Mid- to long-term mechanical performance of left bundle branch area pacing: a comprehensive echocardiographic comparison of capture modalities.

AIMS: Left bundle branch area pacing (LBBAP) electrical performance is well documented. Nevertheless, the long-term mechanical implications, and differences between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP), remain unclear. This study assessed mechanical performance of LBBAP in a mid- to long-term post-implantation setting and compared capture types. METHODS AND RESULTS: In this prospective, single-centre study, 88 patients with preserved left ventricular ejection fraction and successful LBBAP underwent paired echocardiography during intrinsic and paced rhythm (median 18 months post-implant). Two-dimensional, speckle-tracking and myocardial work (MW) indices were analysed. Adjusted linear mixed-effects models for repeated measures compared LBBAP vs. intrinsic rhythm and LBBP vs. LVSP differences. Independent predictors of changes in MW indices were sought with multivariate regression. Left bundle branch area pacing showed lower left ventricular volumes than intrinsic rhythm and a decrease in global longitudinal strain (16.2% vs. 16.8%, P = 0.040). Global constructive work (2232.8 vs. 2028.8 mmHg%, P < 0.001) and global wasted work (266.2 vs. 219.1 mmHg%, P = 0.003) were higher during pacing, without differences in global work index (1607.8 vs. 1536.7 mmHg%, P = 0.171) or global work efficiency (GWE) (88.3% vs. 89.3%, P = 0.092). Between LBBP (n = 63) and LVSP (n = 25), no statistically significant differences were found in any parameter after covariate adjustment (all P > 0.28). In multivariate analysis, LVSP independently predicted modest GWE decrease. CONCLUSION: In patients with preserved LVEF, LBBAP maintains global mechanical performance comparable to intrinsic rhythm while increasing constructive and wasted work. Mechanical performance is largely similar between LBBP and LVSP, supporting the physiological value of LBBAP regardless of capture type.