Pulmonary embolism is a blockage in one of the pulmonary arteries in your lungs. In most cases, pulmonary embolism is caused by blood clots that travel to the lungs from deep veins in the legs or, rarely, from veins in other parts of the body (deep vein thrombosis).
Because the clots block blood flow to the lungs, pulmonary embolism can be life-threatening. However, prompt treatment greatly reduces the risk of death. Taking measures to prevent blood clots in your legs will help protect you against pulmonary embolism.
Pulmonary embolism symptoms can vary greatly, depending on how much of your lung is involved, the size of the clots, and whether you have underlying lung or heart disease.
Common signs and symptoms include:
- Shortness of breath. This symptom typically appears suddenly and always gets worse with exertion.
- Chest pain. You may feel like you’re having a heart attack. The pain is often sharp and felt when you breathe in deeply, often stopping you from being able to take a deep breath. It can also be felt when you cough, bend or stoop.
- Cough. The cough may produce bloody or blood-streaked sputum.
Other signs and symptoms that can occur with pulmonary embolism include:
- Rapid or irregular heartbeat
- Lightheadedness or dizziness
- Excessive sweating
- Leg pain or swelling, or both, usually in the calf caused by a deep vein thrombosis
- Clammy or discolored skin (cyanosis)
Pulmonary embolism occurs when a clump of material, most often a blood clot, gets wedged into an artery in your lungs. These blood clots most commonly come from the deep veins of your legs, a condition known as deep vein thrombosis (DVT).
In many cases, multiple clots are involved in pulmonary embolism. The portions of lung served by each blocked artery are robbed of blood and may die. This is known as pulmonary infarction. This makes it more difficult for your lungs to provide oxygen to the rest of your body.
Occasionally, blockages in the blood vessels are caused by substances other than blood clots, such as:
- Fat from the marrow of a broken long bone
- Part of a tumor
- Air bubbles
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Although anyone can develop blood clots and subsequent pulmonary embolism, certain factors can increase your risk.
Medical conditions and treatments
You’re at higher risk if you or any of your family members have had venous blood clots or pulmonary embolism in the past.
In addition, some medical conditions and treatments put you at risk, such as:
- Heart disease. Cardiovascular disease, specifically heart failure, makes clot formation more likely.
- Cancer. Certain cancers — especially brain, ovary, pancreas, colon, stomach, lung and kidney cancers, and cancers that have spread — can increase the risk of blood clots, and chemotherapy further increases the risk. Women with a personal or family history of breast cancer who are taking tamoxifen or raloxifene also are at higher risk of blood clots.
- Surgery. Surgery is one of the leading causes of problem blood clots. For this reason, medication to prevent clots may be given before and after major surgery, such as joint replacement.
- Disorders that affect clotting. Some inherited disorders affect blood, making it more prone to clot. Other medical disorders such as kidney disease can also increase your risk of blood clots.
- Coronavirus disease 2019 (COVID-19). People who have severe symptoms of COVID-19 have an increased risk of pulmonary embolism.
Blood clots are more likely to form during periods of inactivity, such as:
- Bed rest. Being confined to bed for an extended period after surgery, a heart attack, leg fracture, trauma or any serious illness makes you more vulnerable to blood clots. When the lower extremities are horizontal for long periods, the flow of venous blood slows and blood can pool in the legs, sometimes resulting in blood clots.
- Long trips. Sitting in a cramped position during lengthy plane or car trips slows blood flow in the legs, which contributes to the formation of clots.