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Deep Vein Thrombosis (DVT)

As the name suggests, deep vein thrombosis (DVT) is caused by clot and thrombus forming in the deep veins of the leg. The deep veins are blocked and the leg becomes swollen and painful. This is an emergency which requires hospital treatment because sometimes clot and thrombus can break off from the veins in the leg and lodge in the lungs - a pulmonary embolus. A large pulmonary embolus can be fatal.

Initial treatment requires blood thinning drugs such as heparin and Warfarin to stop further clot forming in the veins and to prevent pulmonary embolus.

DVTs are more common in patients on the contraceptive pill, during pregnancy, after surgical operations or people who have fractures of the leg bones requiring immobilisation of the leg in plaster. Some people have an inborn tendency to thrombosis or are prone to thrombosis because of another illness.

In most patients the body removes the clot and thrombus from the deep veins so that they reopen. However, this takes many months and although the vein is open again the valves are permanently destroyed resulting in a condition known as deep venous insufficiency. This often results in a permanently swollen leg which is prone to ulceration. In some patients severe swelling of the leg persists because segments of the deep veins remain blocked - a condition known as deep venous obstruction.

The cause of persistent symptoms can be diagnosed by a combination of specialised non-invasive diagnostic tests including colour Duplex ultrasound and venous plethysmography.

Travel-related deep vein thrombosis:
Economy class syndrome

The risks of DVTs occurring during travel and air travel is not a new phenomena as the condition was first reported back in the 1950s. Neither is the condition confined to air travel. Many patients are at risk of DVT during long distance car, coach and rail travel and this is well reported in scientific literature.

The title of economy class syndrome is also misleading. Upgrading to business class or even first class will not necessarily protect you. The most famous victim of in flight DVT was American president Richard Nixon on board the presidential jet, Air Force One, travelling back from a visit to China.

Certain people are at increased risk of travel related DVT in general. These include:

  • people with varicose veins, venous eczema, venous ulceration
  • previous deep vein thrombosis (particularly with persistent leg swelling)
  • recent surgery or childbirth
  • family history of DVT or certain blood disorders
  • significant medical conditions such as diabetes, cancer, and heart failure

Prevention of travel-related DVT

The main causative factors are thought to be dehydration, which makes the blood thicker and more likely to thrombose (clot) and lack of leg muscle contraction which causes less pumping of venous blood out of the leg.

Many people are at increased risk before they ever get on the plane because the whole airport experience, including travelling to the airport, is associated with sitting around and either not drinking or drinking dehydrating agents such as coffee and alcohol. The plane journey itself merely finishes off a process which started hours before.

General measures you can take to try and reduce the risk are:

Avoid dehydration - drink plenty of fluids before, during and after the journey and avoid dehydrating beverages like tea, coffee and alcohol.

Exercise - there are three venous muscle pumps in the leg - the foot, the calf muscle pump and the thigh pump. Use these muscle groups regularly before, during and after the journey.

Balloon foot exercisers - commercial devices are available for use in flight. You compress each side of the device alternately with your feet thereby exercising the foot and calf. Evidence is available that these increase venous blood flow but there is limited evidence on actual prevention of DVT.

Compression stockings - compress the veins and help prevent venous stasis.

Aspirin - ½ aspirin a day decreases the stickiness of the blood and helps prevent thrombosis in other conditions so it seems sensible but there is no strong scientific evidence of its efficacy in travel-related DVT. Aspirin is contraindicated for some pre-existing medical conditions.

Specific Preventative Measures

Specific measures are available for people at particularly high risk e.g. previous travel-related DVT, previous spontaneous DVT, known blood coagulation conditions, known predisposing conditions.  These involve the use of anticoagulants such as subcutaneous heparin injections or oral warfarin.

The decision to use these agents is a careful balance of risks and benefits and requires a thorough assessment of all relevant factors.

A deep vein thrombosis is caused by clot and thrombus forming in the deep veins of the leg.

ultrasound picture of a deep vein thrombosisUltrasound picture of a deep vein thrombosis.

Technician performing ultrasound scan for DVT
Technician performing ultrasound scan
for DVT.