Independently from this study, patients have agreed to a cardiac catheterization (angiogram - an x-ray picture of the heart) and possible angioplasty procedure and/or stenting as part of clinical care. During the cardiac catheterization if the blockage is bad enough an inflatable balloon attached to the end of a thin tube (called a catheter) is positioned in the narrowed part of the coronary artery. The balloon is then inflated, which opens the artery so that blood can flow more easily. After the balloon angioplasty procedure, a stent may be placed in the coronary artery. A stent is an expandable metal tube that helps to hold the artery open so that blood can continue to flow through the artery.