Unidirectional blocks and ectopic foci induced by coupling an ischemic and a normal ventricular cell

This study deals with the behavioural zones of a system composed of a normal myocardial cell (NC) coupled by an electric resistance R to an ischemic, depolarized by an added steady current I, (DC) cell. When varying I, we evidenced 3 levels of stationary solutions corresponding to low (L), medium (M) and high (H) values of the resting potential. In the L zone, we evidenced unidirectional block (UB) effects with respectively 2 (R=20) or 1 (R=50) thresholds of depolarization. From 2 Hopf bifurcation points, emerge branches of periodic solutions corresponding to ectopic foci (EF) coexisting with L or M types of resting potential. In these zones, we found again UB effects with, in case of propagation, a locking of the system to a rhythmic activity. This theoretical study represents a unified approach of some types of UB and EF related to ischemia.