Flows in stenotic vessels

The relationship between flow in the arteries, particularly the wall sheer stresses, and the sites where atherosclerosis develops has motivated much o f the research on arterial flow in recent decades. It is now well accepted that it is sites where shear stresses are low, or change rapidly in time or space, that are most vulnerable. These conditions are likely to prevail at places where the vessel is curved; bifurcates; has a junction, a side bran ch, or other sudden change in flow geometry; and when the flow is unsteady. These flows, often but not always involving flow separation or secondary m otions, are also the most difficult ones in fluid mechanics to analyze or c ompute. In this article we review the modeling studies and experiments on s teady and unsteady, two-and three-dimensional flows in arteries, and in art erial geometries most relevant in the context of atherosclerosis. These inc lude studies of normal vessels--to identify, on the basis of the fluid mech anics, lesion foci--and stenotic vessels, to model and measure flow in vess els after the lesions have evolved into plaques sufficiently large to signi ficantly modify the flow. We also discuss recent work that elucidates many of the pathways by which mechanical forces, primarily the wall shear stress es, are transduced to effect changes in the arterial wall at the cellular, subcellular, and genetic level.