An Anatomical CT-Based Framework for Optimizing Left Bundle Branch Area Pacing of the Human Cardiac Conduction System

Left bundle branch area pacing (LBBAP) outcomes depend on implanted lead's proximity to the origin of the left bundle, yet current fluoroscopic guidance commonly uses fixed His-to-lead distances and thus ignores anatomical variances.

To derive a computed tomography (CT)-based framework for optimizing fluoroscopic LBBAP targeting that will best identify conduction system proximity while avoiding the tricuspid septal leaflet and aortic sinuses.

Coronary CT scans from 27 patients were used to build 3D models. We identified the left bundle origin, His bundle, right ventricular (RV) apex, and tricuspid annulus and simulated leads entering co-axially along the left bundle system: 15 and 20 mm from the tricuspid annulus. In RAO 30, the His-to-RV apex horizontal line defined a reference segment (0% His, 100% apex). Next, vertical displacement was measured perpendicular to it, with the His level as 0, and values above or below reported as ±, but presented as % of the reference segment.

At 20 mm from each tricuspid annulus, all targets in RAO 30 clustered at approximately one- third of the horizontal His distance-to-RV apex. Vertical displacements separated the identified targets: the septal targets lay close to the His levels (-1.6±10.8%); superior above (+15.8±6.8%), and inferior below (-32.4±18.7%). The septal fascicular targets provided the best balance of feasibility and precision, with the closest proximities to the left bundle origins (18.9±4.5 mm).

This suggested CT-derived framework can be used to identify the septal fascicle regions as the most practical LBBAP targets, targeting proximity to the conduction system.