Ablation Procedures Research Articles

Impact of magnetic data collection prior to electroanatomic model creation on acute outcomes in de novo AF procedures

Abstract Background As ablation and electroanatomical mapping technology evolve, workflows change to maximize the impact on procedural efficacy, safety, and efficiency. In a magnetic-primary navigation mode, optimization of the magnetic-impedance field links (VoXels) must be considered to provide accurate environments for anatomic modeling, mapping, and lesion placement. To achieve this accuracy and optimize speed of data collection, many operators have adopted the strategy of collecting VoXels using an ablation catheter prior to introduction of a multipolar mapping catheter. However, the impact of this workflow on procedural metrics has not yet been quantified in a multicenter, international cohort. Objective Assess the impact of optimizing the magnetic navigation field using an ablation catheter prior to collecting left atrial (LA) data using a high-density diagnostic tool on acute outcomes in de novo atrial fibrillation (AF) ablation procedures. Methods Acute observational data from 199 de novo pulmonary vein isolation (PVI) cases was prospectively collected from 56 operators at 42 centers in Europe, the US, and Australia. Procedural metrics, modeling workflow, ablation technology used, and acute outcomes were collected. Results Of 199 de novo AF (62.3% PAF) ablation procedures, VoXels were collected with an ablation catheter prior to LA map collection with a multipolar catheter in 65/199 (32.7%) cases; the remainder collected with multipolar catheter first. An irrigated, contact force sensing RF ablation catheter was used in all procedures. Mean procedure duration was similar in procedures in which VoXels were collected prior to map collection (VC) compared to those that did not (nVC) (107.0±46.8 min and 115.4±59.2 min, respectively (p=0.28)). Mean fluoroscopy time was significantly reduced in VC cases compared to nVC cases (3.0±4.5 min and 5.3±5.6 min, respectively (p=0.002)). Total RF duration was significantly reduced in VC cases compared to nVC cases (904±444s and 1063±632s, respectively (p=0.04)). There was also a significant reduction in fluid delivered through the ablation catheter in VC cases, 369±159mL, compared to nVC cases, 520±243mL (p<0.001). Acute success rates were similar between groups: 98.5% for VC cases and 99.2% for nVC cases (p=0.64). Conclusion In this international cohort, cases where VoXels were collected prior to map and model collection had significantly reduced fluoroscopy times, RF durations, and fluid volumes delivered through the ablation catheter, potentially as a result of improved model quality. Despite the introduction of an additional step to the workflow, there was a trend toward shorter procedures when VoXels were collected prior to map and model collection, although it did not achieve statistical significance. Better quantification of the impact of this workflow on model quality, along with analysis of long-term patient outcomes, is warranted.Procedure Duration Comparison_VC vs. nVCFluoroscopy Comparison_VC vs. nVC

Multicenter retrospective evaluation of a patient-tailored electrogram-based ablation strategy using an artificial intelligence software in repeat atrial fibrillation ablation procedures

Abstract Background While pulmonary vein isolation (PVI) is the gold standard approach of treatment of atrial fibrillation (AF), the optimal strategy in case of AF recurrences for redo patients is not well established. Several studies described the usefulness of ablating in atrial regions exhibiting abnormal electrograms, i.e. spatio-temporal dispersion, during AF and an artificial intelligence (AI) electrograms (EGMs)-based software solution has been developed and validated to obtain real-time adjudications of multipolar electrograms in de novo patients. Purpose This study sought to evaluate the novel AI-EGMs-based software approach for redo-AF ablation procedures. Methods This study was a retrospective, multicentric, nonrandomized study. Patients with recurrent symptomatic AF were enrolled in 7 European centers. Redo ablation procedures were performed using the AI software and acute and long-term outcomes after ablation were evaluated. Results A total of 117 patients with refractory symptomatic AF admitted for redo procedure were included with 30% paroxysmal, 42% short-standing persistent and 28% long-standing persistent AF at the time of the redo procedure. During the index procedures, a previous PVI ablation was performed in all patients while additional ablation such as lines and EGM-based ablation was performed in 64 patients (55%). Out of 117 patients, 30 (26%) presented with structural heart disease, 61 (52%) with hypertension, 31 (26%) with a BMI >30, 16 (14%) a sleep apnea syndrome and 24 (20%) had an antiarrhythmic treatment at the time of the procedure. The average AF history was 6.54 ± 4.15 years with an average sustained duration equal to 25 ± 62 months. AI-EGMs-based AF ablation was performed in all patients and easily integrated in the physicians’ workflow during redo procedures. AF termination, i.e. AF regularization or sinus rhythm conversion, occurred in 82/117 patients (71%) with sinus rhythm conversion by ablation in 79/117 patients (68%). After a mean follow-up of 11 ± 5 months, 81% of patients were free from documented AF, with or without antiarrhythmic drugs (AADs) after one redo procedure and 60% of patients were free from any documented atrial arrhythmia, with or without AADs, after one redo procedure per patient. Furthermore, we observed that 77%, 84% and 82% of patients were free from documented AF with or without AADs in paroxysmal, short-standing and long-standing persistent AF patients respectively, and that 71%, 59% and 49% of patients were free from any documented atrial arrhythmia with or without AADs in paroxysmal, short-standing and long-standing persistent AF patients respectively. Conclusions This retrospective study reports that patient-tailored spatiotemporal dispersion ablation is a relevant and standardized approach for repeat AF ablation. This was obtained with an AI-EGMs-based software solution, which may be added to the operative workflow of redo AF procedures.

Long-term success and predictors of atrial arrhythmia recurrence following left atrial flutter ablation

Abstract Background In recent years, success rate of left atrial flutter (LAFL) ablation has witnessed improvement, attributed to enhanced comprehension of the arrhythmia mechanism and technological advancements. However, the recurrence rate and specific types of atrial arrhythmias, along with their potential predictors, remain inadequately understood. Purpose The aim of this study is to assess the factors influencing the efficacy, safety, and long-term success of radiofrequency (RF) ablation for LAFL. Methods Patients with sustained LAFL undergoing RF ablation were included in the study. LAFL mapping employed a combination of activation, voltage, and entrainment with 3D electroanatomical mapping. RF ablation targeted a protected isthmus of slow conduction, and if not localized, it involved creating lines of conduction block transecting the reentrant circuit or empirically created lines. Ablation success was defined as clean arrhythmia termination during RF application and no LAFL induction with pacing maneuvers. Follow-up included outpatient visits at 6 and 12 months. Ablation success at follow-up was defined as the absence of arrhythmia recurrence (≥30s) at regular outpatient or emergency department visits. Clinical and electrophysiological characteristics were analyzed and correlated with ablation success, complications, and freedom from arrhythmia recurrences at follow-up. Results The study included 104 consecutive patients undergoing LAFL ablation (67.5 ± 11.3 years, 67% male). Clinical characteristics comprised 12 with HFrEF, 44 with structural heart disease, 25 with valvular heart disease, 43 with previous pulmonary vein isolation (PVI) ablation, and 39 with significant left atrium enlargement. Simultaneous cavotricuspid isthmus ablation (CTI) was performed in 46 patients. LAFL cycle length was 293±68 ms, with more than one LAFL mechanism (2.0±0.8 mechanisms) demonstrated in 76 patients (73%). The most common LAFL mechanism was perimetral reentry (37%). LAFL was successfully ablated 83% of cases, with 7 patients experiencing complications (4 tamponades and 3 sinus node dysfunctions following LAFL termination). At a median follow-up of 28 months, 35 patients (34%) had AFL recurrence, and 15 of them required a second ablation procedure. No factor was associated with LAFL recurrence, except for a short LAFL cycle length (P=0.04) at the ablation procedure. Demonstration of more than one LAFL mechanism (P=0.48) or LAFL termination by focal or linear RF application (P=0.99) were not associated with AFL recurrences at follow-up. Conclusions Despite the relatively high efficacy of LAFL ablation, the rate of atrial arrhythmia recurrences at follow-up after a single procedure remains elevated, predominantly in the form of AFL rather than AF. Short LAFL cycle length at the index procedure appears to be a significant predictor of these recurrences. Arrythmia cycle length proved to be predictive factor of LAFL ablation success rate.Peri-veinal left AFL, LAT map, CranialPeri-veinal left AFL, LAT map, PA

Increased left atrial pressure is associated with fibrosis, elevated mechanical load and ventricular diastolic dysfunction in patients undergoing AF catheter ablation

Abstract Background Increased left atrial filling pressures might be a hallmark feature of atrial cardiomyopathy which has been associated with an increased incidence of atrial fibrillation (AF) recurrence even after successful pulmonary vein isolation (PVI). The interplay between left atrial pressure, measured during the ablation procedure, and other parameters characterising atrial and ventricular remodelling in patients with AF remains elusive. Methods and Results Between 2018 and 2022, 182 patients undergoing PVI for paroxysmal or persistent AF were included in the study. Mean left atrial pressure (mLAP) was measured invasively during the ablation procedure after transseptal puncture. A mLAP higher than 15 mmHg was considered the cut-off value for LA hypertension. Bipolar high-density 3D electro-anatomical maps (Carto) obtained during the procedure were used to manually quantify low-voltage (<0.5 mV) and normal voltage areas of the LA surface and a global low-voltage/normal voltage ratio index was derived. Contemporary transthoracic echocardiography data were included to evaluate LV systolic and diastolic function and blood samples were obtained post-procedurally from all patients. In bivariate linear regression analysis, mLAP reached only modest correlation with E/e’ as an imaging marker of diastolic dysfunction (R=0.31, p=0.005) (Figure 1A), with particular differences in mLAP values between patients with marked diastolic impairment (E/e’ > 15) vs. subgroups with mild dysfunction ( 8 < E/e’ ≤ 15) or normal diastolic function (E/e’ ≤ 8 ) (Figure 1B), log NT proBNP (R=0.34, p<0.001) (Figure 1C) and low-voltage/normal voltage ratio index (R=0.21, p=0.014) (Figure 1D). For a total of 158 patients, data about 1 year recurrence of AF were available, of these 22 (13.9%) had a recurrence after two procedures using cryo-energy for the index PVI and radiofrequency ablation for the re-PVI (second procedure). A Kaplan-Meier analysis and log-rank test showed a trend but no statistical significance regarding an increased AF recurrence rate between patients with and without LA hypertension (χ2 = 2.63, p= 0.09) (Figure 2). Conclusion Direct intra-procedural invasive measurement of LA pressures can offer an important and convenient novel piece of information for patients undergoing catheter ablation procedures for AF, with potential implication for post-procedural recurrence risk stratification. Atrial hypertension is only partially related to LV diastolic impairment, atrial fibrosis and myocardial mechanical load burden.

Catheter ablation of premature ventricle complex from multiples site of origin guided by an ultra-high density mapping system in a single-center

Abstract Background Frequent premature ventricle complex (PVC) could induce cardiomyopathy in some patient. PVC ablation by radiofrequency (RF) is a well-stablished procedure in high density PVC patients and results are consistent and robust in literature, with somewhat differing success rates reported. Catheter ablation of radiofrequency guided by ultra-high density mapping systems (UHDMS), enable a much more accurate reconstruction of the site of origin (SOO). Furthermore, we obtained this anatomic recreation with the analysis of a few number of beats. The UHDMS have demonstrated to be feasible and safe in a wide range / large spectrum of arrhythmic substrates, however, there is lack of evidence of its usefulness in the ablation of PVC. Purpose To determine the safety and utility, both in the acute phase and in the short-medium term, of employing a UHDMS in PVC catheter ablation in a retrospective cohort of patients treated at a single centre. Methods Catheter ablation procedures guided by an UHDMS carried out from July 2015 to January 2021 in a single-center of Spain were retrospectively included. The primary outcomes analyzed were: acute success rate, short-medium success rate (6-month efficacy after ablation), and complication rate related to the procedure. Results One hundred and two procedures, corresponding to 92 patients (mean age 59 ± 14 years, 63% male, 74% without cardiomyopathy, mean LVEF of 60%), were analyzed. The acute success rate was 93%. According the SOO, the lowest acute success rate was PVC from epicardial level (LV Summit) (75%). At 6-month follow-up after the first procedure, the short-medium success rate was up to 84% (no recurrence of the PVC ablated). There were three acute complications related to the procedure (complication rate 2,94%). In 19% (21 out 102) of the procedures, at least two arrhythmic substrates were successfully ablated in a single intervention. Conclusion Catheter ablation guided by an UHDMS showed an excellent safety profile in PVC ablation procedures. Beyond this minor complication rate, this type of technique has improved acute and short-term success rates. This allows us to assert that this type of technique grants a very high success rate and improves previously results. Last but not least, this new approach was useful and accurate in complex patients, providing good results in ablation procedures of two or more arrhythmic substrates without altering the safety profile.

Effectiveness of a novel integrated dilator-needle transseptal crossing device in atrial fibrillation cryoballoon ablation procedures

Abstract Background In cryoballoon ablation (CBA) procedures, left atrial (LA) access is generally achieved using a standard sheath and needle system that is exchanged for the cryoballoon delivery sheath and dilator over a long wire. Sheath exchange has been related with air embolic events in CBA procedures. A novel integrated dilator-needle system, that can be combined with the cryoballoon delivery sheath allowing direct LA transseptal access, was recently introduced. Figure. Objective The purpose of this study is to evaluate the efficacy and safety of this new integrated transseptal access tool compared with the traditional approach in CBA procedures. Methods In this prospective single-center study, consecutive patients who underwent AF CBA procedures were randomly assigned 1:1 to undergo traditional transseptal access (t-TSA) or integrated transseptal access (i-TSA). Patients with foramen ovale or interatrial communication, detected on transesophageal echocardiogram prior to the procedure, were excluded. Transseptal access time was defined as time from superior vena cava to LA insertion of the cryoballoon delivery sheath, after sheath exchange (t-TSA) or directly (i-TSA). Results We evaluated 82 patients (63 males, mean age 59 ± 10 years) indicated to CBA of atrial fibrillation, 42 patients underwent t-TSA and 40 i-TSA. The baseline characteristics of the study population were comparable between groups. Table. Mean CBS transseptal access time was 5 min 6 sec ± 2 min 5 sec in the t-TSA group and 3 min 5 sec ± 2 min 23 sec in the i-TSA group, P < 0.001. Challenging interatrial septa were noted in 3 patients: 1 in t-TSA (1 aneurysmal/elastic) and 2 in i-TSA group (1 lipomatous hypertrophy, and 1 abnormally thickened/fibrotic). No acute complications related to transseptal access were noted in both cohorts. The CBA procedure time and fluoroscopy time were lower in the i-TSA group. Table. There were 1 temporary phrenic nerve injury and 1 vascular complication, both in the t-TSA group. Importantly, no signs of clinical air embolism were noted in both groups. Conclusion This is the first randomized study comparing the traditional approach and the use of a new integrated dilator-needle system. Transseptal crossing in CBA procedures using this integrated tool enables a safe and more efficient workflow, reducing time for transseptal access and avoiding sheath exchange.FigureTable

Feasibility and efficacy of single-shot PFA technology for redo procedures after a previous atrial fibrillation ablation procedure

Abstract Introduction Despite significant technological advancements and a better understanding of atrial tachyarrhythmia pathophysiology, a non-negligible percentage of atrial fibrillation (AF) patients undergoing catheter ablation experiences arrhythmia relapse. Repeat procedures have been traditionally performed via thermal energy systems, which carry a certain risk of collateral damage to adjacent tissues. Pulsed Field Ablation (PFA) has emerged as an alternative non-thermal energy source for cardiac ablation. The main advantage is its selectivity to cardiac tissue. FarapulseTM is the first PFA technology to have received regulatory approval and includes a pentaspline PFA catheter. Although designed for pulmonary vein isolation, its use for extrapulmonary vein site ablation has been previously documented. Purpose To evaluate the feasibility and efficacy of the pentaspline FarawaveTM for redo procedures. Methods Patients referred for a redo procedure using FarapulseTM system were enrolled in 3 high-volume European centers. A workflow (Figure 1.A) was established based on rhythm at presentation (Group 1: sinus rhythm; Group 2: AFL; Group 3: AF). Results A total of 117 patients were included (64 in Group 1, 18 in Group 2, and 35 in Group 3). The mean number of previous procedures was 1.26, and 23 patients (19.66%) had already undergone ≥2 procedures. Previous ablation targets included PVI, either alone (46.15%) or in combination with other targets, including posterior mitral line (39.32%), posterior wall (6.84%), or anterior mitral line (2.56%). Electroanatomical mapping (EAM) was adopted in 15.38% of the cases. Specifically, in 27.78% (n=5) of group 2, 15.63% (n=10) of group 1 and 8.57% (n= 3) of group 3 cases. Additional focal radiofrequency ablation was required in 4 patients for CTI line ablation. Lesion sets are depicted in Figure 2. Mean procedural and LA dwelling time were 95.2 ± 38.0 and 50.7 ± 36.7 minutes, respectively. There was a total of one major complication (intracranial haemorrhage) and 5 minor complications (two vascular site related, and three reversible ST segment changes, related to applications on the mitral annulus area). A total of 100 patients completed at least 3 months of follow-up (FU), with a median FU time was 7.55 months (IQR 5.18 – 11.85). The total number of recurrences was 20, including 2 during the blanking period. Survival function (excluding blanking period) was 88.6 (95% CI 79.7 – 93.8) at 6 months and 80.0% (95% CI 67.3 – 88.3) 12 months. Atrial arrhythmia free-survival was higher in patients presenting in sinus rhythm, compared to the other two groups (p = 0.0135), as displayed in Figure 1.B. Conclusion The proposed stepwise approach to repeat AF ablation procedures based on the use of the single-shot PFA system (with or without EAM) was feasible, safe, fast and effective at one year follow-up.Flow chart and Kaplan Meier curveLesion sets

Implantable Loop Recorders in patients with Brugada Syndrome: the BruLoop Study

Abstract Aims Available data on continuous rhythm monitoring by implantable loop recorders (ILRs) in patients with Brugada syndrome (BrS) are scarce. Aim of this multicentre study was to evaluate the diagnostic yield and clinical implication of a continuous rhythm monitoring strategy by ILRs in a large cohort of BrS patients, and to assess the precise arrhythmic cause of syncopal episodes. Methods and Results A total of 370 patients with BrS and ILRs (mean age 43.5±15.9, 33.8% females) from 18 international centers were included. Overall, 274 (74.1%) were implanted due to symptoms (69.3% syncope, 30.7% palpitations). Over a median follow-up of 3 years, an arrhythmic event was recorded in 30.7% of symptomatic patients (18.6% atrial arrhythmias (AAs); 10.2% bradyarrhythmias (BAs) and 7.3% ventricular arrhythmias (VAs)). In patients with recurrent syncope, the etiology was arrhythmic in 22.4% (59.3% BAs, 25.0% VAs and 15.6% AAs). The ILR led to drug therapy initiation in 11.4%, ablation procedure in 10.9%, implantation of PM in 2.5% and ICD in 8%. At multivariate analysis, the presence of symptoms (HR 2.5, p=0.001) and age >50 years (HR 1.7, p=0.016) were independent predictors of arrhythmic events, while inducibility of VF at EP study (HR 9.0, p<0.001) was predictor of ventricular arrhythmias. Conclusion ILR detects arrhythmic events in nearly 30% of symptomatic BrS patients, leading to an appropriate therapy in 70% of them. The most commonly detected arrhythmias are AAs and BAs, while VAs are detected only in 7% of cases. Symptom status can be used to guide ILR implantation.General ResultsArrhythmias

Pulmonary vein isolation using pulsed field ablation versus high-power-short-duration radiofrequency ablation for paroxysmal atrial fibrillation: efficacy, safety, and long-term follow-up

Abstract Background Pulsed field ablation (PFA) is a novel, nonthermal, cardiac tissue selective ablation modality. To date, radio-frequency (RF) guided high-power-short-duration (HPSD) ablation represents the gold standard for pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). This study investigated the efficacy of PFA-PVI versus HPSD-PVI in terms of single-procedure arrhythmia-free outcome and safety. Methods Consecutive, paroxysmal AF patients who underwent PVI using PFA or HPSD were enrolled. In group PFA, PVI was performed using a 31/35-mm pentaspline PFA catheter. The ablation procedure in group HPSD was performed with HPSD-RF energy (45 watts), using Ablation Index (AI) and the CLOSE protocol. The CLOSE protocol combines AI and ≤6 mm interlesion distance using a 4-mm surround flow catheter. Results A total of 420 patients (group PFA: 211; group HPSD: 209) were included (55% men; age 67 ± 10 years). There was no difference between both groups with regard to age, gender and CHA2DS2-VASc-Score. Complete isolation of all PVs was achieved in 100% of patients. Procedure time was significantly shorter in group PFA (74 ± 41 min vs. 127 ± 34 min; p < 0.001); fluoroscopy time and dose area product were significantly longer in group PFA (18 ± 7 min vs. 4 ± 3 min; p < 0.01 and 555 ± 460 uGym2 vs. 213 ± 273 uGym2; p <0.01). Overall procedural complications were 1,4% in group PFA and 5,2 % in group HPSD (p < 0.01), driven by a higher tamponade rate in group HPSD. During a mean follow-up of 12 months after a single procedure, 170 (81%) patients of group PFA were free of arrhythmia recurrence versus 160 (76%) patients in group HPSD (p = 0.798) (Figure 1). Conclusions PVI using PFA compared to PVI using HPSD shows a similar acute efficacy but a significantly reduced complication rate and a shorter procedure time. One-year clinical success rates are favorable, but not different between groups.Figure 1

Predicting atrial fibrillation recurrence after catheter ablation using an artificial intelligence-enabled electrocardiogram algorithm

Abstract Introduction Predicting atrial fibrillation (AF) recurrence post catheter ablation may help to assess procedural eligibility and determine AF management. While several predictors of AF recurrence post ablation have been established and numerous clinical risk scores have been proposed, their performance remained underwhelming and clinical utility was limited. Hence, new predictors are needed. Artificial intelligence (AI) algorithms using deep neural networks (DNN) to analyze biometrical data might generate such predictors. DNN algorithms have been developed to identify patients with AF based on a 12-lead electrocardiogram (ECG) in sinus rhythm. Whether these algorithms can function as a predictor of AF recurrence after AF ablation remains unknown. Purpose To evaluate the prediction of AF recurrence after ablation using an AI-enabled ECG algorithm trained to predict AF on an ECG in sinus rhythm. Methods This study retrospectively analyzed observational data from the DIGITOTAL study, that monitored AF recurrence with a PPG-based smartphone application in 96 subjects after AF ablation. Patients with a 12-lead ECG in SR available within a timeframe of 3 months before the ablation procedure were included in the analysis. Although all patients had a history of AF, an AF-risk score was calculated by the DNN described elsewhere.1 Results An ECG in sinus rhythm was available in 53 patients (14 women [26.4%]; mean [SD] age, 62.0 [9.7] years) out of the 96 patients followed-up in the DIGITOTAL study. Testing the DNN on the last ECG before the ablation procedure resulted in an area under the receiver operating curve (AUC) of 0.65 (95% CI, 0.49 - 0.80), and an area under the precision recall curve (AUPRC) of 0.56 (95% CI, 0.34 - 0.78). The optimal cutoff score resulted in a sensitivity of 60.0% (95% CI, 36.1% - 80.9%), specificity of 66.7% 66.7% (95% CI, 48.2% - 82.0%), accuracy of 0.64 (95% CI, 0.50 - 0.77), F1-score of 55.8% (95% CI, 38.5% - 74.4%), positive predictive value 52.2% (95% CI, 30.6% - 73.2%) and negative predictive value 73.3% (95% CI, 54.1% - 87.7%). Patients classified in the high-risk group versus low-risk group were more likely to exhibit AF recurrence up to one year after AF ablation (hazard ratio, 2.6; 95% CI, 1.1 - 6.5; P-value = 0.037). Conclusions The AI-enabled ECG algorithm, trained to predict AF on a sinus rhythm ECG, was able to predict AF recurrence after ablation with an accuracy comparable to the existing clinical risk scores. Further studies are needed to determine whether the DNN score can be used as an independent predictor and improve existing risk scores.

Ten-year follow-up results of patients with persistent atrial fibrillation treated by combined pulmonary vein isolation and complex fractionated atrial electrocardiogram ablation

Abstract Background For persistent atrial fibrillation (AF), pulmonary vein isolation (PVI) alone is associated with lower success rate compared to paroxysmal AF and additional strategies are needed. Ablation targeting on complex fractionated atrial electrograms (CFAE) is an alternative method. Although clinical benefits of the strategy combined PVI and CFAE ablation have not been shown by large trials, clinical situations and consequences of this approach have not been clearly demonstrated during very long term follow-up. Purpose This study aimed to retrospectively investigate clinical outcomes of patients with persistent AF treated by the approach combined PVI and CFAE ablation during a follow-up period of 10 years. Methods 73 patients (59.4±8.1 years, 64 male, AF history 5.5 years) with persistent (23, 31.5%) and long-standing persistent AF (50, 68.5%) who underwent combined PVI and CFAE ablation in the first procedure were included. Structural heart disease was found in 9 patients, and a history of ablation for typical atrial flutter (AFL) in 4. A complete CFAE mapping in the left atrium and coronary sinus was performed with a 3-D mapping system (EnSite NavX). All CFAEs defined as electrograms with continuous activities or mean cycle length detected by the system <80 ms were eliminated. All patients were controlled regularly during the first year with 12-lead ECG and Holter monitoring and followed by annual control. The electronic health records for all patients were extensively investigated and the patients were interviewed in 2020-2022. Any documented atrial tachyarrhythmia (ATA) after 3-month blanking period was regarded as recurrence. Results Mean 2.2±1.2 (1-5) ablation procedures were performed in each patient. After index ablation, 18 (24.7%) were free of ATAs during 10-year follow-up. 26 (35.6%) had recurrence of only AF, 6 (8.2%) of only AFL and 23 (31.5%) had both AF and AFL. The proportion of AFL was 39.7% with 6 typical AFL. After multiple ablation procedures, 33 (45.2%) patients were free of ATA during the follow-up. 23 (31.5%) had recurrence of only AF, 5 (6.8%) of only AFL and 12 (16.4%) of both AF and AFL. The proportion of AFL was 23.2% with no typical AFL. At 1-year follow-up, freedom of ATAs in persistent AF was higher than that in long-standing AF (65.2 vs. 40.0%, p=0.033) and no significant difference was found after 2 years (47.8 vs. 34.0%, p=0.129) until 10 years (30.4 vs. 22.0%, p=0.167, Figure 1). No difference was observed between these subgroups after multiple procedures at 10-year follow-up (47.8 vs. 44.0%, p=0.708, Figure 2). Conclusions PVI plus CAFE ablation in patients with persistent AF led to a high recurrence of ATA after index ablation. Difference of ATA-freedom between persistent and long-standing persistent AF groups was found only 1 year after the index procedure, but not during further follow-up. Incidence of post-ablation AFL was particularly high, even after multiple ablation procedures.Figure 1Figure 2

Pulsed-field ablation using a lattice-tip catheter without general anesthesia is feasible for atrial fibrillation ablation

Abstract Background General anesthesia (GA) was employed to titrate lesion formations for a pulsed-field ablation (PFA) using a lattice-tip catheter. The evidence using a lattice-tip catheter without the use of GA is limited. Purpose We conducted a series of exploratory evaluation of a lattice-tip PFA catheter ablation without GA. Methods Patients undergoing their first atrial fibrillation (AF) ablation procedures using a lattice-tip catheter were enrolled in the study. To assess acute outcomes and safety, the patients were divided into two groups: one undergoing the procedure with GA and the other without GA. Procedural characteristics were collected. Results In total, 20 patients (6 with GA, 14 without GA) were enrolled in the current study. One patient in non-GA group needed a larynx mask due to apnea from anesthesia. The pre-ablation 3D mapping time was equivalent between the two group (with GA versus without GA: 17±7 versus 16±5; P=0.762). All first-pass isolations of the pulmonary veins (PV) were successfully achieved, and there was no difference in the number of applications between the right and left PV (with GA versus without GA: 45±8 versus 53±12; P=0.206 and 47±14 versus 49±9; P=0.792). Linear lesions including anterior linear ablation (33% with GA and 36% without GA: P=1.000), roof linear ablation (67% with GA and 71% without GA: P=1.000) and cavo-tricuspid isthmus ablation (0% with GA and 7% without GA: P=1.000) were performed. The ablation, laboratory stay and fluoroscopy times were equivalent between the two group (with GA versus without GA:88±22 versus 97±20; P=0.483, 128±25 versus 111±18; P=0.216 and 9±4 versus 10±2; P=0.902), while the pre-ablation preparation times were shorter in the group without GA (with GA versus without GA:40±17 versus 14±4; P<0.01). There was no major and minor procedural complication in both groups. Conclusions The use of a lattice-tip catheter for ablation without GA has a potential to shorten the whole procedural work-flow including preparing time while maintaining comparable safety and lesion formation to cases where GA is utilized.

Implementation of near zero fluoroscopy in supraventricular tachycardia ablation procedures: a single center experience

Abstract Background Supraventricular tachycardia (SVT) are common cardiac arrhythmias, and catheter ablation has proven to be a very effective treatment, but exposes patients and healthcare providers to radiation. "Near Zero Fluoroscopy" (NZF) techniques, utilizing advanced imaging, aim to reduce radiation exposure while maintaining efficacy. Purpose To present an analysis of near-zero fluoroscopy in SVT ablation procedures, in a tertiary center, since its implementation. Methods We prospectively enrolled 446 SVT-diagnosed patients for this study. All of them underwent NZF procedures using the same specific 3D mapping system, between January/19 and December/22. Patients with atrial fibrillation or macroreentrant atrial tachycardias or when a different mapping system was used, were excluded. All patients provided informed consent. Results Our population had 266 (60%) females and a median age of 39 (IQR 24-51) years. AVNRT was the most frequent arrhythmia documented (229 cases, 51%), followed by Accessory Pathways (AP) (201 cases, 45%) and focal atrial tachycardia (AT) (16 cases, 4%). The ablation success rate was high (405/418, 97%). There was no ablation attempt in 12 patients (9 APs and 3 ATs) and the unsuccessful ablations (7/418 cases, 1,67%) were APs. Overall, fluoroscopy time was 1.1 minutes (IQR 0-2.6). There was no statistically significant difference in the distribution of fluoroscopy time among the types of SVT based on the Kruskal-Wallis test (p 0.14). Observing trends of fluoroscopy use through time, we acknowledge the presence of a learning curve, leading towards shorter times of X-ray during procedures along the first 3 years of implementation of a near-zero strategy. Median times (IQR) of fluoroscopy were as follows: 2019 – 2.25 (0.45-3.4) min; 2020 – 1 (0-2.5) min; 2021 – 0 (0-1.9) min; 2022 – 0.55 (03.05) min. (see BoxPlot) Pairwise comparisons using the Wilcoxon rank-sum test with continuity correction revealed statistically significant differences in medians between all pairs of years, with p-values adjusted for multiple comparisons using the Bonferroni method (p<0.01). In 2022, fluoroscopy time increased, when compared to 2021. We believe this finding can be explained by the fact that in 2022, our department received a new fellow and a young EP consultant (coming from a center where NZF was not the standard for SVT ablation), both being in the lab on a daily basis, explaining this upward trend in fluoroscopy time. There were no acute complications requiring hospital admission or active treatment. Conclusion Our results emphasize the potential of near-zero fluoroscopy techniques to enhance safety and reduce radiation exposure while maintaining a high level of procedural efficacy in the treatment of SVT cases. Absence of acute complications highlighted the safety of these approaches.

In-hospital mortality following catheter ablation procedures in Germany: insights from the VARY project

Abstract Background The number of catheter ablation (CA) procedures has increased significantly over the last decade. 102,737 CA have been performed in Germany in 2021. Although CA of different types of arrhythmias is generally considered to be safe, serious complications, including in-hospital death, may occur. There is a paucity of real-world national healthcare data in Germany. Aim To investigate the overall in-hospital mortality in patients undergoing any type of CA procedure in Germany and to identify variables associated with in-hospital mortality. Methods According to the German law German hospitals are obliged to provide a dataset including case data, diagnosis based on the ICD-10-GM, operational and procedural codes to the Institute for hospital remuneration system (InEK) every year. The VARY project aims at analyzing and monitoring these data to report the real world scenario on patients undergoing CA in Germany. As of now, 22 German centers were contacted by the Institute for Myocardial Infarction Research (IHF). Their Data between 2019 and 2023 provided from seven of those centers were used for this analysis. Datasets from ten centers are pending. Five centers were not able to provide their data. The project is supported by the German Heart Foundation. Results A total 21,028 patients underwent inpatient CA. 49 patients (69.4% males) died in-hospital following a CA procedure resulting in an overall in-hospital mortality rate of 0.23%. A percutaneous epicardial ablation approach was used in 6.1% of the patients who died (Group A) compared to 0.3% in the surviving patients (Group B). Radiofrequency ablation was used in 83.7% vs. 72.6%, cryoablation in 10.2% vs 27.1%. Patients who died were older compared to those who survived (mean age: 66.7 ± 14.6 vs. 62.0 ± 14.4 years, p <0.01) and had more comorbidities such as diabetes (19/49 (38.8.%) vs. 2274/20,979 (10.8%), p <0,01), chronic obstructive pulmonary disease (5/49 (10.2%) vs. 555/20,979 (2.6%), p < 0,01) and heart failure (39/49 (79.6%) vs. 5116/20,979 (24.4%), p <0.01). There was no difference with regards to gender between the two groups. The most common arrhythmia in both groups was atrial fibrillation with 67.3% and 75.3% (p < 0.01). Cardiac arrest was observed in 44.9% of patients in group A compared to only 0.3% in group B. The median hospital stay was longer in group A (19.0 (IQR 8.0; 42.0) vs. 2.0 (IQR 1.0; 3.0), p < 0.01). 46/49 (93.9%) patients who died were treated on an intensive care unit for a median time of 13.5 days (IQR 3.8; 33.8) compared to 1272/20,979 (6.1%) (p < 0.01) in group B. A cardiac implantable electronic device implantation or revision was performed in 18.4% patients in group A (4 defibrillator implantations, 2 pacemaker implantations, 5 revisions) compared to 2.9% in group B (survivors). Conclusion Inpatient catheter ablation procedures in Germany are associated with a very low in-hospital mortality comparable to data reported from the US.

Innovations in arrhythmia management in pregnant woman: catheter ablation without using fluoroscopy

Abstract Background The latest data of effectiveness and safety of catheter ablation without using fluoroscopy in general population suppose wide using of this technology. However, data on pregnant population is limited. Purpose To investigate efficacy and safety of catheter ablation without using fluoroscopy in pregnant women with analyzing obstetric and neonatal outcomes. Methods We studied 47 cases of catheter ablation in pregnant (mean age 25.3±3.9 years, mean gestation age 23.7 ±3.1 weeks) within 24 month follow-up. Ablation was performed under the guidance of CARTO (n=21; 44.7%) and Ensite Precision systems (n=26; 55.3%) without using fluoroscopy in all cases. Results The most common arrhythmia was atrioventricular nodal reentrant tachycardia (n=21; 44.7%), which was followed by Wolff–Parkinson–White syndrome (n=15; 31.9%). Cases of combination of accessory pathways with slow conduction ways (n=3, 6.4%), ventricular tachycardia (n=3, 6.4%) and premature ventricular contraction (n=5; 10.6%) were rare. Ablation without using fluoroscopy was successful in all cases, mean procedural time was 71.9±14.5 minutes. There was one case of complication after ablation procedure: ileofemoral thrombosis, which was treated successfully without termination of gestation (2.1%). We found increased uterine contractile activity and placental abruption in pregnant after ablation in 4.54% and 2.3% cases respectively. Cases of uterine blood flow violation was more frequent: in 15.9% cases. Obstetric outcomes characterized by prevalence of vaginal delivery and delivery in term: in 76.6% and 95.7% cases. There were live births in all pregnant women with normal range of fetal birth weight and Apgar score (3207.4±485 grams and 8.4±1.6 respectively). There were no incidence of mortality and arrhythmia recurrence at follow up. Conclusions Catheter ablation without using fluoroscopy can be effectively and safety performed during gestation with good neonatal and obstetric outcomes.

Pulsed field ablation for complex resistant atrial tachycardia recurring after radiofrequency ablation of persistent atrial fibrillation

Abstract Background There is a limited knowledge on immediate and long-term efficacy of pulsed field ablation (PFA) for residual atrial tachycardia (AT) recurring after persistent atrial fibrillation ablation (AF). Purpose To present immediate and medium-term outcome of PFA (Farapulse) for complex AT recurring after ≥1 radiofrequency ablation (RFA) of primary (longstanding) persistent AF. Methods In 5/2022-10/2023, 81 patients (64±8 years, 19 females) underwent PFA for complex AT in 83 PFA procedures after prior RFA procedure(s); in first (n=21), second (n=33), third (n=23), fourth (n=5), or fifth (n=1) repeat ablation procedure, respectively. Mapping/ablation strategy was directed by the CS activation/entrainment to: 1) no 3D mapping and direct PFA in left atrium (n=67); 2) PFA directly after 3D LA mapping (n=9); 3) PFA following RFA after 3D LA mapping (n=7). AT sources were classified as macroreentry (MRAT) (perimitral, roof-dependent, typical flutter) or localized (LOCAT) in case of smaller reentry or ectopic origin. Results At the procedure onset, persistent AT was present in 58 patients, in the remaining cases AT (n=21) or AF (n=4) were induced. AF eventually occurred at some time of procedure in another 10 patients and was terminated by ablation at LA ridge/CS/LOM region 8x, LA posterior wall 3x, LUPV 1x, RUPV 1x, and RA low lateral wall 1x. Only MRAT, only LOCAT, or both AT types were found at 34 (41%), 35 (42%), and 14 (17%) procedures, respectively. A total of 125 ATs was identified (1, 2, and 3 ATs in 52, 20, and 11 patients). MRAT (n=60) included 32 perimitral ATs, 20 roof-dependent ATs, and 8 typical flutters. LOCAT (n=65) included RUPV source (n=1), LA extraPV sources (n=59), and RA sources (n=5). SR was restored with a 5±7 PFA applications at the site of AF source, total of PFA deliveries was 71±27, and procedure and fluoroscopy times were and 89±37 and 9±5 minutes, respectively. In the 7 patients with initial ineffective 6, 6, 11, 5, 18, 10, and 2 minutes of RFA, the AT was converted into SR by subsequent 1, 4, 1, 13, 4, 24, and 20 PFA applications. All ATs were terminated and noninducibility was achieved in 82 (99%) and 74 (89%) procedures, respectively. In 52 patients with >3 month follow-up, 46 (88%) patients remain in stable SR (41 / 79%) off AAD); 3 and 3 patients have paroxysmal or persistent AT. Conclusion PFA with catheter Farapulse can affect complex/epicardial AT sources resistant to RFA in prior or present ablation procedure; however, there is a certain discrepancy between high efficacy in AT terminating and medium-term clinical outcome.

Linking ablation curves with transmural lesions using a thoracoscopic bipolar biparietal irrigated radiofrequent clamp

Abstract Background The cornerstone of atrial fibrillation (AF) ablation is the achievement of long-lasting transmural lesions. However, it is currently unknown when transmurality is reached during ablation using the thoracoscopic bipolar biparietal irrigated radiofrequent (RF) clamp. Purpose To study the relation between transmural lesions and their corresponding ablation curves using a thoracoscopic bipolar biparietal irrigated RF clamp in pigs. Methods In 4 ventilated pigs, endo-epicardial beating-heart ablation was conducted via sternotomy. In the first 3 pigs, 1 up to 4 ablations were performed at multiple sites on right and left ventricular tissue. Objective indicators of transmurality in the ablation curves were retrospectively identified by visual inspection. After the ablation procedure, the pigs were sacrificed and subsequent macroscopic evaluation was performed. The ablated tissue was excised and immersed in 2,3,5-triphenyltetrazolium chloride-staining at 36 °C. After 90 minutes the lesions were sectioned longitudinally and photographed. The ablated nonviable muscle appears white, and the viable muscle appears red (see Figure 1). In the 4th pig, ablations (up to 5) were applied to the ventricles at multiple sites until one or more of the potential identified indicators were observed in the ablation curve. Subsequent histology was performed as described in the first three pigs. Results Three indicators of transmurality were identified in the ablation curves: type I, a sharp impedance rise (blue peak); type II, three power drops with more than one energy level decline in one curve and type III, a first power drop before 11 seconds with subsequent hovering of power levels between 15 and 25 Wattage (Figure 1). In the first 3 pigs, a total of 20 ablations were performed, with 50% (n = 10) of the ablations considered transmural. In 80% of the transmural lesions one of the three types was observed. Among the transmural lesions, 50%, 10%, and 20% corresponds to type I, II, and III indicators of transmurality, respectively, with 20% remaining inconclusive. In the lesions classified not transmural (n = 10, 50%), no type I, II, or III indicators of transmurality was observed. In the fourth pig, all lesions (n=7) were considered transmural based on macroscopic evaluation, comprising 86% of type I and 14% of type III indicators of transmurality. Conclusion Three promising ablation curve types of transmurality have been identified that are associated with transmural lesions using the bipolar biparietal irrigated RF clamp. Transmurality of the lesion was confirmed by macroscopic histological evaluation. In the next step, these ablation curve types will be tested and validated in the clinical setting.Figure 1

Characterisation of ablation strategies at redo catheter ablation for atrial fibrillation and predictors of arrhythmia recurrence: results from the AFREDO registry

Abstract Background Patients who have undergone prior pulmonary vein isolation (PVI) for atrial fibrillation (AF) often require a repeat ablation for AF recurrence. The optimal ablative strategy for the redo procedure and predictors of AF recurrence thereafter remain largely unknown. Purpose We aimed to characterise the ablation strategies applied at re-PVI and identify possible predictors of AF recurrence. Methods Our single-centre, retrospective study included all consecutive patients who underwent first redo PVI at our centre from 2017 to 2022. Inclusion criteria required at least one available follow-up visit within the first 12 months after the redo procedure. Ablation strategies of the initial and redo procedure were captured. Kaplan-Meier curves were used to illustrate time of AF recurrence, as classified by predictors of outcome determined by multivariable regression analyses. Results We included 215 patients (39.1% female) with a median age of 66.6 years (IQR 58.6-73.2) at the time of redo procedure. The initial PVI was cryoablation in 39.9%, RFA in 57.7% and surgical ablation in 2.4%. After the initial procedure, 55.8% had paroxysmal AF and 44.2% had persistent AF. At the redo procedure, 25.1% of patients were found to have no PV reconnection, whereas 20.5% had a single reconnected PV, and 54.4% had two or more reconnected PVs. A left-sided flutter ablation was performed in 18.8%, a left atrial (LA) roof line in 16.9%, a posterior mitral isthmus line in 5.2%, an anterior mitral isthmus line in 27.9%, and a posterior box lesion in 8.4%. Overall, 34.4% of patients showed areas of low-voltages in the redo procedure. Patients with areas of low voltages were less likely to have any reconnected PVs in the redo-procedure (p<0.001). After the second ablation procedure, 54.0% experienced AF recurrence. Univariable regression analysis revealed moderate (p=0.006) or severe (p= 0.015) LA dilatation, persistent AF (p=0.005), and posterior LA low voltage areas (p=0.011) as significant predictors of AF recurrence after the redo procedure. The number of reconnected PVs at the re-PVI did not predict AF recurrence (p=0.1090). As illustrated in Fig. 1 and 2, patients with paroxysmal AF experienced less AF recurrence compared to those with persistent AF (log-rank p=0.0025). Moreover, moderate or severe LA dilatation at baseline was associated with more frequent AF recurrences (log-rank p=0.0279). Conclusion A significant proportion of patients undergoing re-PVI experienced AF recurrence. We found that persistent AF and moderate or severe LA enlargement emerged as significant predictors of AF recurrence after the redo procedure. Although PV reconnection was observed in more than two thirds of patients at the re-PVI, it did not predict AF recurrence thereafter. However, patients without PV reconnection had significantly more low-voltage areas, which may be indicative of a different AF recurrence mechanism in this subgroup.Figure 1:Type of AFFigure 2:LA dilatation

Comparison of peri-device sealing and procedural outcome after LAA closure in patients with and without isolated left atrial appendage

Abstract Background Catheter-based electrical isolation of the left atrial appendage (LAA) is increasingly performed in patients with symptomatic atrial fibrillation (AF) not responding to pulmonary vein isolation (PVI). Since the electrically isolated LAA is known to be susceptible to thromboembolism, endovascular LAA occlusion (LAAO) is increasingly being used. Objective We performed a procedural and clinical outcome analysis over 12 months in patients receiving two different LAAO device systems and compared those with versus those without LAA isolation (LAAI). Methods Between 08/2021 and 10/2022 we enrolled 83 consecutive patients (median age 73.2 years; median CHA2DS2-VASc Score 3.0; 51 men [61%]) of whom 59 (71%) had LAAI and 24 (29%) no LAAI. All patients had a least one previous catheter ablation procedure of AF. LAAO was done 6 weeks after the last ablation procedure. The main indication for LAAO was the implementation of electrical LAAI. In the no-LAAI group, all patients had lost persistent LAAI. Implanted devices were Watchman FLXTM (n=30) and LAmbreTM (n=53). Pertinent procedural data, periprocedural complications, as well as peri-device leaks (PDL) at 45 days were assessed according to device type. The composite endpoints (death, TIA/stroke, device thrombus, bleeding) and the clinical impact after switch of anticoagulation therapy were assessed at 12 months follow-up. Results The distribution of LAAI/No LAAI were found in 21[70%]/9 patients treated with the Watchman device and in 38[72%]/15 patients treated with the LAmbre device (p=0.87). PDL on follow-up (f/u) TEE was observed in 13/54 LAAI patients (24%) and 10/23 No-LAAI patients (43%, p=0.089). Leak distribution (<3mm/3-5mm/>5mm/no leak) at f/u was different between LAAI groups (LAAI: 12/1/0/41; No LAAI: 5/4/1/13; p=0.027) but not between device types. The mechanisms of leaks according to device type are listed in Table 1. Procedural complications were observed in 6/59 LAAI patients and 0/24 No-LAAI patients (p=0.11). The composite endpoint of death, stroke, severe bleeding, device-related thrombus and thromboembolism was reached by a total of 2 patients (both LAAI with LAmbre device). In 9/13 LAAI-group patients (69%) with PDL (all <6 mm) the sealing effect was assumed to be incomplete with perfusion of the LAA. Post procedural anticoagulation therapy was switched after the control TEE from NOAC/VKA (8/1) to aspirin alone. None of these patients reached the composite endpoint after 12 months. Conclusions LAAO can be performed safely and efficaciously in patients with LAAI. Compared with patients without LAAI after LAAO, the occurrence of minor leaks, periprocedural complications, and composite endpoint events was not different between the two patient groups. Despite the presence of incomplete sealing with perfusion of LAA in the LAAI group, the switch in post-procedural anticoagulation seems to be safe regarding the composite endpoint after 12 months.Mechanism of PDL of the LAmbre DeviceMechanism of PDL between the LAAO types

Radiofrequency catheter ablation for redo procedures after pulmonary vein isolation with the cryoballoon technique: 9-year outcome

Abstract Catheter ablation has become the first line of therapy in patients with symptomatic, recurrent, drug-refractory atrial fibrillation. Cryoablation has been shown to be a safe and effective technique for pulmonary vein isolation. However, there is a significant arrhythmia recurrence rate after cryoablation procedures and there are no established strategies for redo procedures in these patients. Therefore, we have summarized our experience with radiofrequency catheter ablation for redo procedures after pulmonary vein isolation with the cryoballoon technique (including an analysis of pulmonary vein conduction recovery patterns after procedures performed with the first or second generation cryoballoon). Methods Two hundred and twenty patients (paroxysmal AF: 140 patients, persistent AF: 80 patients) had to undergo a redo procedure after initially successful circumferential PV isolation with the cryoballoon technique (First generation: 110 patients (group A); second generation: 110 patients (group B)). The redo ablation procedures were performed using a segmental approach or a circumferential ablation strategy (three-dimensional mapping system) depending on the intra-procedural findings. Results During the redo procedure, a mean number of 1.6 re-conducting PVs were detected (using a circular mapping catheter; group A: 2.2 re-conducting PVs, group B: 1.0 re-conducting PVs). There was a slightly higher incidence of chronic PV reconnections related to the left-sided PV ostia than to the right-sided PVs in both groups. Furthermore, sites of chronic PV reconnection were found more frequently in the inferior parts of the PV ostia than in the superior parts. In 97 patients in group A, a segmental approach was sufficient to eliminate the residual PV conduction because there were only a few recovered PV fibers (1-3 reconnected PVs; group A1). In the remaining 13 patients in group A, a circumferential ablation strategy was used because of a complete recovery of the PV-LA conduction of all four pulmonary veins (group A2). In group B, a segmental approach was sufficient in nearly all patients (109/110) because there was only a minor reconnection of 1-2 PVs. All recovered PVs could be isolated sucessfully again. At 108-month follow-up, 69.1 % of all patients were free from an arrhythmia recurrence (152/220 patients; group A: 72/110 patients (65.5 %), group B: 80/110 patients (72.3 %)). There were no major complications in both groups. Conclusions In patients with an initial circumferential PVI using the cryoballoon technique, a repeat ablation procedure can be performed safely and effectively using radiofrequency catheter ablation. In most cases only a few re-conducting PV fibers were found and therefore, a segmental re-ablation approach seems to be sufficient in the majority of patients (especially in patients treated with the second generation cryoballoon).