Physiological determinants of the leading circle reentry initiated by a point premature excitation in a two-dimensional homogeneous myocardial model

Short current pulses with twice threshold intensity applied during the vulnerable window at the end of the basic propagating wave have been shown to produce unidirectional block in a linear cable model. Similar premature point stimuli failed to initiate asymmetric electrical responses in a 2-D homogeneous myocardial surface (3/spl times/3 cm, 100 /spl mu/ steps, Luo-Rudy AP model). However when an additional planar stimulus was introduced after the basic wave, the point extrastimulus initiated an abnormal double electrical activation, leading to "figure-of-eight" reentry. Time course of restitution of the refractory period after a premature stimulus was found to be the most important electrophysiological parameter to determine duration of the vulnerable window.<>