High Defibrillation Threshold: Brace For Impact Karam Ayoub, MD 1; Travis Richardson , MD11. Division of Cardiac Electrophysiology, Vanderbilt University Medical Center, Nashville, TN, USA.Disclosures : Dr. Richardson has received research funding from Medtronic Inc. and served as a consultant for Philips Inc. and Biosense-Webster Inc.Conflict of interest : noneFunding : noneKey words : Defibrillator , Mortality, Defibrillation Threshold, Sudden Cardiac DeathTotal word count: 1168

Background: Thromboembolism-associated stroke is the most feared complication of Atrial fibrillation (AF). Percutaneous left atrial appendage closure (pLAAC) is indicated for stroke prevention in patients with AF who can’t tolerate long-term anticoagulation. We aim to study gender differences in peri-procedural and readmissions outcomes in pLAAC patients. Methods: Using the national readmission database from January 2016 to December 2018, AF patients undergoing the pLAAC procedure were identified. We used multivariate logistic regression analyses and time-to-event Cox regression analyses to conduct the study. Propensity matching with the Greedy method was done for the accuracy of results. Result: 28,819 patients were included in our study. Among them 11,946 (41.5%) were women and 16,873 (58.6%) were men. The mean age of overall population was 76.1 ± 8.5 years, with women ~ 1 year older than men. The overall rate of complications was higher in women (8.6% vs 6.6%, P<0.001), primarily driven by bleeding-related complications i.e., Major bleed (OR: 1.32 95% CI: 1.03-1.69, p=0.029), blood transfusion (OR: 1.45, 95% CI: 1.06-1.97, p=0.019) and cardiac tamponade (OR: 1.80, 95% CI: 1.13-2.89, p=0.014). Women had two times higher peri-procedural ischemic stroke. There was no difference in peri-procedural mortality. Women remained at 20% and 13% higher risk for readmission at 30 days and 6 months of discharge. Conclusion: Women had higher peri-procedural complications and were at higher risk of readmissions at 30 days and six months. However, there was no difference in mortality during the index hospitalization. Further studies are necessary to determine causality.

Aims: The MicraTM transcatheter pacing system (TPS) (Medtronic) is the only leadless pacemaker that promotes atrioventricular (AV) synchrony via accelerometer-based atrial sensing. Data regarding the real-world experience with this novel system are currently lacking. We sought to characterize patients undergoing MicraTM -AV implants, describe percentage AV synchrony achieved, and analyze the causes for suboptimal AV synchrony. Methods: In this retrospective cohort study, electronic medical records from 56 consecutive patients undergoing MicraTM -AV implants at the Mayo Clinic sites in Minnesota, Florida, and Arizona with a minimum follow-up of 3 months were reviewed. Demographic data, comorbidities, echocardiographic data, and clinical outcomes were compared among patients with and without atrial synchronous-ventricular pacing (AsVP) ≥70%. Results: Fifty-six percent of patients achieved AsVP ≥70%. Patients with adequate AsVP had smaller body mass indices, a lower proportion of congestive heart failure and pulmonary hypertension. Echocardiographic parameters and procedural characteristics were similar across the two groups. Active device troubleshooting was associated with higher AsVP. The likely reasons for low AsVP were persistent atrial arrhythmias, small A4-wave amplitude, and inadequate device reprogramming. Importantly, in patients with low AsVP, subjective clinical worsening was not noted during follow-up. Conclusion: With the increasing popularity of leadless PM, it is paramount for device implanting teams to be familiar with common predictors of AV synchrony and troubleshooting with MicraTM -AV devices.

Introduction: Bradyarrhythmias are an established red flag for storage cardiac conditions including Anderson-Fabry disease (AFD). The prevalence of bradyarrhythmias requiring a pacemaker (PM) and their timing in AFD is unresolved. We evaluated prevalence and predictors of PM requirement in a large AFD cohort, investigating the occurrence of bradyarrhythmias as initial versus late manifestation. Methods: we retrospectively evaluated 82 consecutive AFD patients referred to our multidisciplinary referral centre from 1994 to 2020 with a median follow up of 6.9 years, identifying those requiring pacing. Univariable analysis was performed to identify cardiac features associated with PM implantantion. Results: Five of 82 (6%) AFD patients required PM implantation (5/39, i.e. 13% of those with cardiac involvement), always in the context of advanced cardiomyopathy. In none, bradyarrhythmias were the presenting feature. Indications included sick sinus syndrome in 3 patients, advanced atrio-ventricular block in 2 patients. QRS prolongation during follow up strongly correlated with the onset of bradyarrhythmias. Conclusions: Severe bradyarrhythmias are relatively frequent in patients with AFD cardiomyopathy, but do not represent a mode of presentation, occurring late in the disease course and always in the context of advanced cardiac involvement. Monitoring QRS variations over time may help to identify patients requiring pacing.

Objective: To explore the safety and feasibility of left bundle branch area pacing (LBBAP) in children. Methods: This study observed 12 children attempted LBBAP from 2019 to 2021 in our department prospectively. Clinical data, pacing parameters, electrocardiograms, echocardiographic measurements and complications were recorded at implant and during follow-up. Results: The 12 patients aged between 3 and 14ys and weighted from 13 to 48kg. 11 patients were diagnosed with third-degree AVB and 1 patient (case 4) suffered from cardiac dysfunction due to right ventricular apical pacing (RVAP). LBBAP was successfully achieved in all patients with narrow QRS complexes. LVEF of case 4 recovered on the 3rd day after LBBAP. The median of LVEDD Z score of the 12 patients decreased from 1.75 to1.05 3 months after implantation (p<0.05). The median of paced QRS duration was 103ms. The median of pacing threshold, R-wave amplitude and impedance were 0.85V, 15mV and 717Ω respectively and remained stable during follow-up. No complications such as loss of capture, lead dislodgement or septal perforation occurred. Conclusions: LBBAP can be performed safely in children with narrow QRS duration and stable pacing parameters. Cardiac dysfunction caused by long-term RVAP can be corrected by LBBAP quickly.

The classification of AVNRT is based on HA and VA interval. Typical AVNRT is diagnosed in presence of HA ≤70 ms OR VA interval ≤60 ms and HA>70ms or VA >60ms is required to diagnose atypical AVNRT. This might be fallacious in some clinical situations. The septal VA and the “shortest” VA may be also different depending on clinical scenario .

Cutting through the Fat: Relationship Between Comorbidities and Arrhythmias in Hypertrophic Cardiomyopathy Alan Sugrue MBBCh, MSc; David Lin MD, FHRSCardiovascular Division, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PAManuscript word count: 1223Conflicts of interest: noneFunding: noneAddress for Correspondence:David Lin, MDHospital of the University of Pennsylvania3400 Spruce Street9 Founders PavilionPhiladelphia, PA 19104Email: [email protected]

Ventricular outflow is a common site for idiopathic PVCs and repetitive ventricular arrhythmias. Sites of origin of these arrhythmias may vary from the sites of earliest activation mapped. Better definition of the site of origin can help avoid unnecessary large volume ablation to suppress these arrhythmia.

Epicardial surgical clip is showed to be a safe and effective tool in order to achieve a complete left atrial appendage (LAA) exclusion thus reducing the risk of stroke in patients with atrial fibrillation. Historically, other methods as surgical ligation, internal oversewing or external stapling showed to be largely uneffective with an incidence of LAA residual flow ranging from 25% to 35% thus, increasing per se 5- to 10-fold the risk of stroke. Epicardial LAA exclusion by means of external clip could be potentially released under transesophageal echocardiographic guidance thus increasing the procedural success rate of complete closure with no residual stump left.

Background Magnetic Resonance imaging (MRI) in patients (pts) with MRI-conditional cardiovascular implantable electronic devices (CIED) remain a logistical issue for device programming during the scan. In current practice, a trained person needs to be present on-site to program CIED for MRI scan. This can cause delay in patient care, rescheduling of tests and increase healthcare costs. A novel remote programming (RP) strategy can be utilized to reprogram the CIED remotely. We sought to explore the feasibility and safety of RP of CIED’s in pts undergoing MRI scan. Methods We implemented the Medtronic CIED RP software at our institution after ensuring HIPAA compliance. The MRI technician started the session by contacting an off-site remote operator and placing a programmer wand from 2090 Medtronic programmer over CIED. The remote operator logged into a remote access software and provided a unique access code to the MRI technician. After entering the access code into the programmer, the remote operator was able to program the device as needed. We conducted a periodic audit of the first 209 pts who underwent RP of CIED’s for MRI. Outcomes analyzed were safety parameters during RP. Results Of the 209 MRI scans, 51 scans were performed urgently. There were no connectivity and programming problems or need for MRI rescheduling. In-person reprogramming was not required for any pt. All scans were completed safely in a timely manner, and there were no reports of CIED malfunction. Conclusions Remote programming of CIED’s for MRI scans is a safe and effective strategy.

Background: As pediatric implantable cardioverter defibrillator (ICD) utilization increases, hospital admission rates will increase. Data regarding hospitalizations among pediatric patients with ICDs is lacking. In addition, hospital mortality rates are unknown. This study aimed to evaluate 1) trends in hospitalization rates of admissions over 20 years, 2) hospital mortality, and 3) factors associated with hospital mortality among pediatric admissions with ICDs. Methods: The Kids’ Inpatient Database (2000-2016) was used to identify all hospitalizations with an existing ICD 20 years of age. ICD9/10 codes were used to stratify admissions by underlying diagnostic category as: 1) congenital heart disease (CHD), 2) primary arrhythmia, 3) primary cardiomyopathy, or 4) other. Trends were analyzed using linear regression. Hospital and patient characteristics among hospital deaths were compared to those surviving to discharge using mixed multivariable logistic regression, accounting for hospital clustering. Results: Of 42,570,716 hospitalizations, 4165 were admitted <21 years with an ICD. ICD admissions increased four-fold (p = 0.002) between 2000-2016. Hospital death occurred in 54 (1.3%). In multivariable analysis, cardiomyopathy (OR 3.5, 95%CI 1.1–11.2, p=0.04) and CHD (OR 4.8, 95%CI 1.5–15.6, p=0.01) were significantly associated with mortality. In further exploratory multivariable analysis incorporating a coexisting diagnosis of heart failure, only the presence of heart failure remained associated with mortality (OR 8.6, 95%CI 3.7-20.0, p<0.0001). Conclusions: Pediatric ICD hospitalization are increasing over time and hospital mortality is low (1.3%). Hospital mortality is associated with cardiomyopathy or CHD; however, the underlying driver for in-hospital death may be heart failure.

A left bundle branch block morphology tachycardia with fragmented potentials at the His bundle area Masahiro Toba, MDa, Toshihiro Nasu, CEb, Nobuyoshi Nekomiya, CEb, Ryo Itasaka, CEb, Takao Makino, MDa, Hisashi Yokoshiki, MD, PhDaaDepartment of Cardiovascular Medicine, Sapporo City General Hospital, Sapporo, JapanbDivision of Medical Engineering Center, Sapporo City General Hospital, Sapporo, JapanAddress for correspondence :Hisashi Yokoshiki MD, PhDE-mail:[email protected] of Cardiovascular Medicine Sapporo City General Hospital, Kita-11, Nishi-13, Chuo-ku, Sapporo 060-8604, Japan.Phone: 81-11-726-2211Fax: 81-11-726-7912Key words : longitudinal dissociated his bundle, left bundle branch block morphology tachycardia, fragmented potentials, radiofrequency ablation

Background: Cryoballoon (CB) based pulmonary vein isolation (PVI) has proven to be as effective as radiofrequency (RF) based ablation. Different ablation protocols took the individual time-to-isolation (TTI) into account aiming at shorter but equally or even more effective freeze-cycles. The current study sought to assess the impact of the TTI on PVI durability in patients undergoing a repeat procedure for recurrence of atrial tachyarrhythmia (ATA). Methods and Results: In 205 patients with ATA recurrence after previous CB-based PVI a total of 806 PVs were identified. One hundred-twenty-six out of 806 PVs (16%) were previously treated with a TTI guided ablation (protocol #1; TTI+120 sec.), in 92/806 (11%) PVs TTI was only monitored (m) but fixed freeze-cycles were applied (protocol #2; mTTI) and in 588/806 (73%) a fixed freeze-cycle was applied without TTI-monitoring. There was no difference in the PV-reconduction rate between the groups (P=0.23). The right inferior pulmonary vein (RIPV) showed overall significantly higher reconduction rates compared to the other PVs (RIPV – left inferior PV (LIPV) p<0.003, -left superior PV (LSPV) p<0.001, - right superior PV RSPV p<0.013). In 21 patients (10%) only for the RIPV reconduction was assessed. Conclusions: TTI based CB ablation did not show significant differences regarding PV-reconduction rates compared to the other protocols.

Toward Better Risk Stratification of Asymptomatic Brugada Syndrome Patients? Najla Beydoun MD1 , Charbel Gharios MD2 , Marwan M. Refaat MD3 1 Department of Anesthesiology and Perioperative Medicine, Tufts Medical Center, Boston, MA2 Cardiovascular Imaging Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA3 Department of Internal Medicine, Division of Cardiology, and Department of Biochemistry and Molecular Genetics, American University of Beirut Faculty of Medicine and Medical Center, Beirut, LebanonShort Title: Risk Stratification in Asymptomatic BrSWord Counts: 602

Is Multipoint Pacing Superior to Optimized Single-Point Pacing?Rodolfo San Antonio1, MD; Jose María Tolosana2, MD, PhD; Lluís Mont2, MD, PhD.1Heart Institute, Teknon Medical Center, Barcelona, Spain; University of Barcelona, Spain2Institut Clínic Cardio-Vascular, Hospital Clínic, University of Barcelona, Spain; Institut d’Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Barcelona, Spain; Centro de Investigación Biomédica en Red Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain.Word count: 434

Background: Simultaneous atrial fibrillation (AF) catheter ablation and left atrial appendage closure (LAAC) is sometimes recommended for both rhythm control and stroke prevention. However, the advantages of intracardiac echocardiography (ICE) guidance for this combined procedure have been scarcely reported. To evaluate the clinical outcomes and safety of ICE guided LAAC within a zero-fluoroscopy catheter ablation procedure. Methods and Results:From April 2019 to April 2020, 56 patients with symptomatic AF underwent concomitant catheter ablation and LAAC. ICE with a multi-angled imaging protocol mimicking the TEE echo windows was used to guide LAAC. Successful radiofrequency catheter ablation and LAAC was achieved in all patients. Procedure-related adverse event rate was 3.6%. During the 12-month follow-up, 77.8% of patients became free of arrhythmia recurrences and oral anticoagulants were discontinued in 96.4% of patients. No ischemic stroke occurred despite two cases of device-related thrombosis versus an expected stroke rate of 4.8% based on the CHA2DS2-VASc score. The overall major bleeding events rate was 1.8%, which represented a relative reduction of 68% versus an expected bleeding rate of 5.7% based on the HAS-BLED score of the patient cohort. The incidence of iatrogenic atrial septal defect secondary to a single transseptal access dropped from 57.9% at 2 months to 4.2% at 12 months TEE follow-up. Conclusion:The combination of catheter ablation and LAAC under ICE guidance was safe and effective in AF patients with high stroke risk. ICE with our novel protocol was technically feasible for comprehensive and systematic assessment of device implantation.

Background: Local impedance (LI) can indirectly measure catheter contact and tissue temperature during radiofrequency catheter ablation (RFCA). However, data on the effects of catheter contact angle on LI parameters are scarce. This study aimed to evaluate the influence of catheter contact angle on LI changes and lesion size with 2 different LI-sensing catheters in a porcine experimental study. Methods: Lesions were created by the INTELLANAV MiFi™ OI (MiFi) and the INTELLANAV STABLEPOINT™ (STABLEPOINT). RFCA was performed with 30 watts and a duration of 30 seconds. The CF (0, 5, 10, 20, and 30 g) and catheter contact angle (30°, 45°, and 90°) were changed in each set (n=8 each). The LI rise, LI drop, and lesion size were evaluated. Results: The LI rise increased as CF increased. There was no angular dependence with the LI rise under all CFs in the MiFi. On the other hand, the LI rise at 90° was lower than at 30° under 5 and 10 g of CF in STABLEPOINT. The LI drop increased as CF increased. Regarding the difference in catheter contact angles, the LI drop at 90° was lower than that at 30° for both catheters. The maximum lesion widths and surface widths were smaller at 90° than at 30°, whereas there were no differences in lesion depths. Conclusion: The LI drop and lesion widths at 90° were significantly smaller than those at 30°, although the lesion depths were not different among the 3 angles for the MiFi and STABLEPOINT.

Background: There exists variability in the administration of inpatient sotalol therapy for symptomatic atrial fibrillation(AF). The impact of this variability on patient in-hospital and 30-day post-hospitalization costs and outcomes is not known. Also, the cost impact of intravenous sotalol, which can accelerate drug loading to therapeutic levels, is unknown. Methods: 133 AF patients admitted for sotalol initiation at an Intermountain Healthcare Hospital from January 2017-December 2018 were included. Patient and dosing characteristics were described descriptively, and the impact of dosing schedule was correlated with daily hospital costs/clinical outcomes during the index hospitalization and for 30 days. The CMS reimbursement for 3-day sotalol initiation is $9,263.51. Projections of cost savings were made considering a 1-day load using intravenous sotalol that costs $2,500.00 to administer. Results: The average age was 70.3±12.3 years, 60.2% were male with comorbidities of: hypertension(83%), diabetes(36%), and coronary artery disease(53%). Mean ejection fraction was 59.9±7.8% and median QTc was 453.7±37.6 ms before sotalol. No ventricular arrhythmias developed, but bradycardia(<60 bpm) was observed in 37.6% of patients. The average length of stay was 3.9±4.6(median: 2.2) days. Post-discharge outcomes and rehospitalization rates stratified by length of stay were similar. The cost per day was estimated at $2,931.55 (1:$2,931.55, 2:$5,863.10, 3:$8,794.65, 4:$11,726.20). Conclusions: Inpatient sotalol dosing is markedly variable and results in the potential of both cost gain and loss to a hospital. In consideration of estimated costs, there is the potential for $871.55 cost savings compared to a 2-day oral load and $3,803.10 compared to a 3-day oral load.