Lesion characteristics between cryoballoon ablation and radiofrequency ablation with a contact force-sensing catheter: Late-gadolinium enhancement magnetic resonance imaging assessment

Lesion Characteristics of Pulsed Field Ablation

Pulsed field ablation (PFA) has emerged as a promising, nonthermal technique for arrhythmia ablation, leveraging high-voltage electrical fields to induce electroporation and create precise ablation lesions. Unlike traditional thermal methods such as radiofrequency ablation (RFA) and cryoablation, PFA selectively targets myocardial cells while sparing surrounding tissues, reducing the risk of collateral damage. This review focuses on the key characteristics of PFA lesion formation, drawing comparisons with RFA and cryoablation based on histopathology, imaging, and electroanatomical mapping.

HIgh Power short duration radiofrequency ablation or cryoballoon ablation for paroxysmal Atrial Fibrillation (HIPAF trial)

AIMS

Pulmonary vein isolation (PVI) is a first-line treatment option for paroxysmal atrial fibrillation (PAF). Radiofrequency ablation (RFA) or cryoballoon ablation (CBA) are commonly used modalities. Recent studies demonstrated the superiority and potential benefits of very high-power short-duration (vHPSD) RFA using 70 W compared to conventional RFA (<50 W). Prospective randomized data comparing vHPSD RFA with 70 W with the frequently used CBA in the setting of PAF are lacking.

METHODS AND RESULTS

We conducted a randomized non-inferiority trial involving 170 patients undergoing de novo PVI for PAF. Patients were randomly assigned in a 1:1 ratio to undergo vHPSD RFA or to receive CBA. The composite primary endpoint consisted of (i) any atrial arrhythmia, (ii) new antiarrhythmic drug (AAD) onset, and (iii) re-ablation during 1 year after index procedure. The non-inferiority margin was predefined as a 10% lower 1-year event-free survival rate in vHPSD compared to CBA (delta = -0.1). A total of 170 patients with symptomatic PAF were enrolled and assigned to undergo de novo PVI, with 84 receiving vHPSD and 86 undergoing CBA. The overall study population had a mean age of 65 ± 11 years and included 50.6% women. For vHPSD PVI a 70 W/7 s anterior and 70 W/5 s posterior protocol including 3D mapping was used. Cryoballoon ablation was performed as usual. Successful PVI was achieved in all patients. Overall procedure time for vHPSD was significantly longer (81.1 ± 20.0 vs. 67.7 ± 17.2 min; P < 0.001). However, the mere ablation time was comparable (39.3 ± 15.5 vs. 36.7 ± 14.5 min; P = 0.285). Fluoroscopy time and amount of contrast medium were significantly lower for vHPSD PVI (9.2 ± 3.6 vs. 10.5 ± 4.3 min; P = 0.031; 15.5 ± 5.8 vs. 43.1 ± 30.0 mL; P < 0.001). Complication rates were comparable between groups. One pulmonary vein stenosis occurred after vHPSD. Three pericardial effusions and two transient ischaemic attack were reported after CBA. After a median follow-up of 367 days, 73.8% [n = 62, 95% confidence interval (CI): 63.1-82.8%] of patients in the vHPSD PVI group and 81.4% (n = 70, 95% CI: 71.6-89.0%) in the CBA group remained free of any event. Non-inferiority of vHPSD PVI compared to CBA PVI could not be demonstrated, with a difference of -0.076 [95% CI: (-0.201 to 0.049)] in event-free survival rates off AADs, as the 95% CI includes the delta of -0.1.

CONCLUSION

In this randomized non-inferiority trial comparing vHPSD RFA to CBA for PVI in patients with PAF, non-inferiority of vHPSD RFA could not be shown. Both methods showed comparable safety outcome with a shorter procedure time for CBA.

Distribution of antral lesions with the novel size-adjustable cryoballoon for pulmonary vein isolation and the differences based on left atrial remodeling

INTRODUCTION

The novel cryoballoon with 28 mm or 31 mm adjustable diameters, aims to achieve a wide antral pulmonary vein isolation (PVI). However, the distribution of antral lesions and their variations based on left atrial (LA) remodeling require further clarification.

METHODS

We evaluated 22 patients (67 [59.5-74.8] years, 19 males) who underwent PVI of atrial fibrillation (AF) (13 paroxysmal AF [PAF] and 9 non-PAF) using size-adjustable cryoballoons. LA electro-anatomical mapping was performed post-PVI with three-dimensional mapping systems. We assessed the shapes of the LA and pulmonary veins (PVs) and the distribution of isolated areas (IAs), comparing the results between PAF and non-PAF patients.

RESULTS

In the left PVs (LPVs), the distance between the PV orifice and IA edge (PVos-IA) was larger on the roof and posterior segments (~15 mm) but relatively smaller on the anterior segment near the PV ridge (<10 mm). For the right PVs (RPVs), it was more extensive in the posterior segment (10-15 mm). Comparing PAF and non-PAF, there were no significant differences in the PVos-IA except for the right posterior-carina segment, antrum IA (LPVs: 5.9 ± 1.6 vs. 5.8 ± 0.8 cm², p = .81; RPVs: 4.8 ± 2.3 vs. 4.8 ± 1.2 cm², p = .81), distances between the right and left IAs on the LA posterior wall (LAPW), and un-isolated LAPW area (9.0 ± 4.9 vs. 9.9 ± 2.5 cm², p = .62). No individual PVIs were observed in either group. Two patients exhibited overlapping IAs on the roof, and one patient who underwent 31 mm balloon applications for all PVs exhibited an LAPW isolation.

CONCLUSION

The size-adjustable cryoballoon achieved a wide antral PVI even in non-PAF patients.

Magnetic Resonance Imaging Monitoring of Thermal Lesions Produced by Focused Ultrasound

BACKGROUND

The main goal of the study was to find the magnetic resonance imaging (MRI) parameters that optimize contrast between tissue and thermal lesions produced by focused ultrasound (FUS) using T1-weighted (T1-W) and T2-weighted (T2-W) fast spin echo (FSE) sequences.

METHODS

FUS sonications were performed in ex vivo porcine tissue using a single-element FUS transducer of 2.6 MHz in 1.5 and 3 T MRI scanners. The difference in relaxation times as well as the impact of critical MRI parameters on the resultant contrast-to-noise ratio (CNR) between coagulated and normal tissues were assessed. Discrete and overlapping lesions were inflicted in tissue with simultaneous acquisition of T2-W FSE images.

RESULTS

FUS lesions are characterized by lower relaxation times than intact porcine tissue. CNR values above 80 were sufficient for proper lesion visualization. For T1-W imaging, repetition time values close to 1500 ms were considered optimum for obtaining sufficiently high CNR at the minimum time cost. Echo time values close to 50 ms offered the maximum lesion contrast in T2-W FSE imaging. Monitoring of acute FUS lesions during grid sonications was performed successfully. Lesions appeared as hypointense spots with excellent contrast from surrounding tissue.

CONCLUSION

MRI monitoring of signal intensity changes during FUS sonication in grid patterns using optimized sequence parameters can provide useful information about lesion progression and the success of ablation. This preliminary study demonstrated the feasibility of the proposed monitoring method in ex vivo porcine tissue and should be supported by in vivo studies to assess its clinical potential.

Meta-analysis of high-power short-duration versus cryoballoon ablation for atrial fibrillation

BACKGROUND

The existing literature regarding the treatment strategy for high-power short-duration (HPSD) ablation in patients diagnosed with atrial fibrillation (AF) is currently insufficient. The objective of this study is to perform a comparative analysis evaluating the effectiveness, safety, and procedural efficiency of HPSD versus cryoballoon ablation (CBA) for AF.

METHODS

A comprehensive search was conducted in PubMed, EMBASE, Cochrane Library, Scopus, Web of Science, and ClinicalTrials.gov databases to identify trials comparing HPSD with CBA for AF from their inception until December 25, 2023. Treatment effect measures were expressed as odds ratio (OR), mean difference (MD), accompanied by a 95% confidence interval (CI).

RESULTS

The analysis comprised six eligible trials involving a total enrollment of 2481 patients. No statistically significant disparities were observed in recurrent atrial arrhythmia (OR 0.90; 95% CI, 0.71-1.16) or total complications (OR 0.65; 95% CI, 0.38-1.12) between the two ablation techniques examined in this study. However, HPSD technique exhibited a significantly prolonged procedure time (MD 27.42; 95% CI, 19.03 to 35.81). Conversely, no significant differences were observed between the two modalities in terms of total fluoroscopy duration (MD -4.37; 95% CI -10.70 to 1.96) and ablation time (MD 7.95; 95% CI -3.97 to 19.88). Furthermore, HPSD demonstrated significantly higher odds of extrapulmonary vein (PV) trigger ablation compared to CBA (OR 18.86; 95% CI, 5.12-69.49). The subgroup analyses revealed that CBA continued to exhibit superior procedure time (except for the paroxysmal AF subgroup: [MD 29.52; 95% CI -4.25 to 63.60]), while no significant differences in safety and efficacy (except for the HPSD ≥ 70 W subgroup: [OR 0.44, 95% CI 0.20-0.97]) outcomes were still observed.

CONCLUSION

Among patients undergoing ablation therapy for AF, both HPSD and CBA demonstrate comparable efficacy and safety profiles; however, HPSD is associated with longer procedural time and higher rates of extra-PV trigger ablation.

Anti- and pro-fibrillatory effects of pulmonary vein isolation gaps in human atrial fibrillation digital twins

Although pulmonary vein isolation (PVI) gaps and extrapulmonary vein triggers contribute to recurrence after atrial fibrillation (AF) ablation, their precise mechanisms remain unproven. Our study assessed the impact of PVI gaps on rhythm outcomes using a human AF digital twin. We included 50 patients (76.0% with persistent AF) who underwent catheter ablation with a realistic AF digital twin by integrating computed tomography and electroanatomical mapping. We evaluated the final rhythm status, including AF and atrial tachycardia (AT), across 600 AF episodes, considering factors including PVI level, PVI gap number, and pacing locations. Our findings revealed that antral PVI had a significantly lower ratio of AF at the final rhythm (28% vs. 56%, p = 0.002) than ostial PVI. Increasing PVI gap numbers correlated with an increased ratio of AF at the final rhythm (p < 0.001). Extra-PV induction yielded a higher ratio of AF at the final rhythm than internal PV induction (77.5% vs. 59.0%, p < 0.001). In conclusion, our human AF digital twin model helped assess AF maintenance mechanisms. Clinical trial registration: https://www.clinicaltrials.gov ; Unique identifier: NCT02138695.

Atrial fibrillation progression after cryoablation vs. radiofrequency ablation: the CIRCA-DOSE trial

BACKGROUND AND AIMS

Atrial fibrillation (AF) is a chronic progressive disorder. Persistent forms of AF are associated with increased rates of thromboembolism, heart failure, and death. Catheter ablation modifies the pathogenic mechanism of AF progression. No randomized studies have evaluated the impact of the ablation energy on progression to persistent atrial tachyarrhythmia.

METHODS

Three hundred forty-six patients with drug-refractory paroxysmal AF were enrolled and randomly assigned to contact-force-guided RF ablation (CF-RF ablation, 115), 4 min cryoballoon ablation (CRYO-4, 115), or 2 min cryoballoon ablation (CRYO-2, 116). Implantable cardiac monitors placed at study entry were used for follow-up. The main outcome was the first episode of persistent atrial tachyarrhythmia. Secondary outcomes included atrial tachyarrhythmia recurrence and arrhythmia burden on the implantable monitor.

RESULTS

At a median of 944.0 (interquartile range [IQR], 612.5-1104) days, 0 of 115 patients (0.0%) randomly assigned to CF-RF, 8 of 115 patients (7.0%) assigned to CRYO-4, and 5 of 116 patients (4.3%) assigned to CRYO-2 experienced an episode of persistent atrial tachyarrhythmia (P = .03). A documented recurrence of any atrial tachyarrhythmia ≥30 s occurred in 56.5%, 53.9%, and 62.9% of those randomized to CF-RF, CRYO-4, and CRYO-2, respectively; P = .65. Compared with that of the pre-ablation monitoring period, AF burden was reduced by a median of 99.5% (IQR 94.0%, 100.0%) with CF-RF, 99.9% (IQR 93.3%-100.0%) with CRYO-4, and 99.1%% (IQR 87.0%-100.0%) with CRYO-2 (P = .38).

CONCLUSIONS

Catheter ablation of paroxysmal AF using radiofrequency energy was associated with fewer patients developing persistent AF on follow-up.

Pulmonary vein capture is a predictor for long-term success of stand-alone pulmonary vein isolation with cryoballoon ablation in patients with persistent atrial fibrillation

Background

The mechanisms of AF development and progression are still not completely understood. Despite the relative efficacy of ablation, the risk of AF recurrence is substantial, particularly in patients with persistent AF (perAF). At present we do not have any reliable intra-procedural electrophysiologic predictors of long-term success of AF ablation other than pulmonary vein isolation. We evaluated selected intraprocedural pulmonary vein characteristics that may be helpful in future guidance of persistent AF ablation.

Methods

390 consecutive procedures using cryoballoon for initial AF ablation were divided by clinical presentation (paroxysmal or persistent AF), and by pulmonary vein (PV) response to pacing after completion of ablation (discrete electrogram elicited with pacing-"PV capture" or not-"Control"). Patients were followed (median 20 months) for recurrent atrial arrhythmias as the primary end point of the study.

Results

PV capture was identified in 20.3% and 17.1% and patients with paroxysmal and persistent AF respectively (ns). In patients with persistent AF presence of PV capture was associated with significantly better outcomes compared to patients without PV capture (p < 0.001). In the group "persistent AF and PV capture", an initial strategy of PV isolation and reisolation of the PVs (without additional lesions) for patients with recurrent atrial arrhythmias resulted in 20/23 (87%) patients in sinus rhythm off antiarrhythmic medications at study completion. In patients with paroxysmal AF, PV capture was not associated with outcome benefits. Specific electrophysiologic characteristics of PV (PV capture cycle length: PVCCL) did not have an impact on AF recurrence, although 25% shortening of PVCCL was observed after 60 s periods of pacing at short cycle lengths. No background demographic patient characteristic differences were identified between patients with vs. without PV capture.

Conclusion

The presence of PV capture was associated with better outcomes in patients with persistent AF. PV capture may identify those patients with persistent AF in whom cryoballoon PV isolation alone is sufficient as an initial ablation procedure and as the primary ablation strategy for recurrent AF.

Pulsed field ablation for atrial fibrillation - Lessons from magnetic resonance imaging

Pulsed field ablation (PFA) is a promising technology for the treatment of atrial fibrillation (AF). Due to its unique tissue selectivity, PFA potentially bears superior characteristics as compared to established thermal energy sources in AF ablation procedures. Cardiovascular magnetic resonance imaging (CMR) using late gadolinium enhancement (LGE) is an established tool in the analysis of myocardial fibrosis representing atrial cardiomyopathy as well as ablation-induced atrial scar formation following catheter ablation with thermal energy. Mechanisms of atrial lesion formation differ between thermal ablation and electroporation and its impact on results of CMR imaging are not fully understood until now. In this review article, the potential of CMR imaging for PFA lesion assessment and available data are discussed. Further, additional needs to adopt imaging approaches to the cellular mechanisms of electroporation are considered.

Visualization of fibroblast activation using 68Ga-FAPI PET/CT after pulmonary vein isolation with pulsed field compared with cryoballoon ablation

BACKGROUND

Pulsed-field ablation (PFA) is a novel ablation modality for atrial fibrillation (AF) ablating myocardium by electroporation without tissue-heating. With its different mechanism of tissue ablation, it is assumed that lesion creation is divergent to thermal energy sources. 68Ga-fibroblast-activation protein inhibitor (FAPI) PET/CT targets FAP-alpha expressed by activated fibroblasts. We aimed to assess 68Ga-FAPI uptake in pulmonary veins as surrogate for ablation damage after PFA and cryoballoon ablation (CBA).

METHODS

26 patients (15 PFA, 11 CBA) underwent 68Ga-FAPI-PET/CT after ablation. Standardized uptake values (SUV) and fibroblast-activation volumes of localized tracer uptake were assessed.

RESULTS

Patient characteristics were comparable between groups. In PFA, focal FAPI uptake was only observed in 3/15 (20%) patients, whereas in the CBA cohort, 10/11 (90.9%) patients showed atrial visual uptake. We observed lower values of SUVmax (2.85 ± 0.56 vs 4.71 ± 2.06, P = 0.025) and FAV (1.13 ± 0.84 cm3 vs 3.91 ± 2.74 cm3, P = 0.014) along with a trend towards lower SUVpeak and SUVmean in PFA vs CBA patients, respectively.

CONCLUSION

Tissue response with respect to fibroblast activation seems to be less pronounced in PFA compared to established thermal ablation systems. This functional assessment might contribute to a better understanding of lesion formation in thermal and PFA ablation potentially contributing to better safety outcomes.

Evaluation of Pulmonary Vein Fibrosis Following Cryoballoon Ablation of Atrial Fibrillation: A Semi-Automatic MRI Analysis

Current guidelines recommend the use of cardiac magnetic resonance imaging (MRI) for the management of atrial fibrillation (AF). However, the widespread use of cardiac MRI in clinical practice is difficult to achieve. The aim of the present study is to assess whether cardiac MRI can be adopted to identify ablation-induced fibrosis, and its relationship with AF recurrences. Fifty patients undergoing AF cryoballoon ablation were prospectively enrolled. Cardiac MRI was performed before and 30 days after the index ablation. Commercially available software and a specifically designed image processing workflow were used to quantify left atrium (LA) fibroses. Thirty-six patients were finally included in the analysis; twenty-eight were analyzed with the dedicated workflow. Acute electrical isolation was achieved in 98% of the treated pulmonary veins (PVs). After a median follow-up of 16 months, AF recurrences occurred in 12 patients (33%). In both analyses, no differences were found between the subgroups of patients with and without recurrence in the variation of either LA fibrosis or fibrosis at the ostium of the PV, before and after ablation. The ability to predict arrhythmic recurrences evaluated via the ROC curve of the variations in both LA fibrosis (AUC 0.566) and PV fibrosis (AUC 0.600) was low. Cardiac MRI holds the potential to provide clinically significant information on LA disease and AF progression; however, LA fibrosis cannot be easily identified, either by currently available commercial programs or custom tools.

Pulmonary vein isolation for atrial fibrillation using true high-power short-duration vs. cryoballoon ablation

AIMS

Pulmonary vein isolation (PVI) is achievable and effective using radiofrequency (RF) catheter (CA) or cryoballoon (CB) ablation. The newly introduced high RF-power short-duration ablation (HPSD) technique has shown promising results. Data comparing HPSD- to CB-PVI is sparse. We sought to investigate success rates and procedural differences of HPSD-PVI vs. CB-PVI in patients undergoing ablation for PAF and persAF.

METHODS

Consecutive patients undergoing de novo PVI (HPSD or CB) were included. A power setting of 70W/7 s (70W/5 s at posterior wall) using a flexible tip catheter with enhanced irrigation was considered as true HPSD. Follow-up consisted of out-clinic pts visits, tele-consultation, 48-h Holter ECG, app-based telemonitoring and cardiac implanted electronic devices (CIED) interrogation.

RESULTS

721 patients (46 HPSD, 675 CB) were analyzed. In all HPSD (27 persAF [59%]) and CB patients (423 persAF [63%]), PVI was successfully achieved. Procedure duration was significantly longer for HPSD (91 ± 19 min vs. 72 ± 18 min, p < 0.01). Ablation time was similar in both groups (HPSD: 44 ± 19 min vs. CB: 40 ± 17 min; p = 0.347). No major complications occurred in HPSD. For CB-PVI, in 25 (3.7%; p = 0.296) patients, complications occurred. At a follow-up of 290 ± 135 days, arrhythmia-free survival using HPSD was non-inferior to CB-PVI in the Kaplan-Meier survival analysis (p = 0.096).

CONCLUSION

PVI using HPSD is equally effective and safe to CB-PVI. This analysis revealed a similar arrhythmia-free survival after HPSD and CB with low complication rates. Procedure duration for CB was significantly shorter while LA dwell time excluding mapping was equal. Currently, a prospective trial is conducted to corroborate these findings.

Cryoballoon-Induced Circumferential Pulmonary Vein Fibrosis, Assessed by Late Gadolinium-Enhancement Cardiac Magnetic Resonance Imaging, and Its Correlation with Clinical Atrial Fibrillation Recurrence

BACKGROUND

Prior studies evaluating post-atrial fibrillation (AF) ablation pulmonary vein (PV) ostial gaps via magnetic resonance imaging (MRI) have shown circumferential PV fibrosis in a minority of patients, and their correlation with AF recurrence was weak. These studies were mostly based on radio-frequency AF ablations.

AIM

We aimed to assess cryoballoon ablation-induced PV fibrosis via MRI and its correlation with AF recurrence.

METHODS AND RESULTS

This was a prospective study of consecutive patients with symptomatic AF who underwent pre- and post-ablation MRI to assess baseline and ablation-induced fibrosis, respectively. Post-ablation PV gaps were assessed by new semi-quantitative visual analysis assisted by computerized ADAS analysis. AF recurrence monitored via multiple ECGs and event monitoring at 6 and 12 months post ablation. Nineteen patients with 80 PVs were included, age 56 ± 11, with paroxysmal and persistent AF in 17/19 and 2/19 patients, respectively. Baseline MRI showed minimal LA fibrosis. All patients underwent successful cryoballoon PV electrical isolation. Post-ablation MRI revealed circumferential PV fibrosis among 63/80 (78.8%) PVs and partial fibrosis with major gaps among 17/80 (21.2%) PVs. AF recurred within one year in 5/9 (55.5%) patients with partial PV fibrosis, while no AF recurred among the 10 patients in whom all PVs had circumferential fibrosis (p < 0.01). Similarly, there were significantly more PVs without circumferential fibrosis (due to major gaps) among patients with AF recurrence as compared with patients without AF recurrence (42.9% vs. 13.5%; p < 0.01).

CONCLUSION

Cryoballoon AF ablation results in circumferential PV fibrosis in the majority of PVs, as assessed by a new clinically relevant MRI-LGE analysis. Significant correlation was found between major PV gaps on post-ablation MRI and AF recurrence, suggesting that MRI might have the ability to predict AF recurrence.

The impact of the procedural parameters on the lesion characteristics associated with AF recurrence: Late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) analysis

BACKGROUND

Lesion gaps assessed by late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) are associated with the atrial fibrillation (AF) recurrence after pulmonary vein isolation. Animal studies have demonstrated that the catheter-contact force (CF), stability, and orientation are strongly associated with lesion formation. However, the impact of those procedural factors on the lesion characteristics associated with AF recurrence has not been well discussed.

METHODS

A total of 30 patients with paroxysmal AF who underwent catheter ablation were retrospectively enrolled. Radiofrequency (RF) applications were performed with 35 W for 30 s in a point-by-point fashion under esophageal temperature monitoring. The inter-lesion distance was 4 mm. The lesions were visualized by LGE-MRI 3 months postprocedure and assessed by the LGE volume (ml), gap number (GN), and average gap length (AGL [mm]). The gaps were defined as nonenhancement sites of >4 mm. The procedural factors including the catheter-CF, stability, and orientation were calculated on the NavX system.

RESULTS

Six (20%) of 30 patients had AF recurrences 12 months postablation. A univariate analysis demonstrated that the AGL was associated with AF recurrence (hazard ratio [HR]: 1.20, confidence interval [CI]: 1.03-1.42, p = .02). All AF recurrence were found in patients with an AGL of >7 mm. The catheter-CF and stability were associated with an AGL of >7 mm, but not the orientation (CF-HR: 0.62, CI: 0.39-0.97, p = .038; stability-HR: 0.8, CI: 0.66-0.98, p = .027).

CONCLUSIONS

RF ablation with a low CF and poor catheter stability has a potential risk of creating large lesion gaps associated with AF recurrence.

Plasma protein profiling analysis in patients with atrial fibrillation before and after three different ablation techniques

Background

There are controversies on the pathophysiological alteration in patients with atrial fibrillation (AF) undergoing pulmonary vein isolation using different energy sources.

Objectives

We evaluated the changes in plasma proteins in acute phase post-ablation in patients receiving cryoballoon ablation, radiofrequency balloon ablation, or radiofrequency ablation.

Methods

Blood samples from eight healthy controls and 24 patients with AF were taken on the day of admission, day 1, and day 2 post-ablation and analyzed by the Olink proximity extension assay. Proteins were identified and performed with enrichment analysis. Protein-protein interaction network and module analysis were conducted using Cytoscape software.

Results

Of 181 proteins, 42 proteins in the cryoballoon group, 46 proteins in the radiofrequency balloon group, and 43 proteins in the radiofrequency group significantly changed after ablation. Most of the proteins altered significantly on the first day after ablation. Altered proteins were mainly involved in cytokine-cytokine receptor interaction. Both balloon-based ablations showed a similar shift toward enhancing cell communication and regulation of signaling while inhibiting neutrophil chemotaxis. However, radiofrequency ablation presented a different trend. Seed proteins, including osteopontin, interleukin-6, interleukin-10, C-C motif ligand 8, and matrix metalloproteinase-1, were identified. More significant proteins associated with hemorrhage and coagulation were selected in balloon-based ablations by machine learning.

Conclusion

Plasma protein response after three different ablations in patients with AF mainly occurred on the first day. Radiofrequency balloon ablation shared similar alteration in protein profile as cryoballoon ablation compared with radiofrequency ablation, suggesting that lesion size rather than energy source is the determinant in pathophysiological responses to the ablation.

Quantitative late gadolinium enhancement cardiac magnetic resonance analysis of the relationship between ablation parameter and left atrial tissue lesion following pulmonary vein isolation

Background

The impact of ablation parameters on acute tissue lesion formation after pulmonary vein isolation (PVI) has not been sufficiently evaluated in patients with atrial fibrillation. Radiofrequency ablation lesion can be visualized by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). We sought to quantitatively analyze the relationship between ablation parameter and tissue lesion following PVI at different segments of pulmonary vein (PV) using LGE-CMR.

Methods

Twenty-one patients with atrial fibrillation who underwent PVI procedure were retrospectively enrolled. All patients underwent LGE-CMR examination within 3 days after radiofrequency ablation. Ablation parameters during PVI were documented, including lesion size index (LSI), force-time integral (FTI), power, contact force, temperature, and time of duration. The ablation point was projected onto 3-dimensional (3D) left atrial shell constructed base on LGE-CMR and corresponding image intensity ratio (IIR) was calculated on the same shell. A tissue lesion point was defined when the LGE-CMR IIR was > 1.2.

Results

In total, 1,759 ablation points were analyzed. The ablation parameters and IIRs for each PV segment were significantly different (P < 0.0001). IIRs corresponding to ablation points at posterior of PV tended to be higher than those at non-posterior of PV when similar ablation parameters were applied during ablation. LSI was a better predictor of tissue lesion existence following PVI than FTI, contact force, power, temperature, and duration time at non-posterior wall of PV. The IIR showed positive correlation with LSI at non-posterior wall of PV (non-posterior of right PV, r = 0.13, P = 0.001, non-posterior of left PV, r = 0.26, P < 0.0001).

Conclusion

When similar ablation parameters were applied during PVI, the posterior wall of PV had more severe tissue lesion than non-posterior wall of PV. Therefore, it was reasonable to decrease ablation energy at posterior wall of PV. Moreover, LSI was a better index to reflect tissue lesion quality following PVI at non-posterior of PV.

Use of P wave indices to evaluate efficacy of catheter ablation and atrial fibrillation recurrence: a systematic review and meta-analysis

BACKGROUND

To investigate the changes of P wave indices in atrial fibrillation (AF) patients after catheter ablation and the association between P wave indices and AF recurrence.

METHODS

PubMed, Embase, and Cochrane Database were searched through September 15th 2021 for studies on the association between P wave indices and AF with catheter ablation. Heterogeneity was estimated using the I² statistic, the random effects model was used to calculate the pooled results, and summary receiver operating characteristic curve (SROC) was used to evaluate the predictive value.

RESULTS

Among included fourteen studies with 1674 AF patients, we found significantly decreased P wave dispersion (P_dis) (mean difference [MD]: - 6.5 ms, 95% confidence interval [95% CI]: - 11.81 to - 1.18, P = 0.02) after cryoballoon ablation (CBA) or radiofrequency ablation (RFA), and maximum P wave (P_max) (MD: - 8.57 ms, 95% CI: - 17.03 to - 0.10, P = 0.05) after RFA only, but increased minimum P wave (P_min) (MD: 3.43 ms, 95% CI: 1.07 to 5.79, P < 0.01) after CBA only. P_dis measured before ablation was remarkably higher (MD: 5.79 ms, 95% CI: 2.23 to 9.36, P < 0.01) in patients with recurrence than without; meanwhile, P_max was higher measured both before and after ablation (MD: 6.49 ms, 95% CI: 2.30 to 10.69, P < 0.01 and MD: 11.2 ms, 95% CI: 2.88 to 19.52, P < 0.01). Furthermore, SROC analysis showed acceptable predictive efficiencies of P_dis (AUC = 0.776) and P_max (AUC = 0.759) for AF recurrence.

CONCLUSION

P_dis was significantly decreased after AF catheter ablation. Higher P_dis and P_max may have predictive values for AF recurrence.

Non-invasive assessment of pulmonary vein isolation durability using late gadolinium enhancement magnetic resonance imaging

AIMS

Electrical reconnection of pulmonary veins (PVs) is considered an important determinant of recurrent atrial fibrillation (AF) after pulmonary vein isolation (PVI). To date, AF recurrences almost automatically trigger invasive repeat procedures, required to assess PVI durability. With recent technical advances, it is becoming increasingly common to find all PVs isolated in those repeat procedures. Thus, as ablation of extra-PV targets has failed to show benefit in randomized trials, more and more often these highly invasive procedures are performed only to rule out PV reconnection. Here we aim to define the ability of late gadolinium enhancement (LGE)-magnetic resonance imaging (MRI) to rule out PV reconnection non-invasively.

METHODS AND RESULTS

This study is based on a prospective registry in which all patients receive an LGE-MRI after AF ablation. Included were all patients that-after an initial PVI and post-ablation LGE-MRI-underwent an invasive repeat procedure, which served as a reference to determine the predictive value of non-invasive lesion assessment by LGE-MRI.: 152 patients and 304 PV pairs were analysed. LGE-MRI predicted electrical PV reconnection with high sensitivity (98.9%) but rather low specificity (55.6%). Of note, LGE lesions without discontinuation ruled out reconnection of the respective PV pair with a negative predictive value of 96.9%, and patients with complete LGE lesion sets encircling all PVs were highly unlikely to show any PV reconnection (negative predictive value: 94.4%).

CONCLUSION

LGE-MRI has the potential to guide selection of appropriate candidates and planning of the ablation strategy for repeat procedures and may help to identify patients that will not benefit from a redo-procedure if no ablation of extra-PV targets is intended.

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.

Ablation Lesion Assessment with MRI

Late gadolinium enhancement (LGE) MRI is capable of detecting not only native cardiac fibrosis, but also ablation-induced scarring. Thus, it offers the unique opportunity to assess ablation lesions non-invasively. In the atrium, LGE-MRI has been shown to accurately detect and localise gaps in ablation lines. With a negative predictive value close to 100% it can reliably rule out pulmonary vein reconnection non-invasively and thus may avoid unnecessary invasive repeat procedures where a pulmonary vein isolation only approach is pursued. Even LGE-MRI-guided repeat pulmonary vein isolation has been demonstrated to be feasible as a standalone approach. LGE-MRI-based lesion assessment may also be of value to evaluate the efficacy of ventricular ablation. In this respect, the elimination of LGE-MRI-detected arrhythmogenic substrate may serve as a potential endpoint, but validation in clinical studies is lacking. Despite holding great promise, the widespread use of LGE-MRI is still limited by the absence of standardised protocols for image acquisition and post-processing. In particular, reproducibility across different centres is impeded by inconsistent thresholds and internal references to define fibrosis. Thus, uniform methodological and analytical standards are warranted to foster a broader implementation in clinical practice.

Pulsed Field Ablation to Treat Atrial Fibrillation: A Review of the Literature

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and catheter ablation, which can be used in symptomatic patients refractory to antiarrhythmic therapy. Pulmonary vein isolation (PVI) remains the cornerstone of any ablation procedure. A major limitation of current catheter ablation procedures is important to recognize because even when the PVI is performed in highly experienced centers, PVI reconnection was documented in about 20% of patients. Therefore, better technology is needed to improve ablation lesions. One of the novelties in recent years is pulsed filed ablation (PFA), a non-thermal energy that uses trains of high-voltage, very-short-duration pulses to kill the cells. The mechanism of action of this energy consists of creating pores in the myocardiocyte cell membrane in a highly selective and tissue-specific way; this leads to death of the target cells reducing the risk of damage to surrounding non-cardiac tissues. In particular during the animal studies, PVI and atrial lines were performed effectively without PV stenosis. Using PFA directly on coronary arteries, there was no luminal narrowing, there has been no evidence of incidental phrenic nerve injury, and finally, PFA has been shown not to injure esophageal tissue when directly applied to the esophagus or indirectly through ablation in the left atrium. The aim of this review is to report all published animal and clinical studies regarding this new technology to treat paroxysmal and persistent AF.

The Incidence, Electrophysiological Characteristics and Ablation Outcome of Left Atrial Tachycardias after Pulmonary Vein Isolation Using Three Different Ablation Technologies

Background: Left atrial tachycardias (LAT) are a well-known outcome of pulmonary vein isolation (PVI). Few data are available on whether the catheter used to perform PVI influences the incidence, as well as the characteristics of post PVI LAT. We present data on LAT following PVI by the following three ablation technologies: (1) phased multi-electrode radiofrequency catheter (PVAC), (2) irrigated single-tip catheter (iRF), and (3) cryoballoon ablation. Methods: Using a prospectively designed single-center database, we analyzed 650 patients (300 iRF, 150 PVAC, and 200 cryoballoon) with paroxysmal (n = 401) and persistent atrial fibrillation (AF), who underwent their first PVI at our center. Results: The three populations were comparable in their baseline characteristics; however, the cryoballoon group comprised a higher percentage of patients with persistent AF (p = 0.05). The LAT rates were 3.7% in the iRF group (mean follow-up 22 ± 14 months), 0.7% in the PVAC group (mean follow-up 21 ± 14 months), and 4% in the cryoballoon group (mean follow-up 15 ± 8 months). The predominant mechanism of LAT was macro-reentrant tachycardia. Reconnection of at least one pulmonary vein was observed in 87% of the patients who underwent 3D mapping. No predictors for LAT occurrence were identified. Conclusion: The occurrence of LAT post PVI is rare; the predominant mechanism was macro-reentrant tachycardia. Reconnection of at least one pulmonary vein was observed in nearly all the LAT patients. In our retrospective analysis, the lowest rate of LAT was observed with the PVAC. No predictors for LAT occurrence were identified.

Feasibility of catheter ablation in patients with persistent atrial fibrillation guided by fragmented late-gadolinium enhancement areas

BACKGROUND

A computer simulation model has demonstrated that atrial fibrillation (AF) driver can be attached to heterogeneous fibrosis assessed by late gadolinium enhancement magnetic resonance imaging (LGE-MRI). However, it has not been well elucidated in patients with persistent AF. The aim of this study was to investigate whether radiofrequency (RF) applications in the fragmented LGE area (FLA) could terminate AF or convert it to atrial tachycardia (AT) and improve the rhythm outcome.

METHODS

A total of 31 consecutive persistent AF patients with FLAs were enrolled (FLA ablation group, mean age: 69 ± 8 years, mean left atrial diameter: 42 ± 6 mm). A favorable response was defined as direct AF termination or AT conversion during RF applications at the FLA. The rhythm outcome was compared between the FLA ablation group and FLA burden-matched pulmonary vein isolation (PVI) group.

RESULTS

Favorable responses were found in 15 (48%) of 31 patients in the FLA group (AF termination in seven, AT conversion in eight patients), but not in the PVI group. AF recurrence at 12 months follow-up was significantly less in the FLA ablation group than in the PVI group (4 [13%] vs. 12 [39%] of 31 patients, log-rank p = .023). In patients with a favorable response, AT recurred in 1 (7%) of 15 patients, but AF did not.

CONCLUSIONS

FLA ablation could terminate AF or convert it to AT in half of the patients. No AF recurrence was documented in patients with a favorable response.

Visualization of intensive atrial inflammation and fibrosis after cryoballoon ablation: PET/MRI and LGE-MRI analysis

BACKGROUND

Atrial inflammation plays an important role in initiating atrial fibrosis, which could perpetuate atrial fibrillation (AF). However, the method of visualization of atrial inflammation has not been established. We sought to investigate whether the intensive atrial inflammation caused by cryoballoon ablation (CBA) could be detected by positron emission tomography/ magnetic resonance imaging (PET/MRI) and whether the atrial inflammation could be associated with consequent fibrosis.

METHODS

A total of 10 paroxysmal atrial fibrillation patients after CBA were enrolled. To detect and quantify intensive atrial inflammation, PET/MRI was performed to assess regional 18F-fluorodeoxyglucose (18F-FDG) uptake one day after the CBA, and the standardized uptake values (SUV) max were compared between the pulmonary vein (PV) antrum where CBA could be applied and the healthy left atrial (LA) wall where CBA could not be applied. Furthermore, the atrial inflammation one day after the procedure and atrial fibrosis areas one month after the procedure were three-dimensionally quantified by PET/MRI and late-gadolinium enhancement magnetic resonance imaging (LGE-MRI), respectively.

RESULTS

The mean SUV max at the PV antrum was significantly higher than that on the healthy LA wall (2.12 ± 0.35 vs 1.73 ± 0.30, P = .00021). The volume of the atrial inflammation strongly correlated with that of the atrial fibrosis (r = .94 [.76-.99], P = .00006).

CONCLUSIONS

The atrial inflammation after CBA could be detected by PET/MRI. CBA-induced atrial inflammation was strongly associated with consequent lesion maturation.