A 2D-computer model of atrial tissue based on histographs describes the electro-anatomical impact of microstructure on endocardiac potentials and electric near-fields

Abstract

In experiments with cardiac tissue, local conduction is described by waveform analysis of the derivative of the extracellular potential Φ(e) and by the loop morphology of the near-field strength E (the components of the electric field parallel and very close to the tissue surface). The question arises whether the features of these signals can be used to quantify the degree of fibrosis in the heart. A computer model allows us to study the behavior of electric signals at the endocardium with respect to known configurations of microstructure which can not be detected during the electrophysiological experiments. This work presents a 2D-computer model with sub-cellular resolution of atrial micro-conduction in the rabbit heart. It is based on the monodomain equations and digitized histographs from tissue slices obtained post-experimentum. It could be shown that excitation spread in densely coupled regions produces uniform and anisotropic conduction. In contrast, zones with parallel fibers separated by uncoupling interstitial space or connective tissue may show uniform or complex signals depending on pacing site. These results suggest that the analysis of Φ(e) and E combined with multi-site pacing could be used to characterize the type and the size of fibrosis.

Circumferential Pacing Reveals Microstructure of Cardiac Tissue Preparations from Small Animals – An Approach to Classify Microfibrosis

“…a measure of conduction velocity) might be an additional parameter for tissue classification. The experiments have confirmed the findings of the underlying computer simulation study [4] and therefore enable the classification of the directional dependence of pacing site on parameters obtained from extracellular potentials Φ e . This could provide the basis to characterize and quantify microfibrosis in cardiac tissue by means of potential recordings combined with appropriate stimulus protocols.…”

“…Our hypothesis is that local recordings of extracellular potentials Φ e with high spatial resolution can reveal structural properties of electrical uncoupling structures by applying electrical stimuli around a recording site and analyzing the directional dependence of signal parameters. A recent computer study has confirmed this hypothesis [4]. [5].…”

Electroanatomical Characterization of Atrial Microfibrosis in a Histologically Detailed Computer Model

“…The link between CFAEs and cardiac microstructure has been previously investigated in detail using microscopic size scale computational models of 2D tissue sheets [14], [35], [36]. However, several studies suggest that not only amount of fibrosis, but also its texture is a key factor [7], [37], [38]. …”

A finite element approach for modeling micro-structural discontinuities in the heart

“…the terminal endings of a myocyte along the long axis of the cell, than along the lateral border of a myocyte. The discreteness of the intracellular matrix is reflected in the discontinuous nature of impulse propagation at the microscopic size scale which was demonstrated in numerous studies, both with experimental [1], [2] as well as modeling work [3], [4], [5]. Discontinuous propagation is omnipresent in the heart, even in perfectly healthy tissue, however, at the organ scale discontinuous effects secondary to gap junction coupling are likely to be of lesser relevance, when considering the global dynamics of phenomena such as activation and repolarization sequences or the formation of arrhythmias.…”

“…Such an increase in cleft spaces manifests itself in more pronounced discontinuities in propagation. While cell-to-cell propagation mediated via gap junctions leads to very small delays of some tens of μ s and zig-zag propagation patterns at the size scale of some tens of μ m, conduction delays due to increased cleft spaces, depending on the severity of remodeling, may be orders of magnitude longer, at the size scale of a few milliseconds, with zig-zag pathways at the order of a few millimeters [5]. …”