Embolism Definition and Characterization

An embolism is a clot that occludes blood circulation

Illustration of Deep Vein Thrombosis
Illustration of Deep Vein Thrombosis. Getty Images/BSIP/UIG


Embolus, Emboli, Blood clot

Medical Specialties:

Cardiology, Family practice, Internal medicine

Clinical Definition:

Embolism refers to the occlusion of a blood vessel by an embolus (mass) that moves down the bloodstream and gets lodged in a blood vessel, causing circulation problems. The plural form of embolus is emboli.

In Our Own Words:

An embolism occurs when an embolus (a blood clot, gas bubble, or fat globule that is being carried through the bloodstream) becomes lodged in a blood vessel.

 Embolisms are almost always from a blood clot but other types of emboli are also possible (a fat mass, a foreign body, etc.).

Perhaps the most significant and feared type of embolism is the pulmonary embolism (PE). In a PE, the blood clot typically forms in the veins of the legs, then breaks off and travels to the heart or lodges in the blood vessels of the lungs.

A Closer Look at Pulmonary Emboli

Every year about 100,000 people die of pulmonary embolism in the United States with another 100,000 people dying because of pulmonary embolism plus something else. Many people die of pulmonary embolism within 1 hour of diagnosis even before they can be diagnosed. Within 3 months of a pulmonary embolism, up to 15 percent of people die after experiencing a pulmonary embolism.

Pulmonary emboli choke off the blood supply of the lungs, and our lungs need blood so that we can breathe. In addition to death, pulmonary emboli can also cause a pulmonary infarct wherein a portion of the lung dies or pulmonary hypertension.

Initial signs and symptoms of a pulmonary embolism include chest pain, trouble breathing, increased heart rate and cough. Pulmonary embolism is diagnosed using blood gasses obtained during a blood draw, spiral CT, ventilation-perfusion scans of the lung and pulmonary angiography.

Here are some risk factors for pulmonary embolism:

  • major surgical procedure (many people die of pulmonary embolism shortly after surgery)
  • trauma
  • hip fracture
  • age greater than 40
  • venous stasis
  • blood disorders (Protein C deficiency, Protein S deficiency, Factor V Leiden and so forth)
  • antiphospholipid syndrome (commonly seen in people with lupus)
  • previous history of venous thromboembolism
  • obesity

Pulmonary embolism is treated with anticoagulation. Anticoagulants prevent clotting of the blood.  Initially, patients are started on the anticoagulant drug heparin that is then "bridged" to longer-term warfarin therapy. In recent years, the number of anticoagulant options has increased--especially among hospitalized patients. These new options include low-molecular-weight heparin and Fondaparinux.

A Closer Look at Fat Emboli

Fat embolism most often occurs when a big bone like your femur breaks and releases a fat globule into your blood. Such long-bone fractures typically occur during after a motor vehicle accident or after orthopedic surgery. Fat emboli can travel to the brain or lungs and choke off blood circulation resulting in death.

There is no specific treatment for fat embolism; instead, treatment is supportive and focuses on oxygenation (think ventilators), maintenance of blood pressure using intravenous fluids and so forth.


The Cleveland Clinic. "Pulmonary embolism." Diseases & Conditions. Oct. 2009. Accessed July 2013.

Centers for Disease Control (CDC) and Prevention. "Data & Statistics." June 12, 2012. Accessed July 2013.

The Cleveland Clinic. "Pulmonary embolism." Diseases & Conditions. Oct. 2009. Accessed July 2013.

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