Blood Clots Health Article

Definition

A blood clot is a mass of blood cells and blood components that form to stop the bleeding that occurs when a blood vessel is injured. When a blood vessel is broken, platelets in the blood become sticky and clump together at the site of the injury. They begin to form a mass to stop the flow of blood.

Description

Clotting is the body's normal response to a bleeding injury. It is a necessary function to prevent a person from losing too much blood. Most blood clots dissolve back into the blood when the body has healed the vessel. Blood clots, however, can be potentially dangerous if they occur within healthy blood vessels, or if they do not dissolve when their work is done. A thrombus is a blood clot that forms along the wall of the heart or a blood vessel. This type of clot can slow blood flow, and if the clot becomes large enough, it may stop the flow of blood in the vessel. An embolus is a clot that forms in one area of the body, travels through the bloodstream, and lodges in another vessel in the body. Emboli are less common and more dangerous, because they can cause a sudden blockage in blood flow (embolism), which could be fatal. An embolism occurring in an artery will block blood flow to an organ or tissue, and could cause tissue damage or death. An embolism in:

• a cerebral (brain) artery can cause a stroke
• a coronary artery can cause a heart attack
• a pulmonary (lung) artery can cause shortness of breath or death
• a retinal artery can cause sudden blindness in one eye
• an artery supplying blood to a limb can cause tissue damage and possibly gangrene
• any artery leading to an organ can cause loss of that organ's function

Causes & symptoms

There are several factors that contribute to the formation of blood clots. Phlebitis is a condition that may increase abnormal blood clot formation. Blood diseases or other conditions—especially inflammation—that alter the quality of the blood can also affect clot formation. Plaque formation in the arteries (atherosclerosis) and damaged blood vessels both increase the chance of blood clots because they slow blood flow and provide a place for platelets to collect and form a clot. Genetic factors also play a role in tendency to form blood clots. Diet can have an effect on clot formation, as well. Cholesterol and saturated fats, which are also implicated in atherosclerosis, can contribute to clot formation. People whose diets are low in essential fatty acids, vegetables, and fish, and who do not take in proper amounts of nutrients and antioxidants are also at a higher risk for clots. Conditions or body positions that slow blood circulation—extended bed rest or sitting in a car or airplane for long periods of time—may also cause blood clots to form; although one recent British study suggests that the risk of so-called "traveler's thrombosis" is not as great as has been thought. Blood clots can be caused by increased fibrinogen (a blood-clotting factor) due to estrogen in the late stages of pregnancy and from long-term use of birth control pills. Other factors include varicose veins, childbirth, sickle cell anemia, smoking, obesity, liver disease, and cardiovascular disorders.

There may be no obvious symptoms of a blood clot. When symptoms do occur, they often appear suddenly, and point to the location of the clot. Extreme dizziness that occurs without warning can indicate a clot in a cerebral artery. Sudden complete or partial blindness in one eye could indicate a clot within the retinal artery. A hard blue bulge in a vein, or unexpected pain in an arm or leg, along with numbness, weakness, or another sign that blood is not reaching the area, could indicate a blood clot. Blisters or ulcers on the skin may occur as well. A clot in an artery near a major organ like the heart or lung will produce pain or decreased activity in that organ. Gangrene (death of tissue) may occur if blood flow to a region is blocked for an extended period of time.

Diagnosis

The patient will describe the severity and location of the pain he or she has been experiencing. A physician may also notice such physical signs of a blood clot as the swelling blue bulge, discoloration of a limb, or an ulcer. Medical personnel will also check for a missing or lowered pulse or blood pressure in a limb. A Doppler ultra-sound examination, angiography, or arteriography may be used to detect the location of the clot.