Thrombosis (blood clot)

Thrombosis is a disease of the blood vessels in which a blood clot (thrombus) blocks the blood vessel. In most cases, the pelvic veins and the deep veins of the legs are affected. If a thrombus forms in the varicose veins (superficial veins), this is usually harmless to health - but it increases the risk of developing varicose vein inflammation (phlebitis).

In the case of blood clots in the deep veins of the legs, there is a great risk that the clot will become detached and then be transported with the bloodstream into the lungs, which can cause a so-called pulmonary embolism. This leads to an occlusion of a pulmonary vessel. The pulmonary embolism causes a sudden overload of the heart, which can lead to cardiac arrest.

There is also the possibility of blood clots forming directly in the heart cavities. Especially in people with atrial fibrillation, the risk of thrombus formation in the heart is greatly increased. It is very rare for such clots to form in arteries.

The risk of thrombosis increases with age. On average, about two out of every 1000 people contract this vascular disease every year.

There are three important factors that are causally involved in the development of thrombosis:

• Changes or damage to the vessel wall: for example, due to injuries, inflammation or deposits.
• Changes in blood viscosity (flow properties): thick blood clots more easily than thin blood.
• Slowing of the blood flow rate:for example, during long periods of sitting (air travel) or immobilisation after an operation.

There are many possible causes for a change in these factors. The following are the most important risk factors:

• Use of oral contraceptives (the pill)
• Smoking
• Obesity
• Infections

In about every second person affected, there are also genetic risk factors such as APC resistance (Factor V Leiden). This hereditary disease leads to an increased risk of thrombosis.

Very rarely, a repeated occurrence of thrombosis can also be caused by a previously undiagnosed cancer.

Thrombosis of the deep veins of the leg (DVT, deep vein thrombosis) does not cause any characteristic symptoms. In some cases, there is swelling of the leg. In addition, a feeling of heaviness in the leg and pain in the calves may occur. Elevation of the leg can improve the symptoms.

Thrombosis of the superficial veins can cause severe pain, but is usually harmless to health. The congested veins can be felt as thick strands under the surface of the skin.

Thromboses of the arm veins are also very painful. In these cases, there is also swelling of the arm and a pronounced vein pattern on the surface of the skin.

Because thrombosis often causes only diffuse pain and no clearly identifiable symptoms, a physical examination is first performed to help assess the likelihood of thrombosis. Typical symptoms of thrombosis are pain and swelling of the affected leg, as well as oedema that can be pressed in.

However, a definitive diagnosis can only be made with the help of duplex ultrasonography. This is a special ultrasound technique that can be used to visualise thromboses in the vessels. If the ultrasound is performed through the oesophagus (transoesophageal echocardiography), blood clots in the heart chambers can also be detected.

If there are still uncertainties after the sonography, a so-called phlebography can be performed. This is an X-ray examination in which contrast medium is injected into the veins. Nowadays, however, phlebography is only used in exceptional cases.

In addition, an increased concentration of D-dimer in the blood can be detected by laboratory diagnostics in the case of thrombosis. D-dimers are degradation products of fibrin in the blood - the body's own "glue" for blood clotting. If no D-dimer is detectable, thrombosis can be ruled out with certainty. However, if the value is elevated, this is not a confirmation of a blood clot, as the D-dimer can be elevated in numerous diseases (for example, cancers). The determination of the D-dimer is therefore used for exclusion diagnostics.

Dissolution of the thrombus

The type of therapy depends on the size, age and location of the blood clot. The following two therapeutic goals are the focus of treatment:

• Restoration of blood flow: this treatment goal can only be achieved within 10 days of thrombus formation.
• Prevention of enlargement of the blood clot

Restoration of blood flow can be achieved with the help of medication to dissolve the blood clots (thrombolysis). It is also possible to surgically remove larger thrombi (thrombectomy) or to bridge the blocked section of blood vessel by means of a vascular plastic (bypass).

The fact that the thrombus grows larger over time can be achieved by inhibiting blood clotting. Active substances such as heparin or vitamin K antagonists are used for this purpose.

Preventing thrombus formation

To effectively prevent the recurrence of a thrombus, treatment must be continued for at least six months. In some cases, even lifelong drug treatment is necessary. The use of compression stockings is recommended for blood clots in the leg veins. If possible, patients should avoid prolonged bed rest and make sure they get enough exercise (e.g. walking).

If, despite consistent drug therapy, thromboses repeatedly recur and there is a high risk of life-threatening pulmonary embolisms, a so-called cava shield can be inserted into the vena cava if necessary. This is a kind of sieve which is intended to prevent thrombi from being transported into the lungs with the bloodstream.

Patients who also suffer from atrial fibrillation should be treated with anticoagulant medication, even if no thrombi have been detected in the heart. In this way, the risk of a stroke can be significantly reduced.

Every thrombosis patient is at risk of developing another blood clot. About 30 percent of those affected suffer another thrombosis within 8 years. Men are affected about four times as often as women.

Patients often develop post-thrombotic syndrome after a thrombosis. This is a congestion of the superficial venous system and a permanent weakness of the veins. Post-thrombotic syndrome can lead to oedema (water retention in the tissue), varicose veins, dermatitis (inflammation of the skin) and the formation of ulcers.

The formation of a blood clot can have life-threatening consequences if the thrombus is carried with the bloodstream to the lungs (pulmonary embolism) or to the brain (stroke) and blocks a blood vessel there. In the worst case, embolisms can lead to death. In addition, a blood clot carries the risk of sepsis (blood poisoning) if the thrombus is colonised by bacteria and the inflammation can spread to the bloodstream in this way.

In order to effectively prevent these dangerous complications, the prevention of thrombosis is of particular importance. If possible, the onset of thrombosis should be detected and treated at an early stage.

To reduce the risk of thrombosis, common risk factors such as smoking and being overweight should be avoided. The risk of thrombosis is particularly high in women over thirty who take the pill and smoke.

Preventive medication can significantly reduce the risk of thrombosis. The active ingredient heparin partially inhibits blood clotting, thus preventing the formation of blood clots.

In order to prevent thrombosis as a result of resting after an operation, sufficient exercise should be resumed at an early stage. This increases the speed of blood flow in the veins, which reduces the risk of thrombosis.

To prevent thrombosis, the following points should be observed:

• Leading a smoke-free life
• Healthy diet and weight
• Exercise can reduce the risk of thrombosis - endurance sports are particularly recommended (long walks and cycling also reduce the risk).
• Vein exercises (vein pump) can help prevent blood clots.
• Women with a high risk of thrombosis should avoid the "pill" and, if necessary, use another contraceptive after consulting their doctor.
• Varicose veins should be treated by a doctor.
• Drink enough (e.g. water, tea) so that the blood becomes fluid
• Avoid wearing tight, constricting clothing that restricts blood flow.
• If support stockings are used, they should not be too tight.