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Published on: December 22, 2020
Analysis of Microstructure of the Cardiac Conduction System Based on Three-Dimensional Confocal Microscopy
Daniel Romero1,2, Oscar Camara2, Frank Sachse3
1Grupo de Investigacion e Innovacion Biomedica, Instituto Tecnologico Metropolitano, Medellin, Colombia.
Insights
This study characterizes the distal Purkinje network in rabbit hearts, revealing two cell types and connection structures. Findings offer insights into cardiac electrical conduction and potential treatment impacts.
Area of Science:
- Cardiovascular Science
- Biophysics
- Cell Biology
Background:
- Specialized conducting tissues in ventricles rapidly distribute electrical impulses.
- Characterizing the distal Purkinje network and its junctions with working myocardium is challenging.
Purpose of the Study:
- To characterize the architecture of the distal Purkinje network.
- To differentiate Purkinje cells and segment Purkinje fibers at a cellular scale.
- To mathematically describe the morphology and interconnections of the Purkinje network.
Main Methods:
- Confocal microscopy of rabbit Purkinje cells using wheat germ agglutinin labeling.
- Semi-automated segmentation of 16 3D image stacks.
- Application of graph metrics to analyze Purkinje network complexity.
Main Results:
- Two cell types (tubular and star-like) were identified.
- Two Purkinje-myocardium connection types (2D sheet and funnel) were confirmed.
- The Purkinje cell network lacks small-world connectivity and assortativity properties.
Conclusions:
- The study provides a detailed architectural map of the distal Purkinje network.
- Results aid in developing more realistic computational models of cardiac conduction.
- Enhanced understanding may inform treatments affecting the cardiac conduction system.
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.
