Cryoballoon ablation of atrial fibrillation: a practical and effective approach

[Technical principles of ablation therapy]

Catheter ablation is a standard procedure in modern cardiology. It can significantly improve the quality of life and life expectancy of cardiac arrhythmia patients. Besides cardiac mapping, ablation itself is a fundamental step to successfully treat cardiac arrhythmias. There are various ablation technologies at hand: In traditional radiofrequency (RF) ablation, electrical current flow generates coagulation necrosis. When understanding the biophysical principles of RF ablation, the investigator is capable to adapt lesion geometry and size to the requirements of the procedure and vary them individually. In addition, lesion metric indices evaluate and integrate important parameters such as power, duration, impedance and contact force to standardize and control RF lesions. Cryoablation induces ice crystals within myocardial tissue, which lead to destruction and electrical scarring of the treated tissue. Histologically, cryolesions are well-delineated with preserved tissue architecture and intact endocardium. Pulsed field ablation (PFA) is a novel rising technology, particularly used for pulmonary vein isolation. In contrast to classic thermal technologies (RF and cryoablation), PFA uses pulsed electrical fields to electroporate cardiac tissue and thereby creates damage on a cellular level only.

A pilot clinical assessment of biphasic asymmetric pulsed field ablation catheter for pulmonary vein isolation

Pulsed field ablation (PFA) is a new treatment for atrial fibrillation (AF), and its selective ablation characteristics give it a significant advantage in treatment. In previous cellular and animal experiments, we have demonstrated that biphasic asymmetric pulses can be used to ablate myocardial tissue. However, small-scale clinical trials are needed to test whether this approach is safe and feasible before extensive clinical trials can be performed. Therefore, the purpose of this experiment is to determine the safety and feasibility of biphasic asymmetric pulses in patients with AF and is to lay the foundation for a larger clinical trial. Ablation was performed in 10 patients with AF using biphasic asymmetric pulses. Voltage mapping was performed before and after PFA operation to help us detect the change in the electrical voltage of the pulmonary veins (PV). 3-Dimensional mapping system showed continuous low potential in the ablation site, and pulmonary vein isolation (PVI) was achieved in all four PV of the patients. There were no recurrences, PV stenosis, or other serious adverse events during the 12 months follow-up. The results suggest that PFA using biphasic asymmetric waveforms for patients with AF is safe, durable, and effective and that a larger clinical trial could begin.

Clinical Trial Registration

https://www.chictr.org.cn/, identifier, ChiCTR2100051894.

Cryoballoon ablation of non-PV triggers in persistent atrial fibrillation

Cryoballoon-based catheter ablation has emerged as an efficacious and safe therapeutic intervention for patients with paroxysmal atrial fibrillation (PAF). PAF is primarily associated with the triggers in the pulmonary vein (PV). However, persistent atrial fibrillation (PeAF) is a complex condition that involves changes in the atrial substrate and the presence of non-PV triggers. Therefore, a comprehensive treatment approach is necessary for patients with PeAF. Utilizing a 3D electroanatomical map, the radiofrequency-based ablation technique adeptly identifies and targets the atrial substrate and non-PV triggers. On the other hand, the cryoballoon-based AF ablation was initially designed for PV isolation. However, its single-shot feature makes it a great choice for electrophysiologists looking to address non-PV triggers. It is possible to target the left atrial appendage (LAA), superior vena cava (SVC), left atrial roof, and posterior wall using the apparatus's unique configuration and ablation abilities. This review focuses on the increasing literature regarding cryoballoon-based methods for non-PV trigger ablation. Specifically, it delves into the technical procedures used to isolate the LAA, SVC, and ablate the left atrial roof and posterior wall.

Feasibility study of cryoballoon ablation for atrial fibrillation with KODEX-EPD: a single center experience

To evaluate the feasibility of cryoballoon (CB) ablation of atrial fibrillation (AF) under the guidance of a new three-dimensional (3D) mapping system KODEX-EPD. 40 patients scheduled for CB ablation of AF in the first affiliated Hospital of Xinjiang Medical University from August 2021 to July 2022 were randomly divided into two groups: KODEX-EPD 3D mapping system guidance group (KODEX group, n = 20) and conventional two-dimensional perspective group (standard group, n = 20). The ablation time, operation time, fluoroscopy time, fluoroscopy dose, contrast agent dosage and follow-up data were compared between the two groups. Besides, the feasibility and accuracy of the dielectric sensing system in evaluating pulmonary vein (PV) occlusion in patients with AF during CB ablation were verified. All pulmonary veins were being isolated. The ablation time (36.40 ± 6.72 min vs 35.15 ± 6.29 min, P > 0.05) and the operation time (64.20 ± 11.82 min vs 66.00 ± 13.18 min, P > 0.05) were not statistically different in the two groups. The standard group has longer fluoroscopy time, dose and contrast medium dosage. There were significant differences in fluoroscopy time (532.30 ± 72.83 s vs 676.25 ± 269.33 s, P < 0.05), fluoroscopy dose (110.00 ± 28.64 mGy vs 144.68 ± 66.66 mGy, P < 0.05), and contrast medium dosage (71.90 ± 5.97 ml vs 76.05 ± 5.93 ml, P < 0.05) between the two groups. The learning curves of the first 5 patients and the last 15 patients in the KODEX group were compared. There was no statistical difference in the ablation time (36.80 ± 8.56 min vs 36.27 ± 6.34 min, P > 0.05) or the operation time (69.00 ± 5.00 min vs 62.60 ± 13.10 min, P > 0.05); however, compared to the first 5 patients, fluoroscopy time (587.40 ± 38.34 s vs 513.93 ± 73.02 s, P < 0.05), fluoroscopy dose (147.85 ± 35.19 mGy vs 97.39 ± 8.80 mGy, P < 0.05) and contrast medium dosage (79.60 ± 1.14 ml vs 69.33 ± 4.45 ml, P < 0.05) were significantly decreased. Using pulmonary venography as the gold standard, the sensitivity, specificity of the completely occlusion in KODEX group was 93.6% (95% CI 85-97.6%) and 69.6% (95% CI 54-81.8%); and the sensitivity, specificity of the small leak in KODEX group was 93.1% (95% CI 82.4-97.8%) and 82.0% (95% CI 65.9-91.9%). During an average follow-up of (9.90 ± 1.06) months, there was no statistical difference in arrhythmia recurrence and antiarrhythmic drugs taking after CB ablation between the two groups (P > 0.05). Using the KODEX-EPD system, the CB ablation procedure can correctly evaluate the PV occlusion, and significantly reduce fluoroscopy exposure and contrast medium without significantly increasing the operation time.

A nomogram based on CHADS2 score for predicting atrial fibrillation recurrence after cryoballoon ablation

BACKGROUND

As reported, CHADS₂ scoring system moderately predicts the atrial fibrillation (AF) recurrence, a common event after cryoballoon ablation. We aimed to improve the diagnostic accuracy of the CHADS₂ score by adding several routine auxiliary detection indicators into the scoring system and constructing a CHADS₂ score-based nomogram to predict AF recurrence in patients with paroxysmal AF undergoing cryoballoon ablation.

METHODS

Eighty-four patients with paroxysmal AF undergoing cryoballoon ablation were enrolled. Baseline characteristics were collected. The multivariable Cox proportional hazards model was used to identify the significantly related predictors of recurrence and to construct the nomogram whose performance was evaluated by the discrimination and calibration tests.

RESULTS

Thirty-five patients developed AF recurrence after a mean follow up of 19.0 ± 15.77 months. In the Cox multivariate model, CHADS₂ (>2) (hazard ratio [HR]: 2.38; 95% confidence interval [CI]: 1.14-4.98, p = .021) and albumin-to-globulin ratio (AGR) (HR: 2.49; 95% CI: 1.26-4.92, p < .008) were independent risk factors associated with AF recurrence. In addition to CHADS₂ , AGR and red blood cell distribution width were used to construct the nomogram. As a result, the discrimination of the concordance index for the predictive model of AF recurrence was increased from 0.56 (95% CI: 0.494-0.632) to 0.712 (95% CI: 0.631-0.811). The 24-month one well matched the ideal 45° line among the calibration plots for 6, 12, and 24 months' recurrence-free survival.

CONCLUSION

This novel easy-to-use CHADS₂ score-based nomogram may be used to predict AF recurrence for patient of paroxysmal AF undergoing cryoballoon ablation. Further external validation is still needed.

A Systematic Review and Meta-Analysis of the Direct Comparison of Second-Generation Cryoballoon Ablation and Contact Force-Sensing Radiofrequency Ablation in Patients with Paroxysmal Atrial Fibrillation

The superiority of second-generation cryoballoon (2G-CB) ablation versus contact force-sensing radiofrequency (CF-RF) ablation in patients with paroxysmal atrial fibrillation (AF) was assessed in this systematic review and meta-analysis. Freedom from atrial tachyarrhythmias (ATAs) (OR = 0.89; 95% confidence interval [CI] = 0.68 to 1.17; p = 0.41), freedom from AF (OR = 0.93; 95% CI = 0.65 to 1.35; p = 0.72), and acute pulmonary vein isolation (PVI) (OR = 1.17; 95% CI = 0.54 to 2.53; p = 0.70) between 2G-CB ablation and CF-RF ablation were not different. The procedure time for the 2G-CB ablation was shorter (MD = −18.78 min; 95% CI = −27.72 to −9.85 min; p < 0.01), while the fluoroscopy time was similar (MD = 2.66 min; 95% CI = −0.52 to 5.83 min; p = 0.10). In the 2G-CB ablation group, phrenic nerve paralysis was more common (OR = 5.74; 95% CI = 1.80 to 18.31; p = < 0.01). Regarding freedom from ATAs, freedom from AF, and acute PVI, these findings imply that 2G-CB ablation is not superior to CF-RF ablation in paroxysmal AF. Although faster than CF-RF ablation, 2G-CB ablation has a greater risk of phrenic nerve paralysis.

Objective and subjective assessment of the recurrence of atrial fibrillation after cryoballoon ablation of the pulmonary veins

Background: Adequate diagnosis of recurrent atrial fibrillation after the surgical treatment in patients with paroxysmal forms of the disease appears to be a difficult task. Aims: The manuscript is devoted to a comparative analysis of the results of subjective and objective assessment of atrial fibrillation recurrence after cryoballoon ablation of the pulmonary veins. Material and methods: 301 patients were included in the study. All of them consequentially underwent cryoballoon ablation of the pulmonary veins in the period of October, 2016 November, 2019. The inclusion criteria were as follows: symptomatic atrial fibrillation; confirmation of atrial fibrillation by instrumental diagnostic methods. The exclusion criteria were the following: a combination of atrial fibrillation and atrial flutter at the time of surgery; history of open-heart procedures and catheter procedures to cease atrial fibrillation; the presence of concomitant cardiac and "arrhythmogenic" pathology. Results: In the period of May 01-30, 2020, 100% (n=301) of the patients included in the study were assessed by the method of targeted survey. The median duration of the postoperative period to the time of a patient's survey was 21 (3; 43) months. The interviews have shown that 136 (45%) patients noted a return of complaints associated with atrial fibrillation recurrence in the postoperative period. There was a clear tendency towards a decrease in the total number of patients with complaints of the clinical recurrence of the disease, depending on the time elapsed since the surgical procedure. The longer the period from the moment of surgery, the lower the number of patients with recurrence. Of 136 patients with recurrent complaints associated with atrial fibrillation, 97 (71%) were able to conduct the daily electrocardiogram monitoring. Of these, the instrumental recurrence of atrial fibrillation was confirmed in 59 patients, which amounted to 20% of all the patients included in the study (n=301). Conclusion: To establish the true number of atrial fibrillation recurrence after cryoballoon ablation of the pulmonary veins, a targeted survey of patients is desirable for up to 12 months after the surgery. The patients with complaints which suggest atrial fibrillation recurrence, even if these complaints do not correspond to the preoperative ones, should be invited for the instrumental diagnostics of arrhythmia.

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.

Cryoballoon Ablation for the Treatment of Atrial Fibrillation: A Meta-analysis

BACKGROUND

Ablation therapy is the treatment of choice in antiarrhythmic drugrefractory atrial fibrillation (AF). It is performed by either cryoballoon ablation (CBA) or radiofrequency ablation. CBA is gaining popularity due to simplicity with similar efficacy and complication rate compared with RFA. In this meta-analysis, we compare the recurrence rate of AF and the complications from CBA versus RFA for the treatment of AF.

METHODS

We systematically searched PubMed for the articles that compared the outcome of interest. The primary outcome was to compare the recurrence rate of AF between CBA and RFA. We also included subgroup analysis with complications of pericardial effusion, phrenic nerve palsy and cerebral microemboli following ablation therapy.

RESULTS

A total of 24 studies with 3527 patients met our predefined inclusion criteria. Recurrence of AF after CBA or RFA was similar in both groups (RR: 0.84; 95% CI: 0.65, 1.07; I2=48%, Cochrane p=0.16). In subgroup analysis, heterogeneity was less in paroxysmal AF (I2=0%, Cochrane p=0.46) compared to mixed AF (I2=72%, Cochrane p=0.003). Procedure and fluoroscopy time was less by 26.37 and 5.94 minutes respectively in CBA compared to RFA. Complications, pericardial effusion, and silent cerebral microemboli, were not different between the two groups, however, phrenic nerve palsy was exclusively present only in CBA group.

CONCLUSION

This study confirms that the effectiveness of CBA is similar to RFA in the treatment of AF with the added advantages of shorter procedure and fluoroscopy times.

Meta-analysis of randomized controlled trials on atrial fibrillation ablation in patients with heart failure with reduced ejection fraction

BACKGROUND

The role of catheter ablation (CA) is increasingly recognized as a reasonable therapeutic option in patients with atrial fibrillation (AF) and heart failure (HF).

HYPOTHESIS

We aimed to compare CA to medical therapy in AF patients with HF with reduced ejection fraction (HFrEF).

METHODS

We searched the literature for randomized clinical trials comparing CA to medical therapy in this population.

RESULTS

Six trials with a total of 775 patients were included. AF was persistent in 95% of patients with a mean duration of 18.5 ± 23 months prior enrollment. The mean age was 62.2 ± 7.8 years, mostly males (83%) with mean left ventricular ejection fraction (LVEF) of 31.2 ± 6.7%. Compared to medical therapy, CA has significantly improved LVEF by 5.9% (Mean difference [MD] 5.93, confidence interval [CI] 3.59-8.27, P < 0.00001, I²  = 87%), quality of life, (MD -9.01, CI -15.56, -2.45, P = 0.007, I² = 47%), and functional capacity (MD 25.82, CI 5.46-46.18, P = 0.01, I² = 90%). CA has less HF hospital readmissions (odds ratio [OR] 0.5, CI 0.32-0.78, P = 0.002, I² = 0%) and death from any cause (OR 0.46, CI 0.29-0.73, P = 0.0009, I² = 0%). Freedom from AF during follow-up was higher in patients who had CA (OR 24.2, CI 6.94-84.41, P < 0.00001, I² = 81%.

CONCLUSION

CA was superior to medical therapy in patients with AF and HFrEF in terms of symptoms, hemodynamic response, and clinical outcomes by reducing AF burden. However, these findings are applicable to the very specific patients enrolled in these trials.

Center experience does not influence long-term outcome and peri-procedural complications after cryoballoon ablation of paroxysmal atrial fibrillation: Data on 860 patients from the real-world multicenter observational project

BACKGROUND

The aim of this research was to evaluate whether the procedural data, the incidence of complications, and the long-term freedom from atrial fibrillation (AF) recurrences are influenced by center experience in a paroxysmal AF (PAF) population performing a first-time pulmonary vein isolation (PVI) by cryoballoon ablation (CBA).

METHODS

A total of 860 patients underwent PVI by CBA. Center experience groups were predefined according to the quartiles of the distribution regarding the amount of performed procedures: 3.1%, 10.6%, 22.7% and 63.6% of patients were respectively followed in each group from 1st (less experienced) to 4th (more experienced) quartile of experience.

RESULTS

In the entire population, median procedure and fluoroscopy time were 105 and 25 min, respectively. The median procedure time significantly decreased from 130 to 90 min (P < 0.001) as the center's experience increased. In 47 (5.5%) patients, a peri-procedural complication occurred. As the experience of centers increased, the acute intraprocedural PVI success rate increased (from 94.3% to 98.9%, P = 0.007), whereas there was a tendency towards a decreased incidence of peri-procedure complications (from 7.4% to 4.6%, P = 0.998). The mean 1-year freedom from AF recurrence probability was 78.3%, and the 18-month mean was 68.9% with no difference among the groups with different levels of experience.

CONCLUSION

CBA is a safe and effective treatment for patients with PAF. Peri-procedural complications and procedural times were low in all the analyzed sub-groups, showing a decreasing trend in function of center expertise. The long-term freedom from AF recurrence was not influenced by the level of experience. (clinicaltrials.gov: NCT01007474).

Transseptal Access to the Left Atrium: Tips and Tricks to Keep it Safe Derived from Single Operator Experience and Review of the Literature

BACKGROUND

Transseptal puncture (TSP) remains a demanding procedural step in accessing the left atrium with inherent risks and safety concerns, mostly related to cardiac tamponade.

OBJECTIVE

Based on our own experience with 249 TSP procedures and in-depth literature review, we present our results and offer several tips and tricks that may render TSP successful and safe.

METHODS

This prospective study comprised 249 consecutive patients (146 men), aged 41.6±17.4 years, undergoing TSP by a single operator for ablation of a variety of arrhythmias, mostly related to left accessory pathways (n=145) or left atrial tachycardias (n=33) and more recently, atrial fibrillation (n=70). TSP was guided by fluoroscopy alone in all patients without the use of echocardiography imaging. In addition, an extensive literature review of TSP-related topics was carried out in PubMed, Scopus and Google Scholar.

RESULTS

Among 249 patients, 33 patients were children or young adolescents (aged 7-18 years); 14 patients were undergoing a repeat procedure. Patients with a manifest accessory pathway were the youngest (mean age 33.7±15.9) and patients with atrial fibrillation the oldest (mean age 56.0±10.8 years). A successful TSP was accomplished in 247 patients (99.2%). Two (0.8%) procedures were complicated by cardiac tamponade managed successfully with pericardiocentesis or surgical drainage. Review of the literature revealed no systematic reviews and meta-analyses of TSP studies; however, several patient series have documented that fluoroscopy-guided TSP, with various modifications in the technique employed in the present series, have been effective in 95-100% of the cases with a complication rate ranging from 0.0% to 6.7%, albeit with a mortality rate of 0.018%- 0.2%. Echo imaging techniques were employed in cases with difficult TSP.

CONCLUSION

Employing a standardized protocol with use of fluoroscopy alone minimized serious complications to 0.8% (2 patients) among 249 consecutive patients undergoing TSP for ablation of a variety of cardiac arrhythmias. Based on this single-operator experience and review of the literature, a list of practical tips and tricks is provided for a successful and safe procedure, reserving the more expensive and patient inconveniencing echo-imaging techniques for difficult or failed cases.

Ablation of atrial fibrillation: single-shot techniques poised to dominate rhythm control strategies/the future is here

Over the recent years, the advent of single-shot techniques, such as circular catheter and cryoballoon ablation, has ushered in a new era in the catheter ablation approach and rhythm control strategies of patients with atrial fibrillation (AF). These techniques make it easier to navigate the heart and have the potential to decrease the threshold for, expand the access to, and increase patient and physician acceptance of rhythm-control therapies, that may lead to reduction of the AF disease burden and its socioeconomic impact. Due to technical issues the circular catheter technique is lagging behind, however the cryoballoon approach is progressing at a faster pace both in the field of technical advancements and clinical studies, all contributing to its rapid penetration in the electrophysiological community and rhythm management approaches toward the commonest cardiac arrhythmia. Comparative studies of the conventional point-by-point radiofrequency (RF) ablation technique and the cryoablation approach to pulmonary vein isolation (PVI), which constitutes the cornerstone of all ablation methods, seem to favor the cryoablation technique in certain aspects. The results of current studies converge in their conclusion that cryoablation employing current generation cryoballoons is a simplified and faster method compared to the conventional technique in achieving effective and durable PVI. Furthermore, investigators have recently proposed particular tips and parameters to serve as reliable predictors of successful and durable PVI that may enhance the clinical success of this single-shot ablation technique. These issues will be discussed in this overview and placed into perspective.

Cryoballoon ablation of atrial fibrillation: a practical and effective approach

Medical management of atrial fibrillation (AF), the most common arrhythmia in the general population, has had modest efficacy in controlling symptoms and restoring and maintaining sinus rhythm. Since the seminal observation in 1998 that pulmonary veins host the triggers of AF in the majority of cases, electrical isolation of all pulmonary veins constitutes the cornerstone of ablation in patients with symptomatic AF. However, due to the elaborate and tedious technique of the conventional point-by-point method with radiofrequency ablation guided by electroanatomical mapping, newer, more versatile single-shot techniques, such as cryoballoon ablation, have been sought and developed over recent years and are progressively prevailing. Cryoballoon ablation appears to be the most promising practical and effective approach, and we review it here by presenting all available relevant data from the literature as well as from our own experience in an attempt to apprise colleagues of the significant progress made over the last several years in this important field of electrophysiology.