A pulmonary embolism (PE) is a sudden blockage in a lung artery caused by a blood clot that develops in a blood vessel elsewhere in the body, often in the leg. The clot then travels through the bloodstream to the lungs, where it suddenly forms a blockage of the artery, causing a lack of blood flow that leads to lung tissue damage and low blood oxygen levels that can damage other organs in the body. PE can be life-threatening, especially if a clot is large or if there are many clots.

Symptoms of a pulmonary embolism vary depending on the size of the clot, how much of the lung is involved, and whether there is an underlying medical condition. The most common symptoms include shortness of breath that appears suddenly, chest pain that may become worse when breathing in, lightheadedness, dizziness, or passing out due to a sudden loss in blood pressure, cough, which may contain blood, leg pain or swelling, pain in your back, excessive sweating, and blueish lips or nails. Half of the people who have pulmonary embolism have no symptoms.

PE is often difficult to diagnose because the symptoms of PE are a lot like those of many other conditions and diseases. Along with a complete medical history and physical exam, tests used to look for a PE may include a computed tomographic angiography (CTPA), a pulmonary V/Q scan to show which parts of your lungs are getting airflow and blood flow, D-Dimer blood tests to detect clot formation in your blood, and a chest X-ray of your heart and lungs to rule out other conditions with similar symptoms.

Prompt treatment greatly reduces the risk of death. Treatment for PE usually involves blood-thinning medications, such as heparin, warfarin, or newer oral anticoagulants, to prevent new clots from forming and to prevent existing clots from getting larger. In some cases, surgery or other procedures may be necessary to remove or dissolve the clot.