First, it may it reduce the lumen to such an extent that little or no blood can get through to the heart. Second, atherosclerotic plaque can trigger the formation of blood clots, which form on top of the plaque and block the artery. If either of these occur, a blood clot may be formed that blocks the flow of blood through the arteries. Atherosclerotic plaque can go away but the process by which this happens is still poorly understood. Ironically, atherosclerotic plaque can get worse and get better at the same time in different parts of the coronary arteries.
Blood vessels have a thin lining composed a single layer of a special type cell.
Many scientists think atherosclerosis begins when this inner lining becomes damaged. The result is somewhat like an ulcer on the wall of the blood vessel. The blood vessel wall reacts to this ulcer-like injury by stimulating various types of cells to grow and reproduce. The result is a progressive thickening of the blood vessel wall. As discussed earlier, this area of thickening and rough plaque can stimulate the development of a blood clot, which further reduces the lumen or totally blocks it.