Analysis of Stochastic Generation of Large-Amplitude Oscillations in a 4D Cardiac Action Potential Model

Effects of stochastic disturbances in a four-dimensional cardiac action potential model are investigated. Based on bifurcation analysis, parametric zones of equilibrium and self-oscillations with normal potential or early afterdepolarizations are localized. It is shown that even in the parameter range of stable equilibria of the initial deterministic system, noise can induce large-amplitude oscillations. This phenomenon of noise-induced excitement is confirmed by changes in the distribution of stochastic trajectories and statistics of interspike intervals. To predict and analyze the generation of such large-amplitude oscillations, the technique of stochastic sensitivity functions of 4D attractors is applied and the method of principal directions is developed.