Thromboembolism

Overview

Thromboembolism happens when a blood clot (a thrombus) forms inside a blood vessel and then a piece breaks away and travels through the bloodstream until it lodges in a narrower vessel, blocking blood flow (an embolus). The most common type is venous thromboembolism (VTE), which includes deep vein thrombosis (a clot, usually in the leg) and pulmonary embolism (a clot that travels to the lungs).

Blocked blood flow can damage tissues and organs and, when a large clot reaches the lungs, can be life-threatening. Clots are more likely to form when blood flow is sluggish, when the blood is more prone to clotting, or when a vessel wall is injured. The good news is that thromboembolism is often preventable and, when caught early, treatable with blood-thinning medicines. Recognizing the warning signs and acting quickly can save lives.

Symptoms

Symptoms depend on where the clot forms and where it travels. A deep vein clot in the leg and a clot that reaches the lungs cause very different signs.

• Deep vein thrombosis (leg): Swelling, pain or tenderness, warmth, and redness or discoloration, usually in one leg.
• Pulmonary embolism (lungs): Sudden shortness of breath, sharp chest pain that may worsen with a deep breath, rapid heartbeat, coughing (sometimes with blood), and lightheadedness or fainting.

A large clot in the lungs is a medical emergency. Anyone with sudden severe breathlessness, chest pain, fainting, or coughing up blood should call emergency services immediately, as rapid treatment can be lifesaving.

Causes

Clots tend to form when one or more of three conditions are present: slow blood flow, increased tendency of the blood to clot, or damage to a blood vessel. Common situations include:

• Immobility: Long periods of sitting or bed rest, such as after surgery, during a long flight, or with serious illness.
• Surgery and injury: Especially operations on the hips, knees, abdomen, or pelvis, which can injure vessels and reduce movement.
• Increased clotting tendency: Inherited clotting disorders, cancer, pregnancy, and some hormone medicines such as certain birth control pills.
• Other factors: Smoking, obesity, and a previous clot all raise the risk.

Risk Factors

• Recent major surgery, especially orthopedic, or serious injury
• Prolonged immobility or long-distance travel
• Cancer and some cancer treatments
• Pregnancy and the weeks after childbirth
• Hormone-based birth control or hormone therapy
• Inherited clotting disorders
• Older age, obesity, and smoking
• A previous blood clot

Diagnosis

Doctors assess the likelihood of a clot from symptoms and risk factors and then confirm it with tests.

• D-dimer blood test: Measures a substance released when clots break down; a normal result can help rule out a clot in lower-risk people.
• Ultrasound: The main test for deep vein thrombosis, using sound waves to see clots in the leg veins.
• CT pulmonary angiography: A specialized CT scan that shows clots in the lung arteries.
• Ventilation-perfusion (V/Q) scan: An alternative lung scan used in some situations.
• Additional testing: Sometimes performed to look for an underlying clotting disorder or cancer.

Treatment

The main treatment is blood-thinning medication (anticoagulants), which stops clots from growing and prevents new ones while the body breaks down the existing clot.

• Anticoagulants: Medicines such as injectable heparins and oral blood thinners are the cornerstone of treatment and are usually continued for several months or longer.
• Clot-busting drugs (thrombolytics): Powerful medicines used in severe, life-threatening clots, such as a large pulmonary embolism causing instability.
• Procedures: In selected cases, catheter techniques can remove or break up a clot.
• Inferior vena cava filter: A device placed in a large vein to catch clots in people who cannot take blood thinners.
• Compression stockings: May help relieve leg swelling and discomfort after a deep vein clot.

Treatment length depends on the cause and the risk of another clot, and close follow-up is important because blood thinners increase the risk of bleeding.

Prevention

• Move around and stretch your legs during long trips or after sitting for a long time
• Follow advice to get up and walk soon after surgery
• Use prescribed blood thinners or compression devices around high-risk times such as major operations
• Stay well hydrated, especially on long flights
• Avoid smoking and maintain a healthy weight
• Tell your doctor about any personal or family history of clots before surgery or starting hormone medicines

When to See a Doctor

See a doctor promptly if you have new swelling, pain, warmth, or discoloration in one leg, which can signal a deep vein clot. Seek emergency care immediately for signs of a clot in the lungs:

• Sudden shortness of breath
• Sharp chest pain, especially when breathing in
• Coughing up blood
• Rapid heartbeat, fainting, or feeling about to pass out

These can be life-threatening, and fast treatment greatly improves the outcome.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Venous Thromboembolism (Blood Clots).
2. National Heart, Lung, and Blood Institute (NHLBI). Venous Thromboembolism.
3. Mayo Clinic. Pulmonary embolism — Symptoms and causes.
4. MedlinePlus, U.S. National Library of Medicine. Blood clots.