Blood Clots: Deep Vein Thrombosis

  • Basics

    Deep vein thrombosis (DVT) is a blood clot in a deep vein of the body, usually in the thigh or leg. The deep veins are the main blood vessels returning blood from the tissues of the body back to the heart (such as the femoral vein). Figure 01.

    Click to enlarge: Deep vein thrombosis

    Figure 01. Deep vein thrombosis

    If a blood clot (thrombus) forms in a deep vein, it can block the flow of blood, which prevents the tissues from draining properly. This causing excess fluid accumulation, swelling, warmth, and discomfort in the leg. A blood clot in a deep vein may also break off and travel back to the heart and into the lungs, causing a condition called pulmonary embolism. Pulmonary embolism can be minor and go unnoticed, or it can be significant and cause difficulty breathing, sharp chest pain, and even death. Less commonly, the clots can also travel through the heart back to the rest of the body, including the brain. This is called a paradoxic embolism. A blood clot that travels this way to the brain can be a cause of stroke.

    DVT is different from a clot in a vein close to the surface of the body, such as a vein near the skin or in the calf. These superficial clots, while often uncomfortable, are usually not dangerous and are not treated in the same way as DVT.

    DVT is treated with medications that lower the chances of new clots forming and allow the body to dissolve the clot over time.

  • Causes

    Blood clots in the veins of the legs cause DVT. When the bloodflow in the arteries and veins is blocked, a blood clot (thrombus) may form. A thrombus that forms in the larger veins of the legs may break off and travel through the bloodstream to become an embolus.

    People who have conditions that cause blood to flow slowly in the veins, or who have a higher chance of blood clots, are at greatest risk of developing DVT.

    The condition tends to occur in people who:

    • Have had a previous DVT
    • Are inactive
    • Have damaged blood vessels due to injury or surgery to legs or hips
    • Have blood that clots more easily, such as in some diseases and genetic conditions
    • Are in the hospital on bedrest, such as after a hip operation or other major surgery, or during a major illness.

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