Multi-scale virtual human ventricle

The propagation of excitation waves was described using the monodomain equation⁴³,

where D is the diffusion coefficient tensor for describing the intercellular electrical coupling via gap junctions.

For one-dimensional (1D) simulations, a 15 mm long transmural 1D strand of 100 nodes with spacing 0.15 mm was constructed. The strand length was consistent with the normal range of human transmural ventricle width (4–14 mm) in previous studies^61,62. The ratio of ENDO:MCELL:EPI was set to 37:26:37 as in previous study¹⁴. The diffusion coefficient was set to 0.154 mm²/ms to get a conduction velocity of 71.9 cm/s, which was very close to the 70 cm/s that recorded in the human myocardium⁶³.

The 1D strand was expanded in the y direction to form a 15 × 60 mm² two-dimensional (2D) tissue sheet. Isotropic cell-to-cell coupling was assumed in the idealized model, and the isotropic coefficient was kept the same as in the 1D strand. For the realistic 2D ventricle tissue slice, the D was anisotropic and the coefficients along and perpendicular to the fiber orientation were set to 0.154 and 0.0385 mm²/ms, respectively. For the realistic three-dimensional (3D) bi-ventricle geometry, the anisotropic coefficients were the same as in the 2D realistic tissue slice. The anatomical geometries of realistic 2D ventricular slice and 3D ventricle were reconstructed from DT-MRI^64,65.