (3.3% vs 26.7%, P = .03). There was no significant difference in the percentage of first-pass PVI between the AI-400 group and the AI-350 group (left PVI: 80% vs 73.4%, P = .54; right PVI: 80% vs 60%, P = .1). Neither ablation time nor fluoroscopy time was significantly different between the AI-400 group and the AI-350 group.

CONCLUSIONS

AF ablation guide by AI target value of 350 may reduce esophageal thermal injury and has a similar efficiency on the acute success rate of first-pass PVI compared with an AI target value of 400 at the posterior wall.

Reproducibility of pulmonary vein isolation guided by the ablation index: 1-year outcome of the AIR registry

BACKGROUND

Ablation index (AI) is a new lesion quality marker that has been demonstrated to allow a high single-procedure arrhythmia-free survival in single-center studies. This prospective, multi-center study was designed to evaluate the reproducibility of pulmonary vein (PV) isolation guided by the AI.

METHODS

A total of 490 consecutive patients with paroxysmal (80.4%) and persistent AF underwent first time PV isolation and were divided in four study groups according to operator's preference in choosing the ablation catheter (a contact force (ST) or contact force surround flow (STSF) catheter) and the AI setting (330-450 or 380-500 at anterior wall or posterior wall, respectively).

RESULTS

At 12 months a high rate of freedom from AF recurrences was observed in patients with both paroxysmal and persistent AF (91% vs 83.3%; P = .039). There was no difference in the rate of AF recurrence among the four study groups (4.5% in group ST330-450, 12.2% in group ST 380-500, 14.9% in group STSF330-450, 9.4% in group STSF380-500; P = .083). Recurrence was also similar between patients treated with a ST (8%) or STSF catheter (12.1%; P = .2), and within patients targeting an AI settings of 330 to 450 (10.9%) or 380 to 500 (10.3%; P = .64). In patients with paroxysmal AF, there was no difference (P = .12) in the 1-year freedom from AF recurrence among 14 operators that performed ≥10 ablation procedure.

CONCLUSIONS

An ablation protocol respecting strict criteria for contiguity and quality lesion resulted in high rate of 1-year freedom from AF recurrence, irrespective of the ablation catheters, AI settings, and operator.

Combined local impedance and contact force for radiofrequency ablation assessment

BACKGROUND

The combination of contact force (CF) and local impedance (LI) may improve tissue characterization and lesion prediction during radiofrequency (RF) ablation.

OBJECTIVE

The purpose of this study was to evaluate the utility of LI combined with CF in assessing RF ablation efficacy.

METHODS

An LI catheter with CF sensing was evaluated in swine (n = 11) and in vitro (n = 14). The relationship between LI and CF in different tissue types was evaluated in vivo. Discrete lesions were created in vitro and in vivo at a range of forces, powers, and durations. Finally, an intercaval line was created in 3 groups at 30 W: 30s, Δ20Ω, and Δ30Ω. In the Δ20Ω and Δ30Ω groups, the user ablated until a 20 or 30 Ω LI drop. In the 30s group, the user was blinded to LI.

RESULTS

In vivo, distinction in LI was found between the blood pool and the myocardium (blood pool: 122 ± 7.02 Ω; perpendicular contact: 220 ± 29 Ω; parallel contact: 207 ± 31 Ω). LI drop correlated with lesion depth both in vitro (R = 0.84) and in vivo (R = 0.79), informing sufficient lesion creation (LI drop >20 Ω) and warning of excessive heating (LI drop >65 Ω). When creating an intercaval line, the total RF time was significantly reduced when using LI guidance (6.4 ± 2 minutes in Δ20Ω and 8.1 ± 1 minutes in Δ30Ω) compared with a standard 30-second workflow (18 ± 7 minutes). Acute conduction block was achieved in all Δ30Ω and 30s lines.

CONCLUSION

The addition of LI to CF provides feedback on both electrical and mechanical loads. This provides information on tissue type and catheter-tissue coupling; provides feedback on whether volumetric tissue heating is inadequate, sufficient, or excessive; and reduces ablation time.

Revaluation of the Significance of Demonstrable Exit Block After Radiofrequency Pulmonary Vein Isolation

Background: Demonstration of exit block from the pulmonary vein (PV) to the left atrium after PV isolation (PVI) is not always possible after demonstration of entrance block. We examined factors associated with demonstrable exit block and the relationship between demonstrable exit block and subsequent PV reconnection. Methods and Results: The subjects consisted of 227 patients (908 PV; mean patient age, 59.2±10.8 years; 72.2% male) who underwent radiofrequency PVI, 49 of whom proceeded to the second session after a mean duration of 563.4±456.3 days after the first session. In the first session, exit block was demonstrated in 73.1% of PV, and the predictors were superior PV, longitudinal diameter of the PV, and spontaneous activity in the PV. In the second session (n=49), exit block was demonstrated in 51.0% (33.1% in PV without reconnection vs. 79.7% in PV with reconnection, P<0.0001). Spontaneous activity (OR, 2.74; 95% CI: 1.12-7.03, P=0.0272) and use of a contact force-sensing catheter (OR, 0.42, 95% CI: 0.20-0.85, P=0.0151) were independent predictors of PV reconnection, but demonstrable exit block was not (OR, 1.58; 95% CI: 0.74-3.46, P=0.2377). Conclusions: Inability to demonstrate exit block was not associated with increased risk of future PV reconnection.

Ablation of persistent atrial fibrillation: Challenges and solutions

Catheter ablation is commonly used for treatment of persistent atrial fibrillation (AF). Pulmonary vein isolation (PVI) is still the cornerstone for the procedure, however, outcomes are consistently lower compared to paroxysmal AF. It is hypothesized that it could be due to lack of durable lesions or the presence of non-PV targets that remain after PVI. Numerous advances in ablation catheter technologies and mapping systems may potentially achieve lower recurrence rates in the future. Ongoing research is required to discover the best technique for persistent AF ablation. The purpose of this review is to describe the new, developing technologies that may improve the outcome of this procedure in the persistent AF population.

Persistent atrial fibrillation in the setting of pulmonary vein isolation-Where to next?

Catheter ablation for atrial fibrillation (AF) is indicated in symptomatic patients who are intolerant or refractory to antiarrhythmic therapy. However, outcomes from catheter ablation remain suboptimal in patients with persistent AF. Pulmonary vein antral isolation (PVAI) is established as the cornerstone of AF ablation strategies. The landmark STAR AF II study demonstrated a lack of incremental benefit with adjunctive linear and complex fractionated electrogram ablation beyond PVAI. Randomized studies thus far have failed to consistently show favorable outcomes from other trigger/substrate-based ablation approaches over PVAI alone. In this issue of the journal, we pose an interesting clinical scenario-of a middle-aged female who presents with recurrent persistent AF but was found to have enduring PVAI on repeat electrophysiologic study. Which approach should be undertaken next? In this review article, we aim to provide an overview of ablation strategies beyond PVAI. Finally in light of scant randomized data to guide decision making we have approached leading experts in the field to provide their approach to this scenario.

Long-term impact of catheter ablation on arrhythmia burden in low-risk patients with paroxysmal atrial fibrillation: The CLOSE to CURE study

BACKGROUND

Few studies evaluated the impact of catheter ablation (CA) on atrial tachyarrhythmia (ATA) burden in paroxysmal atrial fibrillation (AF).

OBJECTIVE

In the prospective, patient-controlled CLOSE to CURE study, we determined the longer-term impact of optimized CA on ATA burden by using an insertable cardiac monitor (ICM).

METHODS

A total of 105 patients with paroxysmal AF were implanted with an ICM 65 (interquartile range [IQR] 61-78) days before CA. CA consisted of contact force-guided pulmonary vein isolation targeting an intertag distance of ≤6 mm and a region-specific ablation index. The primary end point was reduction in ICM-detected ATA burden; secondary end points were single-procedure freedom from ATA, quality of life, and adverse events.

RESULTS

The mean age was 62 ± 8 years; the median CHA₂DS₂-VASc score was 1 (IQR 1-2); and the median left atrial diameter was 43 (IQR 39-43) mm. After pulmonary vein isolation (1.13 ± 0.39 procedures per patient), median ATA burden decreased from 2.68% (IQR 0.09%-15.02%) at baseline to 0% (IQR 0%-0%) during the first year and to 0% (IQR 0%-0%) during the second year (reduction in ATA burden 100% [IQR 100%-100%]; P < .001). Single-procedure freedom from any ATA was 87% at 1 year and 78% at 2 years. Quality of life improved significantly across all scores. Adverse events occurred in 5 patients (4.8%).

CONCLUSION

CA has become an effective procedure in paroxysmal AF, with a major impact on ICM-detected ATA burden. Whereas conventional survival analysis suggests a progressive decline in efficacy, we observed that burden reduction is maintained at longer follow-up. These data imply that ATA burden is a more optimal end point for assessing ablation efficacy.

Role of Contact Force Sensing in Catheter Ablation of Cardiac Arrhythmias: Evolution or History Repeating Itself?

Adequate catheter-tissue contact facilitates efficient heat energy transfer to target tissue. Tissue contact is thus critical to achieving lesion transmurality and success of radiofrequency (RF) ablation procedures, a fact recognized more than 2 decades ago. The availability of real-time contact force (CF)-sensing catheters has reinvigorated the field of ablation biophysics and optimized lesion formation. The ability to measure and display CF came with the promise of dramatic improvement in safety and efficacy; however, CF quality was noted to have just as important an influence on lesion formation as absolute CF quantity. Multiple other factors have emerged as key elements influencing effective lesion formation, including catheter stability, lesion contiguity and continuity, lesion density, contact homogeneity across a line of ablation, spatiotemporal dynamics of contact governed by cardiac and respiratory motion, contact directionality, and anatomic wall thickness, in addition to traditional ablation indices of power and RF duration. There is greater appreciation of surrogate markers as a guide to lesion formation, such as impedance fall, loss of pace capture, and change in unipolar electrogram morphology. In contrast, other surrogates such as tactile feedback, catheter motion, and electrogram amplitude are notably poor predictors of actual contact and lesion formation. This review aims to contextualize the role of CF sensing in lesion formation with respect of the fundamental principles of biophysics of RF ablation and summarize the state-of-the-art evidence behind the role of CF in optimizing lesion formation.

Pulmonary vein reconnection following cryo-ablation: Mind the "Gap" in the carinae and the left atrial appendage ridge

Pulmonary vein (PV) isolation (PVI) remains cornerstone to ablation of atrial fibrillation (AF). For effective and durable PVI and thus fewer AF recurrences, lesion gaps in transmurality and contiguity responsible for PV reconnection (PVR) could only be addressed when one is cognizant of the potential location and sites where these lesion characteristics may be more prevalent and responsible for PVR. In the case of RF ablation, newer technologies incorporating contact force, time and power with automated monitoring of lesion formation, paying attention to difficult areas (carinae, left superior PV-LAA ridge, right inferior PV) and measuring inter-lesion distance may provide the tools to reduce PVR. On the other hand, the improved thermodynamic characteristics of the latest generation of cryoballloons and operator dexterity to achieve better PV occlusion, may be crucial determinants towards the direction of reduced PVR. Whether newer visualization tools, more vigilant testing during the index ablation procedure in these particular regions, prolonging or adding cryothermic applications, waiting longer to test for entrance and exit block, and/or use of provocative drug testing (isoproterenol/adenosine challenge) might help prevent future PVRs awaits further studies.

Safety and efficiency of porous-tip contact-force catheter for drug-refractory symptomatic paroxysmal atrial fibrillation ablation: results from the SMART SF trial

Aims

THERMOCOOL SMARTTOUCH® SF Catheter is a new contact-force (CF)-sensing catheter with 56-hole porous tip designed for improved cooling and reduced fluid delivery compared with a standard 6-hole open-irrigated catheter. The SMART SF study examined the periprocedural safety, acute effectiveness, and procedural efficiency of the catheter for drug-refractory symptomatic paroxysmal atrial fibrillation (PAF) ablation.

Methods and results

The prospective, open-label, non-randomized SMART-SF was conducted at 17 US sites. Circumferential pulmonary vein (PV) isolation was performed with confirmation of entrance block in all PVs. Stable ablation sites were identified using CARTO VISITAG™ Module. Primary adverse events (AEs; ≤1 week of index procedure), periprocedural AEs within 30 days of ablation procedure, acute effectiveness (confirmation of entrance block for targeted PVs), CF, and procedural parameters were assessed. Overall, 165 patients were enrolled (mean age, 62.7 years; male, 57.9%; white, 97%; left ventricular ejection fraction, 60.1 ± 7%; left atrium diameter, 38.8 ± 6 mm); 159 underwent radiofrequency ablation and comprised the safety cohort. Primary safety performance criteria were met: primary AE rate was 2.5% (4/159; cardiac tamponade [n = 2], thrombo-embolism [n = 1], transient ischaemic attack [n = 1]). All primary AEs resolved/improved within the 1-month follow-up period. Acute procedural effectiveness was attained in 96.2% (95% confidence interval: 92.0-98.6%) of patients. Procedure time, fluoroscopy time, and fluid delivered were observed in comparison to predecessor catheters.

Conclusion

In the SMART-SF trial, the predetermined safety performance goal was met, demonstrating the safety and acute effectiveness of the THERMOCOOL SMARTTOUCH® SF Catheter for PAF ablation.

Evaluation of left atrial linear ablation using contiguous and optimized radiofrequency lesions: the ALINE study

Aims

Achieving block across linear lesions is challenging. We prospectively evaluated radiofrequency (RF) linear ablation at the roof and mitral isthmus (MI) using point-by-point contiguous and optimized RF lesions.

Methods and results

Forty-one consecutive patients with symptomatic persistent AF underwent stepwise contact force (CF)-guided catheter ablation during ongoing AF. A single linear set of RF lesions was delivered at the roof and posterior MI according to the 'Atrial LINEar' (ALINE) criteria, i.e. point-by-point RF delivery (up to 35 W) respecting strict criteria of contiguity (inter-lesion distance ≤ 6 mm) and indirect lesion depth assessment (ablation index ≥550). We assessed the incidence of bidirectional block across both lines only after restoration of sinus rhythm. After a median RF time of 7 min [interquartile range (IQR) 5-9], first-pass block across roof lines was observed in 38 of 41 (93%) patients. Final bidirectional roof block was achieved in 40 of 41 (98%) patients. First-pass block was observed in 8 of 35 (23%) MI lines, after a median RF time of 8 min (IQR 7-12). Additional endo- and epicardial (54% of patients) RF applications resulted in final bidirectional MI block in 28 of 35 (80%) patients. During a median follow-up of 396 (IQR 310-442) days, 12 patients underwent repeat procedures, with conduction recovery in 4 of 12 and 5 of 10 previously blocked roof lines and MI lines, respectively. No complications occurred.

Conclusion

Anatomical linear ablation using contiguous and optimized RF lesions results in a high rate of first-pass block at the roof but not at the MI. Due to its complex 3D architecture, the MI frequently requires additional endo- and epicardial RF lesions to be blocked.

Improving procedural and one-year outcome after contact force-guided pulmonary vein isolation: the role of interlesion distance, ablation index, and contact force variability in the 'CLOSE'-protocol

Aims

We have recently shown that a contact force (CF)-guided ablation protocol respecting region-specific criteria of lesion contiguity and lesion depth ('CLOSE' protocol) is associated with high incidence of acute durable pulmonary vein (PV) isolation (PVI) and a high single-procedure arrhythmia-free survival at 1 year. In the present study, we compared efficiency, safety, and efficacy of 'CLOSE'-guided PVI to conventional CF-guided PVI (CONV-CF).

Methods and results

Fifty consecutive paroxysmal atrial fibrillation (AF) patients underwent PV encircling using a CF-sensing catheter targeting an interlesion distance (ILD) ≤6 mm and ablation index (AI) ≥400 and ≥550 at posterior and anterior wall ('CLOSE' group). Results were compared to the last 50 patients undergoing 'CONV-CF'. All patients underwent adenosine testing after PVI. Arrhythmia recurrence was defined as any atrial tachyarrhythmia (ATA) >30 s on Holter at 3, 6, and 12 months. Clinical characteristics did not differ. Contact force variability was comparable in between both groups (proportion of applications with intermittent contact 2% in 'CLOSE' vs. 1% in CONV-CF, P = 0.67). In the 'CLOSE' group, procedure time and radiofrequency (RF) time per circle were shorter (respectively 149 ± 33 min vs. 192 ± 42 min, P < 0.0001 and 18 ± 4 min vs 28 ± 7.5 min, P < 0.0001) and incidence of adenosine-proof isolation was higher (97% vs. 82%, P < 0.001). No complications were observed in the 'CLOSE' group, one tamponade in the 'CONV-CF' group. At 12 months, single-procedure freedom from ATA was 94% in 'CLOSE' vs. 80% in 'CONV-CF' group (P < 0.05). In both groups, the majority of reconnections at repeat were associated with either ILD > 6 mm and/or AI < 400/550 (100% vs. 83%, P = 0.99).

Conclusion

'CLOSE'-guided PVI improves procedural and 1 year outcome in CF-guided PVI while shortening procedure time. Improvement cannot be explained by differences in CF variability and is most likely due to the strict application of criteria for contiguity and ablation index. A randomized controlled trial is needed to exclude the possible contribution of a learning curve.