FIGURE 7.

Repolarization abnormalities – DADs. (A) Illustrative action potential (AP) traces for four models that produced delayed afterdepolarizations (DADs). (B) Illustrative model producing a DAD. (C) Example of DAD degenerating into an anticipated spontaneous AP. In both models the leakage J_leak from the overloaded SR increased the Ca²⁺ concentrations in cytosol ([Ca²⁺]_i) and subspace ([Ca²⁺]_SS). The RyR-sensitive channels sensed the increased [Ca²⁺]_SS and triggered a spontaneous SR Ca²⁺ release (through J_rel) that was translated by the Na⁺/Ca²⁺ exchanger (I_Naca) into the depolarization of the membrane potential, thus determining the DAD and the anticipated AP.