Conditions: Venous Thrombosis
A venous thrombosis is a blood clot within a vein. A deep venous thrombosis (DVT),is when a venous thrombus occurs in a larger vein, usually in the legs or pelvis. If some clotted blood breaks loose and is carried downstream by flowing blood, the clot may end up in the lungs, a condition called pulmonary embolism. This may be life-threatening.
What is a venous thrombosis?
Venous thrombosis is blockage of a vein caused by a blood clot. A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins, such as in the legs or pelvis. About one third of DVTs involve a condition called pulmonary embolism, in which clotted blood breaks off (embolizes) and flows to the lungs to lodge there, which increases health risk. Superficial venous thrombosis or phlebitis affects the superficial veins of the upper or lower extremity.
Why is venous thrombosis a problem?
The most frequent long-term deep venous thrombosis complication is the less dangerous post-thrombotic syndrome, which can cause pain, swelling, a sensation of heaviness, itching, and in severe cases, skin ulcers.
The most common life-threatening concern with deep venous thrombosis is the potential for a clot to detach from the vein lining and become lodged in a pulmonary artery that supplies blood to the lungs. This is called a pulmonary embolism (PE). Pulmonary embolism is found to occur in about one third of cases of deep venous thrombosis.
Venous thrombosis recurs within ten years in about 30% of individuals after the first venous thrombosis.
What causes a venous thrombosis?
The mechanism behind venous thrombosis formation typically involves some combination of decreased blood flow, increased tendency to clot, changes to the blood vessel wall, and inflammation. Risk factors include recent surgery, older age, active cancer, obesity, infection, inflammatory diseases, antiphospholipid syndrome, personal history and family history of venous thrombosis, trauma, injuries, lack of movement, hormonal birth control, and pregnancy. Venous thrombosis has a strong genetic component. Genetic factors include non-O blood type, deficiencies of antithrombin, protein C, and protein S and the mutations of factor V Leiden and prothrombin G20210A. In total, dozens of genetic risk factors have been identified.
Venous thrombosis becomes much more common with age. The condition is rare in children, but occurs in almost 1% of those older than 85 years annually.
HOw is venous thrombosis prevented?
Prevention of venous thrombosis for the general population includes minimizing the risk factors, particularly avoiding obesity, avoiding smoking and maintaining an active lifestyle. Preventive efforts following low-risk surgery include early and frequent walking. Riskier surgeries generally prevent venous thrombosis with a blood thinner or aspirin, compression stockings, and/or with intermittent pneumatic compression devices on the calves.
Deep venous thrombosis in the right calf (arrow). Image Source: James Heilman, MD, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
How is venous thrombosis identified?
Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some deep venous thromboses have no symptoms.
People suspected of having a deep venous thrombosis can be assessed using a prediction rule such as the Wells score. A “D-dimer” blood test can also be used to assist with excluding the diagnosis or to signal a need for further testing. Diagnosis is most commonly confirmed by ultrasound of the suspected veins.
How is venous thrombosis treated?
The initial treatment for venous thrombosis is to use medicine to make blood less likely to clot, so that a present clot does not expand to a larger clot. Typical medications to “thin” the blood include heparin, rivaroxaban, apixaban, warfarin, aspirin, and clopidogrel, “Thinning” the blood tips the delicate balance away from clotting but toward bleeding, which can also be a major problem. Some blood thinning medications act are active longer than others; the longer-acting medications, while more convenient, may require reversal if significant bleeding were to occur. Reducing the risk of pulmonary embolism may also be achieved through a procedure that places a filter in the main vein running from the pelvis up to the heart (the vena cava). Superficial venous thrombosis or phlebitis affects the superficial veins of the upper or lower extremity and only require anticoagulation in specific situations, and may be treated with anti-inflammatory pain relief only.