A Mechanism for ST Depression Associated with Contiguous Subendocardial Ischemia Short title: Mechanism for ST Depression

Mechanism for ST Depression. Introduction: A mechanism is proposed for ST depression that arises on the epicardial surface above the border between normal and ischemic tissue. Depression is caused by current that flows in a transmural loop that begins and ends at the lateral boundary between healthy and ischemic tissue and that passes through the transmural boundary between healthy and ischemic tissue. The result is ST depression at the epicardium above the lateral boundary. The size and direction of current flow is dictated by differences in the magnitude and orientation of anisotropic conductivity between those boundaries. Methods and Results: Computer simulations verified and quantified the relationship of ST depression and these conductivity differences. We have used computer simulations based on an anatomically accurate, anisotropic model of canine ventricles and a bidomain representation of the effects of ischemia to verify the biophysical basis of this mechanism. Conclusion: ST depression at the epicardium appears above a lateral boundary between healthy and ischemic tissue.