The original HRd formulation, without the changes below, was necessary to reproduce the experimental rate dependence of the L-type, of the AP notch (it decreases with increasing rate) and of the dome morphology in epicardial cells with a prominent notch and “spike and dome” morphology. Prior to the HRd model, no published canine models could reproduce this behavior, as well as the rate dependence of the calcium transient. In the tissue, cells do not exhibit such prominent notch and behave somewhat differently (due to many possible factors that are changed by cell isolation). With the adjustments below, the propagating AP model (upstroke, notch, APD, APD rate-dependence) closely matches experimental tissue data from the dog.
Important Note: These adjustments are intended for simulating conduction properties only, not dynamics of AP repolarization.
- The variable gNa in the formulation of the Na+ current is increased by a factor of 1.4
- The variable ‘pow’ (dynamic activation gate) in the formulation for the L-type is set to a constant value of 1
- The variable ‘vg’ (variable gain) in the formulation for calcium release is set to a constant value of 1