Introduction

Post-thrombotic syndrome (PTS) is a common complication of deep vein thrombosis (DVT), which is characterised by a blood clot in the deep veins, typically in the lower limb. This can cause damage to the venous valves. Under normal conditions, when we walk, our calves act as pumps, pushing the blood up the veins towards the heart. The valves help to hold the blood in compartments as it travels up the leg, against gravity. Valve damage impairs the veins’ ability to hold blood up, causing blood to return down the leg, which is called venous insufficiency. AReduced blood flow from the leg and foot can increase venous pressure, and oedema (fluid retention), as blood moves into tissues, resulting in pain, swelling, and, in severe cases, leg ulcers. 

As DVT causes PTS, the causes are closely linked. Multiple episodes of DVT majorly increase the likelihood of developing PTS symptoms. Additional risk factors include blood coagulation disorder, pregnancy,  and long periods of inactivity (such as prolonged hospital stay) amongst others. 

Understanding thrombosis

Thrombosis occurs when a blood clot forms within a blood vessel, partially or completely blocking it and disturbing the normal flow of blood.  When a vessel is injured, thrombosis (or blood clotting) is a natural reaction to prevent excessive bleeding and promote healing. Blockages can occur in both arteries and veins. Arterial thrombosis reduces blood flow going to tissues as in the cases of stroke and heart attack. In veins, thrombosis stops blood from returning to the heart, and, when this occurs in the deep veins, it is called a deep vein thrombosis (DVT). A DVT can become life-threatening if the clot breaks off and travels to the lungs, causing a blockage in a lung artery (pulmonary embolism). The most common sites for thrombosis are the lower leg, thigh, pelvis, and occasionally the arm. Symptoms of DVT include throbbing pain and swelling, (usually in just one leg), and warm skin that can be painful to touch.¹

Causes and risk factors

While anyone can develop a DVT, certain factors increase the risk. These include:²

• Injury to veins, caused by fracture or surgery
• Slow blood flow due to bed confinement, paralysis, or prolonged periods of inactivity such as during air travel
• Increased oestrogen levels from contraceptive pills, hormone replacement therapy or pregnancy
• Chronic illness, such as heart and lung disease, cancer, or inflammatory bowel disease
• Previous DVT
• Family history of DVT
• Increasing age
• Obesity
• Blood coagulation disorders
• A catheter located in a central vein

Clinical features of post-thrombotic syndrome

Symptoms of PTS can range from mild to severe and they include:²

• Chronic pain, cramping and aching in the affected leg
• Itching, tingling or pins and needles in the leg
• Swelling and oedema
• Skin changes, discolouration and thickening
• Varicose veins
• Venous ulcers

Diagnosis of post-thrombotic syndrome

The assessment of post-thrombotic syndrome largely relies on clinical examination, as there is currently no definitive test recommended as the gold standard. The Villalta scale is the main clinical assessment used to diagnose lower extremity post-thrombotic syndrome. The test is based on the assessment of 6 subjective symptoms, 6 objective signs, and whether there is venous ulceration. A diagnosis of post-thrombotic syndrome and its severity is confirmed if there is a venous ulcer or if the score is above 5.

For patients with significant symptoms, it is wise to investigate potential venous issues that could require treatment, like persistent blockages. The primary imaging methods used for this assessment include venous duplex, intravascular ultrasonography (IVUS), and venography. 

During venous duplex, an ultrasound machine is used to assess the direction of the blood flow in the leg veins, and identify any blockages or narrowing in the vessels. The scan usually starts in the groin and involves ultrasound gel, to ensure adequate transmission of the ultrasound waves.

Venography, on the other hand, is an X-ray examination where contrast is injected and blood flow through the veins is assessed. While venography is the most accurate form of imaging, it is ionising, invasive and more expensive than Duplex ultrasound.

Intravascular ultrasound (IVUS) is a technique for imaging inside blood vessels. It uses a specialised catheter with ultrasound technology to create images from within an artery, creating images with a complete 360-degree perspective of the vessel.

Diagnosis also involves a physical examination to assess the lower limb for signs of PTS such as lower limb swelling, skin discolouration or ulceration. A detailed medical history, including any previous DVT episodes, is also taken.³

Prevention strategies

Early detection and treatment of DVT is essential. Lifestyle modifications can reduce risk, such as regular exercise, to keep the blood pumping through the veins. During long periods of sitting or travel, ensure to walk around every hour, and carry out exercises including ankle rotations and buttock squeezes. After surgical procedures follow medical advice and start light exercise as soon as possible. Maintaining a healthy weight and quitting smoking can also help. Studies have indicated that smoking can increase the rate of blood coagulation, thereby increasing the risk of DVT.⁴

Treatment options for post-thrombotic syndrome

Compression stockings can help alleviate swelling associated with PTS by squeezing the ankle and calf to encourage the movement of blood flow back up the leg. This action lowers venous pressure in the leg, subsequently decreasing swelling. Different strengths of compression stockings are available, depending on the severity of venous insufficiency, and therefore the amount of pressure required. They come in different strengths, categorised into Class I, II, or III, with Class III applying the highest pressure.⁵ 

Medications are also available to manage symptoms and improve blood flow. After DVT, anticoagulants are prescribed to reduce the chance of developing PTS and also prevent future DVT. Anti-inflammatory medications, vasoactive drugs, antibiotics and diuretics may also be required.^6,7 Pain relief medication such as paracetamol, aspirin, and pentoxifylline can help to heal ulceration caused by venous insufficiency. Elevation of the affected limb can also help with venous return and reduction of swelling.⁸

Leg ulcers in the context of post-thrombotic syndrome

Venous insufficiency in the leg, caused by damage to the veins, can increase venous pressure, and cause fluid movement into the surrounding tissues, leading to oedema. High venous pressure can result in open sores on the skin, otherwise known as ulcers. Additionally, inflammation within the venous circulation, the vein wall and valve leaflets can contribute to ulceration. Venous ulcers have an irregular shape, with well-defined borders. Commonly reported symptoms can include a feeling of heaviness in the limbs, itching, discomfort, and swelling that tends to worsen as the day progresses and improves when the limbs are elevated. During a physical examination, indications of venous issues, such as varicose veins, swelling, or venous dermatitis, might also be observed.^8,9

Management of leg ulcers

Leg ulcers can drastically impact daily life. Regular wound cleansing can encourage healing by removing bacteria, dead tissue and excess fluid from the surrounding area. Compression stockings can also improve circulation and promote ulcer healing. Moisturising skin can prevent skin dryness and deterioration, leading to ulceration development. Furthermore, surgical interventions can promote ulcer healing. Superficial veins with insufficiency, where the valves do not work properly and cannot stop blood trickling back down the leg, can be treated with minimally invasive procedures such as radiofrequency ablation (RFA), foam sclerotherapy, or endovenous laser treatment (EVLT).^7,10

Quality of life and prognosis

PTS and leg ulceration can significantly negatively affect daily life, particularly affecting mental health. Symptoms such as depression, anxiety and decreased self-esteem can be common, and the presence of ulceration can lead to self-consciousness and social isolation. Sufferers may find it difficult to stand or sit for long periods, affecting their ability to work. This can lead to financial difficulties, along with other burdens such as the cost of medication, bandages, and time off work for surgical interventions. Additionally, there can be strain on relationships, as more help may be needed for daily tasks, and sufferers may find it difficult to attend social gatherings with family and friends. 

The long-term outlook and prognosis depend on the severity of symptoms, overall health and lifestyle, and medical treatment. While PTS is a chronic condition with no current cure, treatments can greatly help to manage symptoms and help improve quality of life. Proper wound care and management, can improve ulcers over time, and some surgical treatments can aid this.

Summary

Post-thrombotic syndrome is caused by a previous DVT, leading to venous valve damage, resulting in venous insufficiency and lead to symptoms such as chronic swelling, pain, skin changes and venous ulceration. Diagnosis involves medical examination, and imaging studies, such as venous ultrasound and venography. Conservative treatment options for PTS symptoms include compression stockings and medical therapy such as anticoagulation. Surgical treatment options are also available to treat insufficiency in the superficial veins, helping to reduce overall leg swelling and aching. Ulceration can significantly impact physical and mental health, and finances, but with adequate treatment, ulceration can heal and quality of life can be improved. Greater awareness of DVT and the associated symptoms is crucial to prevent DVT development and subsequently PTS. Early intervention is also essential to improve outcomes.