A solid mass formed by blood clotting in a blood vessel or in the heart. Blood clots consist of a mesh of protein called fibrin, in which blood cells are captured.
The main risk of a thrombus is occluding a blood vessel and thereby reducing or interrupting blood flow in this vessel.
The negative influence of a thrombus may be manifested at the site where it was formed or at a remote site, where it arrives as embolus.
An example of a condition, in which thrombus causes local damage is Myocardial Infarction. Most Myocardial Infarctions occur through a mixed mechanism of thrombus occurring upon a lipid plaque (Atherosclerosis) which together can totally occlude an artery and prevent blood and oxygen supply to a part of the heart nourished by this particular artery.
An example of a thrombus that has an impact on a remote site is embolism. This is an event of a thrombus formed in the heart, which is expelled during ventricular systole to the Aorta and from there it reaches with the blood stream a remote organ, such as brain or kidney, where it causes an ischemic damage.
There are special medical conditions with increased tendency to embolism. Such are for instance rhythm disorders called Atrial Fibrillation or state after valve replacement. Blood clots formed in the heart may be sent from there as thromboembolism to different body organs and cause an ischemic damage to these organs.
Therefore, patients suffering from such conditions are often treated with drugs preventing blood coagulation (sometimes called blood thinners).