Model 2c on a 1D Ring

Alternans suppression on a 1D Ring

The slope of the APD restitution curve is greater than one for periods less than 300 ms (maximum slope is 4.5), but strong electrotonic effects prevent alternans at all periods.

The applet reproduces the results shown with black lines (Model 2c, see Figure 3 caption in paper for more information).
The applet simulates the propagation of an action potential on a ring (the edge at the right is the same as the edge at the left).

How to use this applet:

  • The Start button generates one action potential which is blocked on the right so that it only propagates to the left.
  • The Stop button then can stop the simulation at any time. The simulation can be resumed by using the Continue button that replaces the Stop button when the simulation is stopped.
  • The simulation speed can be increased or decreased by clicking on the Faster or Slower buttons repeatedly until the desired speed is reached.
  • The Reset button brings the membrane potential of all the cells back to the rest state.
  • The Restart button reinitiates the original single pulse.

    Things to try:

  • The period of the propagating action potential depends on the size of the ring, so that by changing the ring size the period is also changed. At the begining of the simulation the pulse (after a few rotations) will have a period of 379 ms (APD=239 ms, DI=140 ms) for the initial size of the ring (360 points). Slowly decrease the ring size by clicking on the Smaller ring button (each click decreases the ring size by 5 points).
  • Note that for this model no alternans develops for any period (ring size). However, depending on how quickly the size is changed, small-magnitude transient alternans may be observed while the action potential adjusts to the new period. The minimum period is 74 ms (APD=47 ms DI=27 ms, 40 points).
  • Note that changing the ring size while the wave front is at the edges may terminate the reentry. To avoid this problem, change the ring size only when the wave front is not near the left and right boundaries.

    For more information see
    Cherry EM, Fenton FH. (2004) Suppression of alternans and conduction blocks despite steep APD restitution: electrotonic, memory, and conduction velocity restitution effects. Am J Physiol Heart Circ Physiol 286, H2332-H2341.