This applet is used to simulate the activation of human ventricular epicardial, endocardial, and midmyocardial cells using a 4-variable phenomenological model. All 28 parameters of the model can be modified. The model reproduces various experimental data such as (dv/dt)_max, as well as human action potential duration (APD) and conduction velocity (CV) restitution curves (see Bueno A, Cherry EM, Fenton F, Minimal model for human ventricular action potentials in tissue,

Using the applet, the myocyte can be paced at user-specified cycle lengths and the final APD and DI are calculated automatically. In addition, it is possible to visualize the voltage and gating variables.

N(S1's) indicates how many S1 stimuli to apply.

S1 (bcl) indicates the cycle length for the S1 stimuli.

S2 (bcl) indicates the cycle length for the S2 stimulus.

Click "Start" to start the simulation. Use "Replot" to replot on the screen once a check box has been selected or a new value has been entered for S1, S2 or N. Use "Current and Ascii" to plot the total current of the model or obtain ascii data of Voltage vs t. Use the drop-down list box to choose parameters corresponding to epicardial, endocardial, or midmyocardial (M) cells, or choose Arbitrary cell to customize the parameter values. Use the boxes in the lower part of the window to change one or more parameter values.

Things to try:

Change the cell type using the drop-down list box.

To calculate points on APD restitution curves, change N, S1, and S2.

Click in the Ascii check box to obtain the voltage signal as a function of time. (Note that the larger the signal, the longer it takes for the window to appear.)

Change parameter values to view the effects on the voltage and gating variables. For example, change tau_wp and observe the effect on the APD.

We thank Andrew B. Filipski for his work on the applet code.