The Silent Killer - Each year, 600,000 patients will experience Deep Vein Thrombosis.

Rebecca Kyle

Biology, Dr Campton

The Silent Killer

Each year, 600,000 patients will experience Deep Vein Thrombosis. Each year, at least 50,000 and perhaps as many as 200,000 patients will die from blood clots that obstruct blood flow to their lungs. In the UK alone it affects half a million people, many of them aged over 40. (British Medical Association, Complete Family Guide-7).The tragedy of these figures is that most of these problems could be avoided by simple, cost-effective measures. (Preventing Deep Vein Thrombosis and Pulmonary Embolism-2)

Deep vein thrombosis (DVT) refers to the formation of a blood clot within a deep vein, commonly in the thigh or calf. The blood clot can either partially or completely block the flow of blood in the vein. (BUPA- 4)

Deep Vein Thrombosis occurs when the flow of blood is restricted in a vein. In a matter of a few hours, or less, blood can begin to pool and coagulate in the veins, producing an ever-enlarging and hardening blood clot. If or when this clot dislodges (often triggered by decompression after flight), it may move through the body's veins to the lungs or even to the heart where even a small clot can block critical blood flow causing rapid death or, at best, paralysis.

DVT may develop during a long flight and has been dubbed ‘economy class syndrome’ because the cheaper seats in a plane have less leg room, encouraging minimal movement. DVT can be caused by a narrowed or blocked vein in which blood gathers and clots. This can be brought on by an injury to the vein (such as a sharp blow to the leg), or following surgery or radiation therapy (cancer- killing X- rays). (BUPA-4)In addition, DVT can occur during pregnancy as there is then an increased tendency for the blood to form clots (this is a natural mechanism to prevent excessive bleeding during child- birth). DVT can also occur as the result of severe infection, liver disease and some cancers (Preventing
Deep Vein Thrombosis and Pulmonary Embolism-2)

Those thought to be most at risk include people aged over 40, heart patients, people who have had a clot before, those with relatives who have suffered one, people who have had recent surgery, those who have had a stroke or cancer and women who are pregnant, on the Pill or on hormone replacement therapy. Also some people are not born with vital ‘blood thinning’ substances and are therefore always more susceptible to blood clots. (Department of Health-3)

Although anyone can develop DVT on a flight, certain people are more vulnerable, including pregnant women, (due to compression of a vein ...

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Although anyone can develop DVT on a flight, certain people are more vulnerable, including pregnant women, (due to compression of a vein by the foetus during pregnancy), people who are overweight, those whose feet don't reach the floor (because the seat puts more pressure on the backs of their legs), the elderly, smokers and those with coronary artery diseases and certain blood conditions. (BUPA-4)

Once a clot has formed it can grow in size and block other veins. In addition, portions of the clot may break away from the vein wall and travel through the veins into the lung, where it can lodge in a pulmonary artery. This condition is known as pulmonary embolism, and the travelling clot is called an embolus. Pulmonary embolism can be life threatening if the embolus blocks the main pulmonary artery or if there are many clots. Pulmonary embolism can be treated with drugs that dissolve the clot and restore normal blood flow. (American Venous Forum-8)

"Pulmonary embolism remains the most common preventable cause of death in hospital"

(Morrell MT and Dunnill MS (1968) Br J Surg 55, 347-352)

(British Medical Association, Complete Family

Guide-7)

There a number of signs to determine if you believe that you may be suffering from a pulmonary embolism. These include a feeling of apprehension, shortness of breath, sharp chest pain, rapid pulse, sweating, fainting or a cough with bloody sputum.

Over time, untreated DVT may damage a venous valve so that it does not close completely. Consequently, blood flows back into the vein below the valve and collects in the lower leg veins. Pooling of blood in these lower leg veins causes swelling and tissue damage that may lead to painful ulcers. This condition is known as venous stasis disease. (American Venous Forum-8)

Fortunately, prompt treatment of DVT can prevent complications such as pulmonary embolism and venous stasis disease.

If DVT is suspected, additional tests will be needed to confirm the diagnosis. These tests are relatively painless. Your doctor may listen to blood flowing through the veins in your calf and thigh and behind your knee, using a special stethoscope placed on your leg. But the most reliable method of diagnosing DVT is called a duplex scan. An ultrasound microphone is placed on the leg over the affected area, and sound waves measure the veins and blood flow on a screen that is similar to a television.

The duplex scan is very accurate for diagnosing DVT because it shows the vein and any blood clots on the screen. In cases of doubt, an x-ray called a venogram is used. In a venogram, dye is injected into a vein in the foot and an x-ray is taken of the leg. In most cases, if a clot is present it will be shown on the x-ray.

The traditional treatments for DVT are bed rest, elevation of the affected limb and pressure stockings. Patients usually also have their blood thinned, either with tablets or a fluid called Heparin. One such tablet called Warfarin is often continued for three months, whilst the blood circulation finds an alternative route around the blocked vein. But, theses drugs do not dissolve clots that have already formed. Your body’s own system for breaking down clots is needed. (Airport Medical Services-9)

Below is a picture of an ultrasound being used to identify a blood clot. This testing can identify even the smallest blood clot.

Chances of developing DVT from a long flight are thought to be only one in several million. But it can strike any long distance traveller regardless of age, physical condition or gender, also DVT is not just confined to flying economy class. First class passengers are also at risk, as are long distance rail and car passengers when on a long haul.

Below are some alarming facts and figures.

London's Heathrow Airport reports one passenger death a month from DVT. One nearby hospital recorded thirty passenger deaths from DVT in the past three years including a 28-year-old man.
DVT is the fourth leading cause of strokes in the United States. Approximately 2,000 Americans died from travel-related DVT-induced strokes last year! (No one knows how many deaths were not properly attributed to DVT.) (Economy Class Syndroyme-1)
Former Vice President Dan Quayle is one of the more notable victims of Deep Vein Thrombosis, having suffered an attack while on a 1994 flight--he was fortunate to survive.
More people die each year by a pulmonary embolism than do from breast cancer
DVT occurs in approximately two million Americans each year. (Spotlight health-6)

A group of 56 people who suffered DVT while flying and the families of victims are fighting a landmark legal case against 28 airlines for failing to warn them of the about the risks of the condition. Although the case was dismissed by Mr. Justice Nelson on the 20th December 2002, it has not stopped mounting pressure from the media for a public enquiry into the illness. (Guardian newspaper-5)

In response to the growing unrest amongst airline passengers about the effects of DVT, some airlines are offering compression socks on long haul flights. As well as this the government has issued a set of guidelines to airline passengers. It advises passengers on long-haul flights to perform leg exercises in their seats and to get up and walk around when possible. The government also advises people with conditions that make them more vulnerable to clots to seek medical advice before taking a long trip.

Recently a group of students at University College London, decided to set up an experiment to find out how DVT could be prevented. The research team got 200 people to take a long haul flight. 84 of them were given special compression stockings to wear. None of the people who wore the compression stockings suffered from DVT, but one in ten of those who didn't wear the stockings did develop the condition and were immediately treated for it. (Guardian Newspaper-5)

There a number of ways in which somebody could reduce the risk of developing DVT. These include doing some exercise while aboard a long haul flight, taking an aspirin, avoiding dehydration or by wearing compressed hosiery, which is manufactured by a number of companies. (Spotlight Health-6)

“Keep in mind that the heart does not pump the blood back from your feet. What gets the blood back is the muscle action in your legs. This squeezes the veins and pushes the blood along, so you can do simple exercises with your legs while sitting. But the best thing is just to get up and walk around every once in a while.” (Dr Charles Francis. Professor of Medicine at the University of Rochester)