Spiral-wave instability.

Pseudocolor plots of the transmembrane potential V_m illustrating spiral-wave instabilities from our numerical simulations of the 2D ORd model for human ventricular tissue, with spatial gradients in (a) G_Kr, (b) G_K1, and (c) G_NaCa (because G_NaCa decreases with g (Fig 2), the gradient in G_NaCa must be chosen to be the negative of that in Eq (5)); in (a)-(c) the local value of ω decreases from the top of the simulation domain to its bottom. Power spectra of the time series of V_m, from representative points in our simulation domain, are shown for gradients in (d) G_Kr, (e) G_K1, and (f) G_NaCa; the spectra in (d) and (e) are consistent with the onset of spiral-wave turbulence; the power spectrum in (f) shows the continuation of periodic electrical activity, in spite of wave breaks.