Conditions & Treatments

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.

Pulmonary Embolism

When a blood clot forms in a blood vessel somewhere in the body, it can break loose and travel through a vein to the lungs causing a pulmonary embolism (PE).  This can cut off the flow of blood. PE is a medical emergency and may cause death. 

Often, the blood clot is one that formed in the deep vein of the leg. This is called deep vein thrombosis (DVT). Part of the clot breaks off and travels to the lungs.

Health care providers use the term venous thromboembolism (VTE) to describe both PE and DVT. They use the term VTE because the two conditions are very closely related. And, because their prevention and treatment is are also closely related. 

What causes a pulmonary embolism?

Human torso showing heart, lungs, and major veins. Blood clot is in leg vein with arrow showing it traveling up vein to lung causing pulmonary embolism.
A pulmonary embolism occurs when a blood clot forms in a vein and is carried by the blood into the lungs.

The most common cause of a pulmonary embolism is a blood clot (thrombus)  in a large leg vein that breaks off and travels to the lungs (embolus).

DVT in the leg is the most common cause of pulmonary embolism.

An embolus may be from clots in other parts of the body. Or they may be made up of other solids, liquids, or gases that travel to the lungs. For example, one may be made up of fat or air bubbles.

What are the risk factors for pulmonary embolism?

The following may increase your chance of pulmonary embolism:

  • Blood clotting disorder

  • Surgery

  • Injury

  • Not moving for long periods of time, such as being hospitalized, flying or riding long distances, or paralysis

  • Previous blood clots

  • Age over 60 years

  • Cancer and cancer therapy

  • Certain medical conditions, such as heart failure, chronic obstructive pulmonary disease (COPD), high blood pressure, and inflammatory bowel disease, such as ulcerative colitis or Crohn's disease 

  • Certain medications, such as birth control pills  or hormone replacement therapy (estrogen)

  • Pregnancy

  • Obesity

  • Other vein conditions

  • Cigarette smoking

What are the symptoms of a pulmonary embolism?

The following are the most common symptoms of pulmonary embolism:

  • Sudden shortness of breath (most common)

  • Chest pain (usually worse with breathing)

  • A feeling of anxiety

  • A feeling of dizziness, lightheadedness, or fainting

  • Fast heart beat (palpitations)

  • Coughing up blood

  • Sweating

  • Low blood pressure

  • Pain, redness, swelling, or warmth in the leg, arm or other area (symptoms of deep vein thrombosis)

The symptoms of a pulmonary embolism may look like other medical conditions or problems. Always see your doctor for a diagnosis.

How is pulmonary embolism diagnosed?

Pulmonary embolism is often difficult to diagnose. It may look like other conditions and diseases. You doctor will do a complete medical history and physical exam. Other tests may include:

  • Chest X-ray. Images are taken to check the lungs, as well as the heart. 

  • Ventilation-perfusion scan (V/Q scan). A tiny amount of radioactive material is used to check the lungs. The test checks the movement of air and the blood flow in the lungs.

  • Pulmonary angiogram. Dye (contrast) is injected to make highlight the blood vessels in the lungs.

  • C omputed tomography (also called CT or CAT scan). X-rays and computer technology are used to produce detailed images of the lungs. CT with contrast may also be done.

  • Magnetic resonance imaging (MRI). Large magnets, radiofrequencies, and a computerproduce detailed images of organs and structures within the body.

  • Duplex ultrasound (US). A type of ultrasound procedure done to check the blood flowin blood vessels. 

  • Blood  tests. To check the blood's clotting status. This may include a test called D-dimer level. Other blood tests may include checking for inherited (genetic) disorders that affect  blood clotting.  Arterial blood gases to check the amount of oxygen in the blood, may also be done.

  • Electrocardiogram (ECG or EKG). A simple procedures used to evaluate the heart. Abnormalities can be seen with acute pulmonary embolism.

Treatment of pulmonary embolism

Specific treatment will be determined by your doctor based on:

  • How old you are

  • Your overall health and medical history

  • How sick you are

  • How well you can handle specific medications, procedures, or therapies

  • How long the condition is expected to last

  • Your opinion or preference

Treatment for pulmonary embolism includes:

  • Blood thinners (a nticoagulants). These medications decrease the ability of the blood to clot. Examples include warfarin (Coumadin) and heparin. Newer anticoagulants may also be used, including rivaroxaban, apixaban, dabigatran and enoxaparin.

  • Clot busters  (thrombolytic therapy). These medications can be delivered through a catheter, or given intravenously (IV) to break up the clot.

  • Percutaneous thrombectomy. In this procedure, a catheter is inserted to the site of the embolism to remove the clot

  • Vena cava filter. In this procedure, a small metal filter placed in the vena cava. This is the large blood vessel that returns blood from the body to the heart. It prevents clots from traveling to the heart and lungs. These filters may be used if you can’t take anticoagulants  or if you develop additional clots even with anticoagulation treatment.

  • Surgical embolectomy. This is surgical removal of a pulmonary embolism. This procedure is generally done only in severe situations.

Prevention of pulmonary embolism

An effective way to prevent pulmonary embolism is to prevent deep vein thrombosis. This is especially important during hospitalization. Methods include:

  • Medication. Anticoagulants and/or aspirin are often given to prevent DVT.

  • Compression stockings. Elastic stockings that  help keep blood flowing

  • Pneumatic compression devices. A machine that also helps keep blood flowing with gentle pressure

  • Walking. Getting up and moving as soon as possible after surgery or illness.

Avoid sitting, standing, or lying down for long periods without moving your legs and feet.

  • When traveling by car, make frequent stops to get out and move around.

  • On long airplane, train, or bus rides, get up and move around when possible.

  • If you can’t get up, wiggle your toes and tighten your calves to keep your blood moving.

Recognize and change risk factors such as obesity, tobacco use, hormone therapy.

It’s also important to identify genetic defects that increase your risk for DVT and PE. Once identified, appropriate preventative measures can be taken.

Treatment and prevention of DVT may continue after you leave the hospital.  It is important to follow all instructions from health care providers during and after hospital stays.

Treatment Programs

Massachusetts General Hospital understands that a variety of factors influence patients' health care decisions. That's just one reason why we're dedicated to ensuring patients understand their diagnosis and treatment options. Because a single option might not serve all patients, we offer a wide range of coordinated treatments and related services across the hospital. Patients should consult with their primary care doctor or other qualified health care provider for medical advice and diagnosis information.

Select a treatment program for more information:


  • Adult Medicine Imaging
    The Adult Medicine Imaging Program at Massachusetts General Hospital Imaging offers a wide range of diagnostic exams and minimally invasive, image-guided treatments, all provided using leading-edge equipment and interpreted by specialty-trained radiologists.
  • Pediatric Imaging
    The Pediatric Imaging Program at Massachusetts General Hospital Imaging specializes in ensuring the safety and comfort of child patients while providing the latest technology and the expertise of specialized pediatric radiologists.
  • Heart Imaging
    The Heart Imaging Program at Massachusetts General Hospital Imaging provides comprehensive diagnostic cardiac imaging, using state-of-the-art CT and MRI technology and with expert interpretation by specialty-trained cardiovascular radiologists.
  • Vascular Imaging and Intervention
    Working as part of the Fireman Vascular Center, the interventional vascular specialists of the Vascular Imaging and Intervention Program at Massachusetts General Hospital Imaging perform minimally invasive, image-guided treatments for conditions including stroke and peripheral vascular disease. In addition, our specialty-trained radiologists use the latest imaging technologies to provide diagnostic exams for a full range of vascular conditions.
MassGeneral Hospital for Children

  • Hemophilia and Thrombosis Center
    The Hemophilia and Thrombosis Center at MassGeneral Hospital for Children offers comprehensive evaluations and individualized care to children and adults with bleeding disorders due to hemophilia A, hemophilia B, rare clotting factor deficiencies and von Willebrand disease.
Transplant Center

  • Lung Transplant Program
    The Lung Transplant Program at the Massachusetts General Hospital Transplant Center brings together state-of-the-art technology and leading-edge medical and surgical interventions to provide patients with individualized care before and after their lung transplants.
Vascular Center

  • Venous Disease Treatment Program
    Physicians at the Venous Disease Program at the Massachusetts General Hospital Fireman Vascular Center use novel endovenous minimally invasive and endovascular surgical interventions, as well as lifestyle modification strategies to diagnose and treat patients with deep vein thrombosis (DVT), varicose veins and other venous disorders.
Pulmonary and Critical Care Medicine

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