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Funding Acknowledgements Type of funding sources: None. Background The success rate of pulmonary vein isolation (PVI) is lower in patients with persistent compared to paroxysmal atrial fibrillation (AF). In patients with persistent AF, additional isolation of the posterior wall is under investigation to improve ablation success. Pulsed field ablation (PFA) might be superior to conventional methods for posterior wall isolation due to its safety profile and might allow for posterior wall ablation (PWA) rather than posterior wall isolation (PWI) based on its efficiency. Purpose To report our initial experience with PWA using a multipolar PFA catheter. Methods Consecutive patients with PWA during their first PFA procedure for AF between May 2021 and October 2022 at our institution were included. For PWA, the multipolar PFA ablation catheter was used in flower configuration only. With the wire in each of the pulmonary veins and the sheath angulated posteriorly, we first performed 2 x 2 sets of anchor lesions with the catheter rotated by ~30° between sets. Next, with the wire retracted back into the device, single sets of two applications were delivered in an overlapping fashion and without catheter rotation between lesion sets to cover the entire posterior wall between the superior and inferior pulmonary veins. Finally, completeness of PWA was verified by 3D electro-anatomical mapping. Results PWA using PFA was performed in 163 patients (mean age 67 years, 71% male). In 55 patients (34%), PWA was added to PVI during the first AF ablation procedure and the remaining 108 patients (66%) had undergone a median of two (interquartile range 1-3) previous AF ablation procedures using either cryoablation and/or radiofrequency ablation. Of all patients, 45 (28%) had paroxysmal, 93 (57%) persistent AF, and 22 patients (15%) left atrial reentry tachycardia. Median procedure duration and fluoroscopy time were 120 (70-190) min, and 18 (9-36) min, respectively. 3D-EAM showed no residual electrical signal (>0.05 mV) on the posterior wall at the end of the procedure in any patient. No cardiac tamponade, stroke, phrenic nerve injuries, atrio-esophageal fistula, or clinically manifest coronary spasm occurred. A repeat ablation was performed in seven patients (4%) and 3D-EAM showed persisting posterior wall isolation in six (86%) and recurrent roof dependent atrial flutter in one patient. Despite PWA, low-voltage signals were found in four (67%) cases on the superior aspect of the posterior wall. Conclusions Left atrial PWA can be performed safely and efficiently using PFA. Early data on the durability of PWA are promising. The impact of PWA on arrhythmia-free outcome needs to be evaluated in larger, prospective randomized trials.

Funding Acknowledgements Type of funding sources: None. Background A multipolar pulsed-field ablation (PFA) catheter has recently been introduced and showed favorable data in terms of safety and procedural efficiency of pulmonary vein isolation (PVI) for atrial fibrillation (AF). Long-term outcome data in comparison to other ablation modalities however is lacking. Purpose To compare procedural and one-year recurrence data of patients with paroxysmal AF (paroxAF) undergoing a first PVI using PFA, cryoballoon ablation (Cryo), or radiofrequency (RFA). Methods Consecutive patients with paroxAF undergoing a first PVI with PFA at our institution from May to December 2021 were included. For comparison, patients with paroxAF undergoing a first PVI with Cryo or RFA between May 2020 and March 2021 were included. A 3-D electro-anatomical mapping system was used in PFA and RFA, but not in Cryo. The following ablation protocols were used to achieve acute PVI: In the PFA group, the standard 32-applications lesion-set and supplementary applications at the discretion of the operator. In the Cryo group, a time-to-effect plus two minutes strategy and in the RFA group following to the CLOSE protocol. Patients were followed with 7d-Holter ECGs 3, 6, and 12 months after ablation. The primary endpoint was recurrence of any atrial arrhythmias following a blanking period of 3 months. Results A total of 202 patients were included (PFA: 32; Cryo: 82; RF: 88). Age, gender, CHA2DS2-VASc score, LVEF and LAVI did not differ among the groups (Table). Median procedure times were shortest with Cryo (76 [interquartile range 60-95] min) followed by PFA (94 [82-110] min) and RFA (157 [126-211] min, p < 0.01). Fluoroscopy dose was lowest with RFA (1.4 [0.6-2.5] Gycm2) followed by PFA (4.8 [3.5-7.9] Gycm2) and Cryo (5.3 [2.8-10.2] Gycm2, p < 0.01). Median follow-up time in patients without recurrence was 12 [10-12] months for the PFA group, 12 [12-13] months for the Cryo group and 13 [12-13] months for the RFA group. There was a trend towards fewer recurrences of atrial arrhythmias with PFA compared to Cryo and RFA (PFA 7%, Cryo: 25%, RFA: 20%, p = 0.13, Figure). Conclusion Recurrences of atrial arrhythmias 12 months after PFA PVI for paroxAF may be lower compared to Cryo and RFA. Larger prospective randomized studies are needed to confirm this initial experience.

Funding Acknowledgements Type of funding sources: None. Background A novel multipolar pulsed-field ablation (PFA) catheter has recently been introduced for pulmonary vein isolation (PVI). Pre-market data showed high rates for PVI-durability during mandatory remapping studies 90 days after the first procedure. Post-market data on PVI durability and lesion regression, particularly in patients with recurrent atrial arrhythmias, are limited. Purpose To characterize the findings on redo cases after previous PFA procedures. Methods Consecutive patients undergoing a redo procedure after an index PFA PVI between May 2021 and October 2022 were included. 3-D electro-anatomical maps (3D-EAM) were acquired in sinus rhythm at the beginning of the redo procedure and compared to the 3D-EAM acquired after ablation during the index procedure. PV-reconnection was assessed on a per-vein and per-patient level and the sites of reconnections were identified. Furthermore, lesions extent was compared between the two maps. Results Of 265 patients undergoing their first PFA PVI between May 2021 and August 2022, 26 (9.8%) patients with recurrent atrial tachyarrhythmia underwent a redo ablation. The phenotype prior to the first PVI was paroxysmal AF in three patients (12%), persistent AF in 85 patients (85%), and left atrial flutter in one (4%) patient. A 31 mm device was used in 81% of the patients. Posterior wall ablation in addition to PVI was performed in three patients. At the end of the first PFA procedure, 100/102 veins (98%, two common ostia) were isolated as evidenced by post ablation 3D-EAM (two LIPV’s could not be isolated). The recurring arrhythmias were AF, atypical flutter, both, and atrial tachycardia in 14 patients (54%), 5 patients (19%), 6 patients (23%) and 1 (4%) respectively. High-density 3D-EAM identified 65/100 (65%) PVs with persistent isolation. In 7 (27%) patients, all PVs were isolated. Reconnection occurred most frequently in the right inferior PV (11, 42%) followed by the left superior PV (9, 36%), the right superior PV (8, 31%), the left inferior PV (6, 27%), and the left common ostium (1, 50%). The predominant reconnection sites were located anterior of the superior veins, and on the inferior aspect of the right inferior PV (Figure). On the posterior wall, the distance between the lesions of the left pulmonary veins and the right pulmonary veins increased by a median of 5 mm [0, 10] between the index and Redo procedure. Conclusion In patients with recurrent atrial arrhythmias after PFA PVI, PV reconnections were found in 73% of the patients and in 35% of the veins. The reconnections were most prevalent on the anterior aspects of the upper veins, as well as on the inferior aspect of the right inferior vein.

Funding Acknowledgements Type of funding sources: None. Background Conduction system pacing (CSP), encompassing left bundle branch area pacing (LBBAP) and His-bundle pacing (HBP), is a novel pacing strategy, which overcomes limitations of conventional right ventricular pacing. Feasibility and early safety of both strategies have been established previously. While HBP is mentioned as an alternative pacing strategy in the latest European and American pacing guidelines, implantation recommendations regarding LBBAP are scarce. Notably, HBP was described to be associated with a significantly higher procedural failure rate compared to LBBAP, making it potentially more contestable. Purpose To compare procedural outcomes after HBP and LBBAP lead implantation. Methods We prospectively assessed 303 consecutive CSP lead implantation attempts at our center from 08/2018 to 11/2022. 81% of all implantations were performed by two high-volume device implanters. Successful conduction system pacing was established according to standard criteria (HBP: QRS morphology, R-wave peak time in V6, programmed stimulation, visibility of a His potential; LBBAP: R-wave peak time in V6, V1-V6-interpeak interval, programmed stimulation or visibility of a left bundle potential) and pacing thresholds (HBP: Results Patients with a HBP attempt were younger and had a narrower QRS complex but did not differ with respect to left or right ventricular function and dimension (table showing percentages and median values/interquartile ranges). LBBAP systems were more often implanted in lieu of CRT, whereas HBP systems were more commonly used in case of AV block without heart failure (table). Acute procedural success rate, overall procedure duration and fluoroscopy time were significantly better during LBBAP implantations (all p Conclusion Success rates and acute procedural outcomes favor implantation of LBBAP compared to HBP systems.

Funding Acknowledgements Type of funding sources: None. Background Left bundle branch area pacing (LBBAP) is a novel pacing strategy, which overcomes limitations of right ventricular pacing. Conventional stylet-driven and non-stylet-driven leads have been used as a conduction system pacing lead. Procedural outcome data comparing both lead types are, however, scarce. Purpose To compare procedural outcomes during CSP device implantation with respect to the use of stylet-driven vs. non-stylet-driven leads. Methods We prospectively assessed 170 consecutive LBBAP lead implantation attempts at our center from 09/2021 to 11/2022. All implanters had previous experience with His-bundle pacing lead implantation using the non-stylet-driven lead and 91% of all systems were implanted by two high-volume device implanters. Successful conduction system pacing was established according to standard criteria (LBBAP: R-wave peak time in V6, V1-V6-interpeak interval, programmed stimulation or visibility of a left bundle potential) and pacing thresholds ( Results Clinical baseline characteristics, echocardiography/ECG data and indications did not differ between patients, who received a stylet-driven or non-stylet-driven lead (table showing percentages and median values/interquartile ranges). Patients underwent implantation of a non-stylet driven 3830 SelectSure lead in 20% of cases and a stylet-driven lead in 80% of cases (Solia 76%, Ingevity+ 3%, Tendril STS 1%). Electrical outcome data did not differ between lead types. However, procedural success rate was significantly higher using stylet-driven leads (p=0.025) and a trend towards shorter overall intervention duration was observed as well (p=0.1). Conclusion Stylet-driven leads offer higher LBBAP lead implantation success rates while shortening implant duration.

Funding Acknowledgements Type of funding sources: None. Background Left bundle branch area pacing (LBBAP) represents a novel cardiac pacing approach that overcomes limitations of conventional right ventricular (septo-) apical pacing. Feasibility and early safety have been shown previously. However, technical limitations (non-dedicated leads, limited availability of suitable implantation sheats) still may preclude successful conduction system pacing (CSP) lead implantation. So-called drilling and entanglement effects can prevent lead implantation at a suitable site and multiple screw-in attempts may be required. However, lead implantation may ultimately still be unsuccessful. Purpose To evaluate the number of total screw-in attempts until abandonment of LBBAP lead implantation during the procedure. Methods We prospectively assessed 170 consecutive LBBAP lead implantation attempts at our center from 09/2021 to 11/2022. All implanters had previous experience with His-bundle pacing lead implantation. Successful conduction system pacing was established according to standard criteria (R-wave peak time in V6, V1-V6-interpeak interval, programmed stimulation or visibility of a left bundle potential) and pacing thresholds Results Patient baseline characteristics and procedural outcomes are shown in the table (percentages and median values with interquartile range in brackets). Overall CSP lead implantation success rate was 91%. Two patients (1%) experienced complications (one atrial lead dislodgement, one pneumothorax). Median number of screw-in attempts in all interventions was 2 (interquartile range [IQR] 1-4, maximum 12). If implantation was successful, a maximum of four attempts provided already 90% of the overall chance of success (figure). Additional lead implantation attempts rarely provided an additional benefit but prolonged overall implantation duration. Conclusion To balance implantation success rates with procedure duration, the number of screw-in attempts during LBBAP lead implantation may be limited to 4-5 attempts. Bail-out strategies (implantation of a cardiac resynchronization pacemaker or a conventional pacemaker) may be considered if CSP lead implantation is unsuccessful after 4-5 attempts.

Funding Acknowledgements Type of funding sources: None. Background A multipolar pulsed-field ablation (PFA) catheter has recently been introduced and showed favorable data in terms of safety and procedural efficiency of pulmonary vein isolation (PVI) for atrial fibrillation (AF). Long-term outcome data in comparison to other ablation modalities however is lacking. Purpose To compare procedural and one-year recurrence data of patients with persistent AF (persAF) undergoing a first PVI using PFA, cryoballoon ablation (Cryo), or radiofrequency (RFA). Methods Consecutive patients with persAF undergoing a first PVI with PFA at our institution from May to December 2021 were included. For comparison, patients with persAF undergoing a first PVI with Cryo or RFA between May 2020 and March 2021 were included. A 3-D electro-anatomical mapping system was used in PFA and RFA, but not in Cryo. The following ablation protocols were used to achieve acute PVI: In the PFA group, the standard 32-applications lesion-set and supplementary applications at the discretion of the operator. In the Cryo group, a time-to-effect plus two minutes strategy and in the RFA group following to the CLOSE protocol. Patients were followed with 7d-Holter ECGs 3, 6, and 12 months after ablation. The primary endpoint was recurrence of any atrial arrhythmia following a blanking period of 3 months. Results A total of 177 patients were included (PFA: 65; Cryo: 63; RF: 49). Age, gender, CHA2DS2-VASc score, LVEF and LAVI did not differ among the groups (Table). Median procedure time was different among the groups (PFA: 109 [interquartile range 88-130] min, Cryo: 81 [62-96] min, RF: 177 [153-200] min, p < 0.01). Fluoroscopy dose was different among groups: RF (1.9 [0.7-4.9] Gycm2), PFA (8.3 [4.3-19.0] Gycm2), and Cryo (9.5 [4.8-19.1] Gycm2, p Conclusion In patients with persAF, recurrence of atrial arrhythmias 12 months after PFA-PVI only is high, regardless of ablation modality. Assessment of strategies including ablation of extra-PV targets in some patients with persAF is needed.

Funding Acknowledgements Type of funding sources: None. Background Pulsed-field ablation (PFA) has recently been introduced for pulmonary vein isolation (PVI). It might also be of potential value for redo procedures after failed radiofrequency or cryo ablation for atrial fibrillation (AF). Purpose To describe our initial experience using a multipolar PFA catheter for redo procedures after failed AF ablation. Methods Consecutive patients undergoing a redo procedure for recurrent atrial arrhythmias at our institution using a multipolar PFA catheter from Mai 2021 until October 2022 were included. A 3D electro-anatomical bipolar voltage map was generated to identify pulmonary vein (PV) reconnection, quantify the level of isolation (antral vs. ostial isolation), and characterize the extent of extra-PV low-voltage tissue. In case of PV reconnection, re-isolation was performed using PFA, with at least four applications in both basket and flower configuration. In case of only ostial PV isolation, additional PFA applications in flower configuration were delivered to widen the isolation to a more antral level. If all veins were already isolated on an antral level and/or if low-voltage areas were found on the posterior wall, a posterior wall ablation was added with the same PFA device at the discretion of the operator. Results We identified 170 patients (mean age: 64 ±11years, 45 (27%) women), undergoing a redo procedure using PFA. The median number of previous ablations was 1 (range 1-6), the most recent ablation was performed using radiofrequency in 122 (72%), cryo in 42 (25%), and surgery in 5 (3%) patients. In 104 (61%) patients, at least one reconnected PV was found. In total, 244 of 680 PV (36%) showed reconnection. In addition to PV reisolation, additional antral applications were delivered in 205 of 436 still isolated veins (47%). Posterior wall ablation was added in 112 (66%) patients (43% in paroxysmal AF, 78% in persistent AF, Figure). Median procedure duration was 101 minutes (IQR 80-137). There was no cardiac tamponade, no stroke, and no esophageal fistula observed in this cohort. Conclusion For patients with recurrence after catheter ablation of atrial fibrillation, re-ablation using PFA is feasible and safe. Most common ablation targets were the pulmonary veins and the posterior wall. Whether the complementary effect of a different technology improves outcome needs further investigation.

Funding Acknowledgements Type of funding sources: None. Background Pulsed field ablation (PFA) is newly available for pulmonary vein isolation (PVI) and combines the benefits of high procedural efficacy and safety. Independent data on the recurrence-rate of atrial fibrillation (AF) after PVI and on PVI durability during redo procedures are scarce. Purpose We report data on the recurrence rate of AF after first PVI using PFA and first insights into findings of PVI durability during redo procedures. Methods Consecutive AF patients undergoing a first PFA PVI at our center between May 2021 and August 2021 were included. PVI was verified by 3D-electroanatomical mapping (3D-EAM), and additional PFA lesions were applied when necessary until all PV were isolated. Seven-day Holter ECGs were performed at 3 and 6 months after ablation. After a blanking period of 3 months, episodes of AF/AT lasting more than 30 seconds were considered as AF-recurrence. Results 41 Patients, median age 69 (interquartile range 62-73) years, 24% female, 56% persistent AF, underwent first PVI by PFA. All PVs were successfully isolated using a multipolar PFA catheter. Median total procedure time including 3D-EAM was 104 (85-121) min. Total fluoroscopy time and dose were 26 (19-30) min and 671 (323-1248) Gym2. Acute complications occurred in 1 (2.4%) patient (cardiac tamponade requiring drainage). Early recurrence of AF during the blanking period occurred in 1 (2.4%) patient. Median follow-up time was 107 (91-152) days. Recurrence of AF after the blanking period was detected in 5 (12%) patients, 1 (6%) in paroxysmal AF and 4 (17%) in persistent AF patients, respectively. Redo procedures in 3 (7.3%) patients with AF recurrence confirmed durable isolation of 12/12 (100%) pulmonary veins and showed no evidence of PFA lesion regression. Conclusion AF recurrence rates after PVI by means of PFA are low. Durable isolation of 12/12 pulmonary veins (100%) and no evidence of PFA lesion regression was observed during redo procedures in patients with AF recurrence.

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Swiss National Science Foundation Swiss Heart Foundation Background The underrepresentation of women in cardiovascular clinical trials is well described but cannot be fully explained by sex-specific differences in the prevalence of cardiovascular diseases. Data on potential sex- and gender-related differences in study exclusion reasons are scarce. The STAR-FIB cohort study aimed to estimate the age and sex-specific prevalence of screening-detected atrial fibrillation (AF) in 800 hospitalized patients aged 65-84 years using serial seven-day ECGs. Recruitment for study inclusion was stratified by sex (female/male, as stated in the patient’s records) and age (four age bands, ≥65 to Purpose To assess sex and gender differences in patient recruitment for inclusion in the STAR-FIB cohort study. Methods A screening log containing sex-category, age, and reasons for exclusion was maintained. Exclusion criteria are shown in the figure. For the purpose of the present study, an explorative analysis of all exclusion criteria with respect to sex category was done. Results Overall, 11’470 patients were identified for eligibility, 795 patients (49% women; mean age 75 years) were enrolled, and 10’675 patients (52% women vs. 48% men, p =0.13) were not enrolled. The two major exclusion reasons were unwillingness to participate, which was more frequent in women (27.9% of women vs. 18.4% of men, p < 0.01), and the presence of clinical AF, which was more prevalent in men (27.1% of men vs. 20.5 % of women, p < 0.01). A detailed analysis of all exclusion criteria analysed by sex category is provided in the figure. Conclusions Clinical AF was more frequent in men, in accordance with the well described sex-driven (biological) higher prevalence of AF in men. In contrast, we found a higher percentage of women unwilling to participate in this study, which may represent a more gender-based (sociocultural) phenomenon. A further exploration of these findings should be performed and may help to identify and potentially overcome modifiable obstacles for study participation.

Funding Acknowledgements Type of funding sources: None. Introduction Pacemaker (PM) patients may require a later upgrade to an implantable cardioverter-defibrillator (ICD). Limited data exists on this patient population. We sought to characterize this population, to assess predictors for ICD upgrade, and to report the outcome. Methods From our prospective PM and ICD implantation registry, all patients who underwent PM and/or ICD implantations at our center were analyzed. Patient characteristics and outcome of PM patients with subsequent ICD upgrade were compared to age- and sex-matched patients with de novo ICD implantation, and to PM patients without later upgrade. Results Of 1’301 ICD implantations, 60 (5%) were upgrades from PMs. Median time from PM implantation to ICD upgrade was 2.6 years (IQR 1.3-5.4) Of 2’195 PM patients, 28 patients underwent subsequent ICD upgrade, corresponding to an estimated annual incidence of an ICD upgrade of at least 0.33%. Lower LVEF (p=0.05) and male sex (p=0.038) were independent predictors for ICD upgrade. Transplant- and LVAD-free survival was worse both for upgraded ICD patients compared to matched patients with de novo ICD implantation (p=0.05; Figure, panel A), as well as for PM patients with later upgrade compared to matched PM patients not requiring an upgrade (p=0.036; Figure, panel B). Conclusions One of twenty ICD implantations are upgrades of patients with a PM. At least one of 30 PM patients will require an ICD upgrade in the following 10 years. Predictors for ICD upgrade are male sex and lower LVEF at PM implantation. Upgraded patients have worse outcome.

Funding Acknowledgements Type of funding sources: None. Background/Introduction Implantation of an implantable cardiac monitor (ICM) is a simple and straightforward procedure. However, with a growing demand for such implants, workload significantly increases. In January 2020, we established a completely nurse-led ICM implantation service (N-IMPLANT) with a standard operating procedure. Purpose The present study aimed to analyze the safety, efficacy, and patient satisfaction of N-IMPLANT compared to implantation of ICMs by a physician (P-IMPLANT). Method Consenting patients implanted with an ICM were included in a prospective registry, which collects patient characteristics, procedural and remote monitoring data. All patients were followed-up by phone interview four weeks after ICM implantation and a standardized questionnaire was completed. Results Of 321 patients implanted with an ICM (median age 67 years; 33% women), 189 (59%) were N-IMPLANT. Significantly more N-IMPLANT were performed in the outpatient clinic compared to P-IMPLANT (94% vs. 10%; p Conclusion Nurse-led implantation of cardiac monitors is effective without compromising patient safety and has excellent patient satisfaction. N-IMPLANT is a suitable model to reduce the workload of physicians.

Funding Acknowledgements Type of funding sources: None. Introduction Leadless pacemakers (PMs) capable of atrio-ventricular (AV) synchronous pacing have been introduced recently. These devices provide mechanical atrial sensing by detection of the atrial contraction via an accelerometer. Atrial tracking may be disturbed by external influences such as body motions and higher heart rates in real life. To track the amount of AV synchronous pacing, the device statistic classifies all sensed and paced QRS complexes according to presumed AV synchrony. The reliability of this self-diagnostics to estimate the true degree of AV synchrony, however, is insufficiently studied. Purpose To investigate the informative value of the device statistics offered by leadless VDD PMs regarding true AV snychrony. Methods We prospectively included all patients who received a leadless VDD PM between 07/2020 and 05/2021 at our center in this observational study. During the regular outpatient follow-ups, device interrogation was performed, which included evaluation of the PM statistics. True AV synchrony (defined as a QRS complex preceded by a p-wave within 300ms) was analyzed repeatedly during follow-up using Holter ECGs. Results We analysed 34 Holter ECGs from 20 outpatients (816 hours of ECG in total). Patients had a median age of 80 years (interquartile range 76-86 years), 55% were females. For Holter ECG sequences that showed high degree or complete AV-Block (>80% ventricular pacing), the percentage of paced beats that were presumed to be AV synchronous by the device statistic (ratio "AM-VP"/total VP) correlated well with AV synchrony as assessed using Holter-ECGs (Kendall’s τ=0.312, p66.6% presumed AV synchrony (p Conclusion Leadless PMs provide device statistics that show a correlation with true AV synchrony. The clinical setting as well as the device programming (e.g. AV conduction mode switch) significantly influence the predictive value of the different parameters of the device’s statistics.

Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): FP7/2007-2013, №602299, EU-CERT-ICD Objective To validate the performance of a multipolar PFA catheter compared to a standard pentaspline 3D-mapping catheter for endpoint assessment of PVI. Background Pulsed field ablation (PFA) for pulmonary vein isolation (PVI) using single-shot devices combines the benefits of high procedural efficacy and safety. A newly available multipolar PFA catheter allows real-time recording of pulmonary vein (PV) signals during PVI. Methods Patients undergoing first PVI using PFA with the standard ablation protocol (8 applications per PV) were studied. Entrance- and exit-block (10V/2ms) were assessed using the PFA catheter. Subsequently, a high-density bipolar voltage 3D electro-anatomical map (3D-EAM) was constructed using a standard pentaspline 3D-mapping catheter. Additional PFA applications were delivered only after confirmation of residual PV-connection by 3D-EAM. Results In 56 patients, 213 PVs were targeted for ablation. Acute PVI was achieved in 100% of PVs: in 199/213 (93%) PVs with the standard ablation protocol alone and in the remaining 14 PVs after additional PFA applications. Accuracy of PV assessment with the PFA catheter after the standard ablation protocol was 91% (194/213 veins). In 5/213 (2.3%) PVs, the PFA catheter incorrectly indicated PV-isolation. In 14/213 (6.6%) the PFA catheter incorrectly indicated residual PV-conduction due to high-output pace-capture. When the output was reduced to 5V/1ms, pace-capture was reduced to 0.9% (2/213). Conclusion A novel multipolar PFA catheter allows reliable endpoint assessment for PVI. Due to its design, far-field sensing and high-output pace-capture can occur, which may require adjustment of standard pacing outputs for verification of exit-block.

Funding Acknowledgements Type of funding sources: None. Introduction Screening for atrial fibrillation may reveal other, incidental arrhythmias of relevance. We sought to describe such incidental arrhythmias in the prospective STARFIB cohort study, which screened for silent atrial fibrillation in hospitalized patients aged 65-84 years. Method Patients included in the STARFIB cohort study had up to three 7-day Holter ECGs, performed in two-month intervals. We analysed all the 7-day Holter ECGs of study participants for the presence of one of the following incidental arrhythmias: 1) sick-sinus-syndrome (SSS), defined as sinus arrest of ≥3 seconds duration; 2) second or higher degree atrioventricular block (AVB); 3) sustained atrial tachycardia of ≥30 seconds duration (AT); and 4) sustained ventricular tachycardia of ≥30 seconds duration (VT). Results A total of 2’077 Holter ECGs were performed in 794 patients (mean age 74.7 years; 49% females), resulting in a mean cumulative duration of an analyzable ECG signal of 414±136 hours per patient. We found incidental arrhythmias in 94 patients (11.8%). Among these were SSS in 14 patients (1.8%), AVB in 41 (5.2%), AT in 41 (5.2%), and VT in two (0.3%). The median pause duration in SSS was 4 seconds and SSS resulted in pacemaker implantation in one patient with a pause of 9 seconds duration. The most severe type of AVB found per patient was second degree AVB type Wenkebach in 23 patients (2.9%), second degree AVB type Mobitz or 2:1 AV conduction in 10 patients (1.3%) and complete AVB in 8 (1%; maximum pause 18 seconds). AVB led to pacemaker implantation in 9 patients (1.1%). The median duration and heart rate of AT was 2.2 minutes and 144 bpm, respectively. Initiation of betablocker therapy was recommended in 3 patients (0.4%) due to symptomatic AT. The duration and heart rate of VT was 3 minutes at 216 bpm in one patient and 38 seconds at 150 bpm in another. The former patient with VT experienced syncope and an ICD was implanted, whereas in the latter the betablocker dose was increased. One patient died from a non-cardiac cause during a Holter ECG, which showed progressive bradycardia and finally asystole. Conclusion Incidental arrhythmias were frequently discovered during screening for atrial fibrillation and resulted in device therapy in 1.4% of our cohort patients.

Funding Acknowledgements Type of funding sources: None. Background A multipolar pulsed field ablation (PFA) catheter was recently introduced for pulmonary vein isolation and combines the benefits of high procedural efficacy and safety. It may also be used to treat left atrial (LA) reentry tachycardia. Purpose To describe our initial experience using a multipolar PFA catheter for the treatment of LA reentry tachycardia. Methods We included all patients with LA reentry tachycardia treated with a multipolar PFA catheter at our institution. Using 3D electro-anatomical mapping (3D-EAM), we identified the tachycardia mechanism and applied linear lesions either at the left atrial roof, mitral isthmus or on the anterior wall, as appropriate. Positioning of the PFA catheter was verified by integration into 3D-EAM. Applications were performed using 2.0kV with the catheter in basket or flower configuration, depending on ablation site. Bidirectional block across linear lesions was verified using standard criteria. Additional focal radiofrequency ablation (RFA) was used to achieve bidirectional block if necessary. Results We treated 17 LA reentry tachycardia with a multipolar PFA catheter in 13 patients (median age 69 (59-73) years; 5 females). The tachycardia mechanism was identified as roof-dependent in five, peri-mitral in eight and anterior scar-related in four cases. PFA lesion sets consisted of 12 posterior wall isolations (i.e. roof lines), four mitral isthmus lines (MIL) and eight anterior lines. For ablation of the mitral side of the anterior line, we always used the PFA catheter in basket configuration, while we targeted the posterior wall and the superior side of the anterior line exclusively with the catheter in flower configuration. To ablate the MIL we used both flower and basket configurations. Three roof-dependent, six peri-mitral, and four anterior scar-related tachycardias were successfully terminated by PFA (76%). Additional RFA was necessary for two MIL, two anterior lines and no roof line (17%). Finally, we achieved bidirectional block across all lines. PFA triggered, vagal-mediated and reversible AV block was observed in one case. Otherwise, there were no acute procedural complications. Conclusion Linear lesion sets are feasible and safe using a multipolar PFA catheter. Posterior wall isolation by PFA for the treatment of roof-dependent LA reentry tachycardia is highly efficient while anterior lines and MIL remain challenging and may need complementary RFA or a PFA catheter designed for focal or linear ablations.

Funding Acknowledgements Type of funding sources: None. Background Contact force-sensing catheters are widely used for ablation of cardiac arrhythmias. They allow precise quantification of catheter-to-tissue contact, which is an important determinant of lesion size and durability. Moreover, contact force information reduces the risk for cardiac perforation and is used for estimation of lesion size. However, the accuracy of contact force sensors across different manufacturers has not been validated independently. Objective To compare the accuracy and reproducibility of different force sensing catheters used in cardiac electrophysiology procedures. Methods A force measurement setup containing a heated saline water bath and a catheter fixation mechanism was constructed. The setup allows to accurately measure forces applied to a platform with the catheter. We studied four different catheter models, equipped with the following, unique force-measurement technologies (figure 1): 1) multiple-fiber optical sensor; 2) single-fiber optical sensor; 3) inductive sensor; and 4) magnetic field sensors. For each model, we assessed three catheters. Repeated measurements within the force range of 0g to 60g and at electrode-tissue contact angles of 0°, 45°, and 90° were performed and validated against the force measurement unit of our measurement setup. Results For each catheter, at least 500 measurements at different contact forces (equally distributed across the measurement range of 0 to 60 grams) were performed. Correlation of measured-force to real-force was ρSpearman=0.99 for MFOS, ρSpearman=0.98 for SFOS, ρSpearman=0.99 for IS, and ρSpearman=0.98 for MFS. MFS and SFOS showed a higher variance for high forces and increased intra-catheter variability compared to MFOS and IS. IS overestimated higher contact force at 0° and 30°. MFS and SFOS underestimated contact force for higher forces at 30° and 45° (figure 2). Within a clinical range of 5g to 40g, the catheters reached the following root-mean-square-error, independent of contact angle: MFOS 0.88g ±0.68g, SFOS 2.15g ±1.74g, IS 0.88g ±0.72g, and MFS 1.13g ±1.01g. Conclusion Measured contact by force-sensing catheters correlates well with true exerted electrode-tissue force. Despite an excellent overall correlation, some technologies may be prone to significant errors at higher forces (>10g under-/overestimation of true contact force) with potential clinical consequences related to increased risk of perforation.

Funding Acknowledgements Type of funding sources: None. Background Dexmedetomidine and propofol are commonly used drugs for deep sedation during cardiovascular interventions. Patients undergoing these interventions often have impaired sinus node function or atrioventricular (AV) conduction disease. Anesthetics used for deep sedation may further compromise sinus node function and AV nodal conduction, and thereby interfere with the intervention. Purpose To compare the electrophysiological effects of dexmedetomidine and propofol on the function of the sinus node and AV conduction. Methods We randomized patients undergoing first atrial fibrilation ablation 1:1 to deep sedation by dexmedetomidine (DEX group) versus propofol (PRO group), according to a standardized protocol. At the end of the ablation procedure with the patients still deeply sedated and hemodynamically stable, we conducted a standard electrophysiological study and assessed sinus node function, properties of AV conduction and atrial refractoriness. Results Of 160 patients (65±11 years old; 32% female) included into the study, 80 patients were randomized to the DEX and PRO group each. Procedure duration (128±59 minutes) and sedation depth, as assessed by the "Modified Observer’s Assessment of Alertness/Sedation" score (median 3; interquartile range 2, 3), was not different among groups. DEX group patients received a mean of 231±111 mcg of dexmedetomidine and PRO group patients a mean of 657±356 mg of propofol. The table shows the results of the electrophysiological study. DEX group patients had lower sinus rate and longer unadjusted sinus node recovery time (SNRT) at pacing cycle lengths of 600, 500 and 400 ms. However, both corrected (SNRT-RR) and normalized (SNRT/RR) SNRT did not differ among groups. Compared to PRO group patients, AV nodal conduction was slower in DEX group patients as evidenced by longer PR and AH intervals, and a higher Wenckebach cycle length and AV node effective refractory period (ERP) was observed. Conduction properties in the His-Purkinje system were not different among groups, as QRS width and HV interval were similar. An arrhythmia, mainly atrial fibrillation, was induced in 33 patients (21%) during the electrophysiological study, without differences among groups. Conclusions Sinus rate and AV conduction are slower during deep sedation with dexmedetomidine compared to propofol. These differences in electrophysiological effects need to be taken into account when using these anesthetics during cardiovascular interventions.