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BACKGROUND Left bundle branch area pacing (LBBAP) has shown to be a reliable alternative to His bundle pacing (HBP) for physiologic pacing. There are limited data on the intermediate term performance of LBBA pacing leads. Objective: To evaluate the intermediate term performance and safety of LBBAP. METHODS AND RESULTS Patients referred for pacemaker implantation at two academic centers between 02/2019 - 1/2021 were considered for LBBAP. LBBAP was performed by implanting the 3830 lumenless lead using the C315 fixed curve or C304 His deflectable sheath (Medtronic, MN). Implant success rates, complications and electrophysiological parameters were assessed. LBBAP was successful in 566/619 patients (91%). Mean age was 73±12 yrs, 46% were women. 37% had QRSd >130 ms, 25% RBBB, 11% LBBB, 4% IVCD. Pacing indications include sinus node dysfunction in 27%, AV block 56%, CRT 7% and refractory AF 10%. Mean procedural duration was 73±32 mins (median 70 mins) and fluoroscopic time was 10±7 mins (median 8 mins). Baseline QRSd was 119±31ms vs paced QRSd was 113±12ms (p CONCLUSION LBBA pacing is safe and feasible with high success rates and low complication rates during intermediate term follow-up.

BACKGROUND The STAR AF II (Substrate and Trigger Ablation for Reduction of Atrial Fibrillation 2) was a multicenter, randomized trial which randomized patients to pulmonary vein isolation (PVI) alone, PVI plus complex fractionated electrograms (CFE), or PVI plus linear ablation (roof line and mitral line). The study failed to show any additional benefit of additional substrate ablation (CFE or lines) in addition to PVI. However, complete block of linear ablations or total elimination of CFE was not achieved in all patients in the adjuvant ablation arms and this could explain why these additive ablation strategies did not improve outcome. We sought to determine whether completeness of adjuvant linear or CFE ablation affected the outcome of these additive ablation strategies when combined with PVI. METHODS AND RESULTS In STAR AF II, 549 patients were randomized 1:4:4 to PVI alone, PVI plus lines, and PVI plus CFE. In this substudy, outcomes of patients with complete linear block and without complete linear block in the PVI + lines group and outcomes for patients with all CFE regions successfully ablated and without all of them ablated in the PVI + CFE are analysed. Of the 243 patients in the PVI plus lines group who received both mitral and roof lines, bidirectional block across both lines was achieved in 179 (74%) but was not achieved in 65 (26%). At 18 months follow-up, AF recurrence occurred in 107 of 179 patients (59.8%) with complete block conduction block across lines and in 40 of 64 patients (62.5%) without complete block (p=0.89) (Figure 1). Even after 2 procedures, AF recurred in 51.9% of patients with complete linear block and 46% of patients without complete block (p=0.09). Of the 207 patients in the PVI plus CFE group who actually underwent CFE ablation, 188 (91%) had elimination of all CFE sites while all CFE were not eliminated in 19 (9%). At 18 months follow-up, AF recurrence occurred in 117 of 188 patients (62.2%) with all the CFE ablated and in 11 of 19 patients (57.9%) without all CFE ablated (p=0.47) (Figure 1). After 2 procedures, AF recurrence occurred in 56.7% of patients with all CFE ablated and 68.0% of patients without all CFE ablated (p=0.29). CONCLUSION PVI combined with both linear and CFE ablation did not result in less AF recurrence compared to PVI alone even after more than one procedure regardless of how well empiric linear or CFE ablation is performed.

Background The scar and the amount of border zone measured by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) has been proposed as an independent predictor of ventricular arrhythmias in patients with ischemic and non-ischemic cardiomyopathy. However, at the present time, the guidelines are based only on the ejection fraction to recommend an implantable cardioverter defibrillator (ICD) in primary prevention, and only a minority of these patients receive appropriate therapies. So, prevention needs to be improved. Purpose To identify predictors of appropriate therapies in patients with a primary prevention ICD using cardiac magnetic resonance imaging and a dedicated software (ADAS-3D) to characterize the scar. Methods Patients who underwent a LGE-MR prior to ICD implantation in primary prevention were retrospectively included. Clinical and cardiac imaging characteristics were collected. The myocardium was segmented with ADAS-3D software in 10 layers (from endocardium to epicardium). The scar, border zone, core and conducting channels were automatically measured in grams by the software. Results Since 2008 to 2017, 206 patients were included. Mean age was 67±28 years, 80% men, mean ejection fraction 26%±9, 52% with ischemic cardiomyopathy and 48% non-ischemic. The primary endpoint was appropriate therapies and/or sudden cardiac death (SCD). Median follow-up was 46.33 months. 46 patients (22%) reached the primary endpoint. Greater scar mass (36.05 grams vs 21.5 grams; HR 1.04; 95% CI (1.03–1-05), p5.3 grams was independently associated with the primary endpoint (HR: 4.77; 95% CI (1.15–19.73), p=0.03). Conclusions The amount of border zone, core and channel mass measured by LGE-MR and ADAS software are independent predictors of appropriate therapies and SCD in patients with ICD in primary prevention. Scar characterization Funding Acknowledgement Type of funding source: None

Background/Introduction Substrate-guided techniques have changed the approach and results of ventricular tachycardia (VT) ablation and electroanatomical voltage mapping (EAVM) constitutes a diagnostic and therapeutic cornerstone in this field. In current practice normal myocardium is typically characterized by bipolar voltage > 1.5 mV, dense scar Purpose The purpose of this study is to adjust voltage cut off in order to establish the threshold that more accurately define the pathological substrate in VT ablation. Additionally, predictors of usefulness of current thresholds are analyzed. Methods EAVM were created with CARTO3 System and Sensor-Force catheter (Navistar Smart-Touch and Pentaray). We delineated the conducting channels by analyzing the late potentials activation. Based on these channels we looked for the best cut-off values to detect these channels. We describe the baseline characteristics, the best cut-off values for border zone and scar core in our series and we analyzed the accuracy of the current established values to detect the arrhythmogenic VT substrate Results We investigated 51 patients (74,5% males; 41,2% ischemic cardiomyopathy, mean LVEF 38,6% +/-13,6) with sustained monomorphic VT submitted to ablation during 2016 and 2017. The range of the voltage adjustment was from 0,01-1 mV for core area and 0,2-6mV as maximum, with an average of 0,31-1,42mV. Using currently accepted bipolar voltage cut-off Conclusions EAVM is very important to detect scar and channels in VT ablation, but several elements can affect it and recently the traditional voltage values have been questioned. Our study suggests how the threshold as currently applied in daily practice could be acceptable to detect the core scar area, but it has to be reconsidered in NICM, especially regarding the border zone. An evident trend (p = 0,07) suggests a better accuracy of current values to define VT substrate in ischemic patients than in NICM. Abstract Figure. Channel Identification

Funding Acknowledgements No funding acknowledgements OnBehalf VT and sudden cardiac death Background The scar and the amount of border zone measured by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) has been proposed as an independent predictor of ventricular arrhythmias in patients with ischemic and non-ischemic cardiomyopathy. However, at the present time, the guidelines are based only on the ejection fraction to recommend an implantable cardioverter defibrillator (ICD) in primary prevention, and only a minority of these patients receive appropriate therapies. So, prevention needs to be improved. Purpose To identify predictors of appropriate therapies in patients with a primary prevention ICD using cardiac magnetic resonance imaging and a dedicated software (ADAS-3D) to characterize the scar. Methods All consecutive patients who underwent a LGE-MR prior to ICD implantation in primary prevention were prospectively included. Clinical and cardiac imaging characteristics were collected. The myocardium was segmented with ADAS-3D software in 10 layers (from endocardium to epicardium). The scar, border zone, core and conducting channels were automatically measured in grams by the software. Results Since 2008 to 2017, 206 patients were included. Mean age was 67 +/- 28 years, 80% men, mean ejection fraction 26%+/-9, 52% with ischemic cardiomyopathy and 48% non-ischemic. The primary endpoint was appropriate therapies and/or sudden cardiac death (SCD). Median follow-up was 46,33 months. 46 patients (22%) reached the primary endpoint. Greater scar mass (36,05 grams vs 21,5 grams; HR 1.04; 95% CI (1.03-1-05), p 5.3 grams was independently associated with the primary endpoint (HR: 4.77; 95% CI (1.15-19.73), p = 0.03). Conclusions The amount of border zone, core and channel mass measured by LGE-MR and ADAS software are independent predictors of appropriate therapies and SCD in patients with ICD in primary prevention. Abstract Figure. Scar characterization

BACKGROUND Pure left bundle branch (LBB) capture should result in typical RBBB (rsR') morphology. However, numerous paced QRS morphologies are observed during LBB area pacing (LBBAP). There are limited papers describing the various electrocardiographic (ECG) morphologies seen with LBBAP. Objective: To evaluate the various ECG characteristics encountered in LBBAP. METHODS AND RESULTS Patients referred for pacemaker implantation between 08/2019-01/2021 were considered for LBBAP. LBBAP was performed by implantation of a Medtronic 3830 lead 2 cms distal to His and confirmed by previously published criteria. Paced QRS morphology and QRS axis was analyzed. Baseline, ECG, and implantation characteristics are summarized in table 1. Of 264 LBBAP ECGs, the most common morphology seen during unipolar tip pacing was an incomplete RBBB pattern (qR) in V1 in 165 (69.9%) patients. rSR' pattern was seen in 9 (3.2%) and a narrow QS pattern in 60 (21.5%) patients. CONCLUSION Various ECG morphologies may be encountered during successful LBB area capture and are associated with similar QRSd, pacing characteristics and short-term lead performance. These morphologies are due to capture of various structures (RV or LV septum, capture of LBB, LPF +/- RBB) and are likely due to virtual-electrode effect.

BACKGROUND Left bundle branch area pacing (LBBAP) has emerged as a promising pacing modality for physiologic pacing. Atrioventricular heart block is a common complication after a valvular intervention but there are limited data on the performance of LBBAP in this population. The aim of this study is to evaluate the safety and feasibility of LBBAP in patients with valvular interventions. METHODS AND RESULTS Seventy-nine patients were included in this study. All patients underwent surgical or percutaneous valvular interventions. LBBAP was attempted in all patients. Implant success rates, peri- and post procedure ECG, pacing parameters, and complications were assessed at implant, and during follow-up. LBBAP implantation was successful in 75/79 (95 %) patients. Mean age was 70.9 ± 13.8 years and 65 % patients were male. Prior interventions included TAVR (25), SAVR (34), combined surgical AVR plus MVR (6), MVR (8), TVR (1), and PVR (1). Average LVEF was 52.6 ± 10.7 %. Total procedure duration was 74.3 ± 37.3 min and fluoroscopic duration was 9.8 ± 7.0 min. Pacing parameters were stable during follow up period of 8.1 ± 4.9 months. Pacing QRS duration was significantly narrower than baseline QRS duration (130.5 ± 30.6 ms vs. 113.9 ± 14.0 ms, p CONCLUSION LBBAP is feasible and safe pacing modality in patients with prior interventions for valvular heart disease.