While one air passenger every month dies from a blood clot within minutes of landing at Heathrow Airport, deep vein thrombosis is still insurable. Carol Pearson finds out more
Deep vein thrombosis (DVT) is a disease of the circulation and is also known as venous thrombosis, blood clot in the leg, and 'the silent killer'.
DVT occurs when a blood clot forms in one of the body's large veins, blocking the blood flow. Blood that passes through the deepest veins in the calf or thigh flows relatively slowly and when a DVT occurs, it moves so slowly that a solid clot is formed. This then becomes wedged in the vein.
Although most deep vein clots occur in the lower leg or thigh, they can also occur in other parts of the body.
Severity
Deep vein clots in the upper leg are more serious than those in the lower leg because those in the thigh are more likely to travel to the lung.
A pulmonary embolism is a potentially life-threatening complication and occurs when a fragment of a blood clot breaks loose from the wall of the vein and travels to the lungs, blocking the pulmonary artery or one of its branches. The larger the DVT clot, the greater the risk of developing a pulmonary embolism. Symptoms of a pulmonary embolism may include shortness of breath, rapid pulse, excessive sweating, sharp chest pain and very low blood pressure.
A blood clot can also occur in veins that are close to the surface of the skin. This type of blood clot is called superficial venous thrombosis or phlebitis. Blood clots in superficial veins are not dangerous because they cannot travel to the lungs.
DVT is a different disease and does not occur in arteries, only in the large blood vessels that are enclosed by muscle and located in the centre of an arm, leg or lower body.
DVT can occur at any age but is much more common in older people.
Prolonged immobility is one of the primary causes for DVT since most blood clots form in the legs. People should think about their sitting position as sitting requires bending the knees. Maintaining this bent knee position for a long period of time puts pressure and squeezes the vein located behind the knee, which can lead to a blood clot. In this case, the blood clotting is mechanical, interfering with the flow of blood.
The other way blood clots form is chemical. The chemistry of the blood can cause a slow or sluggish flow of blood or cause the blood to clot too quickly. The use of hormones may have an effect on the make-up of the blood.
Symptoms
Only around half of the people with DVT have symptoms. The symptoms may include:
- Swollen area of the leg.
- Enlarged surface veins.
- Pain or tenderness in the leg. The pain is usually in one leg and may be felt only when standing or walking.
- Increased warmth in the area of the leg that is swollen or in pain.
- Red or discoloured skin.
Causes and factors that may increase the risk of developing DVT include:
- Immobilisation. This is the most common cause of slow blood flow in the vein, since movement of the leg muscles helps keep blood flowing through the deep veins. Sitting for long periods (four hours or more) reduces circulation in legs by 50%.
- Trauma to the leg. This is the most common cause of injury to a vein; such as broken bones, severe muscle injury, or surgery.
- Cancer and its treatment – about 20% of patients with symptomatic DVT also have a malignancy.
- Other medical conditions such as varicose veins, or an inherited blood clotting disorder.
- Childbirth. The physical strain of childbirth puts pressure on deep veins, causing them to weaken.
- Smoking tobacco damages blood vessels and doubles the risk of thrombosis.
- Obesity puts pressure on veins, causing them to weaken.
- Taking birth control pills or hormone therapy, including for postmenopausal symptoms.
- Having a central venous catheter, which accounts for almost one in 10 cases of DVT.
The main goals in treating DVT are to stop the clot from getting bigger; prevent the clot from breaking off in the vein and moving to the lungs; as well as reduce the chance of having another blood clot.
Several types of medicine may be used to treat and/or prevent DVT.
Anticoagulants, also known as blood thinners, decrease the blood's ability to clot. They do not break up blood clots that have already formed. The body itself dissolves most clots over time. Anticoagulants can be taken either as a pill (warfarin) or an injection (heparin).
Vena cava filters are used when someone cannot take medicines to thin their blood, or when they are taking blood thinners but continue to develop clots anyway. The filter catches clots that break off in a vein before they move through the bloodstream to the lungs (pulmonary embolism). The filter does not prevent new clots from developing.
Graduated compression stockings can reduce the chronic swelling that can occur after a blood clot has developed in a leg. The swelling is due to damage to the valves in the leg veins. The gentle pressure from the stocking keeps blood from clotting.
Carol Pearson is a Life and Disability Underwriter at Aegon Scottish Equitable
