  Formation of feedback loops of excitation waves (reentrant circuit) around
non-conducting ventricular scar tissue is a common cause of lethal cardiac
arrhythmias, such as ventricular tachycardia. This is typically treated by
rapid stimulation from an implantable device (ICD). However, the mechanisms of
reentry termination success and, more importantly, failure, are poorly
understood. To study such mechanisms, we simulated pacing of anatomical reentry
in an ionic model of cardiac tissue, having significant restitution and
dispersion properties. Our results show that rapid pacing causes inhomogeneous
conduction in the reentrant circuit, leading to successful pacing termination
of tachycardia. The study suggests that more effective pacing algorithms can be
designed by taking into account the role of such dynamical inhomogeneities.
