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Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Grant of the Catalan Society of Cardiology, 2019; Research Grant Josep Font 2019, Hospital Clínic de Barcelona His-Purkinje conduction system pacing (HPCSP) has been proposed as an alternative to cardiac resynchronization therapy (CRT); however, no predictors of echocardiographic response have been described. Septal flash (SF) is a marker of intraventricular dyssynchrony. Methods The study aimed to analyze whether HPCSP corrects SF in patients with CRT indication, and if correction of SF predicts echocardiographic response. Prospective observational study (n=30). Left ventricular ejection fraction (LVEF) was measured with echocardiography at baseline and at 6-month follow-up. Echocardiographic response was defined as increase in 5 points LVEF. ECG Imaging was performed in 2 patients to validate ventricular activation shortening and to study the basal and HPCSP activation pattern. Results HPCSP shortened QRS duration by 48±21ms and SF was significantly decreased (baseline 3.6±2.2mm vs HPCSP 1.5±1.5mm p1.5mm had 81% sensitivity and 80% specificity to predict echocardiographic response (area under curve 0.86, p=0.019). Conclusion HPCSP improves intraventricular dyssynchrony and results in 64% echocardiographic responders at 6-month follow-up. Dyssynchrony improvement with SF correction may predict echocardiographic response at 6-month follow-up (Fig.2.).

Funding Acknowledgements Cardiac Pacing Scholarship from the Spanish Society of Cardiology (SEC) Background Electrocardiogram-based optimization of cardiac resynchronization therapy (CRT) using the fusion-optimized intervals (FOI) method has demonstrated to improve both acute hemodynamic response and left ventricle (LV) reverse remodeling compared to nominal programming of CRT. FOI optimizes the atrioventricular (AV) and ventriculo-ventricular (VV) intervals to achieve the shortest paced-QRS duration. The recent development of multipoint pacing (MPP) enables the activation of the LV from 2 locations, also shortening the QRS duration compared to conventional biventricular pacing. Purpose To determine if MPP reduces the paced-QRS duration compared to FOI optimization. Methods This prospective clinical study included 25 consecutive patients who successfully received a CRT with MPP pacing capability. All patients were in sinus rhythm and had an PR interval below 250 ms. The QRS duration was measured with a 12-lead digital electrocardiography (screen speed of 200 mm/s) at baseline and using 3 different configurations: MPP, FOI and a combined FOI-MPP strategy. In MPP, the intervals were (based on previous studies): 1) AV 130 ms, 2) Right ventricular (RV)-LV2 (Δ1) 5 ms, and 3) LV1-LV2 (Δ2) 5 ms. In FOI, AV and VV intervals were optimized to achieve fusion between intrinsic conduction and biventricular pacing. In FOI-MPP, the Δ2 was set at 5 ms, while AV and Δ1 intervals were optimized using the FOI method. The CRT device was programmed with the configuration that achieved a greater paced-QRS shortening. After 45 days, battery life was estimated. Results Mean age was 65 ± 10 years, 20 were men (80%) and baseline QRS duration was 177 ± 17 ms. The FOI method bested nominal MPP (QRS shortened by 58 ± 16 ms vs 43 ± 16 ms, respectively, p = 0.002). Adding MPP to the narrowest QRS by FOI did not result in further shortening (FOI: 58 ± 16 ms vs FOI-MPP: 59 ± 13 ms, p = 0.81). The final configuration was FOI method alone in most cases (n = 16, 64%) and FOI-MPP in all others (n = 9, 36%; figure). In total, 10 out of 25 patients (40%) were not candidates to MPP due to: 1) pacing thresholds exceeding 3.5 V/0.4 ms at the distal or proximal electrode (8, 32%), and 2) phrenic stimulation (2, 8%). Estimated battery longevity was longer in patients receiving FOI as compared to MPP (8.3 ± 2.1 years vs. 6.2 ± 2.2 years, p = 0.04). Conclusion In CRT, the FOI method is not improved by coupling with MPP. Up to 40% of patients are not candidates for MPP due to high thresholds or phrenic stimulation. The use of MPP in unselected patients would result in a decrease of battery longevity, without any additional benefit over FOI. Abstract Figure.

Funding Acknowledgements Grant from the Catalan Society of Cardiology Background His bundle pacing (HBP) directly stimulates the conduction system and could therefore correct asynchrony and evolve as a more physiological pacing approach. Septal flash (SF) is a fast contraction and relaxation of the septum occurring during the isovolumetric contraction period. It is a specific marker of cardiac dyssynchrony. Purpose Evaluate whether HBP corrects SF in patients with an indication for CRT or RV pacing. Methods A cohort of 20 consecutive patients undergoing HBP at our center was analyzed. HBP indications were: Group A (n = 3): left bundle branch block (LBBB) and left ventricular (LV) dysfunction (LV ejection fraction [LVEF] Patients in groups B and C had a RV backup lead implanted, in line with current recommendations. The presence of SF was analyzed in 2D-echocardiography at 15 days post-implant. SF excursion was quantified using M-mode in parasternal short and long axis views as the highest amplitude of the early inward motion. Baseline SF excursion was determined during intrinsic rhythm (group A) or RV pacing (groups B and C). For each patient, the pair of measurements (baseline, HBP) in the axis with the highest baseline SF was selected. Results Mean LVEFs were 21 ± 8%, 32 ± 6%, and 41 ± 18% for groups A, B and C, respectively. HBP shortened QRS duration by 42 ± 15 ms and 45 ± 23 ms in groups A (Baseline QRS - HBP QRS) and B + C (RV pacing QRS - HBP QRS), respectively. At baseline, all patients except 1 had SF (Fig. 1A). The mean SF excursion was 4.3 ± 1.9 mm, with SF excursion being larger in group A than in the RV-paced groups (6.3 ± 1.5 mm vs. 3.9 ± 1.8 mm for groups A and B + C, respectively, p = 0.04). HBP abolished SF in 3 patients (15%) and, on average, decreased SF excursion by 2.3 mm (95% CI 1.3-3.2), irrespective of pacing indication (Fig. 1B). The degree of SF excursion reduction after HBP significantly correlated with QRS shortening (r = 0.53, p = 0.024) (Fig 1C). Conclusions In conclusion, we show that HBP results in acute correction or decrease of SF, thereby improving LBBB- or RV-induced mechanical dyssynchrony. Abstract Figure. Septal Flash and His pacing