Nonsustained reentry following successive stimulation of cardiac tissue through a unipolar electrode.

Abstract

Using numerical simulations, we predict that nonsustained reentry occurs following a strong, premature stimulus through a unipolar electrode. Our simulations were based on the bidomain model of cardiac tissue, and the active membrane properties were represented by the Beeler-Reuter model. An outwardly propagating wavefront was excited by an initial stimulus (S1). A second stimulus (S2) was then applied through the same electrode. Nonsustained reentry or reentrant-like behavior followed the S2 stimulus for both cathodal and anodal stimulation, and were associated with "break" stimulation but not with "make" stimulation. The direction of spiral-wave rotation was reversed when the polarity of the stimulus was reversed. These complex dynamics occur only for a narrow window of S1-S2 intervals. During anodal S2 stimulation, two different modes of reentry exist. Our simulations also explain the "no response" phenomenon. Our mathematical model predicts that both anodal and cathodal unipolar S2 stimulation results in reentry. This behavior arises from an interaction of virtual anodes and cathodes surrounding the stimulating electrode.