Blood Clots

What are blood clots?

When blood clots, it changes from a liquid to a solid. This is part of the body's normal response to an injury. Normal clotting occurs within seconds and helps limit blood loss by sealing damaged blood vessels when there is an injury. As the body heals, the blood clots dissolve and are reabsorbed by the body without causing problems. However, sometimes blood clots can block the flow of blood and oxygen through a blood vessel. The result can be a heart attack, stroke, loss of vision, blood clots in the lung, or other problems.

A blood clot that partially blocks a vein or artery is known as a thrombus. A blood clot that breaks off and travels through the bloodstream until it gets stuck in a smaller blood vessel and blocks the blood supply is known as an embolus.

How do they occur?

Blood clots can form due to abnormal levels of blood clotting proteins, or because of scars or plaque inside blood vessels. Some conditions make it more likely that you will develop blood clots:

cancer
diabetes
hardening of the arteries
heart valve disease or heart failure
high blood pressure
high cholesterol
immune system disorders such as lupus or rheumatoid arthritis
inflammatory bowel disease
family history of blood clots
pregnancy
previous heart attack or stroke.

Blood clots can result from other problems such as:

being bedridden after surgery
accidents
long-term immobility
use of birth control pills or estrogen replacement therapy
high dose corticosteroid therapy
catheters.

Smokers, those who do not exercise, and obese people have a higher risk for developing blood clots in blood vessels.

What are the symptoms?

About half of people with blood clots have no symptoms until a clot blocks a major vein. When clots block blood flow, symptoms may include:

swelling, redness, or warmth in the calf, ankle, foot, or thigh
pain in the leg
chest pain
shortness of breath
seizures or sudden weakness
severe abdominal pain with vomiting or diarrhea
bluish color of the skin on the leg or toes.

How are they diagnosed?

Your health care provider will ask about your medical history and your symptoms. Your provider will examine you, especially any abnormal areas, such as a swollen leg. Other tests may be done to confirm the diagnosis, such as:

IPG (impedance plethysmography) measures vein function in the arm or leg. Your health care provider or a technologist will place a pressure cuff on your arm or leg and measure how fast the veins empty.
Duplex ultrasound uses both sound echo and Doppler echo signals to make pictures. The ultrasound bounces sound waves off the deep veins in an arm or leg. These echo pictures help locate any blockages. Doppler ultrasound signals measure how fast the blood flows through the veins.
Contrast venography usually shows any blockages in your veins. During venography a special dye is injected into a vein while x-ray pictures are taken.
Angiography uses special x-rays to show the walls of the arteries and any blockage. A special dye that shows up in an x-ray is injected into a blood vessel through a thin tube called a catheter. As the dye flows in the blood vessel, a series of x-rays are taken.
MRI (magnetic resonance imaging) uses magnetism, radio waves, and a computer to make pictures that can show plugged blood vessels.
CT (computed tomography) scan, in which x-rays are taken at different angles and then combined by a computer.

How are they treated?

If the blood clot is in a vein, your health care provider may recommend that you:

Put warm, moist compresses on the inflamed area (be careful to avoid burns).
Rest and elevate your arm or leg while you have pain and swelling, typically for 1 week.
Take an anti-inflammatory drug, such as aspirin or ibuprofen. You may need to take a blood thinner.

If you have blood clots in an artery, or deep in the veins, you may need to take a blood thinner. If you have a condition that puts you at high risk for blood clots you may need to take medicine for the rest of your life.

If you have a heart attack or stroke, you may be given a thrombolytic drug. This type of drug is a powerful clot dissolver that works quickly. Because this medicine makes it much harder for your blood to clot, you must be watched carefully for too much bleeding. It is usually given in a hospital.

A catheter (small tube) may be used to deliver clot buster medicines directly to the clots inside the blood vessels. Catheters may also be used to remove blood clots.

You may need surgery to remove the clot. If you keep having problems, you may have surgery to put a small plastic filter in the large abdominal vein that returns blood to the heart. The filter can trap blood clots and prevent them from reaching your lungs.

How can they be prevented?

Avoid sitting for long periods of time. When you are traveling, move your feet and legs often. Go for short walks if possible.
Avoid crossing your legs and ankles when you sit.
Get regular exercise, according to your health care provider's advice.
Cut back on fats and cholesterol in your diet.
Maintain a healthy body weight.
Elevate your legs when you are in bed or sitting down.
Stop smoking. Smoking increases the risk for blood clots.
Talk with your health care provider about all supplements and nonprescription medicines that you take. Some herbs, such as garlic and ginseng, may affect the way blood clots.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File CRD3607F.HTM Release 9.0/2006