Figure 1. Typical action potential (AP) morphologies recorded from the Epi and Endo surfaces of the canine RVOT. A significant AP spike and dome morphology giving rise to a prominent notch was present throughout the Epi surface. On the Endo surface, manifestation of an AP notch ranged from very prominent to none. A prominent AP notch was recorded from the deep intra-trabecular Endo structures.