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Funding Acknowledgements Type of funding sources: None. Introduction Catheter ablation for atrioventricular nodal reentry tachycardia (AVNRT) is usually performed with radiofrequency (RF) energy, which carries a risk of collateral conduction system injury. Cryoablation is a safer, but less effective alternative. Utilization of the three-dimensional electroanatomic mapping (3D EAM) system can potentially overcome some limitations of cryoablation and possibly improve procedural outcome. Purpose We retrospectively analyzed the feasibility, efficacy, and safety of cryoablation of AVNRT guided by 3D EAM system. Methods In this retrospective study, we analyzed consecutive patients who underwent cryoablation of AVNRT in our institution from April 2017 to May 2022. All procedures were performed with either magnetic-based or impedance-based system. A 3D model of the right atrium was created and important structures were annotated. Cryomapping was performed at the presumed slow pathway location, followed with cryoablation when appropriate. Location of cryoablation was annotated either with a dot superimposed from the distal electrode of the cryoablation catheter to the surface of the 3D model or the position of the cryoablation catheter was snapshotted. Intracardiac echocardiography (ICE) was utilized at the operator’s discretion. Procedural endpoint was AVNRT noninducibility, with up to one atrial echo beat allowed. Follow-up was performed with a visit to an outpatient clinic or with a telephone interview. Results The study included 122 consecutive patients (49/122 male; 33/122 pediatric patients, mean age 40.4 ± 22.1 years; mean BMI 25.0 ± 5.7 kg/m2). Altogether, 128 procedures were performed and 124 slow-fast AVNRT were diagnosed, 4 patients had slow-slow AVNRT. In six patients the procedure was repeated due to the recurrence of AVNRT. In two procedures, cryoablation was performed in the left atrium. Impedance-based 3D EAM system was used in 89.8% (115/128) of cases, while magnetic-based 3D EAM system was used in 10.2% (13/128) of cases. In 21.9% (28/128) of cases ICE was utilized. Median number of cryoablations was 3 (2 – 4) and median ablation time was 720 s (480 – 960 s). Cryomapping during ongoing AVNRT was possible in 52.3% (67/128) of cases, with mean time to termination of 13.4 ± 6.5 s. Mean procedural time was 80.9 ± 39.3 minutes. There were no major complications related to the procedure. Endpoint was achieved in 100% (128/128) of cases. Follow-up was completed in 96.7% (118/122) of cases, mean follow-up time was 484.7 ± 342.0 days. Arrythmia-free survival rate after first procedure was 88.1% (104/118). When all repeated procedures were included, the arrhythmia-free survival rate was 94.9% (112/118). Conclusion Cryoablation of AVNRT with utilization of the 3D EAM system is feasible, effective, and safe. Although, the success rate after first procedure is lower than expected, the procedure can be safely repeated to improve the outcome.

Funding Acknowledgements Type of funding sources: None. Introduction Transseptal puncture (TSP) is routinely performed to gain access into the left atrium for left-sided arrhythmias. Although fluoroscopy is mainly used for visualization of TSP, intracardiac echocardiography has been increasingly used to visualize the TSP. However, the available data to support routine use of ICE for visualization is scarce, particularly for pediatric patients and patients with cardiac implantable electronic devices (CIED). Purpose The purpose of this single-center retrospective study was to evaluate feasibility, efficacy, and safety of ICE guided TSP, also including pediatric patients and patients with CIED. Methods In this retrospective study, we analyzed consecutive patients who underwent ICE guided TSP from July 2014 to December 2021. When TSP was performed in patients with CIED, the device´s parameters were tested before and after the procedure. Adverse events (AE) were classified as those that were directly associated with the TSP and those who might be associated with the TSP. All AE either required an intervention, prolonged hospital stay, or had a negative impact on patient´s health. Results The study included 1360 consecutive patients (44.6% (607/1360) male; mean age 59.1 ± 15.6 years; mean BMI 28.1 ± 5.0 kg/m2), 4.3% (59/1360) of patients were pediatric (the youngest was 4 years old and weighed 17 kg) and 8.9% had a CIED (121/1360 – 56.2% (68/121) single chamber; 33.1% (40/121) dual chamber; 10.7% (13/121) resynchronization device). In majority, atrial fibrillation or atypical atrial flutter were the main indication for TSP (75.4%; 1062/1360), followed by ventricular tachycardia (9.4%; 128/1360), ventricular preexcitation (8.8%; 120/1360), and atrial tachycardia (3.5%; 47/1360). A total of 1839 punctures were performed (64.3% (875/1360) single TSP; 35.7% (485/1360) double TSP). Only in two patients (0.14%; 2/1360) the TSP was initially not possible. In one, it was later performed with radiofrequency needle. In total, there were 0.7% (13/1839) of AE. Two events (0.11%; 2/1839) were directly associated with the TSP. In one patient, a tamponade occurred immediately after a double TSP. In another patient with a dual chamber CIED, the ventricular lead was dislocated during the maneuvering of the TSP assembly. The other 11 events (0.6%; 11/1839 - 2 late tamponades and 9 pericardial effusions) could be associated with the TSP, however, they could also be associated with ablations or maneuvering of the catheters. In patients with CIED, there were 3 AE (2.1%; 3/144) – 1 AE was directly associated with the TSP (ventricular lead dislocation described above) and 2 AE which might be associated with the TSP (1 late tamponade and 1 pericardial effusion). There were no AE (0.0%; 0/60) in pediatric patients. Conclusion ICE guided TSP is an effective and safe method for obtaining left atrial access in adult and pediatric patients. Special care should be given to patients with CIED as lead dislocation is possible.

Funding Acknowledgements Type of funding sources: None. Introduction Catheter ablation (CA) of supraventricular tachycardias (SVTs) in pediatric patients is conventionally performed with the aid of X-ray fluoroscopy. Usage of the three-dimensional (3D) electro-anatomical mapping (EAM) system and the intracardiac echocardiography (ICE) enables zero-fluorscopy ablation, eliminating the harmful effects of the radiation (1-3). Purpose We retrospectively analyzed the feasibility, effectiveness and safety of zero-fluoroscopy radiofrequency and cryoablation of various types of SVTs in pediatric patients. Methods In this retrospective study, we analyzed consecutive pediatric patients who underwent CA procedure due to SVT in our institution from April 2014 to October 2021. All procedures were performed completely without the use of fluoroscopy. A 3D EAM system and ICE were used as the principal modes of catheter visualisation. Left-sided procedures were done with ICE guided transseptal approach. Radiofrequency was the principal energy source, while cryoablation was used for arrhythmia substrates in the proximity of the conduction system. Results The study included 174 consecutive patients (69/174 (66%) female; 12.5 ± 3.9 years; 19.2 ± 3.6 kg/m2). Altogether 176 SVTs were diagnosed and treated. Atrio-ventricular nodal reentry tachycardia (AVNRT) was diagnosed in 45% of cases (80/176), atrio-ventricular reentry tachycardia (AVRT) in 47% (82/176), focal atrial tachycardia (AT) in 7% (13/176), typical atrial flutter (AFL) was treated in only one patient, while 2 patients had multiple arrhythmias (AVNRT and AVRT). In total, 202 procedures were performed. Radiofrequency ablation was performed in 76% (154/202), cryoablation in 20% (40/202) and both in 4% (8/202) of procedures. The acute procedural success rate was 96% (195/202). Procedural success rate was 99% (79/80) for AVNRT, 94% (77/82) for AVRT, 92% (12/13) for AT, and 100% (1/1) for AFL, respectively. There were no major complications in our study group. Follow-up was complete in 99% (172/174) of patients. During the follow-up period of a median of 316 days (181 - 747), 98% of patients were arrhythmia free. On average, 1.16 procedures per patient were performed with the long-term success rate of 99% (79/80), 98% (80/82), 100% (13/13) and 100% (1) for AVNRT, AVRT, AT, and AFL, respectively. Conclusion Zero-fluoroscopy CA of various types of SVTs in pediatric population is a feasible, effective, and safe treatment option.

Funding Acknowledgements Type of funding sources: None. Introduction Traditionally, X-ray fluoroscopy is used during catheter ablation procedures. The utilisation of ionising radiation carries non-negligible stochastic and deterministic risks to the health of both the patient and the professional staff. These effects are cumulative and behave in a linear no-threshold manner and, as such, are especially important in paediatric populations (1). The importance of reducing ionising radiation exposure has been recognised by the American College of Cardiology, which recommends the ALARA (as low as reasonably achievable) principle in all interventional laboratories (2). In recent years, advances in three-dimensional electroanatomical mapping systems and their utilisation have enabled the near-zero and zero-fluoroscopy approaches to be studied (3). Purpose The aim of this study was to evaluate the safety and efficacy of zero-fluoroscopy catheter ablation for supraventricular tachycardias (SVT). Methods 584 consecutive patients referred to our institution for catheter ablation of SVT were analysed. Patients were categorised into two groups; zero-fluoroscopy (ZF) group and conventional fluoroscopy (CF) group. Patient characteristics, procedural information, and follow-up data were compared. Results The ZF group had a higher proportion of paediatric patients (42.2% vs 0.0 %; p < 0.001), resulting in a younger age (30.9 ± 20.3 years vs 52.7 ± 16.5 years; p < 0.001) and lower BMI (22.8 ± 5.7 kg/m2 vs 27.0 ± 5.4 kg/m2; p < 0.001). Procedure time was shorter in the ZF group (94.2 ± 50.4 min vs 104.0 ± 54.0 min; p = 0.002). There were no major complications and the rate of minor complications did not differ between groups (0.0% vs 0.4%; p = 0.304). Acute procedural success as well as the long-term success rate when only the index procedure was considered did not differ between groups (92.5% vs 95.4%; p = 0.155; 87.1% vs 89.2%; p = 0.422). When repeated procedures were included, the long-term success rate was higher in the ZF group (98.3% vs 93.5%; p = 0.004). The difference can be partially explained by the operators’ preferences. Conclusion The safety and efficacy of ZF procedures in adult and paediatric populations are comparable to that of CF procedures.

Background In this retrospective study, we aimed to detect factors related to the acute success rate (ASR) of radiofrequency (RFA) and cryo-ablation (CRA) of SVTs guided by three-dimensional (3D) electroanatomical mapping (EAM) system completely without the use of fluoroscopy (FLR). Methods and results We analyzed 324 consecutive patients with SVTs [age was 30.65±20.71 (3.6–83.1) years, 147 patients Conclusions This study revealed that catheter ablation of SVTs completely without the use of fluoroscopy can be performed with high ASR and without procedural complications. Likewise, ASR of fluoroless ablation was the highest for patients with AVNRT and lowest for patients with AT. Moreover, right-sided SVTs were an independent risk factor for ablation failure. Funding Acknowledgement Type of funding source: None

Funding Acknowledgements None Introduction Cryoablation is considered a safe but somewhat less effective alternative to radiofrequency ablation (RF) for treatment of atrioventricular nodal reentry tachycardia (AVNRT). Additionally, it is traditionally performed with the aid of X-ray fluoroscopy as the principal imaging method causing radiation exposure, which is especially undesired in the pediatric population. Purpose The aim of our study was to assess feasibility, safety and success rate of nonfluoroscopic cryoablation for treatment of AVNRT. Methods Forty-eight consecutive patients with a diagnosed AVNRT (aged 40 ± 22 years, 29 (60%) female, 19 (40%) male) were included in the study. Among the study population, 14 (29%) were pediatric patients aged 11.5 ± 4.1 years. Cryoablation was used at the discretion of the operator. Only three dimensional electroanatomic mapping system and intracardiac electrograms were used to guide catheter movement and positioning. X-ray fluoroscopy was not used. The initial approach in all procedures was cryomapping in the region of the slow pathway during ongoing AVNRT, with a switch to cryoablation when termination of tachycardia within 20 seconds of reaching -30°C was achieved. When cryomapping was not possible due to catheter instability, cryoablation was used during ongoing AVNRT for up to 10 seconds at -70°C or lower. When AVNRT was not readily inducible, termination of slow pathway conduction was targeted with cryomapping during programmed stimulation with atrial extrastimuli. Procedural endpoint was noninducibility of AVNRT. Recorded residual slow pathway conduction was not considered a failure. Results Mean procedural duration was 79 ± 34 minutes. On average, 4 ± 2 cryoablations, with a 240 seconds of cryoablation time per each application. Cryoablation was used as a first choice in 45 (45/48, 93.7%) patients. In the remaining 3 patients (3/48, 6.3%) RF ablation failed as the first choice due to transient AV conduction disturbance and cryoablation had to be used to reach the endpoint. Cryoablation was unsuccessful only in 3 cases (6.6%) where RF ablation was needed to achieve procedural endpoint. Targeting termination of AVNRT during cryomapping or cryoablation was possible in 25 patients (25/48, 52%). In 14 patients AVNRT was not inducible and termination of the slow pathway conduction was targeted instead. In 9 patients inadvertent catheter tip contact mechanically terminated AVNRT or slow pathway conduction; site of mechanical termination was then targeted with cryoablation. After mean follow-up of 349 ± 201 days 47 patients were free of recurrence (47/48, 98%). There were no procedural complications. Conclusions In our study population with adult and pediatric patients, zero-fluoroscopy cryoablation of AVNRT proved feasible, safe and resulted in high success rates. Cryomapping or cryoablation for AVNRT termination was possible in approximately half of the procedures.

Funding Acknowledgements None Introduction Convergent procedure is a minimally invasive surgical approach for treatment of atrial fibrillation (AF) combining epicardial and endocardial radiofrequency (RF) ablation. However, there is conflicting data regarding the rate of major complications after convergent treatment of AF. Apart from common complications the esophageal injury incidence after convergent procedure is not well documented. Purpose Our aim was to assess major complication occurrence after convergent procedure with additional emphasis on the incidence of esophageal injury. Methods One hundred forty-seven consecutive patients (113 male, mean age 59 ± 9 years, BMI 29 ± 5 kg/m2) with persistent (122, 83%) and paroxysmal (25, 17%) AF were treated with convergent procedure that included epicardial RF ablation with coagulation devices (12 lesions, each for 90 s, with 30 W power), combined with endocardial RF catheter ablation for pulmonary vein isolation. The approach for epicardial ablation was diaphragmatic pericardial window through subxiphoid incision. Infusion of cooled saline into the pericardial space during epicardial ablations and monitoring of esophageal temperature with temperature probe were additional precautions to avoid esophageal overheating. All patients had endoscopy of the esophagus at least 2 days after the procedure to assess for presence of esophageal injury. Adverse events resulting in additional intervention or causing long-term disability were defined as major complication. Results During short-term follow-up (minimum of 5 months) major complication rate was 6.1%. Three patients had cardiac tamponade, 4 had abdominal bleeding, 1 had ischemic stroke and 1 had arterial pseudoaneurysm. Esophageal mucosal lesions were observed in 11 patients (7.5%) that did not result in major complication. All lesions were followed with additional endoscopies and resolved without any intervention. Conclusions Complication rate after minimally invasive convergent procedure for treatment of AF in our patient cohort is low. Prevention of esophageal overheating resulted in absence of major esophageal injury.

Funding Acknowledgements None Introduction Conventionally, catheter movement and placement during catheter ablation (CA) is guided by X-ray fluoroscopy. In recent years, an ‘as low as reasonably possible’ principle was established to minimize the ionizing radiation dose received by the patient and the operator. Zero-fluoroscopy approach is at the extreme end of the spectrum of this principle. With exclusion of X-ray fluoroscopy, three-dimensional electroanatomical mapping system and intracardiac echocardiography are used for catheter guidance during ablation procedures. Purpose The aim of our study was to assess and compare procedural parameters and clinical outcomes of conventional X-ray fluoroscopy guided and zero-fluoroscopy CA for treatment of supraventricular tachycardias. Methods Retrospective analysis included CA procedure between April 2014 and May 2019. Five hundred and thirteen (513) patients were selected for analysis; they had confirmed diagnosis of atrioventricular nodal reentry tachycardia (AVNRT) or atrioventricular reentry tachycardia (AVRT). Patients were divided into two groups based on the use of fluoroscopy (conventional approach group - CG; zero-fluoroscopy group - ZF). Procedural data and clinical outcomes were analyzed. Two groups were compared using chi-squared test or Mann-Whithney U test when appropriate. Results There were 249 patients (44.2% males) in CG group, and 260 patients (47.5% males) in ZF group. ZF group included 113 (43.5%) pediatric patients. The groups differed in mean age (53.4 ± 16.4 years vs 30.0 ± 19.8 years (CG vs ZF), p In CG group, all procedures were performed using radiofrequency (RF) energy, whereas in ZF group, cryoablation was used in 18.3% of procedures at the discretion of the operator. Mean procedural duration was longer in CG group (100.1 ± 48.8 vs 90.4 ± 83.0 minutes, p Conclusions Zero-fluoroscopy CA of supraventricular tachycardias is associated with lower procedural success rate, but higher long-term arrhythmia-free survival rate when compared to conventional fluoroscopy guided procedures. It is possible, that these differences are stemming from somewhat different patient populations in both groups.

Background Catheter ablation (CA) of supraventricular tachycardias (SVTs) is traditionally performed with the aid of fluoroscopy. However, ionizing radiation is associated with potentially harmful deterministic and stochastic effects to the patient and operator. Many methods have been suggested to reduce the radiation exposure, one of the methods, which completely eliminates ionizing radiation exposure, is zero-fluoroscopy catheter ablation. Purpose Our aim was to assess feasibility, success rate and safety of zero-fluoroscopy CA for treatment of various right and left-sided SVTs with the use of three-dimensional (3D) electroanatomical mapping system (EAM) and intracardiac echocardiography (ICE). Methods Consecutive 274 patients (140 male, mean age 33.5±21.8 years) with documented SVTs underwent CA in our center from April 2014 to May 2018. All procedures were performed with the 3D EAM without any use of fluoroscopic guidance. ICE was used as primary visual modality when left-sided approach was required. The procedural endpoint for atrioventricular nodal reentrant tachycardia (AVNRT) was nodal rhythm during radiofrequency (RF) energy delivery and non-inducibility. The procedural endpoint for focal atrial tachycardia (AT) was termination and non-inducibility. The procedural endpoint for accessory pathway (AP) mediated tachycardia was absence of bidirectional conduction over the AP. The procedural endpoint for typical atrial flutter (AFL) was bidirectional block over the cavo-tricuspid isthmus. Results One hundred thirty two patients had AVNRT, 79 had AP mediated tachycardia (47 left-sided, 25 septal and 7 right-sided), 31 patients had AT (8 left-sided), 32 patients had AFL. Cryo-ablation was used in 14 (14/132, 10.6%) patients with AVNRT and 5 patients with septal AP (5/25, 20%), RF was used in the rest. The procedural endpoint was achieved in all procedures (100%). During the mean follow-up of 343±253 days the recurrence rate for AVNRT, AP mediated tachycardia, focal AT, AFL was 7.5%, 16.4%, 32.3% and 9.4%, respectively. No procedural complications were observed. Conclusions Zero-fluoroscopy CA of right and left-sided SVTs with the use of the 3DEAM and ICE is feasible, safe and results in promising long-term success rates after single CA procedure. Acknowledgement/Funding None