The presence of stenotic lesions in multiple arteries can lead to a condition called "vascular steal." This occurs when dilation of one vascular network (e.g., during exercise or vasodilator therapy) "steals" blood flow from another region within the organ that is already maximally dilated because of the presence of proximal lesions.
Coronary steal phenomenon refers to the phenomenon in which small vessel dilation and an increase in flow to an area already well-perfused myocardium leads to a decrease in flow to another area of myocardium with borderline perfusion and limited coronary reserve. Coronary steal can occur between 2 arteries connected by collateral vessels (intercoronary steal) or from subendocardium to subepicardium distal to a coronary stenosis (transmural steal).
It is seen with drugs like Dipyridamole, Hydralazine and Isoflurane.