Fig. 1

Simulation of Chaotic EADs. Numerical simulations of EADs using the deterministic AP models PP, PV and UP as outlined in the methods section. Model simulations were carried out for a time span of 2000 seconds, plots show short sections long after possible transients are gone. Positive largest Lyapunov exponents λ of the time series confirm the chaotic nature of the EADs. PP) Chaotic EADs, λ=4.7s ⁻¹, for the periodically forced pacemaker cell model PP with G _K =0.04 mS/ cm² as previously shown in [12]. For I _sti we chose periodic step pulses with PCL = 1.075s, step duration d = 0.002s and step amplitude A = 42 μ A/cm². PV) Chaotic EADs, λ=5.4s ⁻¹, for the periodically paced ventricular cell model PV with G _K =0.282 mS/ cm² as previously reported in [10]. For I _sti we chose periodic step pulses with PCL = 0.7s, step duration d = 0.002s and step amplitude A = 30 μ A/cm². As opposed to A), stimulation of the cell also takes place before full repolarization. UP) Chaotic EADs, λ=2.7s ⁻¹, for the unforced pacemaker cell model UP with G _K =0.039218 mS/ cm². Note that simulated chaotic EADs have previously only been published in context of periodic forcing