Fig. \[slice\_fig\](b) shows the anisotropic dynamics of the re-entry, that is with the fiber orientation data “turned ON”, so that both the anatomically realistic geometry and the anisotropy of the otherwise homogeneous slice of the heart affect the dynamics of the re-entry, causing its drift. In the anisotropic slice, the re-entry also does not terminate at the inexcitable boundaries, but after the faster than in the isotropic case, see the $a.u.$ time labels in the Fig. \[slice\_fig\](a-b), transient first rotation around the septum cuneiform opening, the anatomically realistic anisotropy of the medium turns the initial spiral wave into the fast anatomical re-entry around the septum cuneiform opening, see Fig. \[slice\_fig\](b).

\[3D\] 3D Whole heart MRI-based simulations
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![image](Fig3small.pdf)

![image](Fig4small.pdf)

In the 3D whole heart MRI-based simulations shown in the Fig. \[3D\_iso\]and Fig. \[3D\_aniso\], a counter-clockwise excitation vortex was initiated by the phase distribution method [@chaos], with the initial position of the transmural vortex filament (yellow line) at the prescribed location [*along the $x$ axis*]{} at $y_0=40, z_0=60$. [It can be seen in Fig. \[3D\_iso\] isotropic, and Fig. \[3D\_aniso\] anisotropic 3D simulations that, at $t=0$, there was identical initial location of the filament of the excitation vortex: that is transmurally, roughly 