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This information was reviewed and approved by Chhaya Patel, MD (2/28/2021).

A pulmonary embolism is a blood clot in the blood vessels of the lungs.

Normally, blood clots stop bleeding after an injury by forming a protective seal over the injury and preventing the body from bleeding to death. When a blood clot breaks off of a vein or an artery and travels to the lungs, it can cause serious health problems.

Types of Blood Vessels:

  • Arteries - carry the blood away from the heart to other parts of the body.

  • Veins - carry blood back to the heart to be re-oxygenated.

Blood clots can cause problems anywhere in the body, but when they travel to your lungs, it can make breathing difficult and make it hard for the heart and other organs to work properly. Untreated, blood clots can lead to death.


There are two types of blood clots: 

  1. Arterial blood clots – these form in arteries, including the heart causing a heart attack. Plaque or atherosclerotic buildup usually causes these clots.

  2. Venous blood clots - these form in the veins and are called venous thromboembolism (VTE). This abnormal clotting is caused by being sedentary or bedridden, which can make your blood move slower and significantly increase your risk for developing dangerous blood clots. 

Pulmonary embolism is related to blood clots in the veins (venous thromboembolism or VTE).


Pulmonary Embolism & Deep Vein Thrombosis (DVT)

Deep vein thrombosis occurs when a clot forms in a vein deep in the body. These clots mainly affect the large veins in the calf and thigh. About half of people experiencing DVT don’t show symptoms.

A pulmonary embolism, or PE, is a blood clot that breaks off from the inside of a vein, usually in the thigh, and travels to the lung where it blocks an artery in the lungs. This blockage can permanently damage the affected lung and lower the blood’s oxygen level.

A PE usually causes a blockage in the lung artery suddenly and does not allow normal blood flow to the lungs. This can be life-threatening as it can cause significant difficulty breathing by lowering the level of oxygen in the lungs and increasing the blood pressure in the pulmonary arteries. Increased blood pressure in the lungs can make the right side of the heart work harder which can lead to heart failure.

Symptoms of a PE can include: sudden shortness of breath at rest or activity; unexplained sharp pain in the chest, arm, shoulder, neck or jaw; pale, clammy or bluish-colored skin; rapid heartbeat; cough; excessive sweating; anxiousness; light-headedness, fainting; or wheezing.

When diagnosed and treated early with blood thinning medications, PEs can dissolve. Left untreated, it can cause other serious health problems and death. 

The Centers for Disease Control and Prevention estimate that about 2 out of every 1,000 people in the U.S. develops PE each year. Nearly 2 percent of cancer deaths are caused by pulmonary embolism according to M.D. Anderson.

The main cause of a pulmonary embolism is blood pooling in an arm or leg after being inactive too long, such as after being on bed rest or having surgery. Injury to veins and other medical conditions including congestive heart failure, atrial fibrillation, heart attack and stroke can also cause DVT and PE to develop. Blood clotting issues can also be genetic, caused by hormone replacement therapy, birth control pills and some types of cancer. 

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