  We study a vortex in a nanostripe of an antiferromagnet with easy-plane
anisotropy and interfacial Dzyloshinskii-Moriya interaction. The vortex has
hybrid chirality being N\'eel close to its center and Bloch away from it.
Propagating vortices can acquire velocities up to a maximum value that is lower
than the spin wave velocity. When the vortex is forced to exceed the maximum
velocity, phase transitions occur to a nonflat spiral, vortex chain, and flat
spiral, successively. The vortex chain is a topological configuration
stabilised in the stripe geometry. Theoretical arguments lead to the general
result that the velocity of localized excitations in chiral magnets cannot
reach the spin wave velocity.
