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Duration of anticoagulant treatment for venous thrombosis
This article discusses the treatment options for thrombosis and factors that affect the length of treatment.

Introduction
What medication will I receive for DVT or PE?
How long will I be treated?
How will the doctors know if I need treatment for more than 3 months?
Can heparin be given instead of blood-thinner pills?
References

Introduction
 

If you have DVT or PE, you will need treatment not only to relieve your symptoms but also to prevent further clots from occurring, or a DVT from breaking up and causing PE. Treatment can also help to prevent post-thrombotic syndrome.

Venous thrombosis simply means a blood clot in a vein. This is a common medical problem that usually affects the veins in the leg or pelvis. Clots in the deep veins of the leg, deep within the muscles, not in the superficial veins under the skin, cause most problems. This condition is called deep-vein thrombosis, or DVT for short. DVT is troublesome and can cause a painful and swollen leg. However, a bigger problem is caused if a piece of a clot breaks off and travels to the lung where it can block part of the circulation of blood through the lungs. This is called pulmonary embolism or PE and can be life-threatening. Blood clots in the legs can also have long-term effects, with problems such as pain or discomfort, swelling and even skin ulceration arising many years later. This is called post-thrombotic syndrome.

The key medications used to treat thrombosis are called anticoagulants, sometimes known as ‘blood thinners’. Anticoagulants reduce the ability of the blood to clot. They do not dissolve blood clots that have already formed. Instead, they prevent new clots from forming and stop existing clots from getting bigger. This allows your body time to dissolve clots naturally. Anticoagulants can be given as pills or injections. Blood-thinner pills are called oral anticoagulants. The most commonly used are warfarin and coumadin. The main type of anticoagulant that is given by injection is called heparin. Heparin can either be injected under the skin or given through a vein by a small pump that carefully controls the dose of medication. There are two types of heparin: low-molecular-weight heparin (LMWH) and unfractionated heparin (UFH).

What medication will I receive for DVT or PE?
Treatment of DVT or PE usually begins with heparin injections, either under the skin or through a vein using a small pump. This is because heparin works immediately but blood-thinner pills must be taken for at least 3 days before they are effective at thinning the blood. You will usually be started on blood-thinner pills and heparin at around the same time. Blood tests are used to check when the blood thinner is effective. Once the blood is thinned to the correct level by the blood-thinner pills, the heparin injections can be stopped. This usually takes around 5 to 7 days.

Doctors often prefer LMWH to UFH, which is the older form of heparin. This is because they now know that LMWH is better than UFH for the treatment of DVT and is at least as good for treating PE. In addition, LMWH is often more convenient for you because:

• the dose of LMWH is based on your body weight, whereas the dose of UFH depends on the results of blood tests which need to be done at least once a day
• you can easily inject yourself under the skin once or twice daily with LMWH, instead of receiving a continuous administration of UFH into a vein

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How will doctors know if I need treatment for more than 3 months?

Doctors have recently studied the risks and benefits of giving blood-thinner pills for different lengths of time to patients with blood clots in the veins. They found that some patients benefit from treatment with blood-thinner pills for 6 months or more to protect them against having another clot. The length of time that you should continue treatment will depend on your individual risk factors. Your physician can assess these risk factors and select the appropriate duration of treatment for you in order to reduce your chances of bleeding, while still reducing your chances of another clot. The risk of another clot after stopping treatment with blood-thinner pills depends on two main considerations:  where the blood clot was located whether you have continuing risk factors for a blood clot Patients at low risk of another clot are those with DVT in the calf and those with risk factors that are temporary or no longer present. Examples of temporary risk factors are recent surgery, trauma such as a broken ankle, or a short-term medical illness. Patients at high risk of having another clot are those with an ongoing risk factor. Ongoing risk factors include a medical illness that lasts a long time, such as cancer or any disease that causes you to spend a large amount of the day in bed and to be unable to move about. Patients who develop their first clot even though they have no known risk factors also have a high risk of a repeat blood clot. Using this knowledge, doctors have recommended that:

• patients who develop a blood clot associated with temporary risk factors should usually receive treatment for at least 3 months
• patients who have ongoing risk factors or who develop their first clot without having any known risk factors should usually receive treatment for at least 6 months

Your doctor will also have to take into account your risk of bleeding due to anticoagulant medication. All this information will be used by your doctor to determine the ideal duration of treatment for you.

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