Aneurysm An aneurysm is a weakening and localized dilation in the wall of a blood vessel. Atherosclerosis Atherosclerosis is the formation of yellowish plaques of cholesterol and other lips along the arterial wall. Blood Clot A blood clot is composed of red blood cells, white blood cells, and liquid plasma. Myocardial Infarction Heart attack: A blocked coronary artery may cause muscle cells to die from lack of oxygen creating a non-functional area known as an infarct. Stroke Stroke is an interruption in the blood supply to the brain due to a blockage or rupture causes cells to die from lack of oxygen. Thrombus A thrombus is a blood clot with fibrous strands that forms in a vessel. It may break off and travel through the circulatory system, eventually causing a stoppage of blood flow.