Analysis of Microstructure of the Cardiac Conduction System Based on Three-Dimensional Confocal Microscopy

PLoS One. 2016 Oct 7;11(10):e0164093. doi: 10.1371/journal.pone.0164093. eCollection 2016.

Abstract

The specialised conducting tissues present in the ventricles are responsible for the fast distribution of the electrical impulse from the atrio-ventricular node to regions in the subendocardial myocardium. Characterisation of anatomical features of the specialised conducting tissues in the ventricles is highly challenging, in particular its most distal section, which is connected to the working myocardium via Purkinje-myocardial junctions. The goal of this work is to characterise the architecture of the distal section of the Purkinje network by differentiating Purkinje cells from surrounding tissue, performing a segmentation of Purkinje fibres at cellular scale, and mathematically describing its morphology and interconnections. Purkinje cells from rabbit hearts were visualised by confocal microscopy using wheat germ agglutinin labelling. A total of 16 3D stacks including labeled Purkinje cells were collected, and semi-automatically segmented. State-of-the-art graph metrics were applied to estimate regional and global features of the Purkinje network complexity. Two types of cell types, tubular and star-like, were characterised from 3D segmentations. The analysis of 3D imaging data confirms the previously suggested presence of two types of Purkinje-myocardium connections, a 2D interconnection sheet and a funnel one, in which the narrow side of a Purkinje fibre connect progressively to muscle fibres. The complex network analysis of interconnected Purkinje cells showed no small-world connectivity or assortativity properties. These results might help building more realistic computational PK systems at high resolution levels including different cell configurations and shapes. Better knowledge on the organisation of the network might help in understanding the effects that several treatments such as radio-frequency ablation might have when the PK system is disrupted locally.

MeSH terms

  • Animals
  • Heart Conduction System / anatomy & histology*
  • Heart Conduction System / cytology*
  • Heart Ventricles / anatomy & histology*
  • Heart Ventricles / cytology*
  • Imaging, Three-Dimensional / methods
  • Microscopy, Confocal / methods
  • Myocardium / cytology
  • Purkinje Cells / cytology
  • Rabbits

Grants and funding

This work was supported by Ministerio de Economía y Competitividad, grant number TIN2011-28067 (www.mineco.gov.es): OC; and Ministerio de Economía y Competitividad, the European Commission (European Regional Development Funds - ERDF - FEDER) grant number TIN2014-59932-JIN: RS. Furthermore, we acknowledge awards from the Nora Eccles Treadwell 484 Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We acknowledge Prof. A.F. Frangi, University of Sheffield, UK for his financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.