Towards high resolution computational models of the cardiac conduction system: A pipeline for characterization of Purkinje-ventricular-junctions

The cardiac conduction system (CCS) has been in the spot light of the clinical and modeling community in recent years because of its fundament role in physiology and pathophysiology of the heart. Experimental research has focused mainly on investigating the electrical properties of the Purkinje-ventricular- junctions (PVJs). The structure of the PVJs has only been described through schematic drawings but not thoroughly studied. In this work confocal microscopy was used with the aim of three-dimensional characterization of PVJs. Adult rabbit hearts were labeled with fluorescent dyes, imaged with confocal microscopy and Purkinje fibers differentiated from other cardiac tissue by their lack of transverse tubular system on the membrane. A semi-automatic pipeline to segment the network was implemented, using region growing and manual revisions. The resulting three-dimensional reconstructions were used to compute centerlines of the Purkinje fibers. Highly complex structural configurations were found at a subcellular resolution including anastomoses with furcations of up to 5 paths. We suggest that the presented analysis and parametrization of the centerline skeleton of the PVJs will help to improve automated Purkinje network generation algorithms.