Abstract
What is the post-thrombotic syndrome?
The post-thrombotic syndrome is a condition that sometimes occurs after deep vein thrombosis (DVT) of the leg, or, less commonly, of the arm. Veins are the blood vessels that return blood from the arms, legs, and organs to the heart. In DVT, blood clots form in the veins, often leading to pain, swelling, and redness of the affected limb. These symptoms usually subside, but some patients may go on to develop chronic pain, swelling, and skin changes in the affected leg; this is known as the post-thrombotic syndrome, or PTS. In PTS, symptoms may come and go, and in some patients symptoms may be made worse by prolonged sitting, standing, and sometimes by walking.
Much is unknown about PTS, but it is thought to occur when blood clots damage the valves of the veins, or when persistent blood clots block the flow of blood in the veins. Valves are small flaps of tissue that help keep blood flowing in only one direction. When they are damaged, blood can flow backward (called reflux), leading to swelling and chronic skin changes such as skin darkening (hyperpigmentation), hardening (induration), and, in severe cases, poorly healing sores (ulcers). Similarly, persistent blockage of the vein can cause these problems.
Who is at risk for PTS?
PTS occurs in 20–50% of people who have had a DVT in the legs. It is more common when the DVT affects the veins of the thigh or pelvis, and when clot fills a long segment of the vein. People who have had a recurrence of DVT in the same leg are up to seven to 10 times more likely to go on to have PTS than people with a first DVT, and recurrent DVT is the strongest risk factor for PTS. Others who are more likely to go on to have PTS are overweight or obese people and those aged 65 years and older.
Most patients with DVT are treated with anticoagulant medications, such as warfarin, also known as Coumadin, for at least 3 months after diagnosis. Warfarin treatment is monitored using a blood test called the international normalized ratio, or INR. Several studies have shown that patients whose INR is lower than it should be during the first 3 months of treatment are more likely to develop PTS than patients whose INR is at goal. Recently, newer oral anticoagulant medications have become available for treatment of DVT.
How is PTS diagnosed?
There is no blood test or imaging test that can diagnose PTS. Instead, PTS is diagnosed when someone with a previous history of DVT has leg symptoms such as pain and swelling, in combination with certain findings on physical examination of the leg. The recommended method for a health-care provider to diagnose PTS is known as the Villalta scale (Table 1). Using this scale, the health-care provider asks the patient to rate such symptoms as pain, cramps, itching, and burning of the leg as none, mild, moderate, or severe, with corresponding points of 0–3. Then the provider examines the legs for swelling, redness, dilated veins, skin changes, and other findings, using the same 0–3 scale. The points are summed and the resulting number confirms the diagnosis and its severity. In some cases, patients with previous DVT may have sores on the ankles, or ulcers, that are extremely difficult to heal. These patients are considered to have severe PTS. The leg of a patient with severe PTS is shown in Figure 1.
The Villalta scale used to diagnose post-thrombotic syndrome.
The left leg of a patient with severe post-thrombotic syndrome, with hyperpigmentation (dark brownish discoloration) and an ulcer (non-healing sore). The white appearance is due to a zinc oxide product used in wound care.
How is PTS treated?
PTS is challenging to treat. The mainstay of treatment is elastic compression stockings and leg elevation. Compression stockings may help reduce the size of dilated veins, increase blood flow in the veins, and decrease swelling in the leg (Figure 2). Patients are measured for stockings and instructed to wear them every day, putting them on when they first get up in the morning and taking them off before going to bed at night. Patients with PTS are advised to elevate their legs above the level of the heart several times a day to help with swelling and discomfort. Walking and other exercises of the lower legs may help improve circulation in the veins, so most patients are encouraged to walk and engage in exercises that strengthen the calf muscle and improve flexibility of the leg. Unfortunately, many patients may continue to have symptoms despite wearing stockings and elevating their legs. In these people, pneumatic compression pumps may be tried, along with horse chestnut seed extract, a plant extract that is purchased in health food stores.
Compression stockings remain the mainstay of treatment for PTS.
Patients with severe PTS and ulcers should receive care at a specialized wound care center, as ulcers are slow to heal. Ulcers require strict use of compression stockings (or compression bandages in some cases) to assist in healing.
How is PTS prevented?
Because PTS is difficult to treat, preventing it from occurring is essential. In the past, compression stockings were thought to be helpful in preventing PTS in patients newly diagnosed with DVT, but newer research has shown that they may not be effective. A procedure to break up the clot within the vein using ‘clot-busting’ drugs (fibrinolytic medications) is sometimes used in patients with extensive DVT, but it is not clear whether this potentially risky procedure helps prevent PTS from developing later. A large National Institutes of Health research study, known as the ATTRACT Study, is trying to answer this question (http://attract.wustl.edu).
The only reliable way of preventing PTS is preventing DVT from occurring in the first place. Many people who are hospitalized for medical illness or surgery, especially orthopedic surgery, are at risk for DVT, and most of them are candidates for receiving preventive doses of ‘blood thinners’ or anticoagulant medications while in the hospital. If you are hospitalized, you should always ask your health-care provider about your risk for DVT and make sure you are receiving the appropriate prevention.
Summary
The post-thrombotic syndrome is a fairly common long-term complication of DVT of the legs, and PTS is most likely to occur in people who have had recurrent DVT in the same leg. It is diagnosed based on symptoms and findings on physical examination including leg swelling and skin changes. It is treated using compression stockings, but many people may continue to have symptoms despite wearing stockings. Thus, the best way to avoid PTS is an aggressive approach to DVT prevention.
Footnotes
Declaration of conflicting interest
The authors declare that there is no conflict of interest.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.