Distribution of APD90 from tissue simulations incorporating extrinsic variability. APD90 maps shown are recorded are for (A) the underlying cell distribution, then in (B) at D= 1.171 cm2 s−1, 0.586 cm2 s−1, 0.117 cm2 s−1, and 0.059 cm2 s−1 for the deterministic and stochastic simulation results. Simulation results shown are for the 50th beat in the series, and from the central 0.5 cm of the tissue only.