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Jan 13

What is DVT (deep vein thrombosis)?

So, what is deep vein thrombosis? And what does the evidence say about reducing our risk of developing it?

Deep vein thrombosis is the formation of a blood clot (called a thrombus) in the deep veins of the leg. The clot can be either located in the lower leg or in the thigh, or both. Rarely, a blood clot develops in other veins such as in the arm.

Eventually, the thrombus is in danger of dislocating from the vessels in the leg and going straight into the lung circulation (pulmonary embolism), thus blocking the blood supply of the lung and leading to shortness of breath.

Venous thromboembolism – the term which encompasses both deep vein thrombosis and pulmonary embolism can lead to death from things like stroke, heart attack or respiratory failure. The most important thing to remember regarding blood clot is that detection and treatment is vital. The earlier for both the better outcome for you, the patient.

Who is at risk?

There are three principal mechanisms that increase the likeliness of developing deep vein thrombosis:

  1. Reduced flow of blood (from being immobilized due to illness, leg injury, or long sitting during long-haul flights and car trips)

  2. Increased tendency of blood clotting (due to hereditary diseases such as Factor V Leiden disease)

  3. Injury of blood vessels (from accidents or surgery or even an IV)

The risk of developing a deep vein thrombosis is increased in patients who have previously had deep vein thrombosis or a pulmonary embolism, and in those with a family history of blood clots.

Other risk factors include cancer (or cancer treatment), taking contraceptive pills containing estrogen, hormone-replacement therapy, pregnancy and conditions that cause blood clotting.

As some of these risk factors can be modified and there is a chance to reduce your risk by losing excess weight, quitting smoking (as smoking affects blood clotting and circulation), and using contraception methods other than estrogen containing pills. Consult your physician and discuss ways to reduce your risk.

On long-haul flights, car rides or bus trips, exercise your lower calf muscles. Whenever possible, get up and walk around, or raise and lower the heels while keeping the toes on the floor while sitting.

Get up and walk around as much as possible on long-haul flights. Image from


The first signs of deep vein thrombosis are swelling of the leg. Sometimes there is a localized painful tenderness and a red leg.

In case of the life-threatening complication of lung embolism, the symptoms are sudden shortness of breath with rapid pulse (heart rate), sweating and coughing up blood. If you have any of these symptoms, call 911.

After a series of questions about the onset and characteristics of your symptoms and a thorough physical examination, further testing will confirm the diagnosis. The best way to diagnose a suspected deep vein thrombosis is an ultrasound examination of the leg. In case of a suspected pulmonary embolism, other special imaging diagnostics (CT) need to be applied.

Treatment options

The aims of the treatment are to stop the blood clot from getting bigger, from breaking loose – and drifting into the lung leading to pulmonary embolism – and to reduce the chances of deep vein thrombosis happening again.

Deep vein thrombosis is treated with blood thinners (anticoagulants), usually for a period of three to six months. These are mostly administered as injections in the first days, followed by tablets.

Compression stockings of the lower leg prevent the blood from pooling and subsequent clotting. The stockings should be worn whenever immobile, such as on long-haul flights, car rides, or sitting at work for long periods.

The stockings also prevent one common complication that frequently occurs after deep vein thrombosis: post-thrombotic syndrome, which arises from the damage of the vein valves caused by the blood clot. The syndrome increased swelling of the affected leg, pain and skin discoloration. Chronic venous insufficiency due to deep and superficial venous valve insufficiency can ultimately lead to lower leg and ankle ulcers that are difficult to heal. 

So, should you have an injection or wear compression stockings when you fly?

Long-haul flights (for more than four hours) increase the risk for developing deep vein thrombosis, like every other condition where your movement is restricted. Few studies have been performed to address this question.

It’s important to assess the thrombosis risk on an individual basis. People at the highest risk of travel-related thrombosis who travel more than three hours should wear compression stockings. The stockings need to be individually adjusted to ensure they don’t restrict the blood flow and thereby cause, rather than prevent, thrombosis.

There’s no need to wear compression stockings unless you’re at an increased risk of deep vein thrombosis. Image from

In general, a prophylactic injection of heparin is not recommended. People who have history of a previous venous DVT or thromboembolism and who have more than one risk factor for developing blood clots should consult their physician regarding longer term options. He may recommend low-dosage aspirin therapy and may suggest blood work be taken to check clotting time and for genetic factors that could affect your clotting times. 

In any case, it’s important you try to reduce the modifiable risk factors for deep vein thrombosis, particularly when travelling long distances.

If you think you or someone else has a DVT deep vein thrombus, seek immediate medical attention.

Smart Health Screening

Ultrasound Laboratories, Inc. dba SmartHealth Screening & SonoTech Imaging. We provide abdominal, cardiac and vascular ultrasound imaging services to physicians offices and patients homes. We accept most insurances including Medicare and Medi-Cal. 1-408-829-6486. Office with Saturday appointments at 305 South Drive, suite 7, Mountain View, CA