Thrombosis

What is thrombosis?

The medical term thrombosis describes a partial or complete occlusion of a blood vessel by a blood clot (thrombus). 

Veins are characterized by the function of transporting venous blood from peripheral organs back to the heart. Venous blood flow is relatively slow, which predisposes the vessels to blood clot formation.

The most common type is a deep vein thrombosis (DVT) of the leg. However, venous thrombosis can also occur in pelvic veins, or more rarely, in veins of the upper extremity.

Alongside venous thrombi, arterial thrombi can form. Nevertheless, arterial thromboses are far less common as arteries – transporting blood from the heart to peripheral organs – have a significantly faster blood flow and thicker muscular walls. Another form is cardiac thrombosis, which occurs within the heart.

The likelihood of developing thrombosis increases with age. It is estimated that one in 10,000 people under the age of 60 suffer from deep vein thrombosis annually. In contrast, the incidence rises to one in 100 in individuals aged over 60.

What are the risk factors & causes for developing thrombosis?

The development of a thrombosis can be explained by three factors that form the so-called Virchow’s triad: reduced blood flow (venous stasis), changes in the vessel walls (endothelial injury) and changes in blood composition (hypercoagulability). These are the three main causes of blood clot formation.

Moreover, various risk factors can be identified that contribute to the development of thrombosis.

These include, especially a history of thrombosis and pulmonary embolisms in the past, and prolonged periods of immobilization, for example after long-haul flights or surgery. These factors are associated with a 20- to 30-fold increase in the risk of thrombosis. 

Furthermore, lack of physical activity, obesity, heart conditions (e.g., heart failure,myocardial infarction), smoking, combined oral contraceptive pills, pregnancy, malignant tumors, and clotting disorders (e.g., thrombophilia) are risk factors. Additionally, individuals aged 60 years and over have a higher risk of developing thrombosis.

How does thrombosis manifest?

The symptoms of thrombosis can vary. In addition, many conditions may present with similar symptoms, making a thorough diagnostic evaluation necessary for accurate diagnosis. The most common symptoms are the following:

• Swelling or increased circumference of the affected leg
• A feeling of heaviness and tension in the leg, pain similar to muscle soreness
• Leg tenderness with calf pain during movement
• Shiny skin and warmth over the affected area

Less commonly, thrombosis can cause flu-like symptoms such as fever, increased pulse, and elevated inflammatory markers in the blood.

In general, in only about 50% of cases, thrombosis is diagnosed based on clinical findings. The absence of symptoms does not exclude the diagnosis. In some cases, thrombosis is first detected after the patient presents with a pulmonary embolism as a complication.

50% of patients with deep vein thrombosis present with minor pulmonary embolisms. These form when a blood clot, or part of it, is transported to the heart, from where it is pumped to the lungs. The embolus can become lodged in a pulmonary artery and block blood flow.

Pulmonary arteries transport oxygen-poor blood from the heart to the lungs, where it can be enriched with oxygen. However, in most patients with deep vein thrombosis, a pulmonary embolism remains asymptomatic. The highest risk for pulmonary embolism is in the case of a thrombosis in the pelvic veins.

Around 40% of patients with thrombosis develop chronic venous insufficiency.  This means that the venous outflow of blood is impaired, disrupting the distribution of blood in the affected area (microcirculation disorders). This results in some areas of the affected leg – mostly the lower leg and foot – receiving a reduced blood supply.

Thrombosis specialists: Which physician is a specialist?

The definitive diagnosis of a thrombosis is usually made by a specialist in internal medicine. Various methods can be used to diagnose the condition. The diagnostic evaluation starts with a thorough medical history, during which risk factors for thrombosis are assessed. A physical examination is conducted subsequently.

The risk of a thrombosis is assessed using a so-called Wells-Score. Points are assigned to specific risk factors, and the total score is calculated based on the presence of these factors. The resulting score determines whether the probability of a DVT is high or low.

The next step includes a blood workup, with particular relevance placed on the D-dimer test. If its value is negative, a thrombosis can be ruled out with high probability. In the case of a positive value, further tests are necessary to determine if it is caused by a thrombosis.

Furthermore, a color duplex sonography (also called Doppler ultrasound) can be used to visualize veins blocked by a thrombus. This method allows for assessment of blood flow, determining whether it is reduced or normal. If the ultrasound examination is not conclusive, a phlebography can be performed. This includes the injection of a contrast agent, followed by CT or MRI imaging to visualize the veins and detect possible narrowing.

Therapy: How is a thrombosis treated?

The treatment of a thrombosis aims to prevent its progression and avoid a pulmonary embolism as a complication. Moreover, the affected vessel should be cleared as quickly as possible.

General measures

If a patient can move freely despite suffering from a thrombosis, they should continue to do so. Immobilization is only required in the case of severe pain or for the duration of a therapeutic intervention. In all other cases, it is otherwise contraindicated.

One of the first measures involves wrapping the affected leg until it is replaced by a fitted compression stocking. This step aims to prevent later venous insufficiency.

Medications

Treatment should include anticoagulation i.e., medications that inhibit blood clotting. These are commonly known as blood thinners. Studies have shown that their use has lowered the risk of developing a pulmonary embolism by approximately 60%.

Anticoagulation can be taken orally or administered by injections.

In order to prevent the recurrence of thrombosis, it is recommended to continue anticoagulation for another three to six months. If particular risk factors are present, this period may be extended.

In cases of recurring thrombosis or a thrombosis of unknown origin (idiopathic), long-term anticoagulation may be necessary. Alongside anticoagulation with heparin, so-called factor Xa inhibitors can be used, which block a specific coagulation factor involved in blood clotting.

Further measures

As an alternative to the above-described anticoagulation, thrombolysis can be performed to clear the vessel of a thrombus. This form of treatment reduces the risk of developing venous insufficiency.

These advanced measures are performed as part of a quick surgical procedure. The thrombus can be removed from the vessel using a catheter. This procedure is called a thrombectomy and can be used in combination with thrombolysis.

Thrombolysis differs from anticoagulation in that it uses substances that actively dissolve an existing blood clot.

However, this procedure is less commonly performed as the risk of bleeding elsewhere in the body increases. Indications for thrombolysis include occlusion of a pelvic vein with pronounced symptoms, massive pulmonary embolism, or complete occlusion of all veins in a limb.

How can thrombosis be prevented? 

Thrombosis prophylaxis involves the minimization of modifiable risk factors. For example, prolonged immobilization should be avoided, or if necessary, should be accompanied by additional preventative measures.

During long-haul flights, long car or train journeys, individuals should be encouraged to maintain physical activity. It is recommended to stand up and take a few steps in between. This activates the muscle pump and improves venous blood flow.

In cases of obligatory immobilization, for example, following surgery, patients are given heparin injections and compression stockings to prevent thrombosis. Furthermore, the duration of immobilization should be kept as short as possible, while early mobilization should be initiated promptly.

Following previous thrombosis or pulmonary embolism, patients should receive long-term oral anticoagulation treatment. The duration of anticoagulant treatment depends on the individual risk. Thus, the benefits of prophylactic measures and the risk of bleeding must be taken into account.

Complications and prognosis

The prognosis of a thrombosis depends on the extent and location of the vessel occlusion. The prognosis is very good if the patient does not develop a pulmonary embolism or chronic venous insufficiency as a complication of thrombosis.

However, about 20-50% of all patients with DVT develop chronic venous insufficiency as a long-term complication, though most patients remain mildly symptomatic. The risk of this complication is significantly lower in upper extremity thrombosis.

About half of DVT cases are associated with the development of pulmonary embolism. Although the majority of these cases are clinically mild, a fulminant pulmonary embolism is associated with a high mortality rate. Therefore, accurate diagnosis and treatment are essential.

What physicians and clinics are specialists for thrombosis?

Since thrombosis can lead to serious complications, a thorough diagnostic evaluation and appropriate treatment should be carried out when a pulmonary embolism is suspected. Specialists in internal medicine and vascular medicine are typically responsible for the treatment of thrombosis. Vascular surgeons should be consulted when surgical interventions become necessary.

As the prognosis of the condition depends heavily on the expertise of the treating physician, we made it our mission to connect patients with qualified medical specialists. All physicians listed here have been carefully selected. They are experts in their respective fields and have extensive experience in the treatment of thrombosis. See for yourself the expertise of our specialists and schedule a personal consultation today.