Embolism
(Clot · Pulmonary Embolism · PE)
In this condition factsheet:
The Facts on Embolism
An embolus is a particle that moves about in our blood vessels, either in the
veins or arteries. Most emboli are composed of clotted blood cells. A blood
clot is called a thrombus and a moving blood clot is called a thromboembolus.
As an embolus moves through the body's blood vessels, it's likely to come
to a passage it can't fit through. It lodges there, backing up blood behind
it. The cells that normally get their blood supply via this passage are starved
of oxygen (ischemia) and die. This condition is called an embolism.
Types of Embolism
Pulmonary embolism: This condition is most common in women. In an average
year, there are about 50,000 serious pulmonary embolisms in Canada, leading
to about 5,000 deaths. An embolus, usually formed in the leg, lodges in one
of the arteries of the lungs.
Brain embolism: If a blood clot travels to the brain, this causes an
ischemic stroke or TIA (transient ischemic attack).
Retinal embolism: Small clots that wouldn't block a major artery can
block the smaller blood vessels feeding the retina at the back of the
eye. The result is usually sudden blindness in one eye.
Amniotic embolism: Not all emboli are made of clotted blood. In pregnancy,
the womb is filled with amniotic fluid, which protects the fetus. Amniotic fluid
can embolize and reach the lungs, causing pulmonary amniotic embolism.
Air embolism: Scuba divers who rise to the surface too rapidly can
generate air embolism, bubbles in the blood that can block arterial blood flow.
Causes of Embolism
Most embolisms happen to people who have risk factors for blood clot
formation, like smoking, high blood pressure, high cholesterol, and heart disease.
The primary cause of most pulmonary embolisms is deep vein thrombosis
(DVT). This is a condition in which the veins of the legs develop clots.
Natural agents in the blood often dissolve small clots. Some clots are too big
to dissolve and are big enough to block major blood vessels in the lungs or
in the brain.
Factors that slow blood flow in the legs may promote clotting. People can
develop a DVT or pulmonary emboli after sitting still on long flights or after
immobilization of the leg in a cast, or after prolonged bedrest without moving
the legs. Other factors associated with DVT or pulmonary embolism include cancer,
previous surgery, a broken leg or hip, and genetic conditions affecting the
blood cells that increase the chance of blood clot formation.
Symptoms and Complications of Embolism
The symptoms of pulmonary embolism can be mild or severe. Some people
have many small emboli that can only be detected by special X-ray techniques.
A serious blockage, however, can lead to severe breathing difficulty or death.
Symptoms of pulmonary embolism appear suddenly and include:
- shortness of breath, rapid breathing, or wheezing
- bloody sputum
- cough
- lightheadedness, dizziness, fainting
- sharp chest pain or back pain
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