Postprocedural LGE-CMR comparison of laser and radiofrequency ablation lesions after pulmonary vein isolation

Chronic Ablation Lesions after Cryoballoon and Hot Balloon Ablation of Atrial Fibrillation

BACKGROUND

Chronological changes in ablation lesions after cryoballoon ablation (CBA) and hot balloon ablation (HBA) of atrial fibrillation (AF) remain unclear.

METHODS

Of 90 patients who underwent initial balloon-based catheter ablation of AF and cardiac magnetic resonance imaging (cMRI) 3 months after ablation, data from 48 propensity score-matched patients (24 per group; 34 males; age 62±10 years) were analyzed. High-density pulmonary vein-left antrum (PV-LA) voltage mapping was performed after PV isolation, and low voltage areas around the PV ostia were defined as the total acute ablation lesion area (cm²). cMRI-derived dense fibrotic tissue localized around PVs was defined as the total chronic ablation lesion area (cm²). The percentage of total ablation lesion areas to total PV-LA surface area (%ablation lesion) was calculated during each phase, and %acute ablation lesion and %chronic ablation lesion areas were compared in patients who had undergone CBA and HBA.

RESULTS

The %acute ablation lesion area was larger for the CBA group than for the HBA group (30.8±5.8% vs. 23.0±5.5%, p < 0.001). There was no difference in %chronic cMRI-derived ablation lesion area (24.8±10.8% vs. 21.1±11.6%, p = 0.26) between groups. The rates of chronic AF recurrence were 12.5% and 8.3%, respectively (p = 0.45; log-rank test). LA volume and LA surface area were strongly associated with AF recurrence, but %chronic ablation lesion area was not (27±8% vs. 23±12%, p = 0.39).

CONCLUSION

Large acute ablation lesions after CBA were smaller during the chronic phase. The size of chronic ablation lesions and the rate of AF recurrence were both similar for CBA and HBA.

Percutaneous Treatment Approaches in Atrial Fibrillation: Current Landscape and Future Perspectives

Atrial fibrillation (AF), the most common sustained arrhythmia in clinical practice, represents a major cause of morbidity and mortality, with an increasing prevalence. Pharmacologic treatment remains the cornerstone of its management through rhythm and rate control, as well as the prevention of thromboembolism with the use of oral anticoagulants. Recent progress in percutaneous interventional approaches have provided additional options in the therapeutic arsenal, however. The use of the different catheter ablation techniques can now lead to long arrhythmia-free intervals and significantly lower AF burden, thus reducing the rate of its complications. Particularly encouraging evidence is now available for patients with persistent AF or concomitant heart failure, situations in which catheter ablation could even be a first-line option. In the field of stroke prevention, targeting the left atrial appendage with percutaneous device implantation may reduce the risk of thromboembolism to lower rates than that predicted with conventional ischemic risk scores. Left atrial appendage occlusion through the approved Watchman or Amplatzer devices is a well-established, efficacious, and safe method, especially in high-ischemic and bleeding risk patients with contraindications for oral anticoagulation.

Wide area circumferential ablation for pulmonary vein isolation using radiofrequency versus laser balloon ablation

Background

Persistent atrial fibrillation (AF) is associated with high recurrence rates of AF and atypical atrial flutters or tachycardia (AFT) postablation. Laser balloon (LB) ablation of the pulmonary vein (PV) ostia has similar efficacy as radiofrequency wide area circumferential ablation (RF-WACA); however, an approach of LB wide area circumferential ablation (LB-WACA) may further improve success rates.

Objective

To evaluate freedom from atrial tachyarrhythmia (AFT/AF) recurrence postablation using RF-WACA versus LB-WACA in persistent AF patients.

Methods

This was a retrospective multicenter study. Patients were followed for up to 24 months via office visits, Holter, and/or device monitoring. The primary endpoint was freedom from AFT/AF after a single ablation procedure. Secondary endpoints included freedom from AF, freedom from AFT, first-pass isolation of all PVs, and procedural complications.

Results

Two hundred and four patients were studied (LB-WACA: n = 103; RF-WACA: n = 101). Patients' baseline characteristics were similar except patients in the RF-WACA group were older (64 vs. 68, p = .03). First-pass isolation was achieved more often during LBA (LB-WACA: 88% vs. RF-WACA 75%; p = .04). Procedure (p = .36), LA dwell (p = .41), and fluoroscopy (p = .44) time were similar. The mean follow-up was 506 ± 279 days. Sixty-six patients had arrhythmic events including 24 AFT and 59 AF recurrences. LB-WACA group had higher arrhythmia-free survival (p = .009) after single ablation procedures. In the multivariate Cox regression model, RF-WACA was associated with a higher recurrence of AFT compared with LB-WACA (Adjusted HR 3.16 [95% CI: 1.13-8.83]; p = .03).

Conclusions

LB-WACA was associated with higher freedom from atrial arrhythmias mostly driven by the lower occurrence of AFT compared with RF-WACA.

Visualization of thermal damage using 68 Ga-FAPI-PET/CT after pulmonary vein isolation

PURPOSE

68 Ga-fibroblast-activation protein inhibitor (FAPI) positron emission tomography (PET) is a novel technique targeting FAP-alpha. This protein is expressed by activated fibroblasts which are the main contributors to tissue remodeling. The aim of this proof-of-concept study was to assess 68 Ga-FAPI uptake in the pulmonary vein (PV) region of the left atrium after pulmonary vein isolation (PVI) with cryoballoon ablation (CBA) and radiofrequency (RFA) as a surrogate for thermal damage.

METHODS

Twelve PVI patients (5 RFA, 7 CBA) underwent 68 Ga-FAPI-PET 20.5 ± 12.8 days after PVI. Five patients without atrial fibrillation or previous ablation served as controls. Standardized uptake values of localized tracer uptake were calculated.

RESULTS

Focal FAPI uptake around the PVs was observed in 10/12 (83.3%) PVI patients, no uptake was observed in 2 PVI patients and all controls. Patients after PVI had higher FAPI uptake in PVs compared to controls (SUVmax: 4.3 ± 2.2 vs. 1.6 ± 0.2, p < 0.01; SUVpeak: 2.9 ± 1.4 vs. 1.3 ± 0.2, p < 0.01). All CBA patients had an intense uptake, while in the RFA, group 2 (40%), 1 (20%), and 2 (40%) patients had an intense, moderate, and no uptake, respectively. We observed higher uptake values (SUVpeak) in CBA compared to RFA patients (4.4 ± 1.5 vs. 2.5 ± 0.8, p = 0.02).

CONCLUSION

We demonstrate in-vivo visualization of 68 Ga-FAPI uptake as a surrogate for fibroblast activation after PVI. CBA seems to cause more pronounced fibroblast activation following tissue injury than RFA. Future studies are warranted to assess if this modality can contribute to a better understanding of the mechanisms of AF recurrence after PVI by lesion creation and gap assessment.

Efficacy and Safety of Second and Third-Generation Laser Balloon for Paroxysmal Atrial Fibrillation Ablation Compared to Radiofrequency Ablation: A Matched-Cohort

Laser balloon (LB) has emerged as an interesting strategy for pulmonary vein isolation in paroxysmal atrial fibrillation (AF). A third-generation LB has recently been developed, allowing a continuous ablation set. We aimed to compare the results from our center's experience with second and third-generation LBs to a cohort of matched patients who had undergone radiofrequency ablation (RFA) with contact-force catheters. This retrospective monocenter case-control study included our first 50 LB paroxysmal AF ablations (26 second and 24 third-generation LB) and 50 RFA controls, matched on age, sex and left atrial dilation. The two groups had similar baseline parameters. LB procedures were significantly shorter than RFA (129 (110-160) vs. 160 (119-198) min, p = 0.007). During AF ablation, two major complications occurred in each group. At the one-year follow-up, AF recurrence was diagnosed in 7 (14%) of the LB group vs. 14 (28%) of the RFA group (p = 0.14). Moreover, we observed that third-generation LB procedures were associated with shorter laser applications (22 (19-29) vs. 69 (55-76) min, p < 0.001) and procedural durations (111 (100-128) vs. 151.5 (128.5-167) min, p < 0.001) compared to second-generation LB procedures. In the context of the major increase in the number of AF ablations, LB demonstrated consistent results in terms of clinical success, complications and also reduced procedure durations compared to RFA.

Ablation Modalities for Therapeutic Intervention in Arrhythmia-Related Cardiovascular Disease: Focus on Electroporation

Targeted cellular ablation is being increasingly used in the treatment of arrhythmias and structural heart disease. Catheter-based ablation for atrial fibrillation (AF) is considered a safe and effective approach for patients who are medication refractory. Electroporation (EPo) employs electrical energy to disrupt cell membranes which has a minimally thermal effect. The nanopores that arise from EPo can be temporary or permanent. Reversible electroporation is transitory in nature and cell viability is maintained, whereas irreversible electroporation causes permanent pore formation, leading to loss of cellular homeostasis and cell death. Several studies report that EPo displays a degree of specificity in terms of the lethal threshold required to induce cell death in different tissues. However, significantly more research is required to scope the profile of EPo thresholds for specific cell types within complex tissues. Irreversible electroporation (IRE) as an ablative approach appears to overcome the significant negative effects associated with thermal based techniques, particularly collateral damage to surrounding structures. With further fine-tuning of parameters and longer and larger clinical trials, EPo may lead the way of adapting a safer and efficient ablation modality for the treatment of persistent AF.

Left atrial thickness and acute thermal injury in patients undergoing ablation for atrial fibrillation: Laser versus radiofrequency energies

INTRODUCTION

Thermally induced cardiac lesions result in necrosis, edema, and inflammation. This tissue change may be seen with ultrasound. In this study, we sought to use intracardiac echocardiography (ICE) to evaluate pulmonary vein tissue morphology and assess the acute tissue changes that occur following radiofrequency (RF) or laser ablation for atrial fibrillation (AF).

METHODS AND RESULTS

Patients with AF underwent pulmonary vein isolation (PVI) using irrigated RF or laser balloon. Pre- and post-ablation ICE imaging was performed from within each pulmonary vein (PV). At least 10 transverse imaging planes per PV were evaluated and each plane was divided into eight segments. The PV/atrial wall thickness and the luminal area were measured at each segment. Twenty-seven patients underwent PVI (15 with laser, 12 with RF). Ninety-eight pulmonary veins were analyzed (58 PVs laser; 40 PVs RF). At baseline, there were no regional differences in PV wall thickness in the right-sided veins. The anterior regions of left superior pulmonary vein (LSPV) and left inferior pulmonary vein (LIPV) were significantly thicker compared with the posterior and inferior regions (p < .01). Post-ablation, PV wall thickness in RF group increased 24.1% interquartile range (IQR) (17.2%-36.7%) compared with 1.2% IQR (0.4%-8.9%) in laser group, p = .004. In all PVs, RF ablation resulted in significantly greater percent increase in wall thickness compared with laser. Additionally, RF resulted in more variable changes in regional PV wall thickness; with more increases in wall thickness in anterior versus posterior LSPV (75.4 ± 58.5% vs. 46.8 ± 55.6%, p < .01), anterior versus posterior right superior pulmonary vein (RSPV) (62.9 ± 63.9% vs. 44.6 ± 51.7%, p < .05), and superior versus inferior RSPV (69.1 ± 45.4% vs. 35.9 ± 45%, p < .05). There were no significant regional differences in PV wall thickness changes for the laser group.

CONCLUSIONS

Rotational ICE can be used to measure acute tissue changes with ablation. Regional variability in baseline wall thickness was nonuniformly present in PVs. Acute tissue changes occurred immediately post-ablation. Compared with laser balloon, RF shows markedly more thickening post-ablation with significant regional variations.

A global benchmark of algorithms for segmenting the left atrium from late gadolinium-enhanced cardiac magnetic resonance imaging

Segmentation of medical images, particularly late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) used for visualizing diseased atrial structures, is a crucial first step for ablation treatment of atrial fibrillation. However, direct segmentation of LGE-MRIs is challenging due to the varying intensities caused by contrast agents. Since most clinical studies have relied on manual, labor-intensive approaches, automatic methods are of high interest, particularly optimized machine learning approaches. To address this, we organized the 2018 Left Atrium Segmentation Challenge using 154 3D LGE-MRIs, currently the world's largest atrial LGE-MRI dataset, and associated labels of the left atrium segmented by three medical experts, ultimately attracting the participation of 27 international teams. In this paper, extensive analysis of the submitted algorithms using technical and biological metrics was performed by undergoing subgroup analysis and conducting hyper-parameter analysis, offering an overall picture of the major design choices of convolutional neural networks (CNNs) and practical considerations for achieving state-of-the-art left atrium segmentation. Results show that the top method achieved a Dice score of 93.2% and a mean surface to surface distance of 0.7 mm, significantly outperforming prior state-of-the-art. Particularly, our analysis demonstrated that double sequentially used CNNs, in which a first CNN is used for automatic region-of-interest localization and a subsequent CNN is used for refined regional segmentation, achieved superior results than traditional methods and machine learning approaches containing single CNNs. This large-scale benchmarking study makes a significant step towards much-improved segmentation methods for atrial LGE-MRIs, and will serve as an important benchmark for evaluating and comparing the future works in the field. Furthermore, the findings from this study can potentially be extended to other imaging datasets and modalities, having an impact on the wider medical imaging community.

Cryoballoon vs. radiofrequency lesions as detected by late-enhancement cardiac magnetic resonance after ablation of paroxysmal atrial fibrillation: a case-control study

AIMS

Cryoballoon (CB) ablation has emerged as a reliable modality to isolate pulmonary veins (PVs) in atrial fibrillation. Ablation lesions and the long-term effects of energy delivery can be assessed by delayed-enhancement cardiac magnetic resonance (DE-CMR). The aim of the study was to compare the number, extension, and localization of gaps in CB and radiofrequency (RF) techniques in pulmonary vein isolation (PVI).

METHODS AND RESULTS

Consecutive patients submitted to PVI with CB in whom DE-CMR images were available (n = 30) were matched (1:1) to patients who underwent PVI with RF (n = 30), considering age, sex, hypertension, and diabetes. Delayed-enhancement cardiac magnetic resonance was obtained at 3 months post-procedure, and images were processed to assess the mean number of gaps around PV ostia, their localization, and the normalized gap length (NGL), calculated as the difference between total gap length and total PV perimeter. Patients were followed up for 12 months. The CB and RF procedures did not differ in the mean number of gaps per patient (4.40 vs. 5.13 gaps, respectively; P = 0.21) nor NGL (0.35 vs. 0.32, P = 0.59). For both techniques, a higher mean number of gaps were detected in right vs. left PVs (3.18 vs. 1.58, respectively; P = 0.01). The incidence of recurrences did not differ between techniques (odds ratio 1.87, 95% confidence interval 0.66-4.97; P = 0.29).

CONCLUSION

Location and extension of ablation gaps in PVI did not differ between CB and RF groups in DE-CMR image analysis.

Impact of cryoballoon applications on lesion gaps detected by magnetic resonance after pulmonary vein isolation

INTRODUCTION

Ablation with second-generation cryoballoon technology evolves as an effective and safe alternative to radiofrequency for atrial fibrillation ablation procedures. Nevertheless, the optimal freezing strategy remains unknown. Our objective was to identify the procedural cryoablation parameters predicting successful peri-pulmonary vein (PV) lesions by directly analyzing Postablation gaps in late-gadolinium-enhanced cardiac magnetic resonance (LGE-CMR).

METHODS AND RESULTS

Forty-nine consecutive patients (196 PVs) undergoing ablation with second-generation cryoballoon at our center were included. The number and duration of cryoballoon application to achieve PV isolation were left to operator discretion. Gap number and length were quantified in all patients with a LGE-CMR performed 3 months postablation. Application time (420 ± 217 seconds), number of applications (2.1 ± 1.2), application time after electrical isolation (311 ± 194 seconds) and minimum temperature (-45.8 ± 6.5°C) were similar in the 4 PVs. Gaps were observed in 148 PVs (76%), averaging 1.3 ± 1 gaps per vein. Gaps were longer and more frequent in the right PVs (91% vs 59% in left PVs, P < .001). Neither the number, total duration of applications, nor postisolation application time predicted relative length or number of gaps.

CONCLUSIONS

After successful PV isolation was achieved in patients undergoing cryoablation, increasing the number of applications, the total application time or application time postisolation did not result in a reduction in the number or the relative length of gaps.