An aneurysm occurs when the wall of a blood vessel weakens and balloons out. Like a balloon, the aneurysm can eventually burst. If this happens in a major artery, such as the aorta, it can lead to massive bleeding and death. Atherosclerosis can also upset the delicate balance of blood clots. Clots continually form and dissolve in our bloodstream, and it is important that this balance be kept.
Clots form when blood platelets encounter an injury.
Because the body considers plaque buildup an injury, platelets rush to the scene and begin the clotting process. The formed clot may remain attached to the plaque and continue growing. A clot that grows to the point that it obstructs a blood vessel is called a thrombus. It can shut off the blood supply to some body tissues. If this occurs in a blood vessel that feeds the heart, it is called a coronary thrombosis.