Fluoroscopic target zone for left bundle branch area pacing (LBBAP) optimized for cardiac conduction system proximity: a computed tomography study
M Lis, J Garbacz, A Priadka, T Puto, R Banys, M Krupinski, N Duong, H Roukoz, D Benditt, P Iaizzo, J ReyesAbstract
Background
Optimizing Left bundle branch area pacing (LBBAP) outcomes depends on proximity of the pacing electrode to the cardiac conduction system, particularly the origin of the left bundle. However, current fluoroscopic LBBAP targeting recommendations use fixed distances from the His position and does not account for potential patient-specific septal anatomy variation.
Purpose
To develop a computed tomography–derived fluoroscopic targeting strategy for left bundle branch area pacing that maximizes conduction system proximity while avoiding damage to the tricuspid septal leaflet and aortic sinuses.
Methods
Coronary computed tomography angiography from 27 patients with structurally normal hearts (mean ejection fraction 70±10%) was used to build three-dimensional models (Fig. 1). We identified the left bundle origin, His bundle, right ventricular (RV) apex, and tricuspid annulus and simulated pacing leads co-axially along the left bundle system, entering the septum 20 mm apical to the annulus. In the right anterior oblique (RAO) 30° projection, the His–to–RV apex horizontal line defined a reference segment (0% His, 100% apex). Vertical position was measured perpendicular to it, with the His level as 0, and values above or below reported as ±, but presented as % of the length of the reference segment. For each target, we measured endocardial surface distance from the lead tip to the left bundle origin.
Results
At 20 mm from tricuspid annulus, all targets in RAO 30 clustered at approximately one third of the horizontal His–to–RV apex distance. Vertical position, separated the targets: the septal target lay close to the His level (-1.6±10.8%); superior above (+15.8±6.8%) inferior below (−32.4±18.7%). The septal fascicle target provided the best balance of feasibility and precision, with close proximity to the left bundle origin (19±5 mm), while the anterior trajectory was slightly closer but more cranial (14.0±3.0 mm) and was not feasible in 15.9% of models because it intersected the aortic sinus; the posterior trajectory was more distant (32.7±8.7 mm).
Conclusion
The septal fascicle region was identified as the most practical left bundle branch area pacing target when aiming for cardiac conduction system proximity. In RAO 30, this region is accessible at roughly one third of the His–to–RV apex distance and near the His level on the normalized vertical axis, providing an anatomy-informed reference for LBBAP–proximal lead deployment.Figure 1