Abstract Introduction Pulse-field ablation (PFA) is an emerging atrial fibrillation (AF) ablation technology associated with a favorable safety profile and short procedural times. Elderly patients, in whom AF ablation indications are expanding, may be particularly suitable to PFA. However, in a recent large multicenter trial, patients older than 75 years were not included, so that data on PFA safety and efficacy in this population are scarce. Methods Consecutive patients who underwent PFA of AF at a single academic center were prospectively included in a local registry. Written informed consent was obtained. Clinical, imaging and procedural data was collected and routine care follow-up was performed locally. Results From 2022, out of 345 consecutive patients who underwent PFA of, 42 (13%) were aged ≥75 years. As compared to <75 years-old patients (mean age 61±3 years), elderly patients (mean age 78±4 years) were more frequently females (21 [51%] vs 121 [40%], P=0.02), had more frequently non-paroxysmal AF (27 [65%] vs 164 [54%], P=0.01), significant cardiac comorbidities (9 [21%] vs 33 [11%], P=0.01), and larger indexed left atrial volumes (65 mL/m2 [interquartile range (IQR) 54-76] vs 61 [IQR 54-68], P=0.04). With regards to procedural parameters, the total procedural length was comparable, while elderly patients received more frequently PFA applications outside the pulmonary veins. The rate of major complications was comparable, but 3 cardiac tamponades occurred in patients aged over 75 years, while none occurred in younger patients. After a median follow-up time of 185 days (IQR 65 – 202), the cumulative freedom from sustained atrial arrhythmia recurrence was not statistically different between patients aged over 75 years (75%, 95% confidence interval (CI) [62-84%]) and under 75 years (75%, 95% CI [62-84%], P=0.11). Conclusions PFA appear as a safe and effective technique for AF ablation in elderly patients, although there was an excess of cardiac tamponades in this group

Abstract Background A recent review of 86 patients with short or long-coupled premature ventricular complex (SLC-PVC) initiating idiopathic ventricular fibrillation (IVF) found high success rate in arrhythmia control with quinidine (QND) (83%) or radiofrequency ablation (RFA) (70.8%). Purpose To compare the efficacy of QND vs. RFA therapy in a large patient cohort with SLC-IVF. Methods THESIS included 287 patients with SLC-IVF screened from 58 centers and 1 multicenter group in 22 countries across 4 continents. The study cohort included 146 (50.9%) males, aged 39+14 years at the time of IVF documentation. Therapy groups were defined according to the first therapy given. Therapy success was defined as no VF recurrence. Results Patients presented after aborted cardiac arrest, ICD shocks, syncope, aborted cardiac arrest + arrhythmic storm, arrhythmic storm, palpitations, seizures or were asymptomatic in 121 (42%), 51(18%), 42(14.6%), 27 (9.4%), 23 (8%), 8 (2.8%), 6 (2.1%) and 9 (3.1%), respectively. Fifty-three patients (18.5%) had a prior history of syncope. Eleven (3.8%) patients required ECMO support. Mean shortest and longest coupling interval which triggered VF in the same patient were 304.9+82ms and 341.2+94.1ms, respectively. VF initiation with "long" coupled PVC (coupling interval >350ms) was observed in 41 (18.1%) patients, and VF initiation with both short and long coupled PVC was documented in 30 (13.2%) others. RFA was performed in 112 patients and QND was given to 68 patients. Patients were followed during a mean follow-up of 84.8+64.5 months. Therapy success was achieved in the RFA or QND group in 69 (62.2%) and 49 (71%) patients, respectively (p=0.29). The RV Purkinje was the main targeted ablation site in 46 (47.4%) patients. Treatment success varied according to the site of origin (SOO) of the PVC which triggered VF. Therapy success was higher with QND when PVC SOO based on ECG, was the RV inflow tract (81.3% vs. 57.7%, p=0.048) or when the SOO was not available (67.9% vs 36.4%, p=0.064), and when the coupling interval/QT ratio was <1 (75.5% vs. 57.5%, p=0.03), Figures 1,2. A higher success rate with ablation compared with QND was seen with LV- SOO compared with RV-SOO (82.1% vs 60.3%, p=0.019). Similarly, successful ablation was achieved in 83.3% (n=24) vs. 55.9% (n=68) patients with LV and RV-SOO respectively; p=0.004. One patient expired of sudden cardiac death due to misdiagnosis, while wearing a subcutaneous -ICD, without any drug or ablation therapy. Conclusions SLC-IVF strikes males and females equally. SLC-PVCs triggering the arrhythmia mainly arise from the RV Purkinje system. QND and RFA have similar efficacy in arrhythmia control. Quinidine has a higher treatment success rate in patients with PVC-SOO in the RV inflow area and in those with coupling interval/QT<1.Figure 1Treatment success by SOOFigure 2Treatment success by CI/QT

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Diagnosis of Brugada Syndrome (BrS) is established either by a observing a spontaneous Type 1 Brugada pattern on ECG or by unmasking Type 1 pattern with a drug challenge using a sodium channel blocker in suspected individuals. There are no clear indications on when to apply the Ajmaline provocation test and how to manage positive case. Data regarding the long-term outcome of this population is limited. The present study was designed to evaluate the incidence and identify predictors of arrhythmic events among subjects with Ajmaline induced Brugada ECG. Objectives To evaluate the long-term outcomes of subjects diagnosed with drug induced Brugada ECG. Methods A multicenter international consecutive cohort including all cases of positive Ajmaline provocation test from 5 large electrophysiology centers form Israel, France, and Switzerland Results A total of 130 patients were recruited, the majority were males (70.8%) and Caucasian (97.7%). In our cohort the most frequent indication for performing an ajmaline test was a family history of BrS or sudden cardiac death (43.1%), then a suspicious ECG (38.5%), syncope (16.1%) and 3 with ventricular fibrillation (VF) (2.3%). The common infusion protocols used were 1mg/kg over 5 minutes (56%) and 1mg/kg over 10 minutes (26%). In all centers ajmaline infusion was stopped when type 1 Brugada pattern was observed. No adverse events occurred during the studies. All patients received instructions regarding the avoidance of arrhythmic triggers (specific drugs, alcohol and reduction of fever). During a median follow up time of 36 (7.5-66.9) months, 9 syncope occurred, 15 ICD (3 for secondary prevention because of VF as initial presentation) and 29 ILRs were implanted. No VF or deaths occurred in any of the study groups. Conclusion In the present study of consecutive patients with a positive Ajmaline provocation test, there were no adverse outcomes during a median follow up of 3 years, irrespective of the indication for the test. Our results, indicating a low risk, are in agreement with the current ESC guidelines limiting the diagnosis of Brugada syndrome. Further research is warranted to test whether these patients maybe be managed safely solely by education to avoid arrhythmic triggers.

Abstract Funding Acknowledgements Type of funding sources: None. Background The recent PARTITA trial showed a net clinical benefit of early ventricular tachycardia (VT) ablation in patients with implantable cardioverter defibrillator (ICD) experiencing appropriate shocks. The PARTITA trial analysis, however, was performed in transvenous ICD recipients and data regarding its generalizability in subcutaneous ICD (S-ICD) recipients are lacking. Purpose To test whether VT ablation after an ICD shock or a hospitalization for slow VT impacts long-term clinical outcomes in S-ICD recipients. Methods All patients experiencing an ICD shock or a hospitalization for slow VT (index event) in the multicenter, international, physician-initiated, real-world iSUSI (International SubcutaneouS Implantable Cardioverter Defibrillator) registry were included in the study. Time zero was set as time of first ICD shock / slow VT hospitalization. Patients were stratified based on performance of VT ablation after the index event (VTA+ vs VTA- cohorts). The primary outcome was a combination of device-related appropriate shocks, slow VTs, and cardiovascular mortality during follow-up. Secondary outcomes were device-related appropriate shocks, slow VTs and cardiovascular mortality, taken individually. Results Among 1701 patients enrolled in the iSUSI registry, n=211 were included in this study (n=178 experiencing appropriate shocks; n=33 with slow VTs). After the index event, n=58 (27.5%) underwent VT ablation (VTA+ cohort). No significant differences regarding baseline characteristics between VTA+ and VTA- cohorts were observed: mean age 47.3±16.0 years (VTA+) vs 47.9±17.0 years (VTA-), p=0.799; males 82.8% (VTA+) vs 82.4% (VTA-), p=0.945; mean LVEF 43.8±13.2% (VTA+) vs 42.3±15.5% (VTA-), p=0.530; underlying ischemic cardiomyopathy 31.0% (VTA+) vs 32.7% (VTA-), p=0.8.19; primary prevention implant 36.2% (VTA+) vs 43.4% (VTA-), p=0.434; median number of shocks at index time n=2 [1-4] (VTA+) vs n=2 [1-3] (VTA-), p=0.590. Over a median follow-up of 17.3 [10.4–34.8] months, the combined primary outcome was experienced by 46 (21.8%) patients (Figure 1). VT ablation performance was associated with significantly lower event rates (8.6% vs 26.8%; HR 0.215 [CI 0.100–0.637]; p=0.004), although only a trend towards significance of cardiovascular mortality was observed (HR 0.168 [CI 0.020–1.252]; p=0.081). Among VT ablation, LVEF and ischemic cardiomyopathy, which resulted significantly associated with the primary combined outcome at univariate analysis, only VT ablation remained significantly associated with the outcome of interest at multivariate analysis (HR 0.264 [CI 0.104-0.672], p=0.005) (Figure 1). Survival analysis plotted using Kaplan Meier curves has been reported in Figure 2. Conclusions In a real world registry of S-ICD recipients, VT ablation post ICD shocks or hospitalizations for slow VTs was associated with a combined improved arrhythmic and mortality outcome at long-term follow-up.

Abstract Background The incidence of cardiac arrhythmias following acute coronary syndrome (ACS) is not well-known. Purpose To describe the incidence of clinically relevant cardiac arrhythmias following low-risk ACS, using a connected continuous rhythm monitoring device. Methods In a prospective, single arm and open label, observational study, patients in sinus rhythm and with a left ventricular ejection fraction > 40% discharged home after an ACS were equipped with a rhythm monitoring tee-shirt, providing a high-quality continuous 15-lead electrocardiogram signals. Patients were prompted to wear the device as much as possible, for a maximum length of 30 days. Recorded data were reviewed by two independent cardiologists. The primary endpoint was the occurrence of clinically relevant arrhythmias – defined as either new atrial fibrillation, ventricular tachycardia, accelerated idioventricular rhythm or frequent premature ventricular contractions (≥ 500/day) – detected by the device over the first 30 days after hospital discharge following the ACS. Results From January 2020 to August 2022, 99 patients were discharged home with a functional rhythm monitoring device, among whom 45 (55%) were ST-segment elevation myocardial infarction. The median recording duration was 13 days (range: 1-30), with a median workable signal of 9 days. Recorded data were interpretable in 82 patients. At least one clinically relevant arrhythmia occurred in 10 patients (12.2%) during follow-up. Median time to first arrhythmia was 16,5 days (IQR: 8,5-23). Paroxysmal atrial fibrillation was detected in 3 patients (3.7%), non-sustained ventricular tachycardia in 4 patients (4.9%), accelerated idioventricular rhythm in 3 patients (3.7%) and frequent premature ventricular contractions in 5 patients (6.1%) (Figure 1). None of these arrhythmias were symptomatic. No sustained ventricular tachycardia was detected. Conclusions Asymptomatic cardiac arrhythmias were frequent after ACS in patients considered at low risk for further events. The long-term clinical risk of these arrhythmias remains to be studied.

Abstract Funding Acknowledgements Type of funding sources: None. Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by fibrofatty replacement in the myocardium progressing from the epicardium towards the endocardium and affecting primarily the right ventricle (RV). Little data is available on the distribution of RV electrical abnormalities at the era of epicardial and high-resolution mapping. Purpose To evaluate the extent and distribution of RV epicardial and endocardial low voltage areas and their relationship with ECG abnormalities in ARVC patients. Methods Patients with a definite ARVC diagnosis according to the 2020 Task Force Criteria, who underwent ventricular tachycardia ablation between 2016 and 2022 with a high-density RV 3-dimensional electroanatomic mapping, were included. A custom RV segmentation dividing the RV into 10 segments from endocardial maps was used: anterior and lateral right ventricular outflow tract (RVOT); basal and mid inferior wall; apex; septum; basal anterolateral, basal inferolateral, mid anterolateral and mid inferolateral RV free wall (Figure). A standard definition of electrical scar was used (bipolar voltage ≤0.5 mV), and scar areas were manually delineated. Percentage of scar was defined by the ratio between scar area and the total segment area. ECG abnormal findings, such as epsilon wave and T-wave inversion in precordial leads, were measured before ablation procedure. Results Twenty-nine consecutive definite ARVC patients were included, among whose 24 had epicardial mapping in addition to endocardial mapping. When considering all segments, the epicardial scar (median:70%, interquartile range [IQR] 37-97%) was larger (p<0.0001) than the endocardial scar (9% [IQR] 0-32%). The higher percentage of epicardial scar was found in the basal inferolateral (100% [IQR] 73-100%), basal anterolateral (94% [IQR] 67-100%), RV free wall and lateral RVOT (89% [IQR] 48-100%) segments (Table). Transmural scar was observed mostly in basal inferolateral RV free wall (10 patients, 41%) and basal inferior wall (8 patients, 33%). Patients with major depolarization criteria had a higher percentage of epicardial and endocardial scar as compared to those with no or minor depolarization criteria (respectively 93% [IQR] 59-100% versus 62% [IQR] 28-89%, p<0.0001 and 17% [IQR] 0-42% versus 4% [IQR] 0-23%, p=0.001). There was no significant difference of the percentage of epicardial or endocardial scar in patients with and without major repolarization criteria (respectively 90% [IQR] 49-98% versus 84% [IQR] 43-100%, p=0.91 and 14% [IQR] 11-35% versus 16% [IQR] 0-41%, p=0.73). Conclusion In ARVC, the electrical abnormalities predominate in the basal epicardium. Patients with major depolarization criteria had a higher extent of epicardial and endocardial scar, but there was an association between scar extent and repolarization abnormalities.

Abstract Background One of the current limitations of the S–ICD is the relatively large size of the generator compared to the TV (transvenous) ICD. 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 Aim of this study was 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 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 extended ELISIR 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 patients in both cohorts qualified 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). Figure 1 reports Kaplan–Meier curves showing the combined incidence of device–related complications and inappropriate shocks in the two groups (log–rank p = 0.576). Conclusion No differences 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 in a large multicentered real–world analysis.

Abstract Background Data on patients with heart failure (HF) with a subcutaneous implantable cardioverter defibrillator (S–ICD) are scarce. Objective Aim of this study was to assess clinical outcomes of the S–ICD in HF patients in a real–world analysis from the largest European retrospective S–ICD registry (ELISIR). Methods All consecutive patients undergoing S–ICD implantation at several European institutions were used for the current analysis. The population was classified into two groups: the HF (classified as HF with reduced and mid–range ejection fraction – HFrEF and HFmrEF) vs the no–HF cohort. The primary outcome of the study was the inappropriate shock (IS) rate across the two cohorts. As secondary outcomes, appropriate shocks, cardiovascular mortality and device–related complications during follow–up were assessed Results A total of 1409 patients from the ELISIR registry were included; HF patients represented 57.3% of the entire cohort (n = 701, 86.9% HFrEF; n = 106,13.1% HFmrEF). Over a median follow–up of approximately 2 years, a total of 133 inappropriate shocks were observed in the entire cohort, without significant differences among the two groups (9.2% vs 9.8%, p = 0.689). 133 complex ventricular arrhythmias were adequately recognized and treated, with similar rates of appropriate shocks (9.2% vs 9.8%, p = 0.689). Inappropriate and effective shocks–free survival has been represented in Figure 1 (Kaplan–Meier estimates). At multivariate analysis (Figure 2), age (HR = 0.974 [0.955–0.992], p = 0.005), LVEF (HR = 0.954 [0.926–0.984], p = 0.003), arrhythmogenic right ventricular cardiomyopathy – ARVC (HR = 3.364 [1.206–9.384], p = 0.020) and smart pass + (HR = 0.321 [0.184–0.560], p < 0.001) remained associated with inappropriate shocks. Moreover, a low number of patients (n = 76) experienced device–related complications, more frequently in the HF cohort (6.2% vs 3.8%, p = 0.031) with no significant differences regarding any specific outcome of interest: lead infection (1.1% vs 0.7%, p = 0.381), pocket infection (1.9% vs 0.8%, p = 0.107), pocket hematoma (3.2% vs 2.8%, p = 0.668). Conclusion The use of S–ICD in HF patients did not result in a higher rate of inappropriate shocks when compared to no–HF patients, even when stratifying for LVEF. Only age, LVEF, ARVC e Smart Pass algorithm were predictors of the primary outcome at multivariate analysis. Despite a lower overall rate of complications in the entire cohort, HF patients experienced device–related complications more frequently.

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation is frequently needed to treat ventricular tachycardia (VT) in ARVC patients. Ablation aiming non-inducibility (NI) and late potential (LP) abolition has been shown to be effective1. Simultaneous endo-epicardial mapping demonstrate epicardial involvement in most VT2. However epicardial fat and vicinity of coronary artery may prevent effective epicardial ablation. Aims (a) evaluate endocardial-only ablation guided by epicardial late-potential recording (EA-ELP) to achieve LP abolition (LPA) and NI; (b) measure ablation-index(AI) values allowing epicardial LP suppression by endocardial ablation, as a surrogate for transmurality. Methods From 2019 to 2021 the authors (XW, EG) evaluated EA-ELP in ARVC patients patient referred for ablation. Our ablation protocol was previously described3. Endo and epicardial voltage mapping of the right ventricle (RV) were performed in sinus rhythm using 0.5-1.5 mV threshlods for endocardial scar and 0.5-1 mV for the epicardial. All LP were manually tagged. Programmed ventricular stimulation (PVS) was performed till S4 from the RV apex and other sites, all inducible tolerated VT were mapped. Endocardial ablation was performed with an irrigated tip catheter positioned in front of epi-LP recorded by a multi-electrode catheter aiming to eliminate or delay epi-LP as a surrogate for transmurality. For each lesion fulfilling the «transmurality criteria», the AI values were recorded. Remap was performed to validate LPA and NI was tested. Patient follow-up (FU) rely on telemonitoring in ICD-carriers and holter/exercise test for the others. Results 11 patients were enrolled (9M/2F, mean age 45 years), 9 for VT recurrence (3 redo) and 2 for de novo VT. The median ICD therapy before ablation was 5/patient (mean 1.7). The clinical VT originated from the RV outflow tract (RVOT) in 5 patients, peritricuspid (PT) in 2, RV free wall (RFW) in 4. Substrate were more extended in the epicardium compared to the endocardium: epi-LP and scar surfaces were 42.5 cm2/118 cm2 versus 24.5 cm2/25.5 cm2 for the endocardium. In one patient, additional epicardial lesion was necessary to achieve LPA. The mean ablation duration was 3377 s. Remap showed LPA in all patients and PVS was negative in all (not tested in one due to hemodynamic instability). One patient presented retrosternal hematoma after ablation with spontaneous favorable outcome. Endocardial AI values allowing epi-LP abolition were 595 for the inferior wall, 625 in the RVOT, 604 for PT and 639 for RFW. During a mean FU of 12 months (median 16.5 mths), only one patient had VT recurrence. Conclusion Based on this case-series, EA-ELP appeared as a safe and effective method to treat VT in ARVC. EA-ELP ablation allowed VT suppression in 91 % of patients after an mean FU of 12 mths. The RV endocardial AI needed to suppress epi-LP ranged was between 595-639 and could be used as surrogate for transmurality in ARVC.

Abstract Funding Acknowledgements Type of funding sources: None. Background Data on patients with heart failure (HF) and subcutaneous implantable cardioverter defibrillator (S-ICD) are very scarce and limited to a single prospective analysis from the UNTOUCHED trial. Purpose Aim of this study was to assess clinical outcomes of the S-ICD in HF patients, comparing them with a no-HF population, in a real-world analysis from the largest European retrospective S-ICD registry (ELISIR registry). Methods All consecutive patients undergoing S-ICD implantation at 20 European institutions enrolled in the ELISIR registry were used for the current analysis. According to European Guidelines, the registry population was classified into two groups: the HF cohort (further classified as HF with reduced and mid-range ejection fraction – HFrEF and HFmrEF) vs the no-HF group. The primary outcome of the study was the inappropriate shock (IS) rate across the two cohorts. As secondary outcomes, appropriate shocks, cardiovascular mortality and device-related complications during follow-up were assessed. Results A total of 1409 patients from the ELISIR registry were included in this analysis; HF patients represented 57.3% of the entire cohort (n=701, 86.9% HFrEF; n=106,13.1% HFmrEF). As expected, the HF cohort showed significantly higher rates of cardiovascular risk factors and comorbidities when compared to the no-HF cohort. Over a median follow-up of approximately 2 years, a total of 133 inappropriate shocks were observed in the entire cohort, without significant differences among the two groups (9.2% vs 9.8%, p=0.689). 133 complex ventricular arrhythmias were adequately recognized and treated in the overall cohort, showing similar rates of appropriate shocks (9.2% vs 9.8%, p=0.689). Inappropriate and effective shocks-free survival has been represented in Figure 1, showing Kaplan-Meier estimates comparing HF vs no-HF patients, also stratified by left ventricular ejection fraction (LVEF). The impact of baseline and procedural characteristics on the primary outcome was tested through univariable and multivariable Cox regression analysis in HF patients; at multivariate analysis, only age (HR=0.974 [0.955–0.992], p=0.005), LVEF (HR=0.954 [0.926-0.984], p=0.003), ARVC (HR=3.364 [1.206-9.384], p=0.020) and smart pass algorithm "on" (HR=0.321 [0.184-0.560], p<0.001) remained associated with inappropriate shocks (Figure 2). A low number of patients (n=76) experienced device-related complications, more frequently in the HF cohort (6.2% vs 3.8%, p=0.031) with no significant differences regarding any specific outcome of interest: lead infection (1.1% vs 0.7%, p=0.381), pocket infection (1.9% vs 0.8%, p=0.107), pocket hematoma (3.2% vs 2.8%, p=0.668). Conclusion The rate of inappropriate shocks seems to be comparable in both HF and non-HF patients implanted with S-ICD. However, the rate of device-related complications was slightly more frequent in HF patients.

Abstract 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)

Abstract Funding Acknowledgements Type of funding sources: None. Background Young patients often represent the most suitable candidates for an entirely subcutaenous implantable cardioverter defibrillator (S-ICD) system, since they have to face a lifetime of device therapy and they rarely have a pre-existing or concurrent pacing or cardiac resynchronization therapy (CRT) indication. Moreover, S-ICD offers lower rate and a safer management of lead and major procedure-related complications. To date, a few limited case series and experiences with S-ICD in teenagers and young adults have shown that the S-ICD system is safe and feasible in this population, with a rate of inappropriate shocks (IS) comparable to transvenous (TV) ICD, but focused analysis on a large scale are currently lacking in this setting. Purpose The aim of the current study was to compare the age-related differences observed in patient selection, baseline characteristics, and device long-term associated outcomes in a large real world cohort of S-ICD recipients. The primary outcome of the study was defined as the comparisons of the IS rate observed during the entirety of follow up in the teenagers/young adult vs the adult populations. Rate of complications, freedom from sustained ventricular arrhythmic events, overall and cardiovascular mortality were also assessed in the two cohorts and assessed as secondary outcomes. Methods All S-ICD recipients in the ELISIR project were enrolled in the current study. Patients were classified into teenagers + young adults (≤ 30 years old) vs adults (> 30 years old), depending from patient age at device implantation (Figure 1). Rates of device-related complications and IS were compared between the cohorts. Results A total of 1349 patients were extracted from the ELISIR project. Teenagers and young adults represented 12.4% of the registry (n=56 teenagers; n=112 young adults). Patients were followed-up for a median of 23.1 [12.6–37.9] months. Overall, 117 (8.7%) patients experienced inappropriate S-ICD shocks and 100 (7.4%) device related complications were observed, with no age-related differences. IS resulted more frequent in the teenager and young adult cohort (14.3% vs 7.9%; p=0.006). Figure 2 reports Kaplan Meier curves for the occurrence of IS. At univariate analysis, young age was associated with IS, but after correcting for differences in arrhythmic substrate, this association resulted non-significant (aHR: 1.428 [0.883–2.331]; p=0.146). The use of SMART pass algorithm was instead associated to a strong reduction in IS (aHR 0.367 [0.245–0.548]; p<0.001). Conclusion The use of S-ICD in teenagers/young adults resulted safe and effective. Indeed, the rate of complications between teenagers/young adults and adults was not significantly different. Although a higher rate of IS was observed in the teenagers/young adults, when accounting for differences in baseline substrate and comorbidities, young age did not result associated with an increased risk of IS.

As opposed to ventricular arrhythmias (VA), clinical implications of atrial tachyarrhythmias (AT) in arrhythmogenic right ventricular cardiomyopathy (ARVC) remain scarcely explored. This study sought to evaluate the prevalence and prognostic significance of AT in ARVC. In total, 171 patients diagnosed with ARVC between 1985 and 2018 in a single tertiary center were retrospectively included. Were defined as follows: AT: sustained atrial fibrillation, atrial flutter and focal atrial tachycardia; major adverse cardiovascular events (MAE) as a composite criterion including heart failure, cardiac assistance, transplantation, and death. After a median follow-up of 6 years (IQR 3 to 11), prevalence of AT, MAE and VA were respectively of 16%, 8% and 60%. AT occurred later in the disease course: mean age 54 ± 14.4, while 50% of patients had VA at diagnosis. Age at diagnosis (hazard-ratio [HR]: 1.05, 95% CI [1.02–1.08]; P < 0.001), RVEF (HR: 0.96, 95% CI [0.92–0.99]; P = 0.03) and LVEF (HR: 0.96; 95% CI: 0.92–0.99; P = 0.04) predicted AT occurrence in univariable analysis. Intensive sport activity was significantly associated with AT in survival and multivariable Cox analysis. AT was predictive of MAE occurrence (HR: 2.6, 95% CI [1.1–6.3]; P = 0.03). AT are common in ARVC and AT is associated with intensive sport activity and MAE. Our results mandate careful monitoring of ARVC patients with new-onset AT.

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): INSERM Liliane Bettencourt doctoral grant Background Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is ass­­ociated with complex spatial and temporal right ventricular (RV) wall motion abnormalities. While cardiac magnetic resonance (CMR) is the gold-standard imaging technique, its diagnosic performance remains suboptimal and additional CMR biomarkers reflecting ARVC pathophysiology are needed. Purpose To evaluate the performance of a CMR feature-tracking (FT)-derived parameter combining both longitudinal and radial RV deformation and motion for the characterization of RV wall motion abnormalities in ARVC. Methods Thirty-nine patients with definite or borderline ARVC (median age 45 years, interquartile range 31–51, 56% males) were compared to 20 healthy controls with comparable age, sex and weight distributions. All subjects had 1.5T CMR including short axis and 4-chamber views steady-state free precession acquisitions. A custom FT software adapted to RV wall segmentation and tracking was used to assess RV wall deformation and motion in the 3 space directions resulting in: 1) global longitudinal strain (GLS) estimated on the 4 chamber view from the RV free wall, 2) basal circumferential strain (BCS) and radial motion fraction (BRMF) estimated as an average of short-axis slices comprised in the RV third basal portion. To capture the complex RV motion in ARCV, a longitudinal to radial strain loop (LRSL) was displayed and its area was calculated. Results The ARVC group comprised 28 (72%) patients with definite and 11 (28%) with borderline diagnosis . As compared to controls, LVEF and RVEF were significantly lower in ARVC patients (61(interquartile range (IQR) 52-71) vs. 71%(IQR 55-88) , p = 0.03 and 47%(IQR 16-63) vs. 57%(IQR 49-63) , p = 0.02, respectively), LVEF remaining within normal range limits. While there was no significant difference in RV GLS between ARVC patients and controls (median -17.7%(IQR -24–15) vs. -17.5%(IQR -20.1–15.2), p = 0.67) , BCS and BRMF were significantly lower in ARVC patients vs. controls [-7.5%(IQR -12.3–8.4.) vs. -9.8%(IQR -13.8–8.6.), p = 0.004 and -12.2(IQR -14.4–8.7.) vs. -14.9%(IQR -16.6–13.2) p = 0.0007, respectively] . The LRSL area was significantly and markedly lower in ARVC patients vs. controls [70.6 (IQR 16.3-63.1) vs. 144.1 (IQR 110.4-251.3), p = 0.0002] . LRSL area outperformed RVEF, BCS and BRS in separating ARVC from controls (area under receiving operator characteristics curve 0.82 vs. 0.78, 0.73 and 0.78, respectively). Conclusion In ARVC, a FT-derived parameter combining longitudinal and radial RV wall deformation and motion provided better discrimination of ARVC patients from controls than conventional FT measurements. Its implementation in clinical practice may bolster CMR performance to characterize ARVC wall motion abnormalities. Abstract Figure

Abstract Background In arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), implantable cardioverter-defibrillators (ICD) after an episode of sustained monomorphic ventricular tachycardia (MVT) are currently recommended in most situations. However, radiofrequency catheter ablation (RCA) is effective in reducing recurrent VT and whether MVT is a surrogate of sudden cardiac death is debated when other risk factors are lacking. Purpose To report the outcomes of patients with ARVC/D who underwent RCA of well-tolerated MVT without a back-up ICD. Methods Patients with a definite ARVC/D diagnosis according to the 2010 Task Force revised criteria who underwent RCA of well-tolerated MVT at 9 tertiary centers across 5 countries, without an ICD prior to RCA and in the 3 following months were retrospectively included. Patients presenting with syncope or electrical storm, and patients with left ventricular ejection fraction <50% were excluded. Similar patients implanted with an ICD prior or without RCA in the same period served as controls. Results Sixty-five patients [median age 46.1 years, range (19.5–73.8), 75% males] underwent RCA of MVT between 2003 and 2016. Familial history of ARVC/D was found in 11% of patients. Epsilon-waves were present in 19% and T-waves inversion beyond V2 in 43%. A right ventricular (RV) ejection fraction ≤40% or fractional area change ≤33% was found in 14 (25%) patients. Median left ventricular ejection fraction was 61% (50–70). Clinical presentation was palpitations in 81% of patients and near-syncope in 14%. Prior to RCA, patients were on beta-blockers alone in 18%, class I drugs in 37% and amiodarone in 9%, while 15% of patients were free any antiarrhythmic medication. Only 1 patient (2%) had >1 clinical VT morphology. Median VT rate was 180 (110–270). An epicardial approach was used in 31% patients. The clinical VT was inducible in 84% of patients. The median number of targeted RV site was 1 (1–3) (RV outflow tract in 72%). Full acute success defined inability to induce any VT was achieved in 72% of patients. During a median follow-up time of 49 month (1.4–162), there was no death or aborted cardiac arrest. Survival without VT recurrence was estimated at 82%, 71% and 60%, 12-, 36- and 60-months after RCA. No VT recurrence was observed among patient who had undergone an epicardial ablation. Among patients with VT recurrence, 6 (35%) did not receive an ICD, and 14 (70%) underwent redo RCA. An ICD was implanted in 10 patients, including 5 for VT recurrence. Fifty-eight patients constituted the control group, and 64% had appropriate ICD interventions during follow-up. Conclusions Despite a significant rate of VT recurrence, selected patients with ARVC/D who underwent RCA for stable MVT without an ICD did not experience any arrhythmic death. Further prospective studies are mandatory to precise the respective places of ICD and RCA in the management of ARVC/D patients with well-tolerated MVT. Acknowledgement/Funding None