Blanking period after radiofrequency ablation for atrial fibrillation guided by ablation lesion maturation based on serial MR imaging

Impact of inter-lesion distance and first-pass isolation on outcomes of pulmonary venous isolation for paroxysmal atrial fibrillation

BACKGROUND

Contiguity of ablation lesions is a critical determinant of success for paroxysmal atrial fibrillation (PAF) ablation. Evidence supports maintaining an inter-lesional distance (ILD) ≤ 6 mm during pulmonary venous isolation (PVI). Meanwhile, first-pass isolation (FPI) on PVI outcome in follow-up was not deeply studied. The impact of ILD and FPI on PAF ablation outcomes was investigated.

METHODS

Consecutive PAF patients who underwent first-time antral PVI were recruited. Coordinates of ablation points were extracted from the electro-anatomical mapping system and analyzed using custom-developed software to determine the ILD. A gap is defined as ILD greater than 6 mm. FPI was defined as the achievement of PVI by encircling the ipsilateral veins while simultaneously recording their electrical activity using a multipolar catheter. The primary endpoint was freedom from documented atrial arrhythmias including AF, atrial tachycardia (AT), or atrial flutter (AFL) lasting longer than 30 s during follow-up.

RESULTS

A total of 105 patients underwent first-time antral PVI. During 13.3 ± 0.6 months of follow-up, atrial arrhythmias recurrence was noted in 22.9% of the patients. Atrial arrhythmia recurrence was significantly higher in patients with more gaps (> 2) (37.0% versus 11.9%, P < 0.01), and the number of gaps was an independent predictor of AF/AT/AFL recurrence. (Hazard ratio [HR] 1.20, 95% CI 1.03-1.40, P = 0.02). The group with FPI for at least one ipsilateral pair of PVs exhibited a decreased number of gaps (2.0 versus 7.0, P < 0.01) and demonstrated a significant correlation with a reduction of recurrence (HR 0.26, 95% CI 0.09-0.71, P = 0.01). Among 16 patients who underwent repeat ablation, the number of gaps during the index PVI was associated with PV reconnection (PVR) (P < 0.01).

CONCLUSIONS

Gaps created during PVI are a modifiable determinant of AF/AT/AFL recurrence, and avoidance of gaps is crucial to improve clinical outcomes of PAF ablation. In addition, FPI exhibited a strong predictive capability for clinical success in patients with PAF.

Effective ablation settings that predict chronic scar after atrial ablation with HELIOSTAR™ multi-electrode radiofrequency balloon catheter

BACKGROUND

Radiofrequency balloon (RFB) ablation (HELIOSTAR™, Biosense Webster) has been developed to improve pulmonary vein ablation efficiency over traditional point-by-point RF ablation approaches. We aimed to find effective parameters for RFB ablation that result in chronic scar verified by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR).

METHODS

A chronic canine model (n = 8) was used to ablate in the superior vena cava (SVC), the right superior and the left inferior pulmonary vein (RSPV and LIPV), and the left atrial appendage (LAA) with a circumferential ablation approach (RF energy was delivered to all electrodes simultaneously) for 20 s or 60 s. The electroanatomical map with the ablation tags was projected onto the 3-month post-ablation LGE-CMR. Tags were divided into two groups depending on whether they correlated with CMR-based scar (ScarTags) or non-scar tissue (Non-ScarTags). The effective parameters for scar formation were estimated by multivariate logistic regression.

RESULTS

This study assessed 80 lesions in the SVC, 80 lesions in the RSPV, 20 lesions in the LIPV, and 30 lesions in the LAA (168 ScarTags and 42 Non-ScarTags). In the multivariate analysis, two variables were associated with chronic scar formation: temperature of electrode before energy application (odds ratio (OR) 0.805, p = 0.0075) and long RF duration (OR 2.360, p = 0.0218), whereas impedance drop was not associated (OR 0.986, p = 0.373).

CONCLUSION

Lower temperature of the electrode before ablation and long ablation duration are critical parameters for durable atrial scar formation with RFB ablation.

Ablation-induced left atrial mechanical dysfunction recovers in weeks after ablation

BACKGROUND

The immediate impact of catheter ablation on left atrial mechanical function and the timeline for its recovery in patients undergoing ablation for atrial fibrillation (AF) remain uncertain. The mechanical function response to catheter ablation in patients with different AF types is poorly understood.

METHODS

A total of 113 AF patients were included in this retrospective study. Each patient had three magnetic resonance imaging (MRI) studies in sinus rhythm: one pre-ablation, one immediate post-ablation (within 2 days after ablation), and one post-ablation follow-up MRI (≤ 3 months). We used feature tracking in the MRI cine images to determine peak longitudinal atrial strain (PLAS). We evaluated the change in strain from pre-ablation, immediately after ablation to post-ablation follow-up in a short-term study (< 50 days) and a 3-month study (3 months after ablation).

RESULTS

The PLAS exhibited a notable reduction immediately after ablation, compared to both pre-ablation levels and those observed in follow-up studies conducted at short-term (11.1 ± 9.0 days) and 3-month (69.6 ± 39.6 days) intervals. However, there was no difference between follow-up and pre-ablation PLAS. The PLAS returned to 95% pre-ablation level within 10 days. Paroxysmal AF patients had significantly higher pre-ablation PLAS than persistent AF patients in pre-ablation MRIs. Both type AF patients had significantly lower immediate post-ablation PLAS compared with pre-ablation and post-ablation PLAS.

CONCLUSION

The present study suggested a significant drop in PLAS immediately after ablation. Left atrial mechanical function recovered within 10 days after ablation. The drop in PLAS did not show a substantial difference between paroxysmal and persistent AF patients.

Defining the blanking period, using continuous ECG monitoring, after cryoballoon pulmonary vein isolation

BACKGROUND

Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation. A blanking period (BP) of 3 months is used in clinical trials and practice. However, the optimal BP duration after PVI remains undefined.

OBJECTIVE

The aim of this study was to objectively define, using continuous monitoring by an implantable loop recorder, the optimal BP duration after cryoballoon PVI.

METHODS

We enrolled consecutive patients who had cryoballoon PVI and an implantable loop recorder. We determined the time of the last confirmed episode of AF within the blanking period. This was then correlated with AF recurrence in the first year after ablation.

RESULTS

There were 210 patients (66 ± 9 years; 138 [66%] male; 116 [55%] paroxysmal AF; CHA2DS2-VASc score, 2.5 ± 1.6). We defined 4 distinct groups based on the last AF episode within the BP: no AF days 0-90 (n = 96 [46%]) and last AF 0-30 days (n = 46 [22%]), 31-60 days (n = 18 [9%]), and 61-90 days (n = 50 [24%]). After the 3-month BP, 101 (48%) patients had AF recurrence at 160 ± 86 days. Compared with patients with no AF in the BP, those with recurrent AF and AF burden >0% 30 days after ablation had a significantly greater AF recurrence during long-term follow-up (P = .001).

CONCLUSION

Our data show that the approximately one-third of patients in whom AF occurs and who have a burden of >0% after the first month that follows PVI are at significantly higher risk of long-term recurrent AF. We therefore suggest that the blanking period be limited to a month after cryoballoon PVI.

Analysis of the thickness characteristics of the left atrial posterior wall and its correlation with the low and no voltage areas of the left atrial posterior wall in patients with atrial fibrillation

OBJECTIVE

To analyze the relationship between the thickness of the left atrial posterior wall and the low and no voltage zones in the left atrial posterior wall in patients with atrial fibrillation (AF).

METHODS

61 patients admitted to our cardiology department for AF and radiofrequency ablation of AF from January 1, 2020 to May 30, 2022 were enrolled according to inclusion and exclusion criteria. The atrial wall thickness was measured by CT scan. Baseline data, preoperative cardiac ultrasound data, preoperative biochemical parameters, low voltage zone (fibrotic zone) and no voltage zone (scar zone) in the left atrial posterior wall area, and various parameters of posterior left atrial wall thickness were collected.

RESULTS

The differences of the thickness between the upper, middle and lower mean levels of the left atrial posterior wall were statistically significant (P = 0.004). The results showed that body mass index was weakly positively correlated with the mean level of total left atrial posterior wall thickness (r = 0.426, P = 0.001) and was statistically significant. The remaining indices were positively or negatively correlated with the mean level of total left atrial posterior wall thickness, but none were statistically significant (P > 0.05).

CONCLUSIONS

Both left atrial posterior wall low-voltage zone and voltage-free zone were positively correlated with the mean total left atrial posterior wall thickness, and left atrial posterior wall low-voltage zone and voltage-free zone were significantly positively correlated. Body mass index was weakly positively correlated with total left atrial posterior wall thickness.

Atrial Ablation Lesion Evaluation by Cardiac Magnetic Resonance: Review of Imaging Strategies and Histological Correlations

Cardiac magnetic resonance (CMR) imaging is a valuable noninvasive tool for evaluating tissue response following catheter ablation of atrial tissue. This review provides an overview of the contemporary CMR strategies to visualize atrial ablation lesions in both the acute and chronic postablation stages, focusing on their strengths and limitations. Moreover, the accuracy of CMR imaging in comparison to atrial lesion histology is discussed. T2-weighted CMR imaging is sensitive to edema and tends to overestimate lesion size in the acute stage after ablation. Noncontrast agent-enhanced T1-weighted CMR imaging has the potential to provide more accurate assessment of lesions in the acute stage but may not be as effective in the chronic stage. Late gadolinium enhancement imaging can be used to detect chronic atrial scarring, which may inform repeat ablation strategies. Moreover, novel imaging strategies are being developed, but their efficacy in characterizing atrial lesions is yet to be determined. Overall, CMR imaging has the potential to provide virtual histology that aids in evaluating the efficacy and safety of catheter ablation and monitoring of postprocedural myocardial changes. However, technical factors, scanning during arrhythmia, and transmurality assessment pose challenges. Therefore, further research is needed to develop CMR strategies to visualize the ablation lesion maturation process more effectively.

Evidence-based insights on ideal blanking period duration following atrial fibrillation catheter ablation

AIMS

Despite the general adoption of a 3-month blanking period (BP), increasing scientific evidence suggests an association between early recurrences of atrial tachyarrhythmias (ERAT) and failure of atrial fibrillation catheter ablation (AFCA). The aim of the present study was to perform a diagnostic meta-analysis to derive the ideal BP cut-off following AFCA.

METHODS AND RESULTS

PubMed/MEDLINE databases were screened for articles reporting late recurrences of atrial tachyarrhythmias (LRAT) in AFCA patients experiencing an ERAT (with at least one time cut-off). Seventeen studies were finally included in the analysis, encompassing 5837 AF patients experiencing ERAT after AFCA. A random-effect meta-analysis of diagnostic test accuracy studies with multiple cut-offs was performed. The day at which the ERAT occurred was considered the diagnostic 'test', whereas the different time cut-offs reported in the singular studies were treated as cut-offs of interest in the meta-analysis. Overall, a 27.7 day (95% confidence interval: 10.4-45.1 days) cut-off was identified as the optimal BP duration [area under the summary receiver operating characteristic (AUC-SROC) curve: 0.66, 95% CI: 0.56-0.75]. Specificity (95% CI: 63-85%) and positive predictive value were 76%. At subgroup analysis, the optimal BP cut-off was 39.0 days (95% CI: 26.8-51.2 days, AUC-SROC: 0.63) following radiofrequency AFCA and 30.1 days (95% CI: 0-63.4 days, AUC-SROC: 0.76) after cryoballoon ablation.

CONCLUSION

The present meta-analysis indicates that a 4-week BP represents the optimal cut-off following AFCA. Altogether, these meta-analytic insights support the need of a revision of the actual 3-month BP duration.

Early arrhythmia recurrence after cryoballoon ablation in atrial fibrillation: a systematic review and meta-analysis

BACKGROUND

Early arrhythmia recurrence within the three-month blanking period is a common event that historically has been attributed to reversible phenomena. While its' mechanistic links remain obscure, accumulating evidence support the argument of shortening the blanking period. We aimed to elucidate the association between early and late arrhythmia recurrence after atrial fibrillation cryoablation.

METHODS

The MEDLINE database, ClinicalTrials.gov, medRxiv and Cochrane Library were searched for studies evaluating early and late arrhythmia recurrence rates in patients undergoing cryoablation for AF. Data were pooled by meta-analysis using a random-effects model. The primary endpoint was late arrhythmia recurrence.

RESULTS

Early arrhythmia recurrence was found predictive of decreased arrhythmia-free survival after evaluating 3975 patients with paroxysmal or persistent atrial fibrillation who underwent cryoablation (OR: 5.31; 95% CI: 3.75-7.51). This pattern remained unchanged after sub-analyzing atrial fibrillation type (paroxysmal; OR: 7.16; 95% CI: 4.40-11.65 and persistent; OR: 7.63; 95% CI: 3.62-16.07) as well as cryoablation catheter generation (first generation; OR: 5.15, 95% CI: 2.39-11.11 and advanced generation; OR: 5.83, 95% CI: 3.68-9.23). Studies permitting anti-arrhythmic drug utilization during blanking period or examining early recurrence as a secondary outcome were found to be a significant source of statistical heterogeneity.

CONCLUSION

Our findings suggest that early arrhythmia recurrence is predictive of late outcomes after cryoablation for atrial fibrillation. Identifying which patients deserve earlier re-intervention is an open research avenue. This article is protected by copyright. All rights reserved.

Predictors of clinical success after paroxysmal atrial fibrillation catheter ablation

INTRODUCTION

Contact force (CF) guided ablation of paroxysmal atrial fibrillation (PAF) with stable catheter-tissue contact optimizes clinical success and may increase an operator's ability to achieve pulmonary vein isolation (PVI) in a single encirclement. First pass PVI reduces procedure time but the relationship with long term clinical success is not well understood. This study evaluated patient characteristics and procedural details as predictors of 1-year clinical success after PAF ablation, including first pass isolation.

METHODS

Consecutive de novo PAF ablations were performed with a porous tip CF catheter in 2017 and 2018. All ablations used wide-area circumferential ablation, with first pass isolation captured separately for the left and right pulmonary veins (PVs). CF was held between 10 and 20 g and the catheter was moved every 10-20 s. Radiofrequency energy was set at 40-45 W throughout the atrium. Patient characteristics and procedural details were tested for association with clinical success, defined as freedom from recurrent atrial tachyarrhythmia through 1 year.

RESULTS

A total of 404 patients were included in the study. Clinical success at 1 year was 86.6%. Achieving first pass isolation on at least one ipsilateral PV pair was the most significant predictor of clinical success (p = .0126). After controlling for first pass isolation, only recurrence within the 90-day blanking period was independently predictive (p = .0015). First pass isolation was not associated with early recurrence (p = .2454).

CONCLUSION

In a real-world setting, first pass isolation was highly predictive of 12-month clinical success after CF-guided ablation in a PAF population.

Predictive role of early recurrence of atrial fibrillation after cryoballoon ablation

Aims

The aims of this study were to determine the rate and the predictors of early recurrences of atrial fibrillation (ERAF) after cryoballoon (CB) ablation and to evaluate whether ERAF correlate with the long-term outcome.

Methods and results

Three thousand, six hundred, and eighty-one consecutive patients (59.9 ± 10.5 years, female 26.5%, and 74.3% paroxysmal AF) were included in the analysis. Atrial fibrillation recurrence, lasting at least 30 s, was collected during and after the 3-month blanking period. Three-hundred and sixteen patients (8.6%) (Group A) had ERAF during the blanking period, and 3365 patients (Group B) had no ERAF. Persistent AF and number of tested anti-arrhythmic drugs ≥2 resulted as significant predictors of ERAF. After a mean follow-up of 16.8 ± 16.4 months, 923/3681 (25%) patients had at least one AF recurrence. The observed freedom from AF recurrence, at 24-month follow-up from procedure, was 25.7% and 64.8% in Groups A and B, respectively (P &lt; 0.001). ERAF, persistent AF, and number of tested anti-arrhythmic drugs ≥2 resulted as significant predictors of AF. In a propensity score matching, the logistic model showed that ERAF 1 month after ablation are the best predictor of long-term AF recurrence (P = 0.042).

Conclusion

In patients undergoing CB ablation for AF, ERAF are rare and are a strong predictor of AF recurrence in the follow-up, above all when occur &gt;30 days after the ablation.

Redefining the Blanking Period by a Long-Term Follow-Up after Atrial Fibrillation Ablation Using Second-Generation Cryoballoon

On the basis of radiofrequency ablation of atrial fibrillation (AF), some studies suggested that early recurrences of atrial tachyarrhythmia (ERATs) were associated with late AF recurrence (LAFR), and some also suspected and challenged the current recommended 90 day blanking period. We aim to evaluate the impact of ERAT on long-term success and to determine the optimum blanking period after AF ablation using second-generation cryoballoon (sg-CB). From August 2016 to October 2018, 369 consecutive patients who successfully underwent initial AF ablation using sg-CB at the Fuwai Hospital were finally enrolled. All patients were followed up no less than 12 months. Receiver operating characteristic curve analysis was used to determine the optimum blanking period after AF ablation. There were 62 (16.8%) who experienced ERAT. After a median follow-up of 615 days, 74.5% were free of LAFR after the 90 day blanking period. Incidence of freedom from LAFR during the long-term follow-up was markedly lower in patients with ERAT than in those without ERAT (27.4% versus 84.0%; log-rank P < 0.001). Furthermore, only ERAT (HR 8.579; 95% CI 5.604-13.133; P < 0.001) was significantly associated with an increased risk of LAFR after adjusting for other factors. The optimum cut-off time point for the blanking period was 21.5 days (sensitivity: 71.1%, specificity: 94.1%). In conclusion, ERAT was an independent predictor of LAFR after AF ablation using sg-CB. Based on our findings, blanking period was advised to be shorten to 21.5 days or about 3 weeks instead of 90 days after CB ablation.

Reproducibility of clinical late gadolinium enhancement magnetic resonance imaging in detecting left atrial scar after atrial fibrillation ablation

INTRODUCTION

Late gadolinium enhancement (LGE) cardiac magnetic resonance imaging (MRI) can be used to detect postablation atrial scar (PAAS) but its reproducibility and reliability in clinical scans across different magnetic flux densities and scar detection methods are unknown.

METHODS

Patients (n = 45) having undergone two consecutive MRIs (3 months apart) on 3T and 1.5T scanners were studied. We compared PAAS detection reproducibility using four methods of thresholding: simple thresholding, Otsu thresholding, 3.3 standard deviations (SD) above blood pool (BP) mean intensity, and image intensity ratio (IIR). We performed a texture study by dividing the left atrial wall intensity histogram into deciles and evaluated the correlation of the same decile of the two scans as well as to a randomized distribution of intensities, quantified using Dice Similarity Coefficient (DSC).

RESULTS

The choice of scanner did not significantly affect the reproducibility. The scar detection performed by Otsu thresholding (DSC of 71.26 ± 8.34) resulted in a better correlation of the two scans compared with the methods of 3.3 SD above BP mean intensity (DSC of 57.78 ± 21.2, p < .001) and IIR above 1.61 (DSC of 45.76 ± 29.55, p <.001). Texture analysis showed that correlation only for voxels with intensities in deciles above the 70th percentile of wall intensity histogram was better than random distribution (p < .001).

CONCLUSIONS

Our results demonstrate that clinical LGE-MRI can be reliably used for visualizing PAAS across different magnetic flux densities if the threshold is greater than 70th percentile of the wall intensity distribution. Also, atrial wall-based thresholding is better than BP-based thresholding for reproducible PAAS detection.