Blood clots are the clumps that result from coagulation of the blood (blood hardens to from liquid to solid). A blood clot that forms in a blood vessel or within the heart and remains there is called a thrombus. A thrombus that travels from the blood vessel or heart to another location in the body is called an embolus, and the disorder, an embolism. For example, an embolus that occurs in the lungs is called a pulmonary embolism.

Sometimes, a piece of atherosclerotic plaque, small pieces of tumor, fat clumps, air, amniotic fluid, or other materials can act in the same manner as an embolus.

For more information, see the following:

• Arterial embolism
• Pulmonary embolism
• Deep venous thrombosis
• Renal vein thrombosis
• Atheroembolic renal disease
• Thrombophlebitis
• Stroke
• Heart attack
• Angina

Thrombi and emboli can firmly attach to a blood vessel, and partially or completely block the flow of blood in that vessel. This blockage prevents normal blood flow and oxygen from reaching the tissues in that location. This is called ischemia. If ischemia is not treated promptly it can result in tissue damage, or death of the tissues in that area.