Post-thrombotic syndrome (PTS) is a long-term complication that develops after a deep vein thrombosis (DVT)—a blood clot forming in a major vein, typically in the leg. Although DVT is often successfully managed, the acute event can leave lasting damage to the vascular system. This damage leads to a chronic condition that significantly impacts a person’s quality of life and daily function.
Defining Post-Thrombotic Syndrome
Post-thrombotic syndrome is a form of chronic venous insufficiency that occurs in a limb previously affected by DVT. This condition is a consequence of physical injury sustained during the initial clotting event, rather than a recurrence of the blood clot itself. It is characterized by persistent symptoms related to impaired blood flow in the veins.
PTS is a relatively common outcome following DVT, developing in approximately 20% to 50% of patients, even with appropriate initial treatment. For a diagnosis of PTS to be made, symptoms must typically persist or develop at least three to six months after the initial DVT episode. The severity of the syndrome varies widely, but around 5% to 10% of those affected will develop a severe form that includes debilitating venous ulcers.
Development can span from a few months to a few years after the original clot. Since symptoms can overlap with those of an acute DVT, diagnosis is intentionally delayed to ensure the symptoms are chronic, not residual effects of the initial event. PTS represents a shift from an acute clotting issue to a chronic problem of venous circulation.
How Vascular Damage Leads to PTS
The underlying cause of PTS is physical damage to the veins, resulting in chronic venous hypertension (high pressure within the veins). When a DVT forms, the clot triggers an inflammatory response that can directly injure the delicate walls of the vein. This inflammation and the thrombus often destroy or damage the one-way venous valves inside the affected vessels.
These valves prevent the backflow of blood as it travels up the leg toward the heart. Once damaged, the valves become incompetent, allowing blood to flow backward, a condition known as venous reflux. Additionally, the body’s process of dissolving the clot (recanalization) is often incomplete, leaving scar tissue that partially blocks the vein, known as residual venous obstruction.
Both venous reflux and residual obstruction contribute to chronic ambulatory venous hypertension, meaning pressure remains high, especially when standing or walking. This sustained, high pressure is transmitted to the smaller veins and capillaries in the lower leg. The pressure forces fluid and blood components out of the vessels into the surrounding tissue, leading to the long-term tissue changes characteristic of PTS.
Recognising the Symptoms
Symptoms of post-thrombotic syndrome range from minor discomfort to severely disabling skin changes and wounds. The most frequently reported symptoms involve the affected limb feeling heavy, achy, or tired, particularly toward the end of the day or after prolonged standing. Persistent swelling, known as chronic edema, is a common early sign and often lessens only after the leg is elevated.
Advanced stages of PTS involve changes to the skin and underlying tissue. Chronic venous hypertension causes a characteristic brownish discoloration, called hyperpigmentation, due to the leakage of red blood cells and iron pigment. The skin may also become hardened and thickened, a process known as lipodermatosclerosis, which can feel tender and restrictive.
The severity of the condition is often measured by a physician using a tool like the Villalta scale, which assesses five subjective symptoms and six objective signs. The scale assigns a score based on the presence and intensity of issues like pain, cramping, edema, and skin changes. The most severe manifestation of PTS is the development of a venous ulcer, an open, non-healing sore that forms due to long-standing venous pressure.
Strategies for Managing PTS
The primary goal of managing PTS is to reduce chronic venous hypertension and alleviate symptoms. Conservative measures are the foundation of treatment for nearly all patients. The most important measure is consistent compression therapy, typically administered through graduated elastic compression stockings.
These medical-grade stockings apply external pressure to the limb, counteracting the high pressure within the veins and reducing fluid leakage into the tissue. Patients with significant swelling may benefit from intermittent pneumatic compression devices. These devices use inflatable sleeves that cyclically squeeze the limb to help pump excess fluid out of the leg.
Lifestyle modifications play a significant role in symptom control, including regular physical activity, which strengthens the calf muscle pump and assists in venous return. Elevating the affected limb above heart level several times a day is also recommended to help drain excess fluid. For patients with severe PTS refractory to conservative measures, interventional procedures may be considered. These can include endovascular techniques like venous stenting or surgical repair of damaged venous valves, though these are reserved for select cases.