Phase 1 is genesis of early repolarization Two mechanisms are responsible for phase 1 CL=300 msec BCL= 8000 msec When a notch is not evidence phase l reflects the inactivation of the fast nat channels In cells characterized by a notch, phase I reflects not only the inactivation of nat channels but also activation of a specific K current(transient outward Endo current lto.Phase 1 is genesis of early repolarization • When a notch is not evidence, phase 1 reflects the inactivation of the fast Na+ channels. Two mechanisms are responsible for phase 1: • In cells characterized by a notch, phase 1 reflects not only the inactivation of Na+ channels, but also activation of a specific K+ current (transient outward current [Ito]