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.