Funding Acknowledgements Type of funding sources: None. Background Leadless pacing has evolved as a safe and effective treatment option in selected patients. With the updated generation that allows sensing of atrial contraction, atrioventricular synchronized pacing is now possible in a VDD mode. Previous retrospective analyses have demonstrated that echocardiographic parameters may be helpful in selecting patients with a higher chance of good atrioventricular synchronous pacing behaviour. Purpose Analysis of the early experience with the second generation of leadless pacemaker and the role of ECG parameters to predict a good atrial contraction signal (so-called A4 amplitude) in patients who underwent leadless pacemaker implantation in four tertiary centres. Methods and Results In this retrospective analysis, a total of 136 patients were included. Mean age was 78.0 (64.7 - 84.2 years) years with 48.9 % being male. Coronary artery disease was the leading underlying heart disease with 27.1 % affected patients. 61.7 % of the population suffered from sinus rhythm with complete or intermittent atrioventricular block. The majority of devices were implanted at the mid-septal (61.2 %) or high-septal (25.6 %) right ventricle, respectively. Electrical parameters were optimal at implant (Table 1) and remained stable over time (Table 1). In addition, A4 signal amplitude remained stable too during follow-up compared to the value early after implantation (Table 1). From this entire cohort, patients with an ECG available at implant and those in which the device was working predominantly in the VDD mode were selected for further analyses (62 patients). PR interval measured from the ECG prior to implantation did not correlate with the A4 signal amplitude (Figure 1A; P = NS). Next, P wave amplitudes were measured in all 12 ECG leads. There was a correlation between P wave amplitude from lead V2 with the A4 amplitude (Figure 1B; P = 0.034, R2 = 0.09), whereas the other right-sided ECG leads (V1/aVR), either alone or in combination, did not correlate with the A4 signal amplitude (P = NS). Conclusions In our cohort of patients with the second generation of leadless pacemakers, offering VDD pacing, good electrical parameters can be achieved as it has been observed with the first generation. Also the A4 signal amplitude as a marker for atrial contraction remains stable over time. In regard to ECG parameters measured prior to device implantation, only the P wave amplitude in lead V2 correlated with a amplitude of the A4 signal.

Funding Acknowledgements Type of funding sources: None. Background The subcutaneous implantable cardioverter defibrillator (S-ICD) has become an alternative to transvenous ICDs (tv-ICD), especially in young patients without a need for pacing. One of the current limitations of the S-ICD is the relatively large size of the generator compared to tv-ICDs. There is little evidence whether the size of the current S-ICD generator is associated with an elevated risk of device-related complications in patients with a low body mass index (BMI). Purpose To compare the device-related complications and long-term outcomes in a large real world cohort of S-ICD recipients in patients with a BMI <18 kg/m2 compared to patients with a BMI >18 kg/m2. Methods The iSuSI registry is a European, multi-center, open-label, independent, and physician-initiated observational registry. A total of twenty-two Public and Private Healthcare Institutions from 4 different countries in Europe were involved in the registry. All consecutive patients meeting current guideline indications for ICD implantation and undergoing implantation of a S-ICD device (Boston Scientific, Marlborough, Massachusetts, USA) at 21 European institutions enrolled in the registry were used for the current analysis. Patients were classified into two cohorts, depending on the BMI at the time of device implantations: BMI < 18 kg/m2 versus > 18 kg/m2. Results Out of a total of 1497 pts, 58 pts (3.9%) had a BMI < 18 kg/m2. Patients with BMI <18 kg/m2 were younger (44.6±2.4 vs 50.8±0.4; p=0.004) and more frequently female (58.6% vs 22.3%, p<0.001). No differences in any of the other baseline characteristic were observed. Implantation techniques resulted comparable between the groups (Rates of 2-incision technique: 87.8% vs 91.9%; p=0.256; inter-muscular placement: 89.7% vs 83.3%; p=0.198). Of note, the mean PRAETORIAN score at implantation of patients with BMI <18 kg/m2 was significantly lower (33.8±9.1 vs 54.1±47.3; p=0.035), although the vast majority of pts in both cohorts qualify as at low risk of conversion failure (100% vs 91.4%; p=0.436). Over a median follow up time of 22.4 [11.6–36.8] months, both overall device-related complications (5.2% vs 7.4%) and rates of inappropriate shocks (12.0% vs 8.8%) resulted comparable between the two groups (p =0.517 and p=0.385, respectively). Figure1 reports Kaplan-Meier curves reporting the combined incidence of device-related complications and inappropriate shocks in the two groups (log-rank p = 0.576). Conclusion No difference in device-related complications and long-term outcomes after S-ICD implantation were observed in patients with BMI <18 kg/m2 compared to the remaining recipients from a large, multi-centered S-ICD registry. Figure 1: Kaplan-Meier-survival curve for the combined endpoint of inappropriate shocks (IAS) and device-related complications (DRC)

Funding Acknowledgements Type of funding sources: None. Background Leadless pacing has been established as an alternative approach to transvenous devices for selected patients suffering from bradycardias. While in the majority of cases leadless pacemaker implantation represents a de novo procedure, in an increasing number of patients such a device is used after a previously implanted transvenous pacemaker. Purpose Retrospective analysis of the efficacy and safety outcome in patients who underwent leadless pacemaker implantation in the context of a previously implanted conventional pacemaker. Methods and Results In this retrospective analysis from two large Swiss implantation centres, 257 consecutive patients undergoing leadless pacemaker implantation were included. Of the total cohort, 233 patients were diagnosed with new-onset bradycardias, while in 24 patients a prior transvenous device was present. Out of these 24 patients, 20 subjects required lead extraction of the previous system due to infection (70%, 14 patients), malfunction or other reasons (Table 1). In 3 patients with device-related infection, lead extraction and leadless pacemaker implantation were performed as a single procedure, while in the remaining 11 cases a time window between the two procedures was present (median of 11.5 days with a range of 2 to 186 days). In the population with a previous device, mean age at implantation was 81 ± 9 years which did not differ compared to the de novo cohort. Mean implantation duration was 57 ± 31 minutes in the cohort with a previous device versus 48 ± 191 minutes in the de novo population without a significant difference (P=NS) and with a successful implantation rate of 100% versus 98.7% in the de novo population (P=NS). Electrical device parameters (sensing, impedance, threshold) at implantation and during follow-up (mean 12.5 ± 9.3 months) were similar between the two groups. Eight major periprocedural complications (3.1%) were encountered (4 pericardial effusions, 3 femoral bleedings and 1 intra-abdominal bleeding) in the entire cohort within a 30 days period, of which the majority occurred in the de novo cohort (75 %, 6 of 8). A total of 4 pericardial effusions occurred, which could be managed without the need for cardiac surgery. The were no reinfections registered after leadless pacemaker implantation during follow-up. Conclusions Implantation of a leadless pacemaker in patients with a prior conventional system (with or without extraction of the previous device) was effective and safe in our population of patients.

Funding Acknowledgements Type of funding sources: None. Background Transvenous lead extraction has become a relevant treatment option in patients with device-associated infection, but also in the context of device- and lead dysfunction. Lead extraction can be complicated by a stroke, which may result from paradoxical embolization of lead debrids during lead extraction in the presence of a patent foramen ovale (PFO) with a right-to-left shunt. Purpose Analysis of the presence of a PFO in patients undergoing transvenous lead extraction in a Swiss tertiary centre. Furthermore, different strategies to reduce the risk for stroke due to the presence of a PFO will be summarized. Methods and Results In this retrospective analysis from January 2017 until December 2021, a total of 304 patients who underwent lead extraction were included. In nearly half of the population, lead dysfunction was the leading cause for extraction, while device-associated infection was present in 31 % of the patients. In 14 patients (4.6 %), a right-to-left shunt was detected either during (via transesophageal echocardiography) or prior to the procedure. Prior to the systematic pre-procedural PFO screening, 9 patients with a right-to-left shunt were identified of which 2 patients suffered from a peri-interventional stroke (22 %) while in the population without a PFO no stroke occurred. The remaining 5 patients with a right-to-left shunt were identified prior to the lead extraction procedure (after setting up an institutional PFO screening programm) and were treated accordingly. Since then, no further neurological episodes occurred (Figure 1). If a PFO was identified, an interventional PFO occlusion was performed either prior to the lead extraction (2 of 5 patients) or together with the lead extraction as a single procedure (1 patient). In the 2 other patients, where a device infection was present together with a PFO, the PFO shunt was occluded transiently using a sizing balloon during the lead extraction procedure to avoid to implant a PFO occluder device in an infectious environment. Conclusions Presence of a right-to-left shunt in patients who need to undergo transvenous lead extraction is a known risk factor for embolic strokes. Identification and treatment of this condition prior or during lead extraction is associated with a reduction in stroke events.

Funding Acknowledgements Type of funding sources: None. Background Pulmonary vein isolation (PVI) remains the cornerstone for treating of symptomatic atrial fibrillation (AF). Single-shot PVI technologies have evolved as a standard for first-time PVI. A novel radiofrequency balloon ablation catheter is now available to offer single-shot RF pulmonary vein isolation. Purpose To summarize the early experience using the novel RF balloon ablation catheter for patients undergoing PVI in two tertiary centres in Europe. Methods We prospectively assessed the first 38 consecutive patients undergoing PVI using RF balloon ablation catheter for paroxysmal or persistent AF in two high volume centres. Both centres used a standardised approach including ultrasound-guided vascular access, uninterrupted anticoagulation, transeptal puncture via the RF balloon sheath and a limited 3D mapping software-guided LA geometry created with a circular mapping catheter. Radiofrequency application for 60s to the anterior segments and 20s posteriorly was performed in all cases, phrenic pacing was employed for ablation of right PVs. BHS performed all procedures (except 2 cases due to high BMI and severe sleep apnea) under sedation, while all patients from UHZ underwent PVI procedures with general anaesthesia as per institutional protocol. All patients had an oesophageal temperature probe to assess oesophageal temperature during ablation (passed orally under sedation) and had uninterrupted oral anticoagulation throughout the periprocedural period. Results Overall, mean age was 64±8 years, 23 (61%) were male, 24 (63%) of patients had paroxysmal AF. The majority were de novo interventions (92%). There was no significant difference between the patients demographics in the two hospitals. All veins were isolated in both groups with a total of 144 applications (n = 73 in the sedation group, n = 71 in the GA population). Median fluoroscopy time was comparable (sedation group 1.1 minutes vs GA group 1.2 minutes; P = 0.58), but median procedure time was shorter in the sedation group (65 minute vs 106 minutes; P < 0.001). The median number of RF ablation per patient (sedation group 7 vs GA group 9; P = 0.32) and time to isolation of each vein (sedation group 11 seconds vs GA group 10 seconds; P = 0.9) were similar. Number of acute reconnections requiring further ablations were not significantly different between groups (sedation group 11 [15%] vs GA group 14 [20%]; P = 0.96). One patient sustained transient phrenic nerve injury in the sedation group. Conclusion Our early experience shows the novel HS balloon ablation can be performed effectively, efficiently and safely under either GA or conscious sedition. The RF balloon ablation catheter paradigm lends itself to refined workflows, with low fluoroscopy requirements and a short learning curve even in initial cohorts.