Thrombosis (blood clot)

This is the formation of potentially deadly blood clots in the artery (arterial thrombosis) or vein (venous thrombosis). Once formed, a clot can slow or block normal blood flow, and even break loose and travel to an organ. A clot that travels to the circulation is called an embolism.

VTE (venous thromboembolism) is a condition in which blood clots form (most often) in the deep veins of the leg, pelvis or arms (known as deep vein thrombosis, DVT) and can travel in the circulation and lodge in the lungs (known as pulmonary embolism, PE). VTE is often fatal, but the good news is that many, if not most cases are preventable.

Thrombosis does not discriminate. It can affect anyone regardless of their age, ethnicity or race.
The most important thing you can do to protect yourself from a life-threatening blood clot is to learn if you are at risk. Know the signs and symptoms and contact your health care professional immediately if needed.

Facts and Figures

• every year, there are approximately 10 million cases of VTE worldwide
• up to 60 percent of VTE cases occur during or after hospitalization, making it a leading preventable cause of hospital death.

Risk Factors

VTE does not discriminate. It affects people of all ages, races and ethnicities, and occurs in both men and women. Certain factors and situations can increase the risk of developing potentially deadly blood clots, such as being pregnant or recent birth.

Strong Risk

• being in the hospital for an extended period of time
• having surgery (especially hip, knee and cancer-related surgery)
• not moving for long periods of time (e.g., due to bedrest or long-duration travel)

Moderate Risk

• age (60+)
• personal or family history of blood clots
• cancer/chemotherapy
• using estrogen-based medication (e.g., oral contraceptives or hormone replacement therapy)

Other Factors

• obesity
• pregnancy or recent birth
• smoking
• alcohol consumption

Warning Signs and Symptoms

VTE can occur without any warning signs or symptoms and can go unrecognized and undiagnosed by a healthcare professional. Symptoms that do appear may be associated with either DVT or PE. Tell your doctor, nurse or midwife if you develop any of the symptoms below:

Deep Vein Thrombosis (DVT)

• pain or tenderness, often starting in the calf
• swelling, including the ankle or foot
• redness or noticeable discoloration
• warmth

Pulmonary Embolism (PE)

• unexplained shortness of breath
• rapid breathing
• chest pain (may be worse upon deep breath)
• rapid heart rate
• light headedness or passing out

Research suggests that VTE’s are often preventable, and evidence-based prevention strategies can stop the development of clots in 'at-risk' individuals.

To identify whether a patient is 'at-risk,' healthcare professionals should conduct a VTE risk assessment, which is a tool or questionnaire that gathers information about a patient's age, medical history, medications and specific lifestyle factors. Information is then used to discern a patient’s potential risk (e.g., high, moderate or low risk) for developing blood clots in the legs or lungs.

If you are admitted to a hospital and don't receive an assessment, be proactive. Ask for one.

Individuals who are deemed 'at-risk' should be given appropriate prevention (referred to as "prophylaxis"), which can include:
• anti-clotting medications (e.g., blood thinners, referred to as "anticoagulants")
• mechanical devices (e.g., compression stockings, intermittent pneumatic compression devices or rapid inflation venous foot pumps)

Hospital patients may also be instructed to move around or do foot/leg exercises as soon and as often as possible.


DVT and PE are serious, life-threatening conditions that require immediate medical attention. Treatment can differ by patient but typically includes blood thinning medication to break up clots and prevent new ones from forming.


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