An embolism – from the Greek émbolos meaning “stopper” or “plug” – is the term that describes a condition where an object called an embolus is created in one part of the body, circulates throughout the body, and then blocks blood flowing through a vessel in another part of the body. Emboli (plural of embolus) are not to be confused with thrombi (plural of thrombus), which are clots that are formed and remain in one area of the body without being carried throughout the bloodstream.
What is a pulmonary embolism?
A pulmonary embolism (pulmonary meaning “of the lungs” from the Latin pulmōnārius) occurs when an embolus blocks blood flowing through an artery that feeds the lungs.

Typically, a blood clot first forms in an arm or leg (deep venous thrombosis or DVT) and then eventually manages to break free. The embolus can travel throughout the circulatory system towards the lungs, but eventually it is too large to pass through the small vessels of the lungs and forms a blockage. This prohibits blood from flowing into an area of the lung, and the part of the lung dies because it does not receive oxygen.

It is also possible, though much more rare, for a pulmonary embolism to result from an embolus that is formed from fat droplets, amniotic fluid, or some other particle that enters the bloodstream.

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Who is at risk of developing a pulmonary embolism?
The risk of developing a pulmonary embolism increases with age. People who have or had conditions or diseases that increase the risk of blood clotting are also more likely to develop pulmonary embolisms. In general, risk of pulmonary embolism is high for individuals who have or have had a blood clot in the leg or arm (deep venous thrombosis or DVT) and for those who have had a pulmonary embolism previously.

Long periods of bed rest or inactivity (such as a long airplane flight or car ride) substantially increase the risk of DVT and therefore increase the risk of pulmonary embolism. Other factors that put people at risk include certain cancers, surgeries, inflammatory bowel disease, obesity, pacemakers, catheters in the veins, pregnancy, estrogen supplements, a family history of blood clots, and smoking.
What are the symptoms of embolism?
Symptoms of pulmonary embolism include:

Chest pain
Increased or irregular heart beat
Dizziness
Difficulty catching breath
Rapid breathing
Cough or coughing up blood

Sometimes, more visible symptoms appear in the affected extremity of the deep vein thrombosis, such as:

Swelling
Pain or tenderness
Increased warmth
Red, blue, or discolored skin

More severe pulmonary embolism cases may result in shock, passing out, cardiac arrest, and death.
How are pulmonary embolisms diagnosed?
Diagnosis of embolisms depends on patient history, physical examinations, and a suspicion that a person’s symptoms are due to an embolism. Tests that are frequently employed in order to diagnose pulmonary embolism include:

Pulmonary angiogram – visualizes blood clots in the lungs
Electrocardiogram (EKG) – records the electrical activity of the heart
Arterial blood gas study – measures oxygen, carbon dioxide, and other gases in the blood
Chest x-rays – generates a picture of the heart, lungs, and other internal organs
Pulmonary V/Q scan – two tests that analyze ventilation and structural properties of the lungs
Computerized tomography (CT) scan (with and without contrast) – visualizes abnormalities in the chest, brain, etc.
Ultrasound – high frequency sound waves that measure blood flow velocity and changes in blood flow
d-Dimer test – blood test that can diagnose thrombosis
Electroencephalogram (EEG) – records electrical activity in the brain
Magnetic resonance imaging (MRI) – uses magnetic waves to develop detailed pictures of the brain and other organs

How are pulmonary embolisms treated?
Treatments for embolism are designed to destroy the embolus or clot, stop the clot from getting bigger, and prevent new clots from forming. A first step in treating most embolisms is to treat shock and provide oxygen therapy. Anticoagulant medications such as heparin, enoxaparin, or warfarin are usually administered in order to thin the blood and prevent further clotting.

Clot-busting drugs called thrombolytics may also be administered, but they carry a high risk of excessive bleeding and are generally only used in the critically ill. In addition, very ill people with low blood pressure may receive medication such as dopamine to increase pressure.
How can pulmonary embolisms be prevented?
High risk patients may try various embolism prevention methods, such as taking the drugs heparin or warfarin (anti-coagulants), wearing anti-embolism compression stockings, and using intermittent pneumatic compression of the legs. Compression methods prevent blood clots by forcing blood into deep veins and reducing the amount of pooled blood.

Additional ways to decrease risk of pulmonary embolism include physical activity, regular exercise, and avoiding the aforementioned risk factors.

Peter Crosta M.A.

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