Diffuse and Stringy Fibrosis in a Bilayer Interconnected Cable Model of the Left Atrium

Interconnected cable models of cardiac tissue are known for their numerical stability and performance at high resolution, their handling of strong anisotropy and their interpretation as network of resistors. Building such as mesh is however not straightforward. We developed an approach for automatic construction of 3D bilayer interconnected cable models from left atrial geometry and epi- and endocardial fiber orientation fields. The model consisted of a series of longitudinal and transverse cables intertwined like fabric threads, with a spatial discretization of 100 µm. Diffuse fibrosis was introduced as random uncoupling of cell-to-cell longitudinal and transverse connections. Stringy fibrosis was intended to represent collagenous septa and was implemented as a random set of longitudinal lines of transverse uncoupling (along cables) with Poisson-distributed length. The range of possible uncoupling percentages was assessed by investigating the percolation limit. This modeling approach was tested by simulating activation maps in normal and fibrotic tissues.