What is Deep Vein Thrombosis?

What is Deep Vein Thrombosis?

Deep vein thrombosis or DVT is the medical term for blood clots in the deep veins of the leg — a potentially life-threatening condition.

Blood clots inside a vein can cause pain and swelling of the vein and leg but, more importantly, clots in veins can travel to other parts of the body, for example to the lungs, where the condition is known as pulmonary embolism, and can be dangerous or lethal.

Deep vein thrombosis is different from the clots that can form in the veins that are closer to the surface of the skin, called the superficial veins. Those blood clots cause a different set of symptoms. Blood clots in the veins near the surface of the skin are more painful and cause redness or infection. Blood clots in the veins near the surface of the skin are less dangerous.


deep vein thrombosis

Illustration depicting deep vein thrombosis

What are the symptoms of deep vein thrombosis?

  • Swelling and/or pain usually in the calf or back of the leg
  • Warmth and redness in the involved leg

Deep vein thrombosis can lead to sudden and dangerous pulmonary embolism — like a heart attack, and with similar mortality. One in 3 people with a pulmonary embolism can die suddenly. If you get any of these symptoms, especially if they happen over a short period of time (hours or days), seek medical advice urgently. At the hospital, doctors can run tests to find out if you do have a clot.

What are the causes of deep vein thrombosis?

There are many predisposing causes of deep vein thrombosis. Among the most common is prolonged immobility, such as after an injury or surgery,  or due to a long plane (“coach-class syndrome”) or car ride. Additionally, certain medications including hormones and birth control pills can lead to deep vein thrombosis, as can certain cancers or clotting disorders.

Treating deep vein thrombosis

Deep vein thrombosis is a very serious condition and must be treated with utmost urgency.  DVT is treated with blood-thinner medicines called “anticoagulants,” or “anti-clotting medicines” that keep the clot from getting bigger and traveling to the lung. Both injectable and oral anti-blotting medicines are available.

Additionally, people who have experienced a clot are at risk of developing additional clots, especially in the first few months after the first clot is discovered. It’s important for these patients to take clot-prevention medicines.

Sometimes, stronger “clot-busting” medications are used. In other cases, procedures to remove (“thrombectomy) and dissolve the clot are also needed. Another option is an inferior vena cava filter. The inferior vena cava is the large vein that carries blood from your legs and the lower half of your body back up to your heart. Inferior vena cava filter trap any large clots that form below the location of the filter, preventing them from reaching the lungs.

Preventing deep vein thrombosis

Clots are formed after long periods of inactivity, so activity is a good preventative tool.

  • Every 1 to 2 hours, get up and walk around
  • Wear loose, comfortable clothes
  • While seated, shift your position often, moving your legs and feet frequently
  • Drink lots of fluids
  • If you are at particularly high risk, you can wear knee-high compression stockings


Hospitalized patients may be immobile for long periods and may therefore be administered a low dose of a blood thinner medication to prevent clots from forming. Talk to your doctor before or during hospitalization about whether you will need blood thinners. If you have a strong family history of blood clots, then you must alert your doctor about that.

For more information about how blood clots form in the legs, deep vein thrombosis and pulmonary embolism, including treatment options such as placement of an inferior vena cava filter, then please download the CardioVisual app for iPhone or for Android, and check out the Circulation section of the app.