  Electrical pacing is a common procedure that is used in both experimental and
clinical settings for studying and/or annihilating anatomical reentry. In a
recent study [Comtois and Vinet, Chaos 12, 903 (2002)], new ways to terminate
the one-dimensional reentry using a simple protocol consisting of only two
stimulations were discovered. The probability of annihilating the reentrant
activity is much more probable by these new scenarios than by the usual local
unidirectional block. This paper is an extension of the previous study in which
the sensitivity of the new scenarios of annihilation to the pathway length is
studied. It follows that reentry can be stopped over a limited interval of the
pathway length and that increasing the length beyond the upper limit of this
interval yields to a transition to sustained double-wave reentry. A similar
dynamical mechanism, labeled alternans amplification, is found to be
responsible for both behaviors.
