Deep Vein Thrombosis
A deep vein thrombosis (DVT) is a blood clot that forms in a deep leg vein. These are blood vessels which go through the muscles (not the veins which you can see just below the skin). A calf vein is the commonest site for a DVT whereas thigh veins are less commonly affected.
The following increase the risk of having a DVT.
- Immobility causes blood flow in the veins to be slow and slow flowing blood is more likely to clot.
- A surgical operation lasting more than 30 minutes is the commonest cause of a DVT.
- Any illness or injury that causes immobility increases the risk of a DVT.
- Long journeys by plane, train, etc are thought to cause a slightly increased risk of DVT.
- Faulty blood clotting.
- The contraceptive pill and hormone replacement therapy (HRT) have a small increased risk of a DVT.
- Damage to the inside lining of the vein – if you have already had a DVT, then you have a higher than average risk of having another one sometime in the future.
- Older people are more likely to have a DVT, particularly if you have poor mobility or have a serious illness such as cancer.
- Pregnancy increases the risk. About 1 in 1000 pregnant women have a DVT.
- Obesity increases the risk of having a DVT.
Symptoms of DVT
Typical symptoms are pain, tenderness and swelling of the calf which then becomes warm and red. Sometimes it is difficult for a doctor to be sure of the diagnosis as there are other causes of a painful and swollen calf. You will be seen urgently if you have a suspected DVT and tests will be done to confirm the diagnosis.
There are two potentially serious complications; Pulmonary embolism/ Venous ThromboEmbolism, sometimes referred to as VTE (a blood clot which travels to the lung) and post thrombotic syndrome (persistent calf symptoms).
Pulmonary EMBOLISM/Venous Thromboembolism/vte
In a small number of people part of the blood clot breaks off. This travels in the bloodstream to the heart and gets stuck in the lung. A small pulmonary embolus may not cause any symptoms however, a medium sized embolus can cause breathing problems and chest pain and a large embolus can cause collapse or sudden death.
Without treatment six in ten people who have a DVT develop long-term symptoms in the calf called ‘post-thrombotic syndrome’. These include: calf pain, discomfort, swelling and rashes. An ulcer on the skin of the calf may develop in severe cases. Post-thrombotic syndrome is more likely to occur if the DVT happens in a thigh vein.
The aim is to avoid long periods of immobility which could result in the blood ‘pooling’, activities such as a brisk walk for 30-60 minutes will provide considerable benefits and even sitting calf-excessive will significantly improve the circulation.
Major surgical operations are known to be a risk for a DVT – particularly operations to the hip, lower abdomen and leg. A patient may be given aspirin or heparin prior to a procedure and it is common practice to be asked to exercise shortly after an operation.
When travelling on long plane or train journeys, it is important to take little walks up and down the aisle every so often and exercise calf muscles every now and then whilst sitting in your seat.
The aims of treatment are:
- To prevent the clot spreading up the vein and getting larger.
- To reduce the risk of post-thrombotic syndrome developing.
- To prevent a further DVT in the future.
Anticoagulation alters certain chemicals in the blood to stop clots forming. Initially heparin injections are used followed by warfarin, a serious embolus is rare if anticoagulation treatment is started early after a DVT.
Using compression stockings reduces the risk of developing post-thrombotic syndrome substantially and as symptoms of post-thrombotic syndrome may develop even several years after a DVT, wearing the stocking is a long-term necessity.
If advised to wear a compression stocking it is best to dress whilst lying in bed before getting up and wear it for the entire day until sleep or until rest in the evening with the leg raised.