Blood clotting, or coagulation, is an important process that prevents excessive bleeding when a blood vessel is injured. Platelets (a type of blood cell) and proteins in your plasma (the liquid part of blood) work together to stop the bleeding by forming a clot over the injury. Typically, your body will naturally dissolve the blood clot after the injury has healed. Sometimes, however, clots form on the inside of vessels without an obvious injury or do not dissolve naturally. These situations can be dangerous and require accurate diagnosis and appropriate treatment.
Clots can occur in veins or arteries, which are vessels that are part of the body’s circulatory system. While both types of vessels help transport blood throughout the body, they each function differently. Veins are low-pressure vessels that carry deoxygenated blood away from the body’s organs and back to the heart. An abnormal clot that forms in a vein may restrict the return of blood to the heart and can result in pain and swelling as the blood gathers behind the clot. Deep-vein thrombosis (DVT) is a type of clot that forms in a major vein of the leg or, less commonly, in the arms, pelvis, or other large veins in the body. In some cases, a clot in a vein may detach from its point of origin and travel through the heart to the lungs where it becomes wedged, preventing adequate blood flow. This is called a pulmonary (lung) embolism and can be extremely dangerous.
Am I at Risk?
The risk factors for developing a venous clot are different from those for an arterial clot, and people at risk for getting one are not necessarily at risk for getting the other. Different risk factors or events can cause unnatural clotting; however, each factor may initiate clotting in a different way. There are molecules in your system that signal your body to let it know when, where, and how quickly to form a clot, and genetics plays a role in how quickly your body reacts to these signals. Certain risk factors, such as obesity, slow the flow of blood in the veins, while others, such as age, can increase the body’s natural ability to clot. Even certain medications can affect how quickly your blood clots. The following factors increase your risk of developing a venous blood clot:
- Immobility (including prolonged inactivity, long trips by plane or car)
- Oral contraceptives
- Certain cancers
- Certain surgeries
- Age (increased risk for people over age 60)
- Inherited clotting disorders (family members who have had clots)
- Chronic inflammatory diseases
The risk factors for arterial clots can be modified through changes in lifestyle or by medical treatment:
- Lack of physical activity
- High blood pressure
- High cholesterol
What Are the Symptoms of a Blood Clot?
In addition to knowing your risk factors, it is also important to be aware of the symptoms of blood clots, which vary depending upon where the clot is located:
- Heart – chest pain, often radiating down the left arm and accompanied by shortness of breath, and sweating
- Brain – visual disturbances, weakness, seizures, speech impairment
- Arm or Leg – sudden pain, swelling, tenderness
- Lung – sharp chest pain, rapid pulse, bloody cough, shortness of breath, sweating, fever
- Abdomen – severe abdominal pain, vomiting, diarrhea
How Are Blood Clots Treated?
Blood clots are treated differently depending on the location of the clot and your health. If you are experiencing symptoms and suspect you may have a blood clot, see a doctor immediately.
There have been many research advances made in antithrombotic therapy that have improved the prevention and treatment of blood clots. Some current treatments include:
- Anticoagulants – medicine that prevents clots from forming
- Clot busters – medicine that dissolves blood clots
- Catheter-directed thrombolysis – a procedure in which a long tube, called a catheter, is surgically inserted and directed toward the blood clot where it delivers clot-dissolving medication
- Thrombectomy – surgical removal of a clot
If you are diagnosed with a venous clot, your doctor may refer you to a hematologist, a doctor who specializes in treating blood diseases. People diagnosed with arterial disease who are at risk for developing a clot in their arteries may have several doctors involved in their care, including a cardiologist (a doctor who specializes in conditions of the heart) and possibly a hematologist.
For some patients, participating in a clinical trial provides access to experimental therapies. If diagnosed, you can talk with your doctor about whether joining a clinical trial is right for you.
Are Blood Clots Preventable?
Blood clots are among the most preventable types of blood conditions. There are several ways to decrease your chances of developing a blood clot, such as controlling your risk factors when possible. If you think you may be at risk because of genetic or behavioral factors, talk with your doctor. Also, make sure your doctor is aware of all the medications you are taking and any family history of blood clotting disorders.
Thrombotic Thrombocytopenic Purpura: A Patient's Journey
Where Can I Find More Information?
If you find that you are interested in learning more about blood diseases and disorders, here are a few other resources that may be of some help:
Articles From Hematology, the ASH Education Program Book
The American Society of Hematology (ASH) Education Book, updated yearly by experts in the field, is a collection of articles about the current treatment options available to patients. The articles are categorized here by disease type. If you are interested in learning more about a particular blood disease, we encourage you to share and discuss these articles with your doctor.
Results of Clinical Studies Published in Blood
Search Blood, the official journal of ASH, for the results of the latest blood research. While recent articles generally require a subscriber login, patients interested in viewing an access-controlled article in Blood may obtain a copy by e-mailing a request to the Blood Publishing Office.
This section includes a list of Web links to patient groups and other organizations that provide information.
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