Pulmonary embolism

Last reviewed: May 18, 2024

Pulmonary embolisms are a life-threatening emergency, with 10 to 30% of individuals dying within the month after diagnosis. A blood clot in the lung causes pulmonary embolism. It occurs when a clot in another part of the body (often the arm or leg) travels through the bloodstream and becomes lodged in the blood vessels of the lung. This clot reduces blood flow to the lungs, increases blood pressure in the pulmonary arteries, and lowers oxygen levels in the lungs.

When a clot develops in a vein and stays there, it is called a thrombus. However, an embolus occurs when a blood clot forms in a blood vessel anywhere in the body, breaks off, and moves to another area through the bloodstream. It can lodge in a blood vessel, eventually blocking the blood supply to a particular organ. This blockage of a blood vessel by an embolus is known as embolism.

As the clots block blood flow to the lungs, pulmonary embolism can be fatal. However, the risk of death can be reduced by prompt treatment of the disorder. Taking necessary measures to prevent blood clots in your lungs will go a long way to protect you against pulmonary embolism.


Symptoms of pulmonary embolism can differ, depending on the severity of the clot. Most people with a pulmonary embolism experience various symptoms, while others remain asymptomatic. The most common symptoms of pulmonary embolism (PE) can include:

  • A feeling of anxiety
  • Sudden shortness of breath is the most common symptom
  • Chest pain (usually worse with breathing)
  • A feeling of dizziness, lightheadedness, or fainting
  • Coughing or coughing up blood
  • Irregular heartbeat
  • Palpitations (heart racing)
  • Low blood pressure
  • Sweating Some people may experience symptoms of deep vein thrombosis (DVT) such as :
  • Swelling in the legs
  • Pain in the affected leg
  • Clammy or discolored skin
  • Soreness, tenderness, redness, or warmth in the legs


Pulmonary embolism can occur when:

  • Vessels have been injured, such as from a fracture or surgery, particularly in the legs. Smoking also damages vessels.
  • Conditions like pregnancy, connective tissue disease, cancer, or heart failure increase the risk for PE.
  • Blood collects in the body (usually a leg or arm). Blood pools after prolonged immobility, such as after surgery or during bed rest.
  • PE is more likely in those with a family history of clotting-related disease, like Factor V Leiden.

Other than blood clots, the following can also cause blockages in the blood vessels:

  • Part of a tumor
  • Air bubbles
  • Bone marrow fat of a broken leg bone

Risk factors

Risk factors for pulmonary embolism can include:

  • Family history of blood clotting disorders
  • Increased risk of blood clots due to genetic conditions
  • Injury or surgery (especially of the legs) or orthopedic surgery
  • Restricted movement, such as during long car rides, flying long distances, or paralysis
  • Previous history of clots
  • Cancer and cancer therapy
  • Older age
  • Certain medical conditions, such as chronic obstructive pulmonary disease (COPD), heart failure, stroke, high blood pressure, and inflammatory bowel disease.
  • Obesity
  • Cigarette smoking
  • Estrogen replacement therapy and birth control pills
  • During and after pregnancy
  • Enlarged veins in the legs (varicose veins)


Pulmonary embolism can be detected through the following tests:

  • Computed tomography (CT) scan
  • Pulmonary angiogram
  • Blood tests (including the D-dimer test)
  • Ventilation-perfusion scan (V/Q) scan
  • Chest X-ray
  • Electrocardiogram
  • Ultrasound of the leg
  • Magnetic resonance imaging (MRI) of the lungs or legs

Preventive treatment

Preventive treatment is important to prevent the formation of additional embolisms. Preventing clots in the deep veins in the legs (deep vein thrombosis) will help prevent pulmonary embolism (PE). As such, most hospitals are keen on taking measures to prevent blood clots, including:

  • Blood thinners (anticoagulants): These medicines are generally given to those at risk of clots before and after an operation, and to those admitted to the hospital with medical conditions, such as stroke, heart attack, or complications of cancer. These medicines include warfarin and heparin.
  • Compression stockings: Compression stockings steadily squeeze the legs, helping veins and muscles move blood more efficiently. They provide a simple, safe and cheap way to keep blood from stagnating during and after general surgeries.
  • Leg elevation: Elevating your legs occasionally at night can also be very beneficial.
  • Physical activity: Ensure movement as soon as possible after surgery to prevent pulmonary embolism and overall quick recovery. This is why your doctors suggest you get up, even on your day of surgery, and walk despite feeling pain at the site of surgery.
  • Pneumatic compression: This treatment includes thigh-high or calf-high cuffs that automatically inflate with air and deflate every few minutes to massage and squeeze the veins in the legs to improve blood flow.


Pulmonary embolism (PE) can be treated with the following choices:

Fibrinolytic therapy: These medicines are called clot busters and are given intravenously to break down the clot. These medicines are not used except in life-threatening conditions.

Vena cava filter: In this treatment, a small metal device is placed in the vena cava (the large blood vessel that returns blood from the body to the heart), which may be used to prevent clots from traveling to the lungs. These filters are commonly used when the patient:

  • Can’t get anticoagulation treatment
  • Develop more clots even with anticoagulation treatment
  • Have bleeding problems from anticoagulation medicines

Percutaneous thrombectomy: In this treatment, a thin, long, and hollow tube (catheter) is threaded through the blood vessel to the site of the embolism guided by an X-ray. When the catheter is in place, it is used to break up the embolism, pull it out, or dissolve it using thrombolytic medicine.

Pulmonary embolectomy: This surgery is rarely done to remove a pulmonary embolism. It is only done in severe cases when the PE is very large and the patient cannot receive anticoagulation or thrombolytic therapy due to bleeding disorders or other medical reasons. If the patient is hemodynamically unstable, pulmonary embolectomy may also be considered.

Work cited

This page was last reviewed and updated by on May 18, 2024.