Coronary thrombosis. Light micrograph (LM) of part of a thrombus (red) attached to the interior wall (purple) of the coronary artery of the heart. The fibrous clot, which is packed full of red blood cells, leucocytes and platelets, can prevent oxygen-carrying blood from reaching parts of the heart muscle. If the blood supply to a part of the heart is interrupted, the condition is know as acute myocardial infarction (AMI), or a heart attack, which damages the heart and is potentially fatal. Thrombi (clots) may also block arteries supplying the brain, legs, kidneys, and other areas of the body.