Left bundle branch area pacing: predictors of success
Authors: Estevez Paniagua A , Briongos Figuero S , Sanchez Hernandez A , Munoz Aguilera R 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Frequent conventional pacing of the right ventricle can be deleterious. In the last three years, left bundle branch area pacing (LBBAP) has experienced a great development as a tool for the specific conduction system stimulation.

Methods
Single-center prospective study of consecutive patients with attempted LBBAP for bradycardia or heart failure indications (bailed-out strategy). A 3830-69 lead was implanted using a C-315-His sheath, and we aimed for left bundle branch pacing (LBBP) in all patients. Current criteria to define LBAPP, LBBP (selective or non-selective), and left ventricle septal pacing (LVSP) were used. The goal of our study was to analyze clinical, electrical, and echocardiographic variables that may predict the achievement of LBBP.

Results
We included 149 patients between Feb/20 and Jan/22. Baseline characteristics and pacing indications are shown in table 1. We had success in 145 patients (97.3%): 78.9% were considered LBBP (44.4% SLBBP), and 21.1% LVSP. Paced QRS was significantly higher in patients with wide basal QRS (120.9 ± 15.2 ms vs 110.7 ± 12.6 ms, p&lt;0.001). Likewise, left ventricular activation time (LVAT) in V5/V6 and aVL was shorter in the group with narrow basal QRS (77.2 ± 10.5 vs 83.3 ± 11.4, p&lt;0.001, and 80.0 ± 14.1 vs 87.6 ± 14.4, p &lt;0.001, respectively), being much more frequent to achieve an LVAT &lt;80 ms in the group with narrow QRS (64.9% vs 42.2%, OR 2.6, p = 0.004). Logically, the variation of the paced QRS compared to baseline was also different in both groups (-25.4 ± 12.5 ms in the wide QRS group and + 16.2 ± 13.8 ms in the narrow QRS group). LBBP was achieved to a greater extent in the narrow QRS group (89.2% vs 67.6%, OR 3.9, p=0.002); the difference between selective and non-selective LBBP based on baseline QRS was not significant. Regarding the clinical variables, the presence of hypertension, diabetes mellitus, heart failure or COPD did not show a significant difference in the achievement of LBBP. In contrast, it was significantly less frequent to achieve LBBP in patients with LV systolic dysfunction of any degree (62.0% vs 83.2%, p=0.02), or chronic ischemic heart disease (61.1% vs 82.1%, p=0.04), with a trend in patients with CKD (67.7% vs 82.6%, p=0.06). Also, the bradycardia pacing indication had a significant influence, with the percentage of LBBP being lower in patients with atrioventricular conduction system disease compared to sick sinus syndrome (72.0% vs 85.1%, p=0.04). On the other hand, there was no significant association between the achievement of LBBP and echocardiographic parameters such as interventricular septum thickness, and left atrial volumen.

Conclusions
LBBAP as elective ventricular pacing is feasible, with a high success rate, and in most cases, it is possible to capture the conduction system. However, there appear to be factors that a priori may pose a greater challenge in its achievement, highlighting the electrical conduction system and myocardial disease.