Coronary angiography is the main instrument used to evaluate the presence of stenoses caused by coronary atherosclerosis. An angiogram is a luminogram delineating the shape of the contrast-filled lumen, but it does not supply information about the vessel wall. It has long been recognized that segments with an angiographically “normal” appearance (i.e., without stenosis) may have atheroma when evaluated with more detailed pathology-based tools.