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His bundle pacing was developed while seeking a physiological alternative to biventricular cardiac resynchronization therapy. However, His bundle pacing may not be adequate in all patients. In this scenario, left bundle branch pacing has arisen as a new cardiac resynchronization therapy modality to correct left bundle branch block and restore ventricular synchrony. ( Level of Difficulty: Intermediate. )

Background Multipoint pacing (MPP) in cardiac resynchronization therapy (CRT) activates the left ventricle from two locations, thereby shortening the QRS duration and enabling better resynchronization; however, compared with conventional CRT, MPP reduces battery longevity. On the other hand, electrocardiogram‐based optimization using the fusion‐optimized intervals (FOI) method achieves more significant reverse remodeling than nominal CRT programming. Our study aimed to determine whether MPP could attain better resynchronization than single‐point pacing (SPP) optimized by FOI. Methods This prospective study included 32 consecutive patients who successfully received CRT devices with MPP capabilities. After implantation, the QRS duration was measured during intrinsic rhythm and with three pacing configurations: MPP, SPP‐FOI, and MPP‐FOI. In 14 patients, biventricular activation times (by electrocardiographic imaging, ECGI) were obtained during intrinsic rhythm and for each pacing configuration to validate the findings. Device battery longevity was estimated at the 45‐day follow‐up. Results The SPP‐FOI method achieved greater QRS shortening than MPP (‐56 ± 16 vs. ‐42 ± 17 ms, p < .001). Adding MPP to the best FOI programming did not result in further shortening (MPP‐FOI: ‐58 ± 14 ms, p = .69). Although biventricular activation times did not differ significantly among the three pacing configurations, only the two FOI configurations achieved significant shortening compared with intrinsic rhythm. The estimated battery longevity was longer with SPP than with MPP (8.1 ± 2.3 vs. 6.3 ± 2.0 years, p = .03). Conclusions SPP optimized by FOI resulted in better resynchronization and longer battery duration than MPP.

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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 p&lt;0.0001) (Fig.1). At 6-months, mean LVEF improvement was 8.6% ± 8.7% and 64% of patients were responders. There was a significant correlation between SF correction and increased LVEF (r=0.61, p=0.004). A correction of &gt;1.5mm 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.).