What is a pulmonary embolism?

A pulmonary embolism (PE) is a blood clot that occurs in the lungs.

It can damage part of the lung due to:

  • restricted blood flow
  • decreased oxygen levels in the blood
  • effects on other organs

Large or multiple blood clots can be life threatening. However, immediate emergency treatment for a PE greatly increases your chances of avoiding permanent lung damage.

Explore the interactive 3-D diagram below to learn more about pulmonary embolism symptoms.

Symptoms of a PE depend on the size of the clot and where it gets stuck in the lung.

The most common symptom of a PE is shortness of breath. This may be gradual or sudden.

Other symptoms include:

If you notice one or more of these symptoms, especially shortness of breath, you should seek medical attention immediately.

Read more: How to tell if you have a blood clot.

Blood clots can form for a variety of reasons. PEs are most often caused by deep vein thrombosis (DVT), a condition in which blood clots form in veins deep in the body. The blood clots that most often cause PEs begin in the legs or pelvis.

Blood clots in the deep veins of the body can have several different causes, including:

  • Injury or damage. Injuries like bone fractures or muscle tears can cause damage to blood vessels, leading to clots.
  • Inactivity. During long periods of inactivity, gravity causes blood to collect in the lowest areas of your body, which may lead to a blood clot. This could occur if you’re sitting for a lengthy trip or if you’re lying in bed recovering from an illness.
  • Medical conditions. Some health conditions cause blood to clot easily, which can lead to PE. Treatments that involve surgery often lead to short-term bed rest or limited movement, which can make clotting more likely. Also, certain medical therapies for cancer can have side effects such as clotting in the blood. This puts you at risk for DVT and PE.

There are additional risk factors that increase your odds of having the type of blood clot that can cause PE.

PE has a wide variety of characteristics, ranging from no symptoms to sudden death. The most common presenting symptom is shortness of breath followed by chest pain and cough. However, many people with PE have mild or nonspecific symptoms or are asymptomatic, including people with a large PE.

When you talk with a doctor about your symptoms, they’ll ask about your overall health and any preexisting conditions you may have.

A doctor will typically perform one or more of the following tests to discover the cause of your symptoms:

  • Chest X-ray. This is a standard, noninvasive test that lets a doctor see your heart and lungs to look for other obvious causes of your symptoms. A PE can not be diagnosed with this test. The most common finding of a PE on a chest X-ray is “normal.”
  • Electrocardiography (ECG). An ECG measures your heart’s electrical activity. A PE can not be diagnosed on an ECG. This test will check for other causes of chest pain.
  • Computed tomography pulmonary angiography (CTPA). This test is the first-choice diagnostic imaging method because it’s sensitive and specific for the diagnosis of PE. However, it requires the use of intravenous (IV) contrast. Therefore, people with kidney problems will likely not be able to have this test because contrast may cause or worsen kidney disease. When a CTPA can not be performed, the doctor may instead consider a VQ scan to diagnose a PE.
  • Ventilation/perfusion scan (VQ). A VQ scan is carried out in two parts. In the first part, radioactive material is breathed in, and pictures are taken to look at the airflow in your lungs. In the second part, a different radioactive material is injected into a vein in your arm, and more images are taken to see the blood flow in your lungs. This is mostly reserved for when:
    • you can not receive a CTPA
    • the results of the CPTA were inconclusive
    • more testing is needed
  • Magnetic resonance pulmonary angiography (MRPA). This is not recommended as a first-line test for diagnosing PE, but it may be an imaging option to diagnose PE in people who can neither receive a CTPA nor a VQ scan. Potential advantages of MRPA are that no ionizing radiation is involved, and the examination can be combined with MR venography in the same sitting to look for DVT.
  • Venography. A venogram is an invasive test that is rarely used for the diagnosis of only a DVT. This is a specialized X-ray of the veins in your legs and also requires the use of contrast.
  • Pulmonary angiography. A pulmonary angiography is an invasive test that’s rarely used to diagnose an acute PE. It involves making a small incision so a doctor can guide specialized tools through your veins. The doctor will use contrast to see the blood vessels in the lung.
  • Duplex venous ultrasound. This is a practical and noninvasive test to only diagnose a DVT. It’s important to remember that you can still have a PE even if the ultrasound is negative for a DVT. This test uses radio waves to visualize the blood flow and check for blood clots in your legs.
  • D-dimer test. This is a type of blood test used to screen for signs of a PE or DVT based on the your probability of having a clot. A doctor can not make a diagnosis based on this blood test. If the result is positive, the doctor must confirm the diagnosis with the appropriate imaging method.

Acute PE, a blockage in the lung artery, often from a blood clot, is a common and sometimes fatal disease. When you’re evaluated for a PE, it’s often important for the evaluation to be efficient and avoid unnecessary testing so you can start therapy quickly.

Factors that increase your risk of developing DVT and PE include:

Read more: Learn about the risks of DVT.

Your treatment for a PE depends on the size and location of the blood clot. If the problem is minor and caught early, a doctor may recommend medication as treatment. Some drugs can break up small clots.

A doctor may prescribe:

  • Anticoagulants. Also called blood thinners, medications such as heparin and warfarin prevent new clots from forming in your blood. They can save your life in an emergency situation. Another commonly used category of anticoagulant is the direct oral anticoagulants (DOACs), such as rivaroxaban (Xarelto) and apixaban (Eliquis). These medications are FDA approved for the treatment and prevention of PE and DVT.
  • Clot dissolvers (thrombolytics). These drugs break down a clot to improve blood flow and perfusion. They are reserved for people hospitalized in emergency situations because side effects may include dangerous bleeding problems.

Minimally invasive procedures or surgery may be necessary if you’re unstable because of the problematic clots and you need urgent reperfusion to improve blood flow to your lungs and heart, especially when thrombolytics can not be used.

Some procedures a doctor may use in the case of a pulmonary embolism include:

  • Catheter directed methods. These are used for clot removal and breakdown. A thin tube called a catheter will suction out, break down, or dissolve clots in your pulmonary artery.
  • Open surgery. Doctors use open surgery only in emergency situations when:
    • minimally invasive catheter directed methods are not available
    • medications aren’t working to break up the clot
    • medications are contraindicated or carry too many risks for the patient

After you receive proper treatment for a pulmonary embolism at the hospital, you’ll be advised to treat the underlying cause of the PE or DVT if it’s known.

You’ll most likely start taking anticoagulant medications, such as heparin, warfarin, or newer agents referred to as direct oral anticoagulants (DOACs), to prevent blood clots from returning.

Regularly exercising your legs and practicing health-promoting behaviors are key components of prevention and therapy after a PE. A doctor will give you complete instructions on how to care for yourself to prevent future blood clots.

A pulmonary embolism occurs when a blood clot reaches the lungs. These blood clots often come from deep vein thrombosis, which can result from damage to bone and muscle or from long periods of inactivity. Many times the exact cause of a DVT or PE is unknown despite a thorough evaluation.

A PE can be very dangerous, so it’s important to contact a medical professional if you’re experiencing symptoms such as chest pain, spitting up blood, and fainting.

A doctor will typically prescribe medications that thin the blood and, in certain cases, use medications that break up blood clots. Minimally invasive interventional procedures and surgery may be required in some instances.