Echocardiographic Outcomes of Left Bundle Branch Versus Deep Septal Pacing

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Left bundle branch area pacing (LBBAP) is a rising technique that aims to preserve physiologic activation of the left ventricle. However, left bundle branch capture (LBBC) is not always achieved despite good progression of the lead into the interventricular septum, leading to what has been called deep septal pacing (DSP). In the latter, the conduction system is not captured, whose consequences on systolic function are not well known. The goal of the present work is to evaluate the repercussion on transthoracic echocardiogram (TTE) of capturing or not the left bundle branch. Methods Unicentric prospective study where patients in whom LBBAP was performed were consecutively included if: Previous TTE was available with a left ventricular ejection fraction (LVEF) > 40% A follow-up TTE performed >30 days after the implant was available Ventricular pacing was >40% of the time at the device follow-up LBBC was accepted if any of the following were present: Sudden change of QRS morphology during ventricular threshold test Left bundle potential was registered with an interval to left ventricular activation time (LVAT) equal to stimulus-LVAT time. T-test was used to compare means between continuous variables and chi-squared to test differences between groups in the categorical ones. Two-tailed p value <0.05 was considered statistically significant. Results 20 patients were included, 12 (60%) males, with a mean age of 74.4±10.6 years. Half of the patients (n=10) fulfilled LBBC criteria whereas the rest received DSP. Image 1 summarizes baseline characteristics and differences observed in the control TTE. After a median follow-up of 322 (interquartile range 114-325) days, LVEF increased in LBBC group whereas it decreased in DSP patients. Image 2 shows a slopegraph of the evolution of LVEF by type of stimulation. Indexed LVEDV increased in DSP group, but it was diminished in LBBC patients (p=0.03). Control TTE showed no significant differences in other parameters. Conclusions In non-selected patients with comparable pre-implant baseline characteristics, deep septal pacing was associated with a decrease in LVEF and an increase in LVEDV, while LBB capture showed better outcomes in these two parameters.