Space-time plot of propagating DADs in a ring using the NMf-C2 model. The ring length is 9 cm, too short to support propagation of a reentrant impulse. Instead, because pacing is effectively ceased after the first paced beat, DADs occur spontaneously at various sites and propagate bidirectionally around the ring until they are blocked by refractory areas or self-annihilate on the opposite side of the ring. Electrotonic effects alter the locations of the two propagating DADs as well as the location of a third DAD, which does not trigger a full-amplitude action potential and is damped out as it propagates. Other parameter variations, including the NM-AF, NM-C, and NMf-C, also exhibit propagating DADs for rings just short enough to cause propagation failure.