Figure 1.

Simulated DAD and TA using the AP model. Membrane voltage (upper traces) and submembrane Ca²⁺ concentration ([Ca²⁺]_s, lower traces) during a normal stimulated AP followed by a DAD due to spontaneous Ca²⁺ release which is just above (solid lines) or below (dashed lines) the threshold to trigger an AP. (Black traces) Normokalemia ([K⁺]_o = 5.4 mM); (red traces) hypokalemia ([K⁺]_o = 2.7 mM). (Open arrow) I_Na threshold. The parameters for Gaussian-like function of the clamped spontaneous Ca²⁺ release (see Materials and Methods) were t₀ = 525 ms and σ = 70 ms for all four traces. For normokalemia, Ca_peak = 1.258 μM (black solid) and 1.102 μM (black dashed), respectively. For hypokalemia, Ca_peak = 0.79 μM (red solid) and 0.634 μM (red dashed). To see this figure in color, go online.