Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation (CA) for atrial tachycardia (AT) and atrial flutter (AFL) offers favorable acute and long-term outcomes. Until recently, mapping of AT/AFL was only possible with sequential mapping methods using manually controlled catheters. Even by implementing multielectrode mapping, some limitations exist during mapping of short-lived arrhythmias and ATs with unstable CL. Remote magnetic navigation (RMN) with its atraumatic catheter design has superior safety profile and excellent accuracy. Recently, a novel high-resolution mapping system (AcQMap) can be used in combination with RMN (AcQMap-RMN). Purpose To assess the feasibility, safety and efficacy of AcQMap-RMN guided ablation in the management of complex ATs. Methods All patients undergoing CA for AT/AFL using AcQMap-RMN were included. The AcQMap system utilizes two different types of mapping: Single Position Map (SMP) and SuperMap, allowing mapping of both non-sustained and sustained ATs. Procedural efficiency was characterized by procedure time, total ablation time and radiation doses. Acute success was defined by arrhythmia source elimination. Efficacy data are based on 12-month follow up and number of redo procedures. Procedural safety was evaluated by intra- and post-procedural complications. Results A total number of 76 patients were referred for CA with AT/AFL (mean age 59.0±13.2), including 3 patients with inappropriate sinus tachycardia and 73 patients with AT/AFL. Out of 73 patients, 8 had perinodal AT. From the remaining 65 patients, 38 had de novo, 22 had post-PVI, and 5 patients had post-MAZE AT/AFL. Twenty-nine patients had short-lived ATs and were mapped exclusively by SPM. The mean procedure time was 175.9±61.4 min, mean ablation time 964.0 (IQR 422.0-1693.0) s, and mean radiation dose was 152.0(IQR 86.7-294.0) mGy. Acute success was documented in 70 procedures (92.1%). From de novo AT/AF patients 4 (10.5%), from post-PVI and post-MAZE AT/AFL patients 3 had recurrence at the end of the follow-up period (11.1%). Four patients had redo procedure. Three patients had post-procedural complications including 2 patients with groin hematoma and 1 patient with transient ischemic attack. Conclusion AcQMap-RMN integration offers improved efficiency, high success and low complication rates in complex AT ablation.

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Health of the Czech Republic Background Both left bundle branch pacing (LBBP) and deep septal myocardial pacing (LVSP) are less physiological than His bundle pacing. However, pacing both anode and cathode of the lead that is positioned in the interventricular septum may provide bilateral bundle branch capture, which may result in better interventricular synchrony. Objective To use UHF-ECG to compare ventricular activation between HBp and bilateral bundle branch capture during left bundle branch (LBBPbi) and deep septal myocardial pacing (LVSPbi). Methods Studies were performed in consecutive bradycardia patients. Bipolar pacing was performed with the lead in the LBBP (pseudo right bundle branch block morphology in V1 + proved LBB capture) and LVSP (pseudo right bundle branch block morphology in V1 without proved LBB capture) positions, with the pacing output leading to bilateral bundle branch capture. QRS duration was measured from the first to the last deflection of the QRS in any lead. UHF-ECG electrical dyssynchrony parameters – e-DYS (difference between the first and last ventricular activation) and local depolarization durations in precordial leads (V1-V8d) were calculated. Results In 94 consecutive patients, measurements were performed during HBp (n = 75) and LVSPbi (n = 37) and LBBPbi (n = 64). The average pacing threshold leading to bilateral bundle branch capture was 2.6 V at 0.5 ms. nsHBp led to the shortest QRSd compared to sLBBPbi and LVSPbi (98 vs. 103 vs. 110 ms; p < 0.01). LVSPbi showed smallest e-DYS -2 ms vs. -8 ms during LBBPbi and 11 ms during nsHBp; p < 0.05, but V5-8d were during LVSPbi longer than during nsHBp and LBBPbi (absolute difference 4-9 ms); p < 0.05. No statistical difference in V5-V8d were observed between LBBPbi and nsHBp. Conclusion Bilateral bundle branch capture during LVSP and nsLBBp preserves interventricular synchrony at the same level as HBp and thus leads to more physiological ventricular activation in patients with bradycardia.

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Medtronic Background The investigational Extravascular Implantable Cardioverter-Defibrillator (EV ICD) uses a substernal lead and delivers defibrillation and pacing therapies, including antitachycardia pacing (ATP). Objective To characterize EV ICD system performance through 3 years. Methods The prospective, first-in-human EV ICD Pilot study was conducted at 4 sites in Australia and New Zealand. ICD-indicated patients were enrolled July-December of 2018. Defibrillation testing was conducted for all patients at implant, and chronically per physician discretion. Electrical testing was conducted at pre-hospital discharge, 2 weeks, 4-6 weeks and 3 months post-implant, and every 6 months thereafter. Posture effects on pacing and sensing were evaluated through 3 months. Results Of 26 patients enrolled, 21 underwent the EV ICD implant procedure. There were no intraprocedural complications. After successful implantation and testing, 17 of 21 patients entered chronic follow-up. 14 patients continue follow up, representing 523 patient-months. Eight elective chronic defibrillation tests converted 7 of 7 patients with ≤ 40 J (maximum energy). Five episodes of spontaneous ventricular tachycardia (VT) were detected in 1 patient and either self-terminated or successfully defibrillated with appropriate shock. Over the total course of follow-up, 3 patients received an inappropriate shock due to; lead tip displacement with subsequent P-wave oversensing; Electromagnetic interference (EMI) in a ungrounded hot-tub; and EMI while doing plumbing work on unearthed electrical pipes, resulting in an annualized inappropriate shock rate of 6.9%. Pacing capture thresholds remained stable across time (5.1 ± 2.0 V at implant and 5.5 ± 2.7 V at 3 years); similarly, R-wave amplitudes were stable across time (3.4 ±2.0 mV at implant and 4.2 ± 2.7 mV at 3 years). Pacing thresholds tended to be lowest with the patient lying on the right side and pacing threshold often increased relative to supine position for left-side, prone or bending postures. R-wave amplitude tended to be greater when bending forward. There were 10 system or procedure-related adverse events in 8 patients through 3 years, including 3 elective system removals for: a single inappropriate shock (1), chronic defibrillation testing showing no safety margin in a patient with arrhythmogenic right ventricular dysplasia (1), intolerance to ATP (1 - high pacing threshold and frequent VT). Other than the lead tip displacement within the first 3 months, no additional clinically significant lead displacements have been observed through 3 years. Conclusion The EV ICD is a novel platform for delivering high-voltage therapy. There were no procedure and system related complications observed after the first year post-implant. Lead position and chronic system performance have generally remained stable through 3 years with a low rate of adverse events.

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Both coronary artery calcium (CAC) and epicardial adipose tissue (EAT) had been implicated in coronary artery disease (CAD) and risk of future adverse cardiovascular events. There are scarce data regarding the assessment and association of EAT volume and CAC score (CACS) in atrial fibrillation (AF) patients. Purpose To assess the association between EAT volume and the presence and severity of CAC in patients with AF. Methods Retrospective and single-centre study including consecutive patients with AF undergoing contrast-enhanced cardiac computed tomography for catheter ablation planning, from 2017 to 2019. Patients with known history of CAD and moderate to severe valvular heart disease were excluded. Baseline clinical and demographical data were collected, as well as their cardiovascular risk, based on the SCORE (Systematic Coronary Risk Evaluation) system and cardiovascular risk categories. We assessed CACS (Agatston method) and EAT volume and analysed their association. EAT was defined as the adipose tissue accumulated between the visceral pericardium and the myocardium and was semi-automatically reconstructed by manually tracing the pericardium. Patients were split into three groups according to CACS: 0, 1-99 and ≥100. A logistic regression (LR) analysis was performed to explore the relationship between EAT volume and the presence of CAC (CACS>0), adjusted for age, gender, obesity, diabetes mellitus and hypertension. Results A total of 354 patients were included, with a mean age of 56 ± 12 years, 66% male and 21% with persistent AF. A CHA2DS2-VASc score ≥2 was present in 130 (37%) patients and most patients had low to moderate cardiovascular risk (n=213, 82%). More than half of the patients had a CACS>0 (n=185, 52%), of which 63 patients (18%) had a CACS≥100. The mean EAT volume was 79 ± 39 ml. There was a significant association between EAT volume and the presence of CAC: CACS=0 69 ± 34 ml vs CACS 1-99 84 ± 38 ml vs CACS ≥100 95 ± 45 ml (p<0.001) (Fig. 1). After covariate adjustment (LR model R2 = 0.373, p <0.0001), the presence of CAC was not associated with EAT volume (OR 1.00, 95%CI 1.00 - 1.01, p=0.2) or obesity, and only with higher age, male gender, hypertension and diabetes mellitus (Fig. 2). Conclusion In our cohort of patients with AF undergoing catheter ablation we observed an association between EAT and CACS. Nevertheless, EAT volume was not an independent predictor of CACS and only the classical cardiovascular risk factors remained significant.

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Right ventricular apical pacing (RVAp) may be deleterious to ventricular function and hemodynamics due to pacing induced dyssynchrony. In the last decades, some studies showed that RVAp has been associated with heart failure, deterioration of left ventricular function and high mortality. Some patients (pts) may need, during the follow up (FUP), an upgrade to cardiac resynchronizaon therapy (CRT). New techniques have emerged such as RV lead implantation in the high septum or outflow RV tract (RVOT) and, more recently, His bundle/LB pacing. Purpose To compare the need for upgrade to CRT in patients with RVAp versus septal/RVOT pacing. Methods Retrospective single-center study of consecutive pts that implanted pacemakers in a tertiary center between January 1995 and December 2020. We collected data regarding pacing indication, RV pacing site (apex versus septum/RVOT) and need for an upgrade to CRT during follow up (FUP). Our primary endpoint was upgrade to CRT during the FU period. In the model, the impact of localization of the implanted lead on the survival free from upgrade was estimated assuming a neutral effect on mortality. Statistical analysis was performed using T-student test and logistic regression. Results We included 8761 pts, 60.2% (n=5275) were male, with a mean age of 76.5±10.7 years. The main indications for pacemaker implantation were (1) complete atrioventricular (AV) block (2239, 25.6%), (2) sick sinus syndrome (2211, 25.2%), (3) atrial fibrillation with AV block or bradycardia with significant pauses (17.4%) and (4) Mobitz II 2nd degree AV block (1467, 16.7%). RVAp was performed in 1746 (20%) patients and RVOT/septal pacing in 6933 patients (80%; RVOT in 657 (9,5%)). During FUP, 26 (1,5%) RVAp pts and 52 (0,8%) RVOT/septal pacing pts underwent upgrade to CRT, in a total of 78 pts (CRT-P in 54 patients and CRT-D in 24 patients). We observed that patients with RVAp had twice the risk of CRT upgrade during FUP (OR: 2,0 (IC 95% 1,25-3,21), p=0,004) when compared to patients with RVOT/septal pacing. Conclusions Patients with RVAp presented a 2-fold higher risk for upgrade to CRT when compared to patients with RVOT/septal pacing in our center. This retrospective analysis shows that lead implantation in the septum/RVOT should be preferred instead of the apex to reduce pacing induced dyssynchrony and need for CRT upgrade.

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Recently, a classification with four types of septal longitudinal strain patterns was described using a speckle tracking based strain analysis in echocardiography suggesting pathophysiological continuum of LBBB-induced LV remodeling. Little data exist on feature tracking cardiac magnetic resonance (FT-CMR) in LBBB patients, and whether such patterns could be reproduced in CMR is not established yet. Purpose In this study, we aimed to: 1) Assess and reproduce the new strain patterns classification by CMR and 2) Evaluate its association with LV remodeling and myocardial scar in a LBBB cohort. Methods Single center registry which included LBBB patients with septal flash (SF) referred to CMR to assess the structural cause of LV dysfunction. LBBB was defined according to Strauss criteria as strict LBBB, non-strict LBBB or nonspecific LV conduction delay. A semi-automated FT-CMR was used to quantify myocardial strain and detect the four septal longitudinal and radial strain patterns, according to the recent classification (LBBB-1 through LBBB-4) – Figure. Extent of SF was visually scored as mild, moderate, or prominent. Results A total of 115 patients were included (mean age 66±11 years; 57% men; 38% with ischemic heart disease). Median duration of QRS was 150± 26ms and majority of the patients (n=90, 78%) were classified as strict LBBB. In longitudinal strain analyses LBBB-1 was observed in 23 (20%), LBBB-2 in 37 (32.1%), LBBB-3 in 25 (21.7%), and LBBB-4 in 30 (26%) patients. Patients at higher LBBB stages (longitudinal or radial pattern) had more prominent septal flash, greater LV volumes, lower LV ejection fraction and lower absolute global longitudinal, circumferential and radial strain values compared with patients in less advanced stages (p < 0.05 for all) - table. There was no difference between patterns in clinical characteristics, ischemic etiology, QRS duration and time delay between septal and lateral LV wall. Late gadolinium enhancement (LGE) was found in 63 patients (54.8%), with a septal location in 34 (29.6%) patients, lateral in 4 (3.5%) patients, septal and lateral in 11 (9.6%) patients. Furthermore, no difference was found for LGE presence, distribution or location between the four strain patterns. Conclusions Among patients with LBBB, our study found a good association between longitudinal and radial strain patterns with the degree of LV remodeling and LV dysfunction by FT-CMR analysis. Additionally, myocardial fibrosis didn’t seem to interfere with the staged LBBB classification.

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch Heart Foundation Introduction Arrhythmogenic cardiomyopathy (ACM) is a heterogeneous progressive disease. Identification of patients at risk for malignant ventricular arrhythmias is challenging, making extensive cardiac follow-up necessary. CineECG provides insight in the average cardiac pathway of cardiac electrical activity. In previous studies, CineECG proved useful to detect disease progression. Objective Evaluate the applicability of CineECG to monitor disease progression in plakophilin-2 (PKP2) pathogenic mutation carriers. Methods To compute the CineECG, a 3D heart/torso model and 12 lead ECG is used. From 68 PKP2 pathogenic mutation carriers, all raw ECGs were extracted from the patient database. In pathogenic mutation carriers with definite ACM, the ECG ±2 years before (ECG1), at (ECG2) and ±2 years after (ECG3) diagnosis were selected. In pathogenic mutation carriers without definite ACM, the most recent ECG (ECG2) and the ECG ±2 years before (ECG1) were selected. CineECGs were computed for the QRS complex and the distance between CineECG location at end QRS was determined per subject for subsequent CineECGs. Results In 53 pathogenic mutation carriers ≥2 ECGs were available. 33 pathogenic mutation carriers were diagnosed with definite ACM of whom 4 had an ECG before, at and after diagnosis. Average distance between CineECG location at end QRS was 7.8±6.8 mm. In pathogenic mutation carriers with definite ACM, CineECG before and at diagnosis (figure, example 1&2) were different whereas CineECG at and after diagnosis did not always change. In pathogenic mutation carriers without definite ACM, in 14/19 changes in CineECG were observed (figure, example 3), whereas in the others (figure, example 4) not. Conclusion Our preliminary results show that CineECG provides additional insight in the changes of cardiac activation in ACM patients and may enable detection of disease progression. Further analysis will also include cardiac repolarization.

Abstract Funding Acknowledgements Type of funding sources: None. Background Transvenous Lead Extraction (TLE) scoring systems have proven to be a reliable method to predict TLE difficulty, thus improving procedure safety and efficacy. Nevertheless, TLE has shown a significant mortality rate during the subsequent follow-up, up to 33% at 10 years, with historical data showing several procedural and clinical characteristics associate with this poor outcome. Purpose We aimed to investigate the association between difficult TLE procedures and long-term mortality, using a specific scoring system [Lead Extraction Difficulty (LED)] to identify difficult/simple procedures. Methods Consecutive patients underwent TLE procedures between January 2014 and January 2016 at Spedali Civili Hospital, Brescia, Italy, were prospectively considered to receive a follow-up during 2021. TLE difficulty was retrospectively assessed in all patients using the LED index score (number of leads to extract + years from implant of the oldest lead to remove + 1 [for a dual-coil implantable cardioverter defibrillator lead] – 1 [in case of confirmed vegetations along the lead]). According to the score, "high-difficult" procedures were defined for a LED >10. Patient long-term follow-up was obtained by review of medical records from patient surveys or from the referring institution/family practitioner. Univariate analysis and multivariate logistic regression were used to identify factors associated with long-term mortality. Kaplan-Meier estimates were used to investigate survival during the follow-up. Two-sided P<.05 was considered significant. Results A total of 466 permanent leads were removed in 249 patients with a clinical success rate of 99.1%, and without major acute complications. The mean time follow-up was 6.7 (5.9-7.1) years, with a cumulative all-cause mortality rate of 17.7%. Clinical characteristics, indication for TLE, and mortality during follow-up are reported in the Table. Among all variable associated with mortality at univariate analysis, only LED index >10 independently predicted the mortality during the follow-up at logistic regression (OR 2.98; 95% CI: 0.081-1.4; p=0.028). Survival plots for individuals underwent high/low difficult TLE are shown in the Figure. Mortality at 1, 3, and 5 years following TLE was highest among patients with LED index >10 (1.1%, 12.6%, and 26.3%, respectively). Conclusions Cumulative long-term mortality following TLE was confirmed to be high. Of interest it resulted highest among patients following high-difficult TLE procedure. LED index score resulted a useful tool to predict long-term mortality after procedure. This finding should be considered when approaching TLE procedures in order to estimate the risk/benefit ratio over the time.

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific Background/Introduction Pulmonary vein isolation (PVI) using a cryoballoon is well-established for the treatment of paroxysmal atrial fibrillation (PAF). Initial experience with a novel cryoballoon (CB) with a stable low balloon pressure (POLARx, Boston Scientific) has demonstrated acute procedural safety and efficacy in de novo PVI procedures in patients with paroxysmal AF. However, to date, there is limited multicenter data on real world acute outcomes and procedural characteristics with this novel cryoballoon. Purpose The purpose of POLAR ICE was to provide real-world data on the acute and chronic outcomes of cryoballoon ablation with POLARx for the treatment of PAF. Here we report on the initial acute outcomes up to 3 months including procedural efficacy, safety, and biophysical parameters. Methods POLAR ICE, a prospective, non-randomized, multicenter (international) registry (NCT04250714), enrolled 400 patients across 19 centers, between Aug 2020 and May 2021. This study included any patients indicated for treatment of PAF with the POLARx cryoablation system. The study protocol did not mandate any specific cryodosing regimen, this was left to the operator. Procedural characteristics, such as time to isolation (TTI), cryoablations per pulmonary vein, balloon nadir temperature, and occlusion grade were recorded. PVI was confirmed with entrance block testing. Results Complete PVI was achieved in 96.1% of PVs (1437/1496). Procedure and fluoroscopy times were 69.0±25.2 min and 15.8±10.0 min, respectively. Left atrial dwell time was 47.3±18.8 min. The cryoablation characteristics by vein are shown in the Table 1. An average of 4.9±1.8 ablations were performed per patient (1.3±0.7 per vein). Grade 3 or 4 occlusion was achieved in 98.1% of PVs reported. Electrical isolation was achieved with an average TTI of 50±33.8s and in 81.4% of PVs isolation required only a single cryoablation. Nadir temperatures across all pulmonary veins averaged -56.3± 6.5C. Time to -40C was 32.9±11s and Time to Thaw (0C) was 19.5±6.7s across all veins. PVI was performed on atypical anatomies (12 LCPV, 7 RMPV, & 3 RCPV) in 19 pts. Serious adverse events included phrenic nerve palsy (0.5%), tamponade (0.5%), AV block (0.3%), stroke (0.3%), and transient ischemic attack (0.3%). Conclusions Real world usage data on the novel CB suggests that this device is safe and effective, with a PV isolation success rate of 96.2% and 81.4% of PVs isolated with a single cryoablation. These data are in keeping with reports on other cryoballon systems and have markedly shorter procedure times than have been previously reported on this cryoballon.

Abstract Funding Acknowledgements Type of funding sources: None. Background Preprocedural contrast-enhanced cardiovascular magnetic resonance (CMR) or computed tomography (CT) imaging of the left atrium (LA) and pulmonary veins (PVs) is usually employed to facilitate catheter mapping and ablation of atrial fibrillation (AF). Incidental findings (IFs) are common on cardiac imaging prior to AF catheter ablation (AFCA). However, previous studies were of small size and have mainly focused on radiological extracardiac IFs detected on preprocedural CT scan. Purpose To assess the prevalence of major cardiac and extracardiac IFs on routine preprocedural CMR in a large cohort of consecutive patients scheduled for first-time AFCA, and to report its impact on clinical decision-making and management. Methods All consecutive patients who underwent routine preprocedural CMR prior to first-time AFCA between April 2015 and March 2019 were considered for analysis. Main exclusion criteria were referral for repeat AFCA; prior cardiac CT or CMR imaging; and general contraindication to CMR or AFCA. All CMR examinations consisted of survey images with full thoracic coverage, cardiac cine and late-gadolinium enhancement imaging, and three-dimensional contrast-enhanced CMR angiography of the LA/PVs. An IF was defined as major when any newly detected finding either resulted in cancellation of the AFCA procedure or intentional deviation from the standard AFCA protocol. In patients with accessory or anomalous PVs the ablation strategy was individually tailored aiming at isolation of all PVs. Results Two thousand consecutive patients (62±10 years; 59% male) with paroxysmal (48%) or persistent (52%) AF were included. Among the entire study cohort 172 patients (8.6%) had a total of 184 cardiac (75%) and extracardiac (25%) major IFs (Fig. A+B). Preprocedural detection of a major IF resulted in cancellation of the scheduled AFCA procedure in 88 patients (4.4%). Forty-two patients (2.1%) have thereupon never been ablated, 46 patients (2.3%) underwent postponed AFCA after a median time from CMR imaging of 83 (32-213) days. The remaining 84 patients with major IF (4.2%) underwent an individualized approach to AFCA (Fig. A). The most common major IFs were accessory or anomalous PVs in 76 (3.8%), extracardiac abnormalities suspicious of malignancy in 29 (1.5%), and positive stress perfusion imaging in 19 (1.0% overall; 7.2% of 261 tested) patients. In 19 patients (1.0%) preprocedural CMR detected a previously unknown intracardiac thrombus or structural cardiac disease. Conclusion Unexpected major IFs on routine preprocedural CMR affected clinical decision-making and therapeutic management in 8.6% of patients scheduled for first-time AFCA at our institution. Whether preprocedural CMR imaging may improve safety and outcome of AFCA needs to be addressed in future research.