When you cut or injure yourself, your body stops the bleeding by forming a blood clot. Proteins and particles in your blood, called platelets, stick together to form the blood clot.
blood clot formation
The process of forming a clot is called coagulation. Normal coagulation is important during an injury, as it helps stop a cut from bleeding and starts the healing process. However, the blood shouldn't clot when it's just moving through the body. If blood tends to clot too much, it is referred to as hypercoagulable state or thrombophilia.
Are hypercoagulable states dangerous?
Hypercoagulable states can be dangerous, especially when these conditions are not identified and treated properly. People with hypercoagulable states have an increased risk for blood clots developing in the arteries (blood vessels that carry blood away from the heart) and veins (blood vessels that carry blood to the heart). A clot inside a blood vessel is also called a thrombus or an embolus.
Blood clots in the veins or venous system can travel through the blood stream and cause deep vein thrombosis (a blood clot in the veins of the pelvis, leg or arm) or a pulmonary embolism (blood clot in the lungs).
Blood clots in the arteries can increase the risk for stroke, heart attack, severe leg pain, difficulty walking, or even the loss of a limb.
What causes hypercoagulable states?
Hypercoagulable states are usually genetic (inherited) or acquired conditions. The genetic form of this disorder means a person is born with the tendency to form blood clots. Acquired conditions are usually a result of surgery or a medical condition that increases the risk of hypercoagulable states.
Inherited hypercoagulable conditions include:
- Factor V Leiden (the most common)
- Prothrombin gene mutation
- Elevated levels of fibrinogen
- Deficiencies of natural proteins that prevent clotting (called anticoagulant proteins - such as antithrombin, protein C and protein S)
- "Sticky" platelets
- Abnormal fibrinolytic system, including hypoplasminogenia, dyspasminogenia, and elevation in levels of PAI-1
- Elevated levels of factor VIII (still being investigated as an inherited condition)
Acquired hypercoagulable conditions include:
- Cancer
- Recent trauma or surgery
- Pregnancy and exogenous estrogen use (including use of oral contraceptive pills-birth control pills)
- Hormone replacement therapy
- Prolonged bed rest or immobility, heart attack, stroke and other illnesses that lead to decreased activity
- Heparin-induced thrombocytopenia (decreased platelets in the blood due to heparin)
- Airplane travel
- Antiphospolipid antibody syndrome
- Previous deep vein thrombosis or pulmonary embolism
- Myeloproliferative disorders such as polycythemia vera or essential thrombocytosis
How is a hypercoagulable state diagnosed?
Careful medical history
Certain conditions increase a person's risk for developing blood clots, but do not necessarily indicate a genetic hypercoagulable state. Therefore, a careful evaluation of the patient's personal and family medical history is needed. Patients who should be screened for hypercoagulable states include those who have:
- A family history of abnormal blood clotting
- Abnormal blood clotting at a young age (less than 50 years old)
- Thrombosis in unusual locations or sites: such as the portal (liver) , mesenteric (intestinal) and cerebral (brain) veins
- Blood clots that occur without a clear (idiopathic) cause
- Blood clots that recur
- A history or frequent miscarriages
- Stroke at a young age
Laboratory testing
Laboratory tests (blood tests) should be performed only after clinical evaluation. These tests should be reserved for people who have one of the conditions listed previously.
Laboratory tests should be performed at a specialized coagulation laboratory and interpreted by a pathologist or clinician with expertise in coagulation, vascular medicine or hematology.
Testing is best performed when the patient is not having an acute clotting event.
More common lab tests include:
- PT-INR: Prothrombin time (PT or protime) test is used to calculate your International Normalized Ratio (INR). Your INR will help your health care provider determine how fast your blood is clotting and whether your medication dose needs to be changed. This test is used to monitor your condition if you are taking Coumadin.
- Activated partial thromboplastin time (aPTT): measures the time it takes blood to clot; certain chemicals are added to the test. This test is used to monitor your condition if you are taking heparin.
- Fibrinogen level
- Thrombin time: measures the time it takes the blood to clot
Some of the test listed previously help to detect the antiphospholipid antibody syndrome or dysfibinogenemias, conditions that can be associated with hypercoagulable states.
Tests used to help diagnose inherited hypercoagulable states include:
- Genetic tests include factor V Leiden (Activated protein C resistance) and Prothrombin gene mutation (G20210A)*
- Antithrombin activity
- Protein C activity
- Protein S activity**
- Fasting plasma homocysteine levels
*Factor V Leiden and prothrombin gene mutation (G20210A) are the more commonly identified genetic defects that increase a person's risk for blood clotting. Because of the very low prevalence of these disorders in Asian and African-American populations, it may be most appropriate to limit testing to Caucasian patients.
**Additional lab tests, such as measurement of free (active) and total protein S antigen levels, may be required in order to validate protein S activity assay results.
Other tests used to help diagnose acquired hypercoagulable states include tests for:
- Anticardiolipin antibodies (ACA), part of the antiphospholipid antibody syndrome
- Lupus anticoagulants (LA), part of the antiphospholipid antibody syndrome
- Hyperhomocysteinemia
- Heparin antibodies
The presence of antiphospholipid antibodies (ACA) and a lupus anticoagulant (LA) is important when evaluating someone who has had current miscarriages or arterial thrombosis.
Testing helps identify whether the patient is at risk for further clotting and helps determine an appropriate course and length of treatment to prevent future clots. Testing also may help to identify relatives who don't currently have symptoms but may be at risk.
How are hypercoagulable states treated?
Anticoagulant medications
In most cases, treatment consists of anticoagulant medications (also called blood thinners). Anticoagulants decrease the blood's ability to clot and prevent the formation of additional clots.
Anticoagulant medications include warfarin (Coumadin), heparin, low molecular weight heparin and fondaparinux (Arixtra).
If you are prescribed Coumadin (warfarin):
- You will need to have frequent blood tests, called the PT-INR to evaluate how well the medication is working
- You should order and wear a medical identification bracelet so you can receive proper medical care in an emergency situation
- You may bleed or bruise more easily when you are injured. Call your doctor if you experience heavy or unusual bleeding or bruising
- Certain nonprescription medications affect the function of anticoagulants. Do not take any other medications without first consulting your doctor.
- Ask your doctor for specific dietary guidelines when taking warfarin. Consuming too much vitamin K (found in brussel sprouts, spinach, and broccoli) can affect the function of the medication.
- You should not take warfarin if you're pregnant or planning to become pregnant. Ask your doctor about switching to a different type of anticoagulant medication.
Warfarin comes in tablet form and is taken orally (by mouth).
Heparin is a liquid and administered either through an intravenous (IV) line that delivers the medication directly into the vein,or by injections given in the hospital.
Low molecular weight heparin is injected beneath or under the skin (subcutaneously). It is given once or twice a day and can be taken at home.
Fondaparinux (Arixtra) is a new medication that is also injected subcutaneously.
You and your family will be instructed on how to take the anticoagulant medication that is prescribed.
The type of anticoagulant medication prescribes, how long you will need to take it, and the type of follow-up monitoring depends on your diagnosis and a discussion of the risks and benefits of these medications with your doctor.
As with any medication, it is important to know how and when to take your anticoagulant according to your doctor's guidelines, and to have frequent blood tests, as ordered by your doctor.
For more information:
Call the Miller Family Heart & Vascular Institute Resource Nurse at 216.445.9288 or toll-free 866.289.6911 or e-mail us using the Contact Us form. We would be happy to answer your questions. To make an appointment in Vascular Medicine, please call 216.445.8022 or toll-free 800.223.2273, extension 5-8022.
Resource:
National Library of Medicine
