The Post-Thrombotic Syndrome

What is the post-thrombotic syndrome?
The post-thrombotic syndrome (PTS) is a complication from having had a blood clot known as a deep vein thrombosis (DVT). Many people who have had a DVT of the leg or arm recover completely; others may be left with symptoms and physical signs in the affected limb(s) that are collectively known as the post-thrombotic syndrome. Overall, PTS occurs in 20-40 percent of patients after an episode of lower extremity DVT, making it the most common complication. PTS can still occur even though appropriate anticoagulant treatment for DVT was given.

Why is PTS a problem?
PTS is a frequent side-effect of DVT and, while symptoms can wax and wane over time, it is a chronic, lifelong condition. PTS leads to patient suffering and disability and is costly to society. Severe PTS can cause painful venous ulcers or sores that are difficult to treat and tend to recur. They occur in 5-10 percent of patients.

Why does PTS occur?
When a clot forms in a vein, the valves inside the vein can be damaged by the clot or by the surrounding inflammation. The damaged valves as well as residual clot create an obstacle for blood returning from the leg veins back to the heart, which results in increased venous pressures in the leg.

What are the symptoms of PTS?
Typical symptoms of PTS include leg pain, aching, heaviness or tiredness, swelling, cramping and itching. The number and type of symptoms may vary from person to person. Symptoms tend to get worse when standing or walking, and tend to improve with rest and leg elevation. Clinical signs of PTS that may be seen on the leg include leg edema (swelling), brownish skin pigmentation, bluish discoloration of the leg/foot/toes, especially when standing, formation of new varicose veins, dry flaky skin (eczema), hardening of the skin and leg ulceration (typically above the ankle bone on the inside of the leg). PTS usually develops within the first six months after DVT, but can occur up to two years after the clot.

What are the risk factors for developing PTS after DVT?
It is difficult to predict which patients with DVT will go on to develop PTS. Nevertheless, several factors have been identified that appear to increase a person's risk. These include larger and more extensive DVTs (i.e., those occurring higher up in the leg veins), obesity in patients and having another DVT in a leg with a previous DVT. Older age and poorer quality of anticoagulation (medication used to keep the blood from forming clots)¹ for the initial DVT may also be risk factors. Recent studies also indicate that persistence of DVT symptoms and signs at one month after the blood clot are associated with a higher risk of developing PTS.

Prevention and treatment of PTS
Compression stockings (knee-length, Class II compression of 30 to 40 mmHg) worn daily for two years after DVT have been shown in some studies to reduce the risk of developing PTS. These may be cumbersome to wear for some patients, and research on the benefit of compression stockings for the prevention of PTS is still ongoing. However, the JCAHO and American College of Chest Physicians highly recommend their use.

Preventing recurrence of DVT is also important. This is achieved with appropriate duration of anticoagulation therapy for the initial DVT event and the use of various preventive steps during high-risk periods once the patient stops taking anticoagulants.

Steps that may help patients who already have PTS include leg elevation, use of compression stockings during the day to reduce leg edema, analgesics (painkilling medication) for pain management, and various intermittent compressive devices to help reduce the swelling for severe cases of PTS. Leg ulcers require specific care with compressive and topical therapies.

Surgical or balloon dilation procedures on the deep leg vein(s) such as catheter-directed thrombolysis (dissolving of the clot) are not currently recommended as standard of care for the treatment of PTS, although some studies have shown that aggressive treatment of a DVT during the acute stages using these and other techniques may help prevent PTS. It is not yet known whether weight loss or exercise aimed at strengthening the leg muscles have a role to play in treating PTS, but these are usually recommended. Plus, maintaining a normal body weight and exercising regularly (30 minutes per day on most days of the week) are important for overall cardiovascular health.

As current options to prevent and treat PTS each have limitations, more research is needed on better ways to manage PTS.

1. (i.e., INRs that are too low in the initial few months of therapy) International Normalization Ratio (INR) is the standard unit for reporting the clotting time of blood.

About the Authors:
Nathalie Routhier, MD is Assistant Professor at University of Montreal. She trained as a Fellow in Thrombosis at the Jewish General Hospital in Montreal and completed a Master's Degree in Neuroscience at McGill University. She is a working as staff in Internal Medicine specialized in Thrombosis at Sacré-Coeur Hospital in Montreal.

Susan R. Kahn, MD is an internist and clinical epidemiologist based at the Jewish General Hospital in Montreal, where she is Director of the Thrombosis Program. She also is Professor with Tenure in the Department of Medicine and Associate Member in the Department of Epidemiology and Biostatistics, McGill University. Dr. Kahn holds a National Research Scholar award from the Fonds de la recherche en santé du Québec, has been awarded numerous peer-reviewed research grants and has published and presented widely in the field of thromboembolism.