Illustrative Computer Simulation
Programmed stimulation with a single extrastimulus following a basic
drive was simulated for sites around the anatomic reentry circuit shown
in figure 5 and Video 1. In this model, proximity to the entrance/exit
regions of the channel determine whether reentry will occur in response
to an extrastimulus. S1 wavefronts propagate through the channel, the S2
wavefront blocks and fails to enter the adjacent entrance to the
channel, but propagates to the other side with a sufficient to allow
entry into the channel and initiation of reentry. This is an
oversimplification of the complex anatomic and electrophysiologic
heterogeneity in VT-causing substrate, but illustrates the marked effect
that pacing site can have on inducibility of a simple circuit.