What is a pulmonary embolism? A pulmonary embolism (PE) is a
blood clot that develops in a blood vessel elsewhere in the body
(most commonly from the leg), travels to an artery in the lung,
and forms an occlusion (blockage) of the artery. A blood clot
(thrombus) that forms in a blood vessel in one area of the body,
breaks off, and travels to another area of the body through the
bloodstream is called an embolus. An embolus can lodge itself in
a blood vessel, blocking the blood supply to a particular organ.
This blockage of a blood vessel by an embolus is called an
embolism. An embolism to the lung may cause serious life-
threatening consequences and, potentially, death. Most commonly,
a PE is the result of a condition called deep vein thrombosis
(blood clot in the deep veins of the leg). The circulatory
system: The heart, arteries, capillaries, and veins make up the
body's circulatory system. Blood is pumped with great force from
the heart into the arteries, then into the capillaries (small
blood vessels in the