Overview

Post-thrombotic syndrome describes the long-term effects that can happen after a blood clot (called a deep vein thrombosis or DVT) in the legs.

About 1 in 3 (33%) people who have a DVT get some level of post-thrombotic syndrome within 5 years. However, most symptoms happen within the first 2 years. There's a higher risk of post-thrombotic syndrome if:

• you have a history of more than 1 DVT (recurrent DVT)
• your first DVT was extensive and affected the veins in your pelvis and groin

A DVT causes a blockage in the vein, which affects the blood flow from the leg back to the body. At first this is managed with anticoagulant medicines, which stop the blood clotting as quickly as usual.

Sometimes, despite this treatment, some blockage remains and can lead to symptoms of post-thrombotic syndrome.

DVT can also damage the valves in the veins, which help the blood return to the heart. Veins that are scarred with old clots, and damaged valves, can cause:

• post-thrombotic syndrome
• chronic venous insufficiency, which is when your leg veins do not allow blood to flow back up to your heart as fast as it should

Thrombosis may not show any symptoms (asymptomatic). This means that post-thrombotic syndrome can appear even if you have not previously been diagnosed with DVT.

Symptoms of post-thrombotic syndrome

The symptoms of post-thrombotic syndrome are diferent for each person. They may include:

• long-term (chronic) pain, aching and heaviness of the leg
• itching
• pins and needles
• swelling (oedema) of the leg
• varicose veins
• patches of darker skin (hyperpigmentation) around the ankle and lower leg (this may be more difficult to see on brown or black skin)
• severe cases of breaks on the skin (ulceration)

Chronic venous insufficiency

Some of the symptoms of post-thrombotic syndrome also affect people who have not had a DVT. These cases are called chronic venous insufficiency.

Pain, heaviness and swelling of the leg are often worse after sitting or standing for long periods. Activity such as walking usually helps with these symptoms.

If you have severe symptoms that are not treated, this can lead to skin ulceration (particularly around the ankles).

We normally use a tool called the Villalta score to measure how severe your symptoms are. The clinical nurse specialist (CNS) does this assessment when you come to the clinic.

Differences between DVT and post-thrombotic syndrome

It's often difficult to tell if you have:

• a new DVT
• the long-term effects from post-thrombotic syndrome

The risk of having more than 1 DVT (recurrent DVT) depends on the original cause of your DVT. If you have recurrent DVT, this might be because of an underlying blood clotting issue. A doctor who specialises in blood disorders (haematologist) will investigate, if necessary.